Search Results (148)

Curcuma spp. is a popular ornamental crop valued for its vibrant appearance and suitability for both regular and off-season production. As global emphasis on freshwater conservation increases and with a demand for compact potted plants, reducing water use while maintaining high aesthetic quality presents a key challenge for horticulturists. Potassium silicate (PS) has been proposed as a foliar spray to alleviate plant water stress. This study aimed to evaluate the effects of PS on growth, ornamental traits, and photosynthetic parameters of off-season potted Curcuma cv. ‘Jasmine Pink’ under deficit irrigation (DI). Plants were subjected to three treatments in a completely randomized design: 100% crop evapotranspiration (ETc), 50% ETc, and 50% ETc with 1000 ppm PS (weekly sprayed on leaves for 11 weeks). Both DI treatments (50% ETc and 50% ETc + PS) reduced plant height by 7.39% and 9.17%, leaf number by 16.99% and 7.03%, and total biomass by 21.13% and 20.58%, respectively, compared to 100% ETc. Notably, under DI, PS-treated plants maintained several parameters equivalent to the 100% ETc treatment, including flower bud emergence, blooming period, green bract number, effective quantum yield of PSII (ΔF/Fm′), and electron transport rate (ETR). In addition, PS application increased leaf area by 8.11% and compactness index by 9.80% relative to untreated plants. Photosynthetic rate, ΔF/Fm′, and ETR increased by 31.52%, 13.63%, and 9.93%, while non-photochemical quenching decreased by 16.51% under water-limited conditions. These findings demonstrate that integrating deficit irrigation with PS foliar application can enhance water use efficiency and maintain ornamental quality in off-season potted Curcuma, promoting sustainable water management in horticulture. Full article

Buckwheat (Fagopyrum esculentum Moech) is a “gluten-free” pseudocereal with high-quality proteins and human health properties, increasing its cultivation worldwide. However, the role of nitrogen (N) in plant growth and yield components has received little attention in buckwheat. This study evaluated N’s effect on plant traits, photosynthetic performance, and grain yield components in buckwheat under field conditions. For this, Buckwheat cv. “Mancan” seeds were sown using five N rates: 0, 30, 45, 60, and 90 kg N ha⁻¹. Then, physiological performance and grain yield components were evaluated at harvest. Our study revealed that buckwheat plants subjected to 0 and 30 kg N ha⁻¹ showed the greatest chlorophyll fluorescence a parameters including maximum quantum yield of PSII (Fv′/Fm′), effective quantum yield of PSII (ФPSII), and electron transport rate (ETR) among N treatments; meanwhile, at higher N rates (60 and 90 kg N ha⁻¹), these parameters decayed. Similarly, plants treated with 90 kg N ha⁻¹ showed the lowest CO₂ assimilation among N treatments. In general, stomatal conductance (g_s), transpiration (E), and intrinsic water use efficiency (WUE_i) showed no significant changes among N treatments, with the exception of 30 kg N ha⁻¹, which exhibited the highest WUE_i. Concerning plant traits, plants grown under 60 and 90 kg N ha⁻¹ exhibited the greatest plant height, number of branches, shoot biomass, and internode per plant among N treatments. By contrast, 30 kg N ha⁻¹ showed the highest grain number, yield per plant, and grain yield among N treatments in F. esculentum plants. Based on the physiological and productive parameters, F. esculentum seems to have a low N requirement, exhibiting better results under the lowest N rates (30 kg N ha⁻¹). Therefore, F. esculentum could be considered as an alternative for gluten-free food production with low N requirements in agricultural systems of southern Chile. Nonetheless, more studies are required to understand the effect of N biochemical and molecular regulation on plant traits and grain yield components in buckwheat. Full article

