Plant Growth and Metabolic Responses of Tomato Varieties to Salinity Stress After Thermopriming
Department of Vegetable Crops, Hochschule Geisenheim University, 65366 Geisenheim, Germany
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Author to whom correspondence should be addressed.
Stresses 2025, 5(2), 27; https://doi.org/10.3390/stresses5020027
Submission received: 24 February 2025
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Revised: 26 March 2025
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Accepted: 3 April 2025
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Published: 10 April 2025
(This article belongs to the Collection Feature Papers in Plant and Photoautotrophic Stresses)
Abstract
:Abiotic stresses like heat and salinity challenge crop production, but cultivar-specific adaptability and tolerance inducers can mitigate their impact. This study examined the growth and biochemical responses of five tomato varieties (Adeleza F1, Saint Anna F1, Goudski F1, Bronski F1, and Dunk F1) to thermopriming followed by salinity stresses. Thermopriming initially promoted growth but had variable effects on plant performance under combined stresses. Adeleza F1 and Bronski F1 were less affected, while Goudski F1 and Dunk F1 exhibited delayed development and reduced biomass under salinity stress. Thermopriming enhanced leaf chlorophyll content and antioxidant capacity in some varieties but inconsistently influenced leaf phenolics and flavonoids. Notably, increased flavonoid and anthocyanin accumulation in certain varieties suggests improved stress tolerance, albeit at the cost of growth. However, a consistent priming effect was not observed across all varieties, as combined heat and salt stress had a more severe impact than individual stresses. These findings highlight genotype-specific responses, underscoring the need for optimized (thermo-)priming protocols that balance growth and defense. This study provides valuable insights into the complex interplay of heat and salinity stress in tomatoes, emphasizing targeted strategies for enhancing crop resilience and informing future breeding programs.
1. Introduction
Climate change, characterized by rising temperatures, changing precipitation patterns, and unpredictable extreme weather events such as droughts, is exacerbating the challenges facing agricultural and horticultural production systems worldwide [1,2,3,4]. These environmental changes increase the incidence of abiotic stress events such as heat and salinity, which can significantly reduce crop growth and productivity [5,6]. Salinity can result, for example, from saltwater intrusion into groundwater (in coastal regions) due to the over-exploitation of aquifers, evaporation with inadequate soil infiltration, or the use of reclaimed saline water [7,8]. In addition, the use of fertigation systems can inadvertently concentrate salts in the soil through evaporation, further exacerbating salinity stress under rising temperatures [7].
The resulting accumulation of salts in the root zone of plants generally limits water uptake and causes osmotic stress, while the accumulation of salt ions in the cytoplasm at toxic concentrations can disrupt cell function and nutrient uptake, ultimately leading to reduced plant growth and yield [9,10], and the down-regulation of photosynthesis through reduced chlorophyll content and altered phytohormone levels [11,12,13,14,15,16]. The salinity threshold for the model crop tomato is 2.5 dS m−1, above which yield potential is predominantly reduced, although fruit quality parameters such as total soluble solids and flavonoids may increase under moderate stress [17,18,19,20,21].
Heat stress, another critical abiotic factor, disrupts photosynthesis and accelerates water loss through transpiration, further compounding the challenges posed by salinity stress [15,22,23,24]. Under combined heat and salinity stress, plants experience complex physiological changes, including altered stomatal conductance, oxidative stress, and shifts in photosynthetic efficiency [19,23,25,26]. Such interactions can either mitigate or enhance the effects of individual stressors, depending on the stress intensity and plant species [4,23,27]. For example, heat stress has been shown to enhance salinity tolerance through the induction of antioxidant enzymes and stress-responsive proteins, although higher combined stress levels often result in more severe reductions in growth and yield [28,29,30,31,32].
Tomato plants exhibit moderate susceptibility to heat and salinity, with genotype-dependent variation [24,33,34,35], resulting in yield losses due to reduced fruit set, lower fresh fruit weight, and a higher incidence of diseases such as blossom end rot [36,37,38,39,40]. In contrast, the accumulation of certain phenolic compounds, sugars, and flavonoids in fruits is stress-induced, highlighting the beneficial potential of moderate abiotic (eu)stress application in crop production [41,42,43]. Among these, phenols such as flavonoids and anthocyanins play a critical role in protecting plant tissues from oxidative damage caused by abiotic stress [28,44]. It can therefore be assumed that plants specifically accumulate these metabolites in epidermal tissues to protect themselves from additional stress factors such as heat or increased salinity under the prevailing light and environmental conditions, thereby mitigating cell damage and maintaining both photosynthesis and other metabolic processes. However, genetic diversity among varieties [24,43] results in different levels of susceptibility or tolerance to heat and salinity stress, with some genotypes exhibiting superior physiological and metabolic adaptations under stress conditions [24,45,46,47]. These differences manifest in growth parameters, including plant height, biomass, and fruit yield, as well as in the accumulation of protective metabolites such as antioxidants, osmolytes, and secondary metabolites. This phenomenon is commonly referred to as a genotype-by-environment interaction, which describes how different genotypes respond differently to environmental conditions [48,49]. Understanding these interactions is crucial for optimizing stress management strategies and selecting resilient varieties for sustainable crop production.
To exploit this genetic hardening of plants through artificial pre-stress, transplant priming has gained attention as a promising strategy that effectively induces robust plant defense mechanisms while reducing fitness costs under subsequent stress conditions [50]. The ability of thermopriming, a heat-based priming technique, to enhance tolerance to subsequent salinity stress further underscores the potential of stress adaptation strategies to mitigate climate-related challenges in both agriculture and horticulture [51]. In a changing climate, this approach can contribute to supporting the UN Sustainable Development Goals (SDGs) and the European Green Deal by improving the sustainability of horticulture and agriculture through the development of more resilient crop production systems [52,53]. By examining the interaction of thermopriming with subsequent salinity stresses on five tomato varieties, this study aims to explore these potentially variable responses and provide valuable insights into the physiological traits underlying cross-tolerance and adaptation to abiotic stresses.
2. Results
2.1. Plant Height and Relative Growth Rate
After thermopriming, primed plants of all varieties showed increased height compared to the unprimed control, which was associated with higher relative growth rates (Table A1). This effect on plant height persisted one week later in Adeleza F1 and Bronski F1, while primed transplants of Goudski F1 and Dunk F1 no longer differed in height, and Saint Anna F1 showed reduced height in comparison to the control. Unlike plant height, primed plants of all varieties exhibited reduced relative growth rates compared to controls. The following week (just before the subsequent stress), primed plants of all varieties except Bronski F1 showed lower heights, while Bronski F1 exhibited no differences between treatments.
One week after the salinity stress (21 days after priming, DAP), Dunk F1 and Bronski F1 showed no differences between primed and unprimed plants. In contrast, the primed plants of Adeleza F1 and Goudski F1 exhibited reduced heights under salinity stress compared to the controls. In Saint Anna F1, thermopriming had a predominant effect, whereas salinity stress showed no significant impact on plant height. Relative growth rates were similar across treatments for all varieties during this growth period, except for Bronski F1, where primed plants maintained stable relative growth rates after salt stress.
After a second exposure to salt stress (28 DAP; Figure 1), Adeleza F1 and Goudski F1 responded similarly, with both showing reduced height in primed and stressed plants compared to controls. The other groups displayed no significant differences in plant height. However, in Goudski F1, primed transplants exhibited higher relative growth rates under salinity stress than unprimed plants. Primed Saint Anna F1 and Dunk F1 plants had reduced height, though salinity stress significantly affected only Saint Anna F1, resulting in a reduced plant height compared to the control. Conversely, primed Saint Anna F1 plants had higher growth rates than unprimed plants, though no differences were observed under salinity stress.
In a broader perspective of the whole experimental period, Saint Anna F1, Goudski F1, Bronski F1, and Dunk F1 remained unaffected by any stress treatment in their relative growth rates. Only Adeleza F1 was affected in its relative growth rates by thermopriming, but not by recurrent salinity stress. Throughout the experimental period, Bronski F1 remained unaffected in height by any stress treatment. Overall, recurrent salinity stress had a stronger impact on the plant heights of Adeleza F1, Saint Anna F1, Goudski F1, and Dunk F1 than thermopriming. Notably, in interaction with salt stress, the primed plants of Goudski F1 were reduced in height, whereas unprimed plants showed an increase in height. In Adeleza F1, Saint Anna F1, and Dunk F1, salt-stressed plants were reduced in plant height. Thus, varieties displayed distinct responses to thermopriming and stress conditions with respect to vegetative growth.
2.2. Number of Leaves and BBCH Stages
In terms of plant development, the number of leaves corresponding to the growth stage of Adeleza F1, Saint Anna F1, and Bronski F1 plants did not differ after priming, while thermopriming delayed vegetative development in Goudski F1 and Dunk F1 (Table A1). In the following two weeks, no differences were found between primed and unprimed plants in Goudski F1, Bronski F1, and Dunk F1. The primed plants of Adeleza F1 developed a greater number of leaves compared to the controls after priming. In contrast, Saint Anna F1 showed a delay in the development of primed plants two weeks after priming.
Following salinity stress, Adeleza F1, Saint Anna F1, and Bronski F1 showed no differences in leaf number. In contrast, the primed plants of Goudski F1 and Dunk F1 exhibited delayed growth stages when exposed to salinity stress, as reflected by fewer leaves, compared to their unprimed counterparts. After exposure to recurrent salinity stress, the primed plants of Adeleza F1 displayed a greater number of leaves than unprimed and stressed plants, while no differences were observed between unstressed primed and unprimed groups at this stage (28 DAP). For the other varieties, there were no persistent differences between treatments.
Overall, the treatments had no significant effect on the vegetative development of Saint Anna F1, Goudski F1, and Bronski F1. However, the primed plants of Adeleza F1 showed a tendency to be better able to cope with stress in their leaf development, while the opposite was observed in Dunk F1.
2.3. The Height of the First Inflorescence
At the end of the first experiment, the height of the first inflorescence was lower in the primed plants of Saint Anna F1, Goudski F1, and Dunk F1, with the most pronounced reduction observed in Saint Anna F1 and Goudski F1 under subsequent stress conditions (Table A2). In Adeleza F1, this effect was only evident when the plants were subjected to salinity stress. In contrast, the inflorescence height of Bronski F1 was not affected by any treatment.
2.4. Onset of Inflorescence Flowering
The treatments had no effect on the onset of inflorescence flowering in Saint Anna F1 and Bronski F1 (Table A3). In Adeleza F1, flower development was accelerated in the primed groups, with no influence from recurrent salinity stress. Similarly, thermopriming led to an earlier onset of inflorescence flowering in Dunk F1, but no differences were observed in interaction with the first salinity stress. One week after the second salinity stress, there was no longer any difference between the treatments of Dunk F1. For Goudski F1, the first salinity stress did not result in differences in generative development among treatments; however, after the second salinity stress, primed and salt-stressed plants exhibited a delayed onset of inflorescence flowering compared to unprimed and salt-stressed plants. The unprimed groups did not differ, regardless of prior thermopriming.
2.5. Plant Fresh Matter
The total fresh matter (FM) of the plants was reduced by priming in Saint Anna F1 and Goudski F1, with salinity stress leading to the greatest reduction in Goudski (Figure 2). The primed plants of Dunk F1 only displayed a decrease in total FM under salinity stress. Interestingly, salinity stress increased the total FM in unprimed Bronski F1 plants, though this effect was not observed in the primed group. Adeleza F1 showed no significant changes in total FM between treatments.
Similar effects were observed in the shoot FM of Saint Anna F1 and Goudski F1, where primed plants exhibited a decrease, with a more pronounced reduction in Goudski F1, when exposed to salinity stress (Table A4). In Bronski F1, the primed plants had a lower shoot FM under salinity stress compared to the unprimed plants; however, in the absence of stress, there were no differences between the primed and unprimed groups. In comparison, only priming in interaction with salinity stress resulted in a reduced shoot FM in Dunk F1. Thermopriming did not affect shoot FM in Adeleza F1, but salinity stress caused a significant reduction in unprimed plants.
For leaf FM, both the unprimed plants of Saint Anna F1 and Dunk F1 exhibited a significant increase under salinity stress, while the other groups did not differ (Table A4). A similar trend was observed in Adeleza F1, although no differences were found between the primed and unprimed plants under subsequent salt stress. Bronski F1 showed a clear response to salt stress, with salt-stressed plants having a greater leaf FM, while unstressed groups did not differ in leaf FM. In Goudski F1, priming led to a decrease in leaf FM, and only in unprimed plants did salinity stress lead to an increase in leaf FM.
2.6. Plant Dry Matter
In terms of total plant dry matter (DM), the treatments had no effect on Adeleza F1 (Figure 3). The primed plants of Saint Anna F1 exhibited a reduced total DM compared to the unprimed plants, while subsequent salt stress reduced total DM only in the unprimed plants. In Goudski F1 and Bronski F1, thermopriming resulted in a decrease in total DM with no effect of salinity stress. The Dunk F1 transplants showed a reduction in total DM only when exposed to the combination of priming and salinity stress.
Thermopriming had no effect on shoot DM in Adeleza F1, although the primed plants that were salt-stressed had a reduced shoot DM compared to the unstressed plants—an effect that was not observed in the unprimed plants, which showed no difference from the primed plants (Table A4). In Saint Anna F1, all treatments reduced shoot DM compared to the control. In Goudski F1 and Dunk F1, salinity stress reduced shoot DM in primed plants. Bronski F1 showed a reduction in shoot DM due to thermopriming alone, while recurrent salinity stress had no effect.
Leaf DM was unaffected in Adeleza F1 (Table A4). In Saint Anna F1, Goudski F1, and Bronski F1, thermopriming caused a reduction in leaf DM; however, in Saint Anna F1, the primed and salt-stressed plants did not differ significantly from their unprimed counterparts. Dunk F1 displayed a decrease in leaf DM only in plants that were both primed and subsequently salt-stressed.
2.7. Chlorophyll Index
After thermopriming, all varieties exhibited an increased chlorophyll index in the mature leaves of primed plants (Table A5). This effect persisted in the mature leaves of all varieties following the first salinity stress. Salinity stress had no impact on Adeleza F1, Saint Anna F1, and Goudski F1, while the unprimed mature leaves of Bronski F1 indicated higher chlorophyll fluorescence under stress, an effect not observed in the primed plants. In Dunk F1, salinity stress reduced chlorophyll indices, particularly in the primed mature leaves. After the second salinity stress, an increased chlorophyll index was observed in the mature leaves of the primed plants of Adeleza F1 and Saint Anna F1. In contrast, salt-stressed Dunk F1 plants showed a significant reduction in chlorophyll index in both the primed and unprimed groups due to salinity stress. In Goudski F1 and Bronski F1, priming had no effect on the plants’ response to the second salt stress, although in Goudski F1, the primed plants showed a decreased chlorophyll index under salinity, while this was not the case in the unprimed plants.
Just before the first salinity stress (14 DAP), no differences were observed in young leaves between the primed and unprimed plants across all varieties (Table A6). After the first stress, the young leaves of Adeleza F1 and Bronski F1 showed no changes. However, the chlorophyll index was reduced in the young leaves of the primed plants of Saint Anna F1, Goudski F1, and Dunk F1, but only under salinity in Saint Anna F1 and Goudski F1. Following the second salinity stress, these effects persisted only in Goudski F1 and Dunk F1. In the young leaves of unprimed Goudski F1 plants, salinity stress led to an increased chlorophyll index, which was not the case in the primed plants. Dunk F1 exhibited a similar trend, although only the primed, unstressed group had a significantly lower chlorophyll index compared to the unprimed, stressed group.
2.8. Flavonol Index
In the mature leaves of Saint Anna F1, Goudski F1, and Dunk F1, thermopriming did not alter the flavonol index before the subsequent stress (Table A5). However, the primed Adeleza F1 and Bronski F1 plants showed a decreased flavonol content compared to the unprimed controls. After the first salinity stress, the primed Adeleza F1 plants continued to exhibit a lower flavonol content, unaffected by salt stress. In contrast, salinity stress caused a decrease in flavonol content in the mature leaves of Bronski F1, although no significant changes were found in the primed group. No differences were observed among treatments for the other varieties. After the second salinity stress, only Goudski F1 exhibited a significant change in the flavonol index in mature leaves, with the primed and salt-stressed plants showing a higher flavonol content than their unprimed counterparts, though these did not differ from the control group.
Before salinity stress (14 DAP), the young leaves of the primed Bronski F1 and Dunk F1 plants had a lower flavonol index (Table A6). After the first stress, Adeleza F1 remained unaffected, while the flavonol content in the young leaves of Saint Anna F1 and Dunk F1 decreased under salinity. In Dunk F1, the primed and unprimed groups did not differ, whereas in Saint Anna F1, even the primed and unprimed plants showed a reduced flavonol index compared to the control plants. In Bronski F1, only the unprimed groups differed, with priming resulting in a reduced flavonol index. In Goudski F1, a decrease in the flavonol content was only observed in the primed and stressed group. Following the second salinity stress, the young leaves of Adeleza F1 and Bronski F1 showed no effects of the treatments. In Saint Anna F1, the unprimed group displayed a stress-related decrease in flavonol content, while the primed group showed a tendency to accumulate flavonols under stress in young leaves. In Goudski F1 and Dunk F1, salinity stress predominated the priming effect, resulting in a decreased flavonol index in young leaves.
2.9. Anthocyanin Index
After thermopriming, all varieties exhibited a reduced anthocyanin index in mature leaves compared to the unprimed controls, a reduction that persisted following subsequent salinity stress (Table A5). Adeleza F1 and Saint Anna F1 maintained lower anthocyanin levels in mature leaves even after the second salt stress (Figure 4). In contrast, Goudski F1 and Dunk F1 indicated anthocyanin accumulation in the mature leaves of primed plants under salinity stress, while the primed and unstressed group retained a reduced anthocyanin index. No treatment effects were observed in Bronski F1.
In young leaves, no differences in the anthocyanin index were found between the primed and unprimed plants of any variety prior to salt stress (14 DAP) (Table A6). Following salinity stress, the young leaves of Adeleza F1, Saint Anna F1, and Bronski F1 remained unaffected by any treatment. However, Goudski F1 and Dunk F1 showed a higher anthocyanin index in the primed plants compared to unprimed ones, with this increase in Goudski F1 limited to the salt-stressed groups. After the second salinity stress, Adeleza F1 and Bronski F1 still exhibited no change in anthocyanin content in young leaves. In Saint Anna F1 and Goudski F1, salinity stress predominated, leading to a reduced anthocyanin index in young leaves.
2.10. Total Chlorophyll Content
Two weeks after priming, and just before the first subsequent salinity stress (14 DAP), total chlorophyll content (TCC) was higher in the mature leaves of primed plants across all varieties (Table A7). Following salinity stress, Adeleza F1 and Saint Anna F1 showed no differences between treatments, while the primed plants of the other varieties maintained an increased TCC, unaffected by salinity stress. After the second salinity stress, the primed and stressed Goudski F1 plants had a higher TCC compared to the unprimed control (Figure 5). However, no significant differences were observed between the primed and stressed group and its unprimed and stressed counterpart. In Saint Anna F1, the repeated salinity stress had no effect, although the primed and unstressed plants had an increased TCC compared to the unprimed and unstressed plants. All varieties showed a similar response at 28 DAP in young leaves under salinity stress.
2.11. Total Carotenoid Content
Before exposure to salinity stress, priming led to increased total carotenoid content (TCarC) in the mature leaves of Saint Anna F1, Goudski F1, Bronski F1, and Dunk F1, while no differences were observed in Adeleza F1 (Table A7). In response to salinity stress, Goudski F1 and Bronski F1 maintained elevated TCarC in their mature leaves, but the effect was less pronounced in Dunk F1, where only the primed and unstressed plants exhibited higher TCarC compared to the unprimed and stressed plants. Adeleza F1 and Saint Anna F1 showed no treatment effects until after the second salinity stress, at which point salinity led to a decrease in TCarC (Figure 6). In Adeleza F1, this reduction was not significant in the primed plants, whereas in Saint Anna F1, only the primed and unstressed plants maintained an increased TCarC compared to the other treatments. After the second salinity stress, the primed plants of Goudski F1, Bronski F1, and Dunk F1 generally retained a higher TCarC, though this was independent of salt stress in Dunk F1. In young leaves, recurrent salinity stress did not affect TCarC in Saint Anna F1, but the primed and unstressed plants showed an increase in TCarC compared to the controls. In Adeleza F1, the repeated salt stress caused a decrease in TCarC in young leaves, although this effect was significant only in the primed group.
2.12. Total Anthocyanin Content
After priming (14 DAP), no differences in total anthocyanin content (TAC) were observed in the mature leaves of primed and unprimed plants across all varieties (Table A7). In Goudski F1, salinity stress resulted in a higher TAC in the primed plants compared to the unprimed plants. Similarly, Bronski F1 showed an increased TAC under salinity stress in the primed plants, though no differences were found between the unstressed groups. In Adeleza F1, the first salinity stress caused a reduction in TAC, but only in the unprimed plants, while TAC levels remained stable in the primed plants. The primed Saint Anna F1 plants were not affected by recurrent salinity stress, but showed a lower TAC in primed the plants compared to the unprimed plants. Dunk F1 showed no response to any treatment after either salinity stress. After the second salinity stress, the primed Bronski F1 plants displayed a higher TAC under salinity compared to the unprimed plants, with no differences observed between the unstressed groups. In young leaves, the primed Saint Anna F1 saw an increase in TAC with salinity having no effect on this. The primed Goudski F1 plants exhibited a higher TAC in young leaves in response to salinity stress, a response not observed in the unprimed plants.
2.13. Total Phenol Content
Thermopriming had no lasting effect on total phenol content (TPC) in the mature leaves of any variety prior to salinity stress (Table A8). This remained the case even after repeated salinity stress for Saint Anna F1, Goudski F1, and Bronski F1. In contrast, Adeleza F1 exhibited decreased TPC across all groups except the unprimed and unstressed control. In Dunk F1, TPC in mature leaves decreased in the primed plants, though this effect was not observed under salinity stress. After the second salinity stress, the unprimed Goudski F1 plants exposed to salinity stress showed a lower TPC in mature leaves compared to the unstressed plants, while thermopriming had no significant impact.
In young leaves, Adeleza F1 and Dunk F1 showed similar responses to stress, with primed plants that were not exposed to salinity stress displaying a higher TPC than the unprimed plants. Salt stress did not significantly affect TPC in the young leaves of Adeleza F1, resulting in TPC levels in the stressed unprimed plants comparable to those in the unstressed primed plants. By contrast, Bronski F1 exhibited a lower TPC in the young leaves of primed plants compared to unprimed plants, although salinity stress led to similar TPC levels in both the primed and unprimed groups.
2.14. Flavonoid Content Specific for Flavanol and Flavone Luteolin
For flavonoid content specific to flavonol and the flavone luteolin (FCQuercetin), the mature leaves of the primed Adeleza F1 plants exhibited a reduced FCQuercetin compared to the unprimed plants (Table A8). In Saint Anna F1, Goudski F1, Bronski F1, and Dunk F1, priming had no early effect on FCQuercetin in mature leaves. This lack of response persisted after repeated salinity stress in Saint Anna F1, Goudski F1, and Bronski F1, while Dunk F1 showed an increased FCQuercetin in primed and stressed plants compared to primed and unstressed plants, with no differences observed between the primed and unprimed groups. Following the first salinity stress, all treatments in Adeleza F1 resulted in a decreased FCQuercetin in mature leaves compared to the control; however, this effect was no longer observed after the second salt stress. In young leaves, FCQuercetin levels were similar across all treatments for Goudski F1, Bronski F1, and Dunk F1. For Adeleza F1 and Saint Anna F1, the primed and unstressed plants had higher FCQuercetin levels than the unprimed and stressed plants.
2.15. Flavonoid Content Specific for Rutin, Luteolin, and Catechin
In contrast to the FCQuercetin specific to flavonol and flavone luteolin, the plant varieties had a different response to FCCatechin specific for rutin, luteolin, and catechin (Table A8). Two weeks after thermopriming, Adeleza F1 showed no changes in FCCatechin, while Saint Anna F1, Goudski F1, Bronski F1, and Dunk F1 displayed a higher FCCatechin in the mature leaves of primed plants compared to the controls. After the first subsequent salinity stress, Bronski F1 and Dunk F1 retained a higher FCCatechin in the primed groups, though Dunk F1 showed an increase only in the primed and stressed plants compared to the control, with no differences for the unprimed and unstressed plants. The primed Saint Anna F1 plants had an increased FCCatechin in interaction with salinity stress, but not without. However, no differences were found in the FCCatechin of the unprimed Saint Anna F1 plants. After the second salinity stress, only Saint Anna F1 and Bronski F1 responded to the treatments, with the primed and unstressed plants showing an increased FCCatechin compared to the unprimed and unstressed plants. Saint Anna F1 showed a similar response in FCCatechin accumulation in young leaves, while the other varieties showed no effect.
3. Discussion
3.1. Stress-Induced Accumulation of Protective Leaf Compounds
In view of the global challenges posed by heat waves and salinity on crop production, this study analyzed the stress response of five different tomato varieties under thermopriming followed by salt stress. Protective leaf components, such as total phenolics and the subgroups flavonols and anthocyanins, known for their antioxidant role in plants, were used as an indicator of an activated plant defense system [28,44]. In line with previous studies about varying levels of salinity stress [19,54,55], our varieties showed a decrease in total phenolics and flavonoids in tomato leaves under individual or combined stress conditions. In contrast, Liu et al. [56] observed higher phenolic levels in thermoprimed Achillea millefolium, a trend similar to our previous work on the variety Adeleza F1 [51]. However, by examining specific phenolic groups, genotypic differences can be explained. For cherry tomato, Al Hassan et al. [42] described higher phenolic accumulation under salinity stress, which was shown for the cocktail tomato Saint Anna F1, which showed an interaction with salinity stress, leading to higher flavonoid accumulation, related to rutin, luteolin, and catechin, in primed plants compared to unprimed ones. This is consistent with studies reporting increased flavonoids under salinity stress [42,57,58]. The other four cluster tomato varieties also increased specific flavonoid subgroups in young and mature leaves. Thermopriming temporarily increased antioxidant capacity and UV protection by increasing the anthocyanin content in the mature and young leaves of cluster tomatoes Goudski F1, Bronski F1, and Dunk F1. Meanwhile, the mature leaves of Adeleza F1 and Saint Anna F1 showed reduced anthocyanin content. This is in line with studies of improved salt tolerance in tomato and Arabidopsis plants [59,60] and enhanced heat tolerance in transgenic tomato [61].
Primed plants also showed increased leaf carotenoid levels in all varieties except Adeleza F1, supporting their role in photoprotection and the mitigation of oxidative stress [62,63]. Bronski F1 and Goudski F1 exhibited higher carotenoid content after salinity stress, which is in agreement with the findings of Zhou et al. [63], who emphasized that plants synthesize carotenoids to protect themselves from heat stress. However, a decrease in carotenoids under heat stress has also been reported [19,64].
In conclusion, the growth and biochemical responses to thermopriming and salinity stress varied significantly among tomato varieties, highlighting the critical role of genotype in determining stress tolerance. While thermopriming enhanced stress tolerance by promoting the accumulation of protective phenolic compounds, its efficacy was genotype-dependent, emphasizing the need for targeted breeding programs that leverage these insights. Furthermore, incorporating wild tomato species and traditional landraces into thermopriming research could offer valuable perspectives, as these genotypes often exhibit greater resilience due to their evolutionary adaptations. Understanding how these genotypes respond to priming strategies might uncover novel mechanisms of stress tolerance.