Lead (Pb) contamination in Moso bamboo forests poses a challenge in terms of sustainable development and raises concerns about the safety of bamboo shoots for consumption. However, the physiological impacts of Pb stress on Moso bamboo growth and the molecular mechanisms governing its adaptive responses remain poorly understood. This study comprehensively investigated the physiological and transcriptomic responses of Moso bamboo to Pb stress. The results showed that low concentrations (1–10 µM) of Pb stress had minimal adverse effects on biomass accumulation and the photochemical quantum yield of PSII in Moso bamboo. However, at a high Pb concentration (50 µM), the growth of roots was significantly inhibited, while Pb accumulation in the roots and shoots reached 15,611 mg·kg⁻¹ and 759 mg·kg⁻¹, respectively. The uptake of Pb was increased as the external Pb concentration increased, but the xylem loading of Pb reached saturation at 57.79 µM after six-hour exposure. Pb was mainly localized in the epidermis and pericycle cells in the roots, where the thickening of cell walls in these cells was found after Pb treatment. Transcriptomic profiling identified 1485 differentially expressed genes (DEGs), with significant alterations in genes associated with metal cation transporters and cell wall synthesis. These findings collectively indicate that Moso bamboo is a Pb-tolerant plant, characterized by a high accumulation capacity and efficient xylem loading. The tolerance mechanism likely involves the transcriptional regulation of genes related to heavy metal transport and cell wall biosynthesis. Full article

Salt stress severely impairs photosynthesis and development in tomato seedlings. This study investigated the regulatory role of exogenous melatonin (MT) on photosynthetic performance under salt stress by determining chlorophyll content, chlorophyll a fluorescence parameters, Calvin cycle enzyme activities, and related gene expression. Results showed that salt stress significantly reduced chlorophyll content and impaired photosystem II (PSII) functionality, as evidenced by the increased minimum fluorescence (F_o) and decreased maximum quantum efficiency of PSII (F_v/F_m) and effective PSII quantum yield (Φ_PSII). MT application mitigated these negative effects, as reflected by higher F_v/F_m, increased chlorophyll content, and lower non-photochemical quenching (NPQ). In addition, MT-treated plants exhibited improved PSII electron transport and more efficient use of absorbed light energy, as shown by elevated Φ_PSII and qP values. These changes suggest improved PSII functional stability and reduced excess thermal energy dissipation. Furthermore, MT significantly enhanced both the activity and expression of key enzymes involved in the Calvin cycle, including ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), Rubisco activase (RCA), phosphoglycerate kinase (PGK), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), fructose-1,6-bisphosphatase (FBPase), fructose-bisphosphate aldolase (FBA), transketolase (TK), and sedoheptulose-1,7-bisphosphatase (SBPase), thereby promoting carbon fixation and ribulose-1,5-bisphosphate (RuBP) regeneration under salt stress. Conversely, inhibition of endogenous MT synthesis by p-CPA exacerbated salt stress damage, further confirming MT’s crucial role in salt tolerance. These findings demonstrate that exogenous MT enhances salt tolerance in tomato seedlings by simultaneously improving photosynthetic electron transport efficiency and upregulating the activity and gene expression of key Calvin cycle enzymes, thereby promoting the coordination between light reactions and carbon fixation processes. This study provides valuable insights into the comprehensive regulatory role of MT in maintaining photosynthetic performance under saline conditions. Full article