3.2. Developmental Response to Abiotic (Priming) Stresses
The energy allocated to secondary metabolism trades off with plant growth, as activated defenses lead to the accumulation of protective compounds in leaves. This, in turn, was associated with reduced growth performance in all five varieties studied. In our cocktail and cluster tomato varieties, thermopriming resulted in genotype-dependent differences in plant height, developmental stages, flowering patterns, and biomass. As previously shown for thermoprimed Adeleza F1 transplants [51,65,66], these five varieties also exhibited a transient growth increase followed by a decline and subsequent recovery. Hypocotyl elongation resulting from heat stress-induced thermomorphogenesis can be attributed to auxin synthesis, perception, and signaling pathways [67]. While the other four varieties slowed their growth under subsequent salt stress, Bronski F1 maintained a similar final plant height across all treatments. This variety, therefore, appears to be particularly promising for understanding processes of physiological adaptation to heat and salinity.
The large cluster tomato Bronski F1 was able to overcome the adverse effects of heat stress in the form of thermopriming, which disrupts photosynthesis, impairs cellular processes, and increases transpiration to regulate leaf temperature—ultimately leading to excessive water loss and oxidative stress [4,15,24,68]. Plants possess basal (inherent) thermotolerance and acquired (induced and transient) thermotolerance, which can vary between species and genotypes [28]. In our experiments, we observed distinct differences in thermotolerance among tomato varieties. One week after priming, the cluster tomatoes Adeleza F1 and Bronski F1 exhibited increased plant heights, suggesting a positive growth response to thermopriming. In contrast, Goudski F1 and Dunk F1 showed no significant differences at this stage, while the cocktail tomato Saint Anna F1 even displayed a reduced plant height, possibly indicating a negative effect of priming on early growth. In agreement with Wang et al. [69] and Olas et al. [70], Goudski F1 and Dunk F1 showed delayed development, which was also reflected in biomass reductions by Botella et al. [19]. These findings suggest that some varieties are more susceptible to heat stress during early development [24], which may be related to the activation of heat stress transcription factors that regulate protective mechanisms such as heat shock proteins and antioxidant defenses. However, thermotolerance is a complex trait involving multiple signaling pathways and molecular responses, which may explain the observed variation between genotypes [28].
Rivero et al. [26] highlighted that exposure to heat can enhance the salinity tolerance of tomato plants. In contrast, our experiments showed that thermopriming did not enhance or stabilize plant growth under subsequent salinity stress, suggesting its protective effects may be limited under combined stress conditions.
Our study confirmed that combined heat and salinity stress generally reduced biomass more than individual stresses, as previously reported by Li et al. [23]. They also emphasized that different intensities of salt stress combined with heat stress may have different effects on tomato plants. At higher salinity levels (e.g., 200 mM NaCl), salinity likely became the dominant stressor, particularly influencing stomatal responses [23]. Contrary to our results, Lopez-Delacalle et al. [71] found that combined salinity and heat stress enhanced tomato growth compared to salinity stress alone.
Thermopriming increased the chlorophyll index in the leaf epidermis and the total chlorophyll content in mature leaves in all varieties. Shaheen et al. [24] reported a similar initial response in tomato, although chlorophyll levels declined over time under prolonged heat stress to limit photosynthetic energy uptake through chlorophyll degradation, thereby regulating water balance and oxidative defense [4,15,23,24]. In our study, the limited experiment duration may explain why we did not observe a decrease in total chlorophyll content, although the initial increase in primed plants eventually disappeared. Adeleza F1, Saint Anna F1, and Bronski F1 showed resilience to recurrent salinity stress. However, the primed Goudski F1 and Dunk F1 plants exhibited reduced chlorophyll indices under repeated salinity stress—a response not observed in the unprimed plants. This suggests that thermopriming did not trigger a positive defense response but instead increased sensitivity to subsequent salt stress, as salinity also reduces chlorophyll content [14,41,72]. The young leaves of Goudski F1 and Dunk F1 showed lower chlorophyll fluorescence due to priming, but fluorescence increased under salinity stress, indicating elevated stress levels. This aligns with the response of plants under heat stress, where reduced chlorophyll levels enhance drought tolerance [73], a process also triggered by salinity stress [74].
In interaction with salinity stress, delayed flowering was observed in primed, salt-stressed small cluster tomato Goudski F1 plants, consistent with Fan et al. [75], who suggested that thermopriming may delay flowering under heat stress as an adaptive mechanism to avoid reproduction under unfavorable conditions [70]. In contrast, Adeleza F1 and Dunk F1 exhibited accelerated flowering, unaffected by salinity stress, in agreement with Wigge [76]. The flowering of the large cluster tomato Bronski F1 and the cocktail tomato Saint Anna F1 was unaffected by the treatments, possibly because they belong to a different crop type. These findings suggest that thermopriming in tomato, as in other crops, can either shift resources toward stress protection at the expense of reproduction or promote earlier flowering to escape stress, depending on the genotype. This underscores the complex trade-offs plants make in response to environmental stressors. In line with this, Botella et al. [19] observed that the interaction between heat and salt stress has distinct effects on tomato plants, with salinity reducing fruit yield while improving fruit quality, and high temperatures increasing vitamin C content but significantly reducing certain phenolic compounds in fruit.
Further molecular analyses are needed to elucidate these mechanisms. With ever-evolving tomato varieties, trial-based evaluations remain the most effective way to assess thermopriming benefits. Adjustments to thermopriming protocols could significantly alter outcomes.
3.3. Beyond Variety-Specific Responses to Thermopriming and Subsequent Stresses
The potential applicability of thermopriming strategies, as demonstrated in our study, extends beyond tomato plants to other Solanaceae crops, such as pepper and eggplant, raising questions about practical relevance in diverse agricultural systems. This could open pathways to developing breeding markers to support precision breeding programs, enabling the selection of genotypes optimized for thermopriming efficacy. Advances in molecular biology, such as CRISPR-Cas technology, could also play a pivotal role by enabling the targeted introduction of stress resilience traits into related species, further expanding the scope of thermopriming applications. Moreover, the plant microbiome is an essential component of the plant’s immune system. Exploring the potential synergy between microbial priming (e.g., through beneficial bacteria) and thermopriming could offer innovative approaches to enhancing stress tolerance in crops [77].
In the context of future climate modeling, thermopriming strategies could be incorporated into agricultural management practices to tackle the challenges posed by recurring heatwaves and other extreme weather events. By combining genotype-specific stress tolerance mechanisms with climate-adaptive practices, we can enhance the resilience of crops to increasingly variable climates. These strategies align with global sustainability goals, including SDG 2 (Zero Hunger), by increasing yields under environmental stress conditions to enhance food security; SDG 13 (Climate Action), by adapting agriculture to climate change through stress-resilient crops; SDG 12 (Responsible Consumption and Production), by minimizing yield losses caused by environmental stress and promoting sustainable resource use; and SDG 15 (Life on Land), by conserving biodiversity through the preservation of local and resilient genotypes [53].
Future research should explore the scalability of thermopriming across diverse crops and agricultural systems, investigate its integration into sustainable production practices, and develop models for its implementation under projected climate scenarios. By aligning genotype-specific stress tolerance mechanisms with innovative management strategies, we can contribute to the development of resilient agricultural systems capable of mitigating the impacts of climate change while supporting global food security goals.
4. Materials and Methods
4.1. Experimental Conditions
In 2024, three sets of experiments were conducted at Geisenheim University (Geisenheim, Germany) to investigate the effect of thermopriming in interaction with two subsequent salt stresses—two and three weeks after priming—on the growth performance and stress resilience of five tomato (Solanum lycopersicum L.) varieties—Adeleza F1, Saint Anna F1, Goudski F1, Bronski F1, and Dunk F1 (Enza Zaden Deutschland GmbH & Co. KG, Dannstadt-Schauernheim, Germany) (Table 1). Adeleza F1, Dunk F1, and Goudski F1 are small cluster tomatoes with a fruit weight between 90 and 105 g, while Bronski F1 is a large cluster tomato with fruits weighing between 140 and 160 g. Saint Anna F1 is a cocktail tomato variety with fruits weighing between 43 and 48 g, according to the breeder’s specifications. Each cultivation set lasted 44 days after sowing (DAS). The plants were sown in ‘HerkuPak D 77′ multipot trays (Herkuplast Kubern GmbH, Ering/Inn, Germany) in ‘ORANGE Pikier’ peat substrate (PATZER ERDEN GmbH, Sinntal-Altengronau, Germany) and cultivated in climate chambers (Fitotron® HGC 0714, Weiss Technik GmbH, Reiskirchen, Germany), where environmental conditions were set to 22 °C (day)/20 °C (night) air temperature, 70% air humidity, and 200 µmol m−2 s−1 (metal halide lamps) for a 16 h photoperiod (8.56 mol m−2 d−1). Priming was performed at 9 DAS by daily heat shock at 40 °C for 90 min as “thermopriming” according to Körner et al. [65] for seven consecutive days. Seedlings were then potted at BBCH 12 [78] in 12 cm diameter pots with the ‘ORANGE Topf’ peat substrate (PATZER ERDEN GmbH, Sinntal-Altengronau, Germany). For further cultivation, the pots were arranged on tables with flood irrigation in four completely randomized blocks, each containing 20 parcels representing different treatments, with three plants per parcel (n = 12 plants per treatment). The plants were cultivated for 28 days at a 22 °C air temperature during the day and 18 °C at night. Transplants were stressed twice at 14 and 21 DAP with 100 mL of 200 mM NaCl solution (EC: 20 dS m−1) or treated with 100 mL of rainwater as a control. The experimental sets were replicated without overlap in their greenhouse growth periods. After sowing, the multipot plates were watered once a day in the climate chambers without fertilizer, while the potted plants were fertigated once or twice a day (depending on weather conditions and plant development) with 0.5% ‘Ferty 2 mega’ (Hauert HBG Dünger AG, Grossaffoltern, Switzerland). Unlike the first and second sets, the potted transplants in the third set were planted in substrate ridges (Einheitserde SP Topf grob, PATZER ERDEN GmbH, Sinntal-Altengronau, Germany) at 34 DAS to extend the cultivation period. However, for this study, the plants were observed for the same duration as the previous sets up to 44 DAS.
4.2. Plant Measurements
In this study, several vegetative growth parameters were measured in all experimental sets, including plant height, relative growth rate (RGR), the number of leaves, the fresh (FM) and dry matter (DM) of the leaves, shoots, and whole plant, and generative development such as the onset of inflorescence flowering. In the first set of experiments, the height of the first inflorescence was measured at the end of the experiment. Plant FM and DM were only evaluated in the first and second sets of experiments due to the continuation of the third experiment. In addition, only in the first set, the height of the first inflorescence was determined at the end of the experiment. RGR was calculated as follows [79]:
where H1 and H2 are plant heights at times t1 and t2 (one week apart).
RGR = (ln H2 − ln H1)/(t2 − t1),
For measurements of leaf compounds, freshly formed and already fully unfolded true leaves were classified as young and the oldest primary true leaves were classified as mature leaves. Leaf samples were collected at three time points—before the first subsequent stress event (14 DAP), one week later before the second recurrent stress event (21 DAP), and finally at the end of the experiment (28 DAP). At the first two time points, the first (mature) true leaf of six different randomly selected plants per treatment was sampled at each time point from a total of twelve plants per treatment to reduce interference with plant development. At the final time point, one young and one mature leaf from six randomly selected plants were again sampled. Leaf samples were snap-frozen in liquid nitrogen and stored at −80 °C prior to photometrical analysis. The total chlorophyll content (TCC), total carotenoid content (TCarC), total anthocyanin content (TAC; expressed as cyanidin-3,5-O-diglucosid equivalents, CyEs), total phenolic content (TPC; expressed as gallic acid equivalents, GAE), and flavonoid content (FC) were colorimetrically measured using the Infinite M200 microplate reader with Magellan 7.2 software (Tecan Group Ltd., Männedorf, Switzerland) according to Dörr et al. [80]. Two methods were used to selectively determine FC for (i) flavanol and flavone luteolin (FCQuercetin; expressed as quercetin equivalents, QEs) and (ii) rutin, luteolin, and catechin (FCCatechin; expressed as catechin equivalents, CEs) [81]. Three technical replicates were averaged for each undiluted sample to minimize microplate reader bias. In addition, the chlorophylls, flavonols, and anthocyanins of the leaf epidermis were determined non-invasively as indices by leaf transmittance and fluorescence (Dualex®, Pessl Instruments, Weiz, Austria). Dualex measurements were performed on an abaxial leaf spot on twelve plants per treatment daily from DAP 5 in mature leaves and from DAP 14 in young leaves until the end of the experiment.
4.3. Data Analysis
Statistical data analysis was performed in R (version 4.2.2) to identify significant differences between treatments using ANOVA with a linear mixed-effects model (α = 0.05; car package, version 3.1.1) combined post hoc with the estimated marginal means (EMMs, α = 0.05, Tukey-adjusted; emmeans package, version 1.8.4.1) and the cld function (multcomp package, version 1.4.23) for pairwise comparisons (α = 0.05). The lmer models (lmerTest package, version 3.1.3) were specified based on random variables including the experimental set, a completely randomized block design as the design of the experiment, and leaf age (for leaf compounds), with heat units (growing degree days, GDD) as a covariate correlated with all parameters (Kendall rank correlation test; stats package, version 4.2.2). GDDs were calculated based on the difference between the daily mean temperature and the lower threshold temperature (base temperature) [82]. The pollen package (type C; version 0.82.0) was used for these calculations, employing a base temperature of 10 °C and a maximum base temperature of 30 °C [83]. When the minimum temperature was below the lower threshold, it was replaced with the lower threshold value. Similarly, if the maximum temperature exceeded the upper threshold, it was substituted with the upper threshold value. To assess overall effects for the entire data collection period of each parameter, the date and repeated measures were additionally included as random variables. Prior to the statistical analysis of the Dualex indices and leaf compounds, outliers were removed using the interquartile range criterion. For ANOVA, daily Dualex indices in the mature leaves were analyzed in three periods—after thermopriming and before salt stress (from 5 DAP to 14 DAP), after the first salt stress (to 21 DAP), and after the second salt stress (to 28 DAP). In comparison, the Dualex indices of young leaves were analyzed after thermopriming and just before salt stress (14 DAP), after the first salt stress (to 21 DAP), and after the second salt stress (to 28 DAP). The number of flowering inflorescences was similarly analyzed for the two periods before and after the second salt stress at 21 DAP. Colorimetrically measured leaf compounds were evaluated only at specific sampling dates—14 DAP (before salinity stress), 21 DAP (one week after the first salinity stress), and 28 DAP (one week after the second salinity stress). Plots were generated using the ggplot2 package (version 3.4.1).
Author Contributions
Formal analysis, T.K.; investigation, T.K.; data curation, T.K.; writing—original draft, T.K.; writing—review and editing, J.Z. and S.R.-S.; visualization, T.K.; supervision, J.Z. and S.R.-S.; project administration, S.R.-S. All authors have read and agreed to the published version of the manuscript.
Funding
The project HortiPrimed is supported by the funds of the Federal Ministry of Food and Agriculture (BMEL) based on a decision by the parliament of the Federal Republic of Germany via the Federal Office for Agriculture and Food (BLE) under the Federal Programme for Ecological Farming. Funding number: 2819NA123.
Institutional Review Board Statement
Not applicable.
Informed Consent Statement
Not applicable.
Data Availability Statement
The data presented in this study are available on request.
Acknowledgments
The authors wish to thank Enza Zaden Deutschland GmbH & Co. KG for the donation of the tomato seeds used for the experiments. Furthermore, we wish to express our gratitude to Norbert Mayer and Rebecca Jessica Ochs for their technical support, as well as to all of the involved gardeners.
Conflicts of Interest
The authors declare no conflicts of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of the data; in the writing of the manuscript; or in the decision to publish the results.
Appendix A
Table A1.
The plant height, relative growth rate (RGR), and leaf number of tomato plants measured at various days after priming (DAP). The data are presented as the mean ± standard deviation for five varieties. Statistical analysis was performed between treatments within each variety. Significant differences between the treatment groups within each variety on each DAP are denoted by different letters, where the letter ‘a’ represents the group(s) with the lowest values. The four treatments are—unprimed and unstressed (CC), unprimed and salt-stressed (CS), primed and unstressed (PC), and primed and salt-stressed (PS).
Table A1.
The plant height, relative growth rate (RGR), and leaf number of tomato plants measured at various days after priming (DAP). The data are presented as the mean ± standard deviation for five varieties. Statistical analysis was performed between treatments within each variety. Significant differences between the treatment groups within each variety on each DAP are denoted by different letters, where the letter ‘a’ represents the group(s) with the lowest values. The four treatments are—unprimed and unstressed (CC), unprimed and salt-stressed (CS), primed and unstressed (PC), and primed and salt-stressed (PS).
| Treat. | Variety | DAP | Plant Height | n | RGR | n | Leaf Number | n | |||
|---|---|---|---|---|---|---|---|---|---|---|---|
| [cm] | [cm cm−1 d−1] | ||||||||||
| CC | Adeleza F1 | 0 | 7.52 | ±1.14 a | 98 | 0.12 | ±0.02 a | 98 | 2.0 | ±0.1 a | 98 |
| 7 | 10.31 | ±1.16 a | 72 | 0.14 | ±0.03 b | 72 | 4.1 | ±0.4 a | 72 | ||
| 14 | 27.78 | ±2.89 b | 96 | 0.14 | ±0.01 b | 96 | 6.7 | ±0.9 a | 96 | ||
| 21 | 60.62 | ±6.12 b | 60 | 0.12 | ±0.02 a | 60 | 9.9 | ±0.8 a | 60 | ||
| 28 | 90.67 | ±6.11 b | 33 | 0.06 | ±0.02 a | 29 | 12.4 | ±1.4 ab | 30 | ||
| Bronski F1 | 0 | 4.58 | ±0.91 a | 95 | 0.11 | ±0.03 a | 93 | 1.9 | ±0.4 a | 95 | |
| 7 | 6.32 | ±1.26 a | 72 | 0.17 | ±0.06 b | 72 | 3.4 | ±0.6 a | 72 | ||
| 14 | 19.75 | ±3.42 a | 96 | 0.17 | ±0.02 b | 96 | 5.9 | ±0.8 a | 96 | ||
| 21 | 44.88 | ±3.98 a | 60 | 0.12 | ±0.02 b | 60 | 9.3 | ±0.7 a | 60 | ||
| 28 | 70.88 | ±7.48 a | 33 | 0.07 | ±0.01 ab | 27 | 11.5 | ±1.4 a | 30 | ||
| Dunk F1 | 0 | 5.38 | ±1.00 a | 93 | 0.13 | ±0.03 a | 92 | 1.8 | ±0.5 b | 92 | |
| 7 | 7.15 | ±1.11 a | 72 | 0.17 | ±0.05 b | 72 | 3.4 | ±0.5 a | 72 | ||
| 14 | 21.93 | ±3.22 b | 96 | 0.16 | ±0.02 b | 96 | 5.8 | ±0.8 a | 96 | ||
| 21 | 53.73 | ±4.25 a | 60 | 0.13 | ±0.02 a | 60 | 9.4 | ±0.7 ab | 60 | ||
| 28 | 84.52 | ±6.03 b | 33 | 0.07 | ±0.01 a | 29 | 11.5 | ±1.3 a | 30 | ||
| Goudski F1 | 0 | 4.39 | ±1.02 a | 84 | 0.12 | ±0.02 a | 72 | 1.6 | ±0.6 b | 76 | |
| 7 | 6.18 | ±1.04 a | 71 | 0.17 | ±0.06 b | 71 | 3.1 | ±0.6 a | 71 | ||
| 14 | 18.69 | ±2.65 b | 95 | 0.16 | ±0.02 b | 95 | 5.6 | ±0.9 a | 95 | ||
| 21 | 42.28 | ±6.50 b | 60 | 0.12 | ±0.03 a | 60 | 9.5 | ±0.8 ab | 60 | ||
| 28 | 67.52 | ±5.38 b | 33 | 0.07 | ±0.02 ab | 25 | 11.4 | ±0.7 a | 30 | ||
| Saint Anna F1 | 0 | 4.81 | ±0.79 a | 98 | 0.11 | ±0.01 a | 98 | 2.0 | ±0.0 a | 98 | |
| 7 | 7.24 | ±1.02 b | 72 | 0.17 | ±0.05 b | 72 | 3.9 | ±0.3 a | 72 | ||
| 14 | 21.54 | ±2.35 b | 96 | 0.16 | ±0.02 b | 96 | 6.8 | ±0.9 b | 96 | ||
| 21 | 48.32 | ±3.29 c | 60 | 0.11 | ±0.02 a | 59 | 10.4 | ±0.5 a | 60 | ||
| 28 | 77.27 | ±4.26 b | 33 | 0.06 | ±0.01 a | 25 | 12.6 | ±1.0 a | 30 | ||
| CS | Adeleza F1 | 21 | 59.38 | ±4.57 ab | 60 | 0.12 | ±0.02 a | 60 | 10.0 | ±0.6 a | 60 |
| 28 | 88.36 | ±4.62 ab | 33 | 0.06 | ±0.01 a | 27 | 12.2 | ±1.4 ab | 30 | ||
| Bronski F1 | 21 | 44.75 | ±4.93 a | 60 | 0.11 | ±0.03 a | 60 | 9.1 | ±0.8 a | 60 | |
| 28 | 70.64 | ±6.71 a | 33 | 0.06 | ±0.01 a | 27 | 11.4 | ±1.4 a | 30 | ||
| Dunk F1 | 21 | 53.75 | ±7.11 a | 60 | 0.12 | ±0.03 a | 60 | 9.5 | ±0.9 b | 60 | |
| 28 | 83.03 | ±8.99 b | 33 | 0.07 | ±0.02 a | 29 | 11.7 | ±2.0 a | 30 | ||
| CS | Goudski F1 | 21 | 44.53 | ±4.02 b | 59 | 0.12 | ±0.02 a | 59 | 9.6 | ±0.8 b | 59 |
| 28 | 68.69 | ±4.57 b | 32 | 0.07 | ±0.01 a | 26 | 11.4 | ±1.1 a | 29 | ||
| Saint Anna F1 | 21 | 47.05 | ±3.96 bc | 60 | 0.11 | ±0.02 a | 60 | 10.2 | ±0.9 a | 60 | |
| 28 | 72.88 | ±4.86 a | 33 | 0.07 | ±0.01 ab | 27 | 12.5 | ±1.0 a | 30 | ||
| PC | Adeleza F1 | 0 | 8.33 | ±1.09 b | 99 | 0.13 | ±0.01 b | 98 | 2.0 | ±0.2 a | 99 |
| 7 | 10.77 | ±1.22 b | 72 | 0.12 | ±0.03 a | 72 | 4.3 | ±0.5 b | 72 | ||
| 14 | 26.83 | ±3.38 a | 96 | 0.13 | ±0.02 a | 95 | 7.0 | ±1.0 b | 96 | ||
| 21 | 59.82 | ±5.26 ab | 60 | 0.12 | ±0.02 a | 60 | 10.0 | ±0.7 a | 60 | ||
| 28 | 89.97 | ±6.53 ab | 33 | 0.06 | ±0.01 a | 29 | 12.3 | ±1.0 ab | 30 | ||
| Bronski F1 | 0 | 5.97 | ±0.97 b | 98 | 0.14 | ±0.02 b | 96 | 1.8 | ±0.4 a | 95 | |
| 7 | 6.71 | ±1.12 b | 72 | 0.13 | ±0.05 a | 72 | 3.4 | ±0.5 a | 72 | ||
| 14 | 19.04 | ±2.68 a | 96 | 0.15 | ±0.02 a | 96 | 6.0 | ±0.9 a | 96 | ||
| 21 | 43.77 | ±4.86 a | 60 | 0.12 | ±0.02 ab | 60 | 9.3 | ±0.8 a | 60 | ||
| 28 | 71.00 | ±5.12 a | 33 | 0.07 | ±0.01 b | 27 | 11.6 | ±1.7 a | 30 | ||
| Dunk F1 | 0 | 6.43 | ±1.09 b | 99 | 0.16 | ±0.02 b | 96 | 1.6 | ±0.5 a | 93 | |
| 7 | 7.03 | ±0.84 a | 72 | 0.12 | ±0.04 a | 72 | 3.4 | ±0.5 a | 72 | ||
| 14 | 19.36 | ±2.49 a | 96 | 0.14 | ±0.02 a | 96 | 5.8 | ±1.0 a | 96 | ||
| 21 | 49.08 | ±6.15 a | 60 | 0.14 | ±0.07 a | 60 | 9.4 | ±0.5 ab | 60 | ||
| 28 | 79.82 | ±4.86 a | 33 | 0.07 | ±0.01 a | 27 | 11.7 | ±1.0 a | 30 | ||
| Goudski F1 | 0 | 4.83 | ±1.65 b | 99 | 0.15 | ±0.04 b | 75 | 1.2 | ±0.7 a | 82 | |
| 7 | 6.12 | ±1.01 a | 72 | 0.13 | ±0.05 a | 72 | 3.0 | ±0.6 a | 72 | ||
| 14 | 16.95 | ±2.69 a | 96 | 0.15 | ±0.02 a | 96 | 5.6 | ±0.9 a | 96 | ||
| 21 | 43.45 | ±4.48 b | 60 | 0.12 | ±0.03 a | 60 | 9.7 | ±0.9 b | 60 | ||
| 28 | 69.09 | ±6.05 b | 33 | 0.07 | ±0.01 a | 29 | 11.6 | ±0.9 a | 30 | ||
| Saint Anna F1 | 0 | 5.15 | ±0.62 b | 99 | 0.12 | ±0.01 b | 99 | 2.0 | ±0.2 a | 99 | |
| 7 | 6.89 | ±1.05 a | 72 | 0.14 | ±0.04 a | 72 | 3.9 | ±0.4 a | 72 | ||
| 14 | 19.67 | ±2.81 a | 96 | 0.15 | ±0.01 a | 96 | 6.5 | ±1.1 a | 96 | ||
| 21 | 45.78 | ±4.26 ab | 60 | 0.12 | ±0.01 a | 60 | 10.3 | ±0.8 a | 60 | ||
| 28 | 72.58 | ±6.37 a | 33 | 0.07 | ±0.01 b | 27 | 12.5 | ±1.0 a | 30 | ||
| PS | Adeleza F1 | 21 | 57.98 | ±5.92 a | 60 | 0.12 | ±0.03 a | 60 | 10.1 | ±0.5 a | 60 |
| 28 | 87.00 | ±4.56 a | 33 | 0.06 | ±0.01 a | 27 | 12.7 | ±1.7 b | 30 | ||
| Bronski F1 | 21 | 44.68 | ±4.04 a | 60 | 0.12 | ±0.02 ab | 60 | 9.4 | ±0.7 a | 60 | |
| 28 | 69.52 | ±5.09 a | 33 | 0.07 | ±0.01 ab | 25 | 11.5 | ±1.4 a | 30 | ||
| Dunk F1 | 21 | 48.38 | ±7.57 a | 58 | 0.12 | ±0.03 a | 58 | 9.0 | ±0.9 a | 58 | |
| 28 | 78.27 | ±8.00 a | 33 | 0.07 | ±0.02 a | 27 | 11.1 | ±0.9 a | 30 | ||
| Goudski F1 | 21 | 36.60 | ±6.44 a | 58 | 0.11 | ±0.04 a | 58 | 9.2 | ±1.0 a | 58 | |
| 28 | 59.73 | ±5.64 a | 33 | 0.08 | ±0.02 b | 23 | 11.2 | ±1.1 a | 30 | ||
| Saint Anna F1 | 21 | 44.70 | ±2.97 a | 60 | 0.12 | ±0.02 a | 60 | 10.4 | ±0.8 a | 60 | |
| 28 | 71.06 | ±4.44 a | 33 | 0.07 | ±0.01 ab | 25 | 12.2 | ±1.1 a | 30 | ||
Table A2.
The inflorescence height of tomato plants measured at 28 days after priming (DAP). The data are presented as the mean ± standard deviation for five varieties. Statistical analysis was performed between treatments within each variety. Significant differences between the treatment groups within each variety on each DAP are denoted by different letters, where the letter ‘a’ represents the group(s) with the lowest values. The four treatments are—unprimed and unstressed (CC), unprimed and salt-stressed (CS), primed and unstressed (PC), and primed and salt-stressed (PS).