The potato (Solanum tuberosum L.) is highly dependent on water availability, with physiological sensitivity varying throughout its phenological cycle. In the context of increasing water scarcity and greater climate variability, identifying critical periods where water stress negatively impacts productivity and tuber quality is essential. This study evaluated the physiological response of potatoes under different deficit irrigation strategies in field conditions, and aimed to determine the irrigation reduction thresholds that optimize water use efficiency without significantly compromising yield. Five irrigation regimes were applied: well-watered (T1; irrigation was applied when the volumetric soil moisture content was close to 35% of total water available), 130% of T1 (T2, 30% more than T1), 75% of T1 (T3), 50% of T1 (T4), and 30% of T1 (T5). Key physiological parameters were monitored, including gas exchange (net photosynthesis, stomatal conductance, and transpiration), chlorophyll fluorescence (Fv’/Fm’, ΦPSII, electron transport rate), and photosynthetic pigment content, at three critical phenological phases: tuberization, flowering, and fruit set. The results indicate that water stress during tuberization and flowering significantly reduced photosynthetic efficiency, with decreases in stomatal conductance (gs), effective quantum efficiency of PSII (ΦPSII), and electron transport rate (ETR). In contrast, moderate irrigation reduction (75%) lowered the seasonal application of water by ~25% (≈80 mm ha⁻¹) while maintaining commercial yield and tuber quality comparable to the fully irrigated control. Intrinsic water use efficiency increased by 18 ± 4% under this regime. These findings highlight the importance of irrigation management based on crop phenology, prioritizing water supply during the stages of higher physiological sensitivity and allowing irrigation reductions in less critical phases. In a scenario of increasing water limitations, this strategy enhances water use efficiency while ensuring the production of tubers with optimal commercial quality, promoting more sustainable agricultural management practices. Full article

Nitrogen is a key element in promoting crop growth and development and improving photosynthesis. This study aimed to study the response of two rice genotypes to the restoration of N supply after varying periods of N deficiency. We used the low-nitrogen-tolerant rice Jijing 88 (JJ 88) and the nitrogen-sensitive rice variety Xinong 999 (XN 999) as test materials. The results of this study indicated that, compared to XN 999, JJ 88 has a higher content of the photosynthetic pigments. Photosynthesis in JJ 88 has strong adaptability under low-nitrogen conditions. Upon an increase in the nitrogen supply level, the maximum regeneration rate of ribulose biphosphate (RuBP, J_max) and the maximum carboxylation rate of RuBP (V_cmax) in JJ 88 showed a relatively large increase. The chlorophyll fluorescence parameters, including the effective quantum yield of photosystem II (Φ_PSII), the efficiency of excitation capture by open PSII centers (Fv′/Fm′), photochemical fluorescence quenching (qP), and the electron transfer rate (ETR) decreased slightly, while the non-photochemical fluorescence quenching (NPQ) increased slightly. Under low-nitrogen conditions, low-nitrogen-tolerant rice varieties maintain reasonable growth during the seedling stage. With an increase in the nitrogen supply level, the dry matter accumulation, photosynthetic pigment content, photosynthesis, and electron transfer ability of plants improve, but not to normal nitrogen supply levels. However, compared with XN 999, JJ 88 has a more proactive recovery ability. The research results provide valuable guidance for the breeding of nitrogen-efficient rice varieties and nitrogen fertilizer management. Full article

Mulberry (Morus alba L.), a species of significant ecological and economic importance, is widely cultivated for sericulture, soil conservation, and environmental restoration. Despite its remarkable resilience to environmental stresses, the combined impact of elevated CO₂ (eCO₂) and drought stress on aboveground–root–soil interactions remains poorly understood, particularly in the context of global climate change. Here, we investigated the effects of eCO₂ and drought on physiological leaf and root indicators, nutrient absorption and allocation, and soil properties in mulberry seedlings. Mulberry seedlings were grown in environmentally auto-controlled growth chambers under ambient CO₂ (420/470 ppm, day/night) or eCO₂ (710/760 ppm) and well-watered (75–85% soil relative water content, RWC), moderate-drought (55–65% RWC), or severe-drought (35–45% RWC) conditions. Results showed that both above- and below-ground plant biomass production were significantly promoted by eCO₂, particularly by 36% and 15% under severe drought, respectively. This could be attributed to several factors. Firstly, eCO₂ improved leaf photosynthesis by 25–37% and water use efficiency by 104–163% under drought stresses while reducing negative effects of drought on the effective quantum yield of PSII photochemistry and the photochemical quenching coefficient. Secondly, eCO₂ significantly decreased proline accumulation while increasing soluble sugar contents, as well as peroxidase and superoxide dismutase activities, in both leaves and roots under drought stress. Lastly, eCO₂ promoted soil sucrase, urease, and phosphatase activities, as well as plant nitrogen, phosphorus and potassium uptake while facilitating their allocation into roots under drought stress. These findings demonstrate that eCO₂ enhanced the drought tolerance of mulberry plants through improvements in photosystem II efficiency, water use efficiency, antioxidative defense capacity, and nutrient uptake and allocation, providing critical insights for sustainable mulberry plantation management under future climate change scenarios. Full article