Table A2.
The inflorescence height of tomato plants measured at 28 days after priming (DAP). The data are presented as the mean ± standard deviation for five varieties. Statistical analysis was performed between treatments within each variety. Significant differences between the treatment groups within each variety on each DAP are denoted by different letters, where the letter ‘a’ represents the group(s) with the lowest values. The four treatments are—unprimed and unstressed (CC), unprimed and salt-stressed (CS), primed and unstressed (PC), and primed and salt-stressed (PS).
| Variety | Treat. | Inflorescence Height | n | |
|---|---|---|---|---|
| [cm] | ||||
| Adeleza F1 | CC | 73.67 | ±4.42 b | 12 |
| CS | 78.17 | ±4.69 b | 12 | |
| PC | 73.33 | ±8.69 b | 12 | |
| PS | 63.67 | ±4.03 a | 12 | |
| Bronski F1 | CC | 51.00 | ±4.39 a | 12 |
| CS | 50.83 | ±3.79 a | 12 | |
| PC | 48.50 | ±4.50 a | 12 | |
| PS | 49.17 | ±2.79 a | 12 | |
| Dunk F1 | CC | 71.17 | ±5.37 b | 12 |
| CS | 71.00 | ±3.52 b | 12 | |
| PC | 61.67 | ±9.64 a | 12 | |
| PS | 66.67 | ±9.02 ab | 12 | |
| Goudski F1 | CC | 62.17 | ±4.15 c | 12 |
| CS | 61.83 | ±3.69 c | 12 | |
| PC | 57.50 | ±2.47 b | 12 | |
| PS | 53.67 | ±2.67 a | 12 | |
| Saint Anna F1 | CC | 53.67 | ±0.98 c | 12 |
| CS | 51.17 | ±5.06 c | 12 | |
| PC | 47.50 | ±3.34 b | 12 | |
| PS | 43.83 | ±1.40 a | 12 | |
Table A3.
The number of flowering inflorescences of tomato plants measured during two periods—before (2) and after (3) the second salt stress at 21 days after priming (DAP). The data are presented as the mean ± standard deviation for five varieties. Statistical analysis was performed between the treatments within each variety during each period. Significant differences between treatment groups within each variety on each DAP are denoted by different letters, where the letter ‘a’ represents the group(s) with the lowest values. The four treatments are—unprimed and unstressed (CC), unprimed and salt-stressed (CS), primed and unstressed (PC), and primed and salt-stressed (PS).
Table A3.
The number of flowering inflorescences of tomato plants measured during two periods—before (2) and after (3) the second salt stress at 21 days after priming (DAP). The data are presented as the mean ± standard deviation for five varieties. Statistical analysis was performed between the treatments within each variety during each period. Significant differences between treatment groups within each variety on each DAP are denoted by different letters, where the letter ‘a’ represents the group(s) with the lowest values. The four treatments are—unprimed and unstressed (CC), unprimed and salt-stressed (CS), primed and unstressed (PC), and primed and salt-stressed (PS).
| Period | Variety | Treat. | Number Flowering Inflorescences | n | |
|---|---|---|---|---|---|
| 2 | Adeleza F1 | CC | 1.0 | ±0.0 a | 32 |
| CS | 1.0 | ±0.0 a | 39 | ||
| PC | 1.0 | ±0.0 b | 86 | ||
| PS | 1.0 | ±0.0 b | 102 | ||
| 2 | Bronski F1 | CC | 1.0 | ±0.0 a | 74 |
| CS | 1.0 | ±0.0 a | 57 | ||
| PC | 1.0 | ±0.0 a | 86 | ||
| PS | 1.0 | ±0.0 a | 85 | ||
| Dunk F1 | CC | 0.0 | ±0.0 a | 0 | |
| CS | 1.0 | ±0.0 ab | 11 | ||
| PC | 1.0 | ±0.0 b | 28 | ||
| PS | 1.0 | ±0.0 b | 26 | ||
| Goudski F1 | CC | 0.0 | ±0.0 a | 0 | |
| CS | 0.0 | ±0.0 a | 0 | ||
| PC | 1.0 | ±0.0 a | 6 | ||
| PS | 0.0 | ±0.0 a | 0 | ||
| Saint Anna F1 | CC | 1.0 | ±0.0 a | 108 | |
| CS | 1.0 | ±0.0 a | 77 | ||
| PC | 1.0 | ±0.0 a | 108 | ||
| PS | 1.0 | ±0.0 a | 106 | ||
| 3 | Adeleza F1 | CC | 1.0 | ±0.1 a | 408 |
| CS | 1.0 | ±0.2 a | 398 | ||
| PC | 1.2 | ±0.4 b | 412 | ||
| PS | 1.1 | ±0.4 b | 414 | ||
| Bronski F1 | CC | 1.1 | ±0.3 a | 405 | |
| CS | 1.1 | ±0.3 a | 411 | ||
| PC | 1.2 | ±0.4 a | 407 | ||
| PS | 1.2 | ±0.4 a | 416 | ||
| Dunk F1 | CC | 1.0 | ±0.0 a | 343 | |
| CS | 1.0 | ±0.1 a | 364 | ||
| PC | 1.0 | ±0.1 a | 371 | ||
| PS | 1.1 | ±0.2 a | 339 | ||
| Goudski F1 | CC | 1.0 | ±0.1 b | 195 | |
| CS | 1.0 | ±0.0 b | 227 | ||
| PC | 1.0 | ±0.0 b | 246 | ||
| PS | 1.0 | ±0.0 a | 113 | ||
| Saint Anna F1 | CC | 1.2 | ±0.4 a | 420 | |
| CS | 1.3 | ±0.4 a | 410 | ||
| PC | 1.3 | ±0.5 a | 416 | ||
| PS | 1.3 | ±0.5 a | 417 | ||
Table A4.
The fresh matter (FM) and dry matter (DM) of the shoots and leaves of tomato plants measured at 28 days after priming (DAP) in the first two sets. The data are presented as the mean ± standard deviation for five varieties. Statistical analysis was performed between treatments within each variety. Significant differences between the treatment groups within each variety on each DAP are denoted by different letters, where the letter ‘a’ represents the group(s) with the lowest values. The four treatments are—unprimed and unstressed (CC), unprimed and salt-stressed (CS), primed and unstressed (PC), and primed and salt-stressed (PS).
Table A4.
The fresh matter (FM) and dry matter (DM) of the shoots and leaves of tomato plants measured at 28 days after priming (DAP) in the first two sets. The data are presented as the mean ± standard deviation for five varieties. Statistical analysis was performed between treatments within each variety. Significant differences between the treatment groups within each variety on each DAP are denoted by different letters, where the letter ‘a’ represents the group(s) with the lowest values. The four treatments are—unprimed and unstressed (CC), unprimed and salt-stressed (CS), primed and unstressed (PC), and primed and salt-stressed (PS).
| Variety | Treat. | FM Shoot | FM Leaf | DM Shoot | DM Leaf | n | ||||
|---|---|---|---|---|---|---|---|---|---|---|
| [g] | ||||||||||
| Adeleza F1 | CC | 80 | ±12 b | 109 | ±9 a | 10 | ±2 ab | 20 | ±1 a | 24 |
| CS | 76 | ±9 a | 115 | ±6 b | 9 | ±1 ab | 20 | ±1 a | 24 | |
| PC | 80 | ±9 b | 110 | ±7 a | 10 | ±1 b | 19 | ±2 a | 24 | |
| PS | 76 | ±10 ab | 110 | ±8 ab | 9 | ±1 a | 19 | ±2 a | 24 | |
| Bronski F1 | CC | 70 | ±12 ab | 96 | ±8 ab | 8 | ±2 b | 18 | ±2 bc | 24 |
| CS | 72 | ±11 b | 104 | ±7 c | 8 | ±1 b | 19 | ±2 c | 24 | |
| PC | 68 | ±10 ab | 92 | ±11 a | 8 | ±1 a | 16 | ±2 a | 24 | |
| PS | 67 | ±10 a | 98 | ±9 b | 8 | ±1 a | 17 | ±2 ab | 24 | |
| Dunk F1 | CC | 76 | ±13 b | 99 | ±12 a | 9 | ±2 b | 17 | ±2 b | 24 |
| CS | 74 | ±8 b | 108 | ±6 b | 8 | ±1 b | 17 | ±1 b | 24 | |
| PC | 73 | ±12 b | 102 | ±9 a | 8 | ±2 b | 17 | ±1 b | 24 | |
| PS | 67 | ±8 a | 98 | ±10 a | 8 | ±1 a | 16 | ±3 a | 24 | |
| Goudski F1 | CC | 69 | ±10 c | 94 | ±8 b | 8 | ±1 b | 15 | ±1 b | 24 |
| CS | 68 | ±9 c | 98 | ±7 c | 7 | ±2 b | 15 | ±2 b | 22 | |
| PC | 65 | ±7 b | 89 | ±6 a | 7 | ±1 ab | 14 | ±1 a | 24 | |
| PS | 59 | ±11 a | 88 | ±8 a | 7 | ±2 a | 14 | ±2 a | 24 | |
| Saint Anna F1 | CC | 76 | ±7 c | 94 | ±7 a | 9 | ±1 b | 17 | ±1 b | 24 |
| CS | 73 | ±6 bc | 100 | ±8 b | 8 | ±1 a | 16 | ±2 b | 24 | |
| PC | 70 | ±7 ab | 85 | ±7 a | 8 | ±1 a | 15 | ±2 a | 24 | |
| PS | 70 | ±7 a | 96 | ±9 a | 8 | ±1 a | 16 | ±2 ab | 24 | |
Table A5.
The chlorophyll index, flavonol index, and anthocyanin index of mature tomato leaves measured during three periods—after thermopriming and before salt stress (from 5 to 14 days after priming, DAP; 1), after the first salt stress (to 21 DAP; 2), and after the second salt stress (to 28 DAP; 3). The data are presented as the mean ± standard deviation for five varieties. Statistical analysis was performed between the treatments within each variety during each period. Significant differences between treatment groups within each variety on each DAP are denoted by different letters, where the letter ‘a’ represents the group(s) with the lowest values. The four treatments are—unprimed and unstressed (CC), unprimed and salt-stressed (CS), primed and unstressed (PC), and primed and salt-stressed (PS).
Table A5.
The chlorophyll index, flavonol index, and anthocyanin index of mature tomato leaves measured during three periods—after thermopriming and before salt stress (from 5 to 14 days after priming, DAP; 1), after the first salt stress (to 21 DAP; 2), and after the second salt stress (to 28 DAP; 3). The data are presented as the mean ± standard deviation for five varieties. Statistical analysis was performed between the treatments within each variety during each period. Significant differences between treatment groups within each variety on each DAP are denoted by different letters, where the letter ‘a’ represents the group(s) with the lowest values. The four treatments are—unprimed and unstressed (CC), unprimed and salt-stressed (CS), primed and unstressed (PC), and primed and salt-stressed (PS).
| Variety | Period | Treat. | Chlorophyll Index | Flavonol Index | Anthocyanin Index | n | |||
|---|---|---|---|---|---|---|---|---|---|
| Adeleza F1 | 1 | CC | 19.89 | ±3.93 a | 0.37 | ±0.13 b | 0.20 | ±0.05 b | 667 |
| PC | 21.92 | ±4.44 b | 0.36 | ±0.13 a | 0.18 | ±0.04 a | 719 | ||
| 2 | CC | 21.05 | ±3.64 a | 0.33 | ±0.13 b | 0.21 | ±0.04 b | 359 | |
| CS | 21.33 | ±3.54 a | 0.33 | ±0.12 ab | 0.20 | ±0.04 b | 338 | ||
| PC | 22.95 | ±3.88 b | 0.32 | ±0.12 a | 0.20 | ±0.04 a | 347 | ||
| PS | 23.02 | ±3.74 b | 0.32 | ±0.13 a | 0.19 | ±0.05 a | 370 | ||
| 3 | CC | 21.87 | ±2.54 a | 0.34 | ±0.15 a | 0.20 | ±0.03 b | 373 | |
| CS | 21.76 | ±2.94 a | 0.33 | ±0.13 a | 0.22 | ±0.05 b | 349 | ||
| PC | 23.47 | ±2.56 b | 0.33 | ±0.13 a | 0.18 | ±0.04 a | 369 | ||
| PS | 22.54 | ±2.89 ab | 0.36 | ±0.14 a | 0.19 | ±0.05 ab | 374 | ||
| Bronski F1 | 1 | CC | 20.61 | ±4.27 a | 0.32 | ±0.12 b | 0.20 | ±0.04 b | 705 |
| PC | 22.31 | ±4.58 b | 0.31 | ±0.12 a | 0.18 | ±0.04 a | 755 | ||
| 2 | CC | 22.04 | ±3.81 a | 0.30 | ±0.11 b | 0.17 | ±0.03 c | 381 | |
| CS | 22.28 | ±3.75 b | 0.29 | ±0.11 a | 0.17 | ±0.04 b | 373 | ||
| PC | 23.49 | ±4.00 c | 0.30 | ±0.12 ab | 0.19 | ±0.05 a | 378 | ||
| PS | 23.74 | ±3.90 c | 0.27 | ±0.11 a | 0.18 | ±0.04 a | 372 | ||
| 3 | CC | 22.91 | ±2.49 ab | 0.30 | ±0.12 a | 0.19 | ±0.04 a | 663 | |
| CS | 22.44 | ±2.38 a | 0.30 | ±0.12 a | 0.19 | ±0.04 a | 717 | ||
| PC | 23.71 | ±2.76 b | 0.30 | ±0.12 a | 0.17 | ±0.03 a | 743 | ||
| PS | 22.85 | ±3.31 ab | 0.30 | ±0.12 a | 0.20 | ±0.05 a | 690 | ||
| Dunk F1 | 1 | CC | 21.51 | ±4.40 a | 0.36 | ±0.12 a | 0.19 | ±0.04 b | 745 |
| PC | 23.37 | ±4.78 b | 0.36 | ±0.14 a | 0.17 | ±0.04 a | 744 | ||
| 2 | CC | 23.20 | ±3.95 ab | 0.32 | ±0.11 a | 0.19 | ±0.04 c | 743 | |
| CS | 22.83 | ±4.10 a | 0.32 | ±0.12 a | 0.20 | ±0.04 c | 687 | ||
| PC | 24.77 | ±4.30 c | 0.32 | ±0.13 a | 0.17 | ±0.04 a | 719 | ||
| PS | 24.53 | ±3.98 b | 0.31 | ±0.13 a | 0.17 | ±0.04 b | 736 | ||
| 3 | CC | 23.74 | ±3.29 a | 0.31 | ±0.10 a | 0.15 | ±0.04 ab | 734 | |
| CS | 23.13 | ±3.68 a | 0.30 | ±0.11 a | 0.16 | ±0.04 b | 753 | ||
| PC | 25.30 | ±2.71 b | 0.31 | ±0.11 a | 0.17 | ±0.04 a | 728 | ||
| PS | 22.66 | ±3.97 a | 0.33 | ±0.15 a | 0.17 | ±0.04 b | 693 | ||
| Goudski F1 | 1 | CC | 20.10 | ±4.10 a | 0.33 | ±0.11 a | 0.21 | ±0.04 b | 724 |
| PC | 22.13 | ±4.62 b | 0.34 | ±0.13 a | 0.19 | ±0.04 a | 756 | ||
| 2 | CC | 21.45 | ±3.90 a | 0.30 | ±0.12 a | 0.18 | ±0.03 b | 401 | |
| CS | 22.00 | ±3.91 a | 0.30 | ±0.10 a | 0.18 | ±0.05 b | 402 | ||
| PC | 23.58 | ±3.75 b | 0.30 | ±0.11 a | 0.17 | ±0.05 a | 413 | ||
| PS | 23.27 | ±4.23 b | 0.31 | ±0.14 a | 0.19 | ±0.05 a | 398 | ||
| 3 | CC | 22.30 | ±2.96 ab | 0.31 | ±0.13 ab | 0.24 | ±0.07 ab | 395 | |
| CS | 22.17 | ±3.54 ab | 0.28 | ±0.09 a | 0.19 | ±0.05 ab | 391 | ||
| PC | 23.36 | ±2.95 b | 0.28 | ±0.10 a | 0.19 | ±0.04 a | 411 | ||
| PS | 21.78 | ±4.16 a | 0.33 | ±0.15 b | 0.18 | ±0.05 b | 406 | ||
| Saint Anna F1 | 1 | CC | 19.72 | ±3.91 a | 0.33 | ±0.13 a | 0.21 | ±0.04 b | 708 |
| PC | 22.34 | ±4.08 b | 0.33 | ±0.11 a | 0.18 | ±0.04 a | 737 | ||
| 2 | CC | 21.13 | ±3.44 a | 0.30 | ±0.11 a | 0.15 | ±0.03 b | 411 | |
| CS | 20.66 | ±3.29 a | 0.30 | ±0.12 a | 0.17 | ±0.04 b | 417 | ||
| PC | 23.50 | ±3.27 b | 0.30 | ±0.12 a | 0.20 | ±0.07 a | 400 | ||
| PS | 23.18 | ±3.63 b | 0.30 | ±0.11 a | 0.18 | ±0.04 a | 406 | ||
| 3 | CC | 19.80 | ±3.12 a | 0.35 | ±0.12 a | 0.18 | ±0.05 b | 403 | |
| CS | 19.66 | ±2.98 a | 0.35 | ±0.14 a | 0.18 | ±0.06 b | 394 | ||
| PC | 22.57 | ±3.70 b | 0.31 | ±0.12 a | 0.20 | ±0.07 a | 390 | ||
| PS | 21.71 | ±3.55 b | 0.32 | ±0.10 a | 0.20 | ±0.06 a | 403 | ||
Table A6.
The chlorophyll index, flavonol index, and anthocyanin index of young tomato leaves measured during three periods—after thermopriming and just before salt stress (14 days after priming, DAP; 1), after the first salt stress (to 21 DAP; 2), and after the second salt stress (to 28 DAP; 3). The data are presented as the mean ± standard deviation for five varieties. Statistical analysis was performed between the treatments within each variety during each period. Significant differences between treatment groups within each variety on each DAP are denoted by different letters, where the letter ‘a’ represents the group(s) with the lowest values. The four treatments are—unprimed and unstressed (CC), unprimed and salt-stressed (CS), primed and unstressed (PC), and primed and salt-stressed (PS).
Table A6.
The chlorophyll index, flavonol index, and anthocyanin index of young tomato leaves measured during three periods—after thermopriming and just before salt stress (14 days after priming, DAP; 1), after the first salt stress (to 21 DAP; 2), and after the second salt stress (to 28 DAP; 3). The data are presented as the mean ± standard deviation for five varieties. Statistical analysis was performed between the treatments within each variety during each period. Significant differences between treatment groups within each variety on each DAP are denoted by different letters, where the letter ‘a’ represents the group(s) with the lowest values. The four treatments are—unprimed and unstressed (CC), unprimed and salt-stressed (CS), primed and unstressed (PC), and primed and salt-stressed (PS).
| Variety | Period | Treat. | Chlorophyll Index | Flavonol Index | Anthocyanin Index | n | |||
|---|---|---|---|---|---|---|---|---|---|
| Adeleza F1 | 1 | CC | 26.29 | ±4.26 a | 0.40 | ±0.09 a | 0.12 | ±0.03 a | 96 |
| PC | 27.19 | ±3.85 a | 0.38 | ±0.10 a | 0.11 | ±0.03 a | 94 | ||
| 2 | CC | 28.98 | ±4.10 a | 0.43 | ±0.11 a | 0.10 | ±0.03 a | 422 | |
| CS | 28.81 | ±3.56 a | 0.44 | ±0.10 a | 0.10 | ±0.03 a | 423 | ||
| PC | 28.85 | ±3.78 a | 0.42 | ±0.11 a | 0.10 | ±0.02 a | 419 | ||
| PS | 28.55 | ±3.71 a | 0.42 | ±0.10 a | 0.10 | ±0.02 a | 419 | ||
| 3 | CC | 31.14 | ±3.56 a | 0.60 | ±0.17 a | 0.09 | ±0.02 a | 409 | |
| CS | 31.78 | ±3.47 a | 0.58 | ±0.15 a | 0.09 | ±0.02 a | 410 | ||
| PC | 30.96 | ±3.40 a | 0.62 | ±0.18 a | 0.09 | ±0.02 a | 403 | ||
| PS | 30.81 | ±3.70 a | 0.62 | ±0.19 a | 0.10 | ±0.02 a | 400 | ||
| Bronski F1 | 1 | CC | 24.27 | ±3.50 a | 0.34 | ±0.12 b | 0.14 | ±0.02 a | 94 |
| PC | 24.05 | ±3.10 a | 0.30 | ±0.12 a | 0.13 | ±0.02 a | 92 | ||
| 2 | CC | 25.61 | ±3.11 a | 0.41 | ±0.12 b | 0.13 | ±0.02 a | 418 | |
| CS | 25.19 | ±3.40 a | 0.39 | ±0.12 ab | 0.13 | ±0.03 a | 425 | ||
| PC | 25.16 | ±3.14 a | 0.37 | ±0.13 a | 0.13 | ±0.03 a | 421 | ||
| PS | 24.91 | ±2.78 a | 0.38 | ±0.13 ab | 0.13 | ±0.02 a | 421 | ||
| 3 | CC | 27.05 | ±3.02 a | 0.64 | ±0.22 a | 0.13 | ±0.03 a | 407 | |
| CS | 27.08 | ±3.11 a | 0.65 | ±0.20 a | 0.12 | ±0.03 a | 413 | ||
| PC | 26.90 | ±2.93 a | 0.64 | ±0.21 a | 0.13 | ±0.02 a | 411 | ||
| PS | 27.21 | ±2.92 a | 0.63 | ±0.20 a | 0.12 | ±0.02 a | 412 | ||
| Dunk F1 | 1 | CC | 26.45 | ±4.49 a | 0.36 | ±0.10 b | 0.12 | ±0.03 a | 94 |
| PC | 26.78 | ±3.28 a | 0.33 | ±0.10 a | 0.11 | ±0.03 a | 96 | ||
| 2 | CC | 28.91 | ±3.77 c | 0.40 | ±0.11 c | 0.10 | ±0.02 a | 417 | |
| CS | 28.22 | ±3.77 bc | 0.38 | ±0.11 ab | 0.10 | ±0.03 ab | 416 | ||
| PC | 27.84 | ±3.63 ab | 0.39 | ±0.13 bc | 0.11 | ±0.02 bc | 418 | ||
| PS | 27.28 | ±2.88 a | 0.36 | ±0.12 a | 0.11 | ±0.02 c | 420 | ||
| 3 | CC | 30.54 | ±3.20 ab | 0.67 | ±0.19 b | 0.10 | ±0.02 ab | 402 | |
| CS | 31.31 | ±3.39 b | 0.57 | ±0.16 a | 0.09 | ±0.02 a | 404 | ||
| PC | 29.73 | ±3.39 a | 0.67 | ±0.21 b | 0.10 | ±0.03 b | 407 | ||
| PS | 30.27 | ±3.73 ab | 0.59 | ±0.21 a | 0.10 | ±0.02 ab | 402 | ||
| Goudski F1 | 1 | CC | 24.68 | ±4.41 a | 0.31 | ±0.11 a | 0.13 | ±0.03 a | 93 |
| PC | 25.10 | ±3.58 a | 0.31 | ±0.10 a | 0.13 | ±0.02 a | 94 | ||
| 2 | CC | 26.18 | ±3.67 b | 0.36 | ±0.12 b | 0.12 | ±0.03 ab | 417 | |
| CS | 25.97 | ±3.44 b | 0.37 | ±0.12 b | 0.12 | ±0.03 a | 414 | ||
| PC | 25.91 | ±3.05 b | 0.36 | ±0.11 b | 0.13 | ±0.03 ab | 423 | ||
| PS | 25.23 | ±3.16 a | 0.33 | ±0.11 a | 0.13 | ±0.02 b | 419 | ||
| 3 | CC | 28.29 | ±3.43 a | 0.66 | ±0.18 b | 0.12 | ±0.03 b | 406 | |
| CS | 29.66 | ±3.08 b | 0.59 | ±0.17 a | 0.11 | ±0.02 a | 402 | ||
| PC | 28.24 | ±3.32 a | 0.66 | ±0.20 b | 0.12 | ±0.03 b | 403 | ||
| PS | 28.63 | ±3.88 a | 0.57 | ±0.16 a | 0.12 | ±0.03 ab | 392 | ||
| Saint Anna F1 | 1 | CC | 26.31 | ±4.94 a | 0.32 | ±0.09 a | 0.12 | ±0.03 a | 92 |
| PC | 26.16 | ±4.08 a | 0.30 | ±0.10 a | 0.12 | ±0.03 a | 93 | ||
| 2 | CC | 28.69 | ±3.82 b | 0.39 | ±0.10 b | 0.11 | ±0.03 a | 421 | |
| CS | 27.92 | ±4.04 ab | 0.37 | ±0.09 a | 0.11 | ±0.03 a | 415 | ||
| PC | 27.77 | ±3.58 ab | 0.36 | ±0.10 a | 0.11 | ±0.02 a | 424 | ||
| PS | 27.31 | ±3.45 a | 0.36 | ±0.10 a | 0.11 | ±0.03 a | 423 | ||
| 3 | CC | 31.26 | ±3.26 a | 0.58 | ±0.14 b | 0.11 | ±0.02 c | 414 | |
| CS | 31.87 | ±4.12 a | 0.53 | ±0.13 a | 0.10 | ±0.02 a | 409 | ||
| PC | 30.88 | ±3.81 a | 0.53 | ±0.12 a | 0.10 | ±0.02 bc | 412 | ||
| PS | 31.58 | ±3.59 a | 0.56 | ±0.17 ab | 0.10 | ±0.02 ab | 412 | ||
Table A7.
The total chlorophyll content (TCC), total carotenoid content (TCarC), and total anthocyanin content (TAC; expressed as cyanidin-3,5-O-diglucosid equivalents, CyEs) of mature and young tomato leaves, expressed on a dry matter (DM) basis, and measured at various days after priming (DAP). The data are presented as the mean ± standard deviation for five varieties. Statistical analysis was performed between treatments within each variety. Significant differences between treatment groups within each variety on each DAP are denoted by different letters, where the letter ‘a’ represents the group(s) with the lowest values. The four treatments are—unprimed and unstressed (CC), unprimed and salt-stressed (CS), primed and unstressed (PC), and primed and salt-stressed (PS).
Table A7.
The total chlorophyll content (TCC), total carotenoid content (TCarC), and total anthocyanin content (TAC; expressed as cyanidin-3,5-O-diglucosid equivalents, CyEs) of mature and young tomato leaves, expressed on a dry matter (DM) basis, and measured at various days after priming (DAP). The data are presented as the mean ± standard deviation for five varieties. Statistical analysis was performed between treatments within each variety. Significant differences between treatment groups within each variety on each DAP are denoted by different letters, where the letter ‘a’ represents the group(s) with the lowest values. The four treatments are—unprimed and unstressed (CC), unprimed and salt-stressed (CS), primed and unstressed (PC), and primed and salt-stressed (PS).
| Variety | Treat. | Leaf Age | DAP | TCC | TcarC | TAC | n | |||
|---|---|---|---|---|---|---|---|---|---|---|
| [µg mg−1 DM−1] | [µg CyEs mg−1 DM−1] | |||||||||
| Adeleza F1 | CC | Mature | 14 | 1.6 | ±0.3 a | 1.4 | ±0.2 a | 1.7 | ±0.7 a | 46 |
| 21 | 1.7 | ±0.4 a | 1.3 | ±0.2 a | 2.0 | ±0.5 b | 30 | |||
| 28 | 1.7 | ±0.6 a | 1.4 | ±0.3 b | 1.8 | ±0.6 a | 30 | |||
| Young | 28 | 2.4 | ±0.9 a | 1.9 | ±0.6 ab | 1.1 | ±0.7 a | 29 | ||
| CS | Mature | 21 | 1.6 | ±0.3 a | 1.3 | ±0.3 a | 1.7 | ±0.3 a | 27 | |
| 28 | 1.8 | ±0.7 a | 1.1 | ±0.2 a | 1.7 | ±0.5 a | 30 | |||
| Young | 28 | 2.6 | ±1.0 a | 1.9 | ±0.7 a | 1.2 | ±0.6 a | 30 | ||
| PC | Mature | 14 | 1.7 | ±0.3 b | 1.4 | ±0.2 a | 1.6 | ±0.5 a | 48 | |
| 21 | 1.8 | ±0.4 a | 1.4 | ±0.3 a | 1.9 | ±0.5 ab | 30 | |||
| 28 | 1.8 | ±0.6 a | 1.4 | ±0.2 b | 1.7 | ±0.5 a | 30 | |||
| Young | 28 | 2.5 | ±0.8 a | 2.1 | ±0.6 b | 1.2 | ±0.5 a | 29 | ||
| PS | Mature | 21 | 1.8 | ±0.4 a | 1.4 | ±0.2 a | 1.8 | ±0.5 ab | 30 | |
| 28 | 1.7 | ±0.7 a | 1.2 | ±0.3 ab | 1.6 | ±0.5 a | 30 | |||
| Young | 28 | 2.5 | ±0.8 a | 1.9 | ±0.6 a | 1.0 | ±0.5 a | 29 | ||
| Bronski F1 | CC | Mature | 14 | 1.7 | ±0.3 a | 1.4 | ±0.3 a | 1.8 | ±0.6 a | 47 |
| 21 | 1.6 | ±0.4 ab | 1.3 | ±0.2 ab | 2.0 | ±0.4 ab | 28 | |||
| 28 | 1.6 | ±0.9 a | 1.1 | ±0.2 a | 1.7 | ±0.6 ab | 30 | |||
| Young | 28 | 2.3 | ±0.9 a | 2.0 | ±0.7 a | 1.2 | ±0.6 a | 30 | ||
| CS | Mature | 21 | 1.5 | ±0.2 a | 1.2 | ±0.1 a | 1.7 | ±0.3 a | 25 | |
| 28 | 1.5 | ±0.7 a | 1.0 | ±0.1 a | 1.6 | ±0.6 a | 30 | |||
| Young | 28 | 2.4 | ±1.0 a | 1.8 | ±0.8 a | 1.2 | ±0.7 a | 29 | ||
| PC | Mature | 14 | 1.9 | ±0.3 b | 1.6 | ±0.2 b | 1.8 | ±0.5 a | 48 | |
| 21 | 1.8 | ±0.4 bc | 1.4 | ±0.3 bc | 1.9 | ±0.4 ab | 30 | |||
| 28 | 1.7 | ±0.7 a | 1.3 | ±0.3 b | 1.7 | ±0.5 ab | 30 | |||
| Young | 28 | 2.5 | ±0.9 a | 2.0 | ±0.7 a | 1.2 | ±0.7 a | 30 | ||
| PS | Mature | 21 | 1.9 | ±0.3 c | 1.5 | ±0.2 c | 2.1 | ±0.6 b | 25 | |
| 28 | 1.7 | ±0.8 a | 1.2 | ±0.2 a | 1.8 | ±0.4 b | 30 | |||
| Young | 28 | 2.5 | ±1.1 a | 1.9 | ±0.8 a | 1.2 | ±0.6 a | 30 | ||
| Dunk F1 | CC | Mature | 14 | 1.6 | ±0.2 a | 1.4 | ±0.2 a | 1.6 | ±0.6 a | 48 |
| 21 | 1.7 | ±0.4 a | 1.4 | ±0.2 ab | 1.8 | ±0.4 a | 27 | |||
| 28 | 2.0 | ±0.9 a | 1.5 | ±0.3 b | 1.8 | ±0.6 a | 30 | |||
| Young | 28 | 2.5 | ±1.0 a | 2.0 | ±0.7 a | 1.2 | ±0.6 a | 29 | ||
| Dunk F1 | CS | Mature | 21 | 1.8 | ±0.5 ab | 1.3 | ±0.2 a | 2.0 | ±0.6 a | 29 |
| 28 | 1.7 | ±0.6 a | 1.2 | ±0.2 b | 1.6 | ±0.4 a | 28 | |||
| Young | 28 | 2.6 | ±0.9 a | 2.0 | ±0.7 a | 1.2 | ±0.6 a | 30 | ||
| PC | Mature | 14 | 2.0 | ±0.3 b | 1.7 | ±0.2 b | 1.7 | ±0.5 a | 48 | |
| 21 | 2.0 | ±0.4 c | 1.5 | ±0.2 b | 1.7 | ±0.5 a | 29 | |||
| 28 | 2.0 | ±0.8 a | 1.5 | ±0.2 a | 1.6 | ±0.5 a | 30 | |||
| Young | 28 | 2.5 | ±0.9 a | 2.0 | ±0.6 a | 1.2 | ±0.7 a | 30 | ||
| PS | Mature | 21 | 1.9 | ±0.3 bc | 1.5 | ±0.2 ab | 1.9 | ±0.6 a | 29 | |
| 28 | 2.0 | ±0.9 a | 1.2 | ±0.3 a | 1.7 | ±0.4 a | 30 | |||
| Young | 28 | 2.7 | ±1.0 a | 1.9 | ±0.7 a | 1.3 | ±0.8 a | 29 | ||
| Goudski F1 | CC | Mature | 14 | 1.6 | ±0.3 a | 1.4 | ±0.3 a | 1.7 | ±0.6 a | 48 |
| 21 | 1.5 | ±0.5 a | 1.3 | ±0.2 ab | 1.7 | ±0.4 ab | 27 | |||
| 28 | 1.6 | ±0.8 a | 1.3 | ±0.3 a | 1.5 | ±0.5 a | 29 | |||
| Young | 28 | 2.3 | ±0.7 a | 1.9 | ±0.6 a | 1.1 | ±0.5 ab | 29 | ||
| CS | Mature | 21 | 1.6 | ±0.4 ab | 1.2 | ±0.2 a | 2.0 | ±0.7 b | 28 | |
| 28 | 1.9 | ±1.0 ab | 1.2 | ±0.4 a | 1.6 | ±0.5 a | 30 | |||
| Young | 28 | 2.5 | ±0.9 ab | 2.0 | ±0.7 a | 1.2 | ±0.6 ab | 30 | ||
| PC | Mature | 14 | 1.8 | ±0.3 b | 1.6 | ±0.2 b | 1.8 | ±0.5 a | 39 | |
| 21 | 1.8 | ±0.3 ab | 1.5 | ±0.2 c | 1.7 | ±0.6 a | 29 | |||
| 28 | 1.8 | ±0.9 ab | 1.5 | ±0.4 b | 1.6 | ±0.5 a | 30 | |||
| Young | 28 | 2.3 | ±0.8 a | 1.9 | ±0.7 a | 1.1 | ±0.6 a | 30 | ||
| PS | Mature | 21 | 1.8 | ±0.3 b | 1.4 | ±0.2 bc | 1.9 | ±0.6 b | 29 | |
| 28 | 1.8 | ±0.7 b | 1.3 | ±0.2 ab | 1.5 | ±0.5 a | 29 | |||
| Young | 28 | 2.6 | ±0.8 b | 2.0 | ±0.7 a | 1.3 | ±0.6 b | 29 | ||
| Saint Anna F1 | CC | Mature | 14 | 1.6 | ±0.2 a | 1.4 | ±0.2 a | 1.7 | ±0.6 a | 47 |
| 21 | 1.5 | ±0.4 a | 1.2 | ±0.2 a | 1.9 | ±0.4 b | 26 | |||
| 28 | 1.3 | ±0.9 a | 1.0 | ±0.3 a | 1.7 | ±0.4 b | 30 | |||
| Young | 28 | 2.8 | ±0.9 a | 2.2 | ±0.6 a | 1.4 | ±0.6 a | 28 | ||
| CS | Mature | 21 | 1.6 | ±0.5 a | 1.3 | ±0.3 a | 1.8 | ±0.6 ab | 31 | |
| 28 | 1.5 | ±0.9 ab | 1.0 | ±0.3 a | 1.7 | ±0.6 ab | 30 | |||
| Young | 28 | 3.1 | ±0.9 ab | 2.3 | ±0.6 ab | 1.6 | ±0.8 ab | 30 | ||
| PC | Mature | 14 | 1.8 | ±0.3 b | 1.5 | ±0.2 b | 1.7 | ±0.6 a | 48 | |
| 21 | 1.6 | ±0.5 a | 1.3 | ±0.3 a | 1.7 | ±0.6 a | 30 | |||
| 28 | 1.7 | ±1.0 b | 1.3 | ±0.3 b | 1.5 | ±0.5 a | 30 | |||
| Young | 28 | 3.2 | ±0.7 b | 2.5 | ±0.5 b | 1.8 | ±0.7 b | 30 | ||
| PS | Mature | 21 | 1.7 | ±0.4 a | 1.3 | ±0.3 a | 1.8 | ±0.7 ab | 30 | |
| 28 | 1.4 | ±0.9 ab | 1.0 | ±0.2 a | 1.5 | ±0.4 ab | 26 | |||
| Young | 28 | 2.9 | ±0.9 ab | 2.2 | ±0.7 a | 1.4 | ±0.7 ab | 29 | ||
Table A8.
The total phenolic content (TPC; expressed as gallic acid equivalents, GAE) and flavonoid contents (FCQuercetin, specific for flavanol and flavone luteolin; and FCCatechin, specific for rutin, luteolin, and catechin) of mature and young tomato leaves, expressed on a dry matter (DM) basis, and measured at various days after priming (DAP). The data are presented as the mean ± standard deviation for five varieties. Statistical analysis was performed between the treatments within each variety. Significant differences between treatment groups within each variety on each DAP are denoted by different letters, where the letter ‘a’ represents the group(s) with the lowest values. The four treatments are—unprimed and unstressed (CC), unprimed and salt-stressed (CS), primed and unstressed (PC), and primed and salt-stressed (PS).
Table A8.
The total phenolic content (TPC; expressed as gallic acid equivalents, GAE) and flavonoid contents (FCQuercetin, specific for flavanol and flavone luteolin; and FCCatechin, specific for rutin, luteolin, and catechin) of mature and young tomato leaves, expressed on a dry matter (DM) basis, and measured at various days after priming (DAP). The data are presented as the mean ± standard deviation for five varieties. Statistical analysis was performed between the treatments within each variety. Significant differences between treatment groups within each variety on each DAP are denoted by different letters, where the letter ‘a’ represents the group(s) with the lowest values. The four treatments are—unprimed and unstressed (CC), unprimed and salt-stressed (CS), primed and unstressed (PC), and primed and salt-stressed (PS).
| Variety | Treat. | Leaf Age | DAP | TPC | FCQuercetin | FCCatechin | n | |||
|---|---|---|---|---|---|---|---|---|---|---|
| [µg GAE mg−1 DM−1] | [µg QE mg−1 DM−1] | [µg CE mg−1 DM−1] | ||||||||
| Adeleza F1 | CC | Mature | 14 | 6.2 | ±2.7 a | 10.3 | ±1.3 a | 11.2 | ±2.3 b | 46 |
| 21 | 8.0 | ±1.6 b | 10.3 | ±1.4 a | 14.2 | ±4.5 b | 30 | |||
| 28 | 7.6 | ±1.3 a | 10.5 | ±2.2 a | 13.0 | ±4.5 a | 30 | |||
| Young | 28 | 12.7 | ±1.7 a | 13.9 | ±1.8 a | 18.4 | ±6.5 ab | 29 | ||
| CS | Mature | 21 | 7.0 | ±0.7 a | 9.7 | ±1.8 a | 11.7 | ±2.9 a | 27 | |
| 28 | 7.4 | ±1.6 a | 10.2 | ±2.7 a | 13.3 | ±5.9 a | 30 | |||
| Young | 28 | 12.1 | ±2.2 a | 14.1 | ±2.0 a | 18.3 | ±6.2 a | 30 | ||
| PC | Mature | 14 | 5.8 | ±2.1 a | 10.2 | ±1.3 a | 10.9 | ±2.3 a | 48 | |
| 21 | 7.0 | ±1.2 a | 10.2 | ±1.6 a | 12.4 | ±4.4 a | 30 | |||
| 28 | 7.4 | ±1.0 a | 10.3 | ±2.3 a | 13.0 | ±4.6 a | 30 | |||
| Young | 28 | 13.8 | ±2.5 b | 14.6 | ±1.4 a | 20.9 | ±3.0 b | 29 | ||
| PS | Mature | 21 | 6.6 | ±0.9 a | 10.1 | ±1.8 a | 12.1 | ±4.7 a | 30 | |
| 28 | 7.5 | ±1.3 a | 10.4 | ±3.2 a | 12.9 | ±5.8 a | 30 | |||
| Young | 28 | 12.9 | ±1.6 ab | 14.0 | ±1.2 a | 19.9 | ±4.7 ab | 29 | ||
| Bronski F1 | CC | Mature | 14 | 6.1 | ±2.2 a | 10.3 | ±1.5 a | 11.1 | ±2.6 a | 47 |
| 21 | 6.9 | ±1.1 a | 9.7 | ±1.5 a | 12.4 | ±4.2 a | 28 | |||
| 28 | 7.1 | ±1.3 a | 9.3 | ±2.5 a | 11.8 | ±4.6 a | 30 | |||
| Young | 28 | 15.7 | ±3.1 b | 15.4 | ±1.8 a | 21.1 | ±3.5 a | 30 | ||
| CS | Mature | 21 | 6.4 | ±0.8 a | 9.3 | ±1.6 a | 11.4 | ±4.2 a | 25 | |
| 28 | 7.2 | ±1.9 a | 9.4 | ±2.5 a | 12.6 | ±5.9 a | 30 | |||
| Young | 28 | 15.0 | ±3.0 ab | 15.3 | ±1.4 a | 20.5 | ±4.4 a | 29 | ||
| PC | Mature | 14 | 5.9 | ±2.0 a | 10.6 | ±1.3 b | 10.6 | ±1.9 a | 48 | |
| 21 | 7.0 | ±1.1 a | 10.5 | ±1.3 b | 12.1 | ±3.8 a | 30 | |||
| 28 | 7.2 | ±1.0 a | 10.1 | ±2.0 b | 12.4 | ±4.1 a | 30 | |||
| Young | 28 | 13.8 | ±2.9 a | 14.9 | ±2.0 a | 20.8 | ±4.9 a | 30 | ||
| PS | Mature | 21 | 7.2 | ±1.5 a | 10.5 | ±1.6 b | 11.9 | ±3.7 a | 25 | |
| 28 | 7.0 | ±0.9 a | 9.8 | ±2.1 ab | 12.4 | ±4.8 a | 30 | |||
| Young | 28 | 14.1 | ±2.3 a | 14.8 | ±1.9 a | 20.3 | ±5.8 a | 30 | ||
| Dunk F1 | CC | Mature | 14 | 5.9 | ±2.3 a | 10.1 | ±1.2 a | 10.7 | ±2.3 a | 48 |
| 21 | 7.1 | ±1.1 b | 9.9 | ±1.5 a | 13.2 | ±5.3 a | 27 | |||
| 28 | 7.0 | ±1.1 a | 10.8 | ±1.7 a | 12.9 | ±4.7 ab | 30 | |||
| Dunk F1 | CC | Young | 28 | 12.6 | ±2.0 a | 14.1 | ±1.3 a | 19.6 | ±4.5 a | 29 |
| CS | Mature | 21 | 7.2 | ±1.4 b | 10.1 | ±1.6 ab | 13.0 | ±5.4 a | 29 | |
| 28 | 7.2 | ±2.3 a | 10.0 | ±2.3 a | 12.0 | ±4.5 ab | 28 | |||
| Young | 28 | 13.3 | ±2.4 ab | 14.2 | ±1.4 a | 20.9 | ±4.1 a | 30 | ||
| PC | Mature | 14 | 5.7 | ±2.5 a | 10.9 | ±1.4 b | 11.0 | ±2.4 a | 48 | |
| 21 | 6.2 | ±1.0 a | 10.2 | ±1.6 ab | 12.6 | ±6.2 a | 29 | |||
| 28 | 6.8 | ±0.6 a | 10.5 | ±2.0 a | 11.7 | ±3.9 a | 30 | |||
| Young | 28 | 14.0 | ±3.3 b | 15.1 | ±1.6 a | 21.5 | ±7.0 a | 30 | ||
| PS | Mature | 21 | 6.7 | ±1.5 ab | 10.5 | ±1.6 b | 12.6 | ±3.9 a | 29 | |
| 28 | 7.2 | ±1.3 a | 10.7 | ±2.9 a | 13.9 | ±6.3 b | 30 | |||
| Young | 28 | 12.7 | ±2.2 a | 15.2 | ±2.9 a | 19.3 | ±5.6 a | 29 | ||
| Goudski F1 | CC | Mature | 14 | 5.8 | ±1.9 a | 9.8 | ±1.4 a | 10.4 | ±2.2 a | 48 |
| 21 | 6.8 | ±1.0 a | 9.5 | ±1.7 a | 11.3 | ±4.5 a | 27 | |||
| 28 | 7.0 | ±1.1 b | 9.4 | ±2.2 a | 11.5 | ±4.1 a | 29 | |||
| Young | 28 | 13.7 | ±1.8 a | 14.5 | ±1.7 a | 21.3 | ±4.1 a | 29 | ||
| CS | Mature | 21 | 7.3 | ±1.9 a | 9.9 | ±1.3 a | 11.5 | ±3.4 a | 28 | |
| 28 | 6.4 | ±0.8 a | 9.8 | ±2.6 a | 11.4 | ±4.4 a | 30 | |||
| Young | 28 | 13.3 | ±3.3 a | 15.1 | ±2.5 a | 20.5 | ±4.6 a | 30 | ||
| PC | Mature | 14 | 6.1 | ±2.4 a | 10.3 | ±1.4 b | 10.6 | ±2.5 a | 39 | |
| 21 | 6.7 | ±1.9 a | 10.0 | ±1.8 a | 11.9 | ±6.1 a | 29 | |||
| 28 | 6.7 | ±0.7 ab | 10.0 | ±1.8 a | 11.5 | ±3.9 a | 30 | |||
| Young | 28 | 13.1 | ±1.7 a | 14.4 | ±2.3 a | 19.4 | ±5.4 a | 30 | ||
| PS | Mature | 21 | 7.0 | ±1.7 a | 10.1 | ±1.6 a | 11.9 | ±4.1 a | 29 | |
| 28 | 6.8 | ±1.5 ab | 9.7 | ±1.9 a | 12.4 | ±4.3 a | 29 | |||
| Young | 28 | 12.5 | ±2.2 a | 14.1 | ±2.9 a | 19.2 | ±4.7 a | 29 | ||
| Saint Anna F1 | CC | Mature | 14 | 5.7 | ±2.1 a | 9.9 | ±1.3 a | 10.7 | ±2.2 a | 47 |
| 21 | 6.8 | ±1.1 a | 9.0 | ±2.0 ab | 10.6 | ±3.0 a | 26 | |||
| 28 | 7.2 | ±1.2 a | 8.8 | ±2.4 a | 11.8 | ±4.6 a | 30 | |||
| Young | 28 | 14.3 | ±2.5 a | 14.7 | ±1.8 a | 21.5 | ±4.1 a | 28 | ||
| CS | Mature | 21 | 6.6 | ±1.2 a | 9.5 | ±2.0 ab | 12.0 | ±4.4 a | 31 | |
| 28 | 6.9 | ±1.1 a | 9.4 | ±3.4 ab | 11.4 | ±5.9 a | 30 | |||
| Young | 28 | 13.4 | ±2.6 a | 14.9 | ±2.0 ab | 20.8 | ±5.5 a | 30 | ||
| PC | Mature | 14 | 5.5 | ±2.2 a | 10.2 | ±1.2 b | 10.7 | ±2.6 a | 48 | |
| 21 | 6.3 | ±1.1 a | 9.1 | ±1.9 a | 11.5 | ±5.3 a | 30 | |||
| 28 | 6.8 | ±0.8 a | 9.6 | ±2.7 b | 11.4 | ±4.3 a | 30 | |||
| Young | 28 | 14.8 | ±3.0 a | 15.9 | ±2.3 b | 25.0 | ±4.1 b | 30 | ||
| PS | Mature | 21 | 6.8 | ±1.2 a | 9.9 | ±2.1 b | 12.4 | ±4.6 a | 30 | |
| 28 | 6.8 | ±0.8 a | 8.7 | ±2.5 ab | 11.6 | ±5.1 a | 26 | |||
| Young | 28 | 13.8 | ±2.6 a | 15.1 | ±3.2 ab | 22.6 | ±6.7 ab | 29 | ||
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Figure 1.
Boxplots showing the plant height at 28 DAP across four treatments—unprimed and unstressed (control; light blue), unprimed and salt-stressed (yellow), primed and unstressed (orange), and primed and salt-stressed (red). Significant differences between treatment groups within each variety are denoted by different letters, where the letter ‘a’ represents the group(s) with the lowest values (ANOVA with EMMs post hoc test, α = 0.05). The sample size for each treatment group is n = 20 to 21.
Figure 1.
Boxplots showing the plant height at 28 DAP across four treatments—unprimed and unstressed (control; light blue), unprimed and salt-stressed (yellow), primed and unstressed (orange), and primed and salt-stressed (red). Significant differences between treatment groups within each variety are denoted by different letters, where the letter ‘a’ represents the group(s) with the lowest values (ANOVA with EMMs post hoc test, α = 0.05). The sample size for each treatment group is n = 20 to 21.
Figure 2.
Boxplots showing the total fresh matter at 28 DAP across four treatments—unprimed and unstressed (control; light blue), unprimed and salt-stressed (yellow), primed and unstressed (orange), and primed and salt-stressed (red). Significant differences between treatment groups within each variety are denoted by different letters, where the letter ‘a’ represents the group(s) with the lowest values (ANOVA with EMMs post hoc test, α = 0.05). The sample size for each treatment group is n = 12.
Figure 2.
Boxplots showing the total fresh matter at 28 DAP across four treatments—unprimed and unstressed (control; light blue), unprimed and salt-stressed (yellow), primed and unstressed (orange), and primed and salt-stressed (red). Significant differences between treatment groups within each variety are denoted by different letters, where the letter ‘a’ represents the group(s) with the lowest values (ANOVA with EMMs post hoc test, α = 0.05). The sample size for each treatment group is n = 12.
Figure 3.
Boxplots showing the total dry matter at 28 DAP across four treatments—unprimed and unstressed (control; light blue), unprimed and salt-stressed (yellow), primed and unstressed (orange), and primed and salt-stressed (red). Significant differences between treatment groups within each variety are denoted by different letters, where the letter ‘a’ represents the group(s) with the lowest values (ANOVA with EMMs post hoc test, α = 0.05). The sample size for each treatment group is n = 12.
Figure 3.
Boxplots showing the total dry matter at 28 DAP across four treatments—unprimed and unstressed (control; light blue), unprimed and salt-stressed (yellow), primed and unstressed (orange), and primed and salt-stressed (red). Significant differences between treatment groups within each variety are denoted by different letters, where the letter ‘a’ represents the group(s) with the lowest values (ANOVA with EMMs post hoc test, α = 0.05). The sample size for each treatment group is n = 12.
Figure 4.
Boxplots showing the Anthocyanin index from 22 to 28 DAP across four treatments—unprimed and unstressed (control; light blue), unprimed and salt-stressed (yellow), primed and unstressed (orange), and primed and salt-stressed (red). Significant differences between treatment groups within each variety are denoted by different letters, where the letter ‘a’ represents the group(s) with the lowest values (ANOVA with EMMs post hoc test, α = 0.05). The sample size for each treatment group is n = 387 to 417.
Figure 4.
Boxplots showing the Anthocyanin index from 22 to 28 DAP across four treatments—unprimed and unstressed (control; light blue), unprimed and salt-stressed (yellow), primed and unstressed (orange), and primed and salt-stressed (red). Significant differences between treatment groups within each variety are denoted by different letters, where the letter ‘a’ represents the group(s) with the lowest values (ANOVA with EMMs post hoc test, α = 0.05). The sample size for each treatment group is n = 387 to 417.
Figure 5.
Boxplots showing the Chlorophyll index from 22 to 28 DAP across four treatments—unprimed and unstressed (control; light blue), unprimed and salt-stressed (yellow), primed and unstressed (orange), and primed and salt-stressed (red). Significant differences between the treatment groups within each variety are denoted by different letters, where the letter ‘a’ represents the group(s) with the lowest values (ANOVA with EMMs post hoc test, α = 0.05). The sample size for each treatment group is n = 387 to 417.
Figure 5.
Boxplots showing the Chlorophyll index from 22 to 28 DAP across four treatments—unprimed and unstressed (control; light blue), unprimed and salt-stressed (yellow), primed and unstressed (orange), and primed and salt-stressed (red). Significant differences between the treatment groups within each variety are denoted by different letters, where the letter ‘a’ represents the group(s) with the lowest values (ANOVA with EMMs post hoc test, α = 0.05). The sample size for each treatment group is n = 387 to 417.
Figure 6.
Boxplots showing the total carotenoid content (TCarC) at 28 DAP across four treatments—unprimed and unstressed (control; light blue), unprimed and salt-stressed (yellow), primed and unstressed (orange), and primed and salt-stressed (red). Carotenoid content is expressed on a dry matter (DM) basis. Significant differences between the treatment groups within each variety are denoted by different letters, where the letter ‘a’ represents the group(s) with the lowest values (ANOVA with EMMs post hoc test, α = 0.05). The sample size for each treatment group is n = 26 to 30.
Figure 6.
Boxplots showing the total carotenoid content (TCarC) at 28 DAP across four treatments—unprimed and unstressed (control; light blue), unprimed and salt-stressed (yellow), primed and unstressed (orange), and primed and salt-stressed (red). Carotenoid content is expressed on a dry matter (DM) basis. Significant differences between the treatment groups within each variety are denoted by different letters, where the letter ‘a’ represents the group(s) with the lowest values (ANOVA with EMMs post hoc test, α = 0.05). The sample size for each treatment group is n = 26 to 30.
Table 1.
Summary of experimental settings.
| Sets: | 3 |
|---|---|
| Duration: | 44 days |
| Period: | |
| Set 1: | 17 April–31 May 2024 |
| Set 2: | 21 May–4 July 2024 |
| Set 3: | 19 June–2 August 2024 |
| Timing of thermopriming (days after sowing): | 9–16 |
| Timing of recurrent salt stress (days after sowing): | |
| 1st stress event: | 30 |
| 2nd stress event: | 37 |
| Number of varieties: | 5 |
| Number of treatments: | 20 |
| Number of blocks (tables): | 4 |
| Number of parcels per block: | 20 |
| Number of plants per parcel: | 3 |
| Total number of plants per treatment: | 12 |
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Körner, T.; Zinkernagel, J.; Röhlen-Schmittgen, S. Plant Growth and Metabolic Responses of Tomato Varieties to Salinity Stress After Thermopriming. Stresses 2025, 5, 27. https://doi.org/10.3390/stresses5020027
AMA Style
Körner T, Zinkernagel J, Röhlen-Schmittgen S. Plant Growth and Metabolic Responses of Tomato Varieties to Salinity Stress After Thermopriming. Stresses. 2025; 5(2):27. https://doi.org/10.3390/stresses5020027
Chicago/Turabian StyleKörner, Tobias, Jana Zinkernagel, and Simone Röhlen-Schmittgen. 2025. "Plant Growth and Metabolic Responses of Tomato Varieties to Salinity Stress After Thermopriming" Stresses 5, no. 2: 27. https://doi.org/10.3390/stresses5020027
APA StyleKörner, T., Zinkernagel, J., & Röhlen-Schmittgen, S. (2025). Plant Growth and Metabolic Responses of Tomato Varieties to Salinity Stress After Thermopriming. Stresses, 5(2), 27. https://doi.org/10.3390/stresses5020027