Mercury (Hg) poses significant risks to human health, the environment, and plant physiology, with its effects influenced by chemical form, concentration, exposure route, and organism vulnerability. This study evaluates the physiological impacts of Hg on Handroanthus impetiginosus (Ipê Roxo) seedlings through SPAD index measurements, chlorophyll fluorescence analysis, and Hg quantification in plant tissues. Four-month-old seedlings were exposed for eight days to distilled water containing Hg at 0, 1, 3, 5, and 7 mg L⁻¹. The SPAD index decreased by 28.17% at 3, 5, and 7 mg L⁻¹, indicating reduced photosynthetic capacity. Chlorophyll a fluorescence analysis revealed a 50.58% decline in maximum efficiency (Fv/Fm) and a 58.33% reduction in quantum yield (ΦPSII) at 7 mg L⁻¹, along with an 83.04% increase in non-photochemical quenching (qn), suggesting oxidative stress and PSII damage. Transpiration decreased by 26.7% at 1 mg L⁻¹ and by 55% at 3, 5, and 7 mg L⁻¹, correlating with Hg levels and leaf senescence. Absorption, translocation, bioconcentration, and bioaccumulation factors varied among treatments. Hg accumulated mainly in stems (40.23 μg g⁻¹), followed by roots (0.77 μg g⁻¹) and leaves (2.69 μg g⁻¹), with limited translocation to leaves. These findings highlight Hg’s harmful effects on H. impetiginosus, an ecologically and commercially valuable species, addressing a gap in research on its Hg tolerance and phytoremediation potential. Full article

Sweet basil (Ocimum basilicum) is valued for its culinary and medicinal properties. It thrives in full sunlight and long daylight hours under natural conditions. This study examined the effects of extended photoperiod on sweet basil grown in a hot and humid tropical greenhouse. Some plants received only natural sunlight (SL), while others had SL supplemented with LED light for 6 h (6 h) before sunrise and/or after sunset. Plants grown under only natural SL (L1) had a smaller leaf number, smaller leaf area per plant, lower shoot, and root productivity than those grown under other light conditions. The shoot fresh weight of basil grown under supplemented LED light for 3 h before sunrise and 3 h after sunset (L2), 6 h after sunset (L3), and 6 h before sunrise (L4) was 2.68, 2.33, and 1.94 times higher than L1 conditions, respectively. The maximum quantum efficiency of PSII, electron transport rate, effective quantum yield of PSII, and Chl a/b ratio were also higher in L2, L3, and L4. The total leaf soluble protein, ascorbic acid, total phenolic compounds, and dietary minerals followed the same trend. Among all treatments, L2 consistently showed significantly higher values, making it the optimal lighting strategy for extended photoperiod. Full article

The tomato is among the crops with the most extensive cultivated area and greatest consumption in our nation; nonetheless, secondary salinization of facility soil significantly hinders the sustainable growth of facility agriculture. Melatonin (MT), as an innovative plant growth regulator, is essential in stress responses. This research used a hydroponic setup to replicate saline stress conditions. Different endogenous levels of melatonin (MT) were established by foliar spraying of 100 μmol·L⁻¹ MT, the MT synthesis inhibitor p-CPA (100 μmol·L⁻¹), and a combination of p-CPA and MT, to investigate the mechanism by which MT mitigates the effects of salt stress on the photosynthetic efficiency of tomato seedlings. Results indicated that after six days of salt stress, the endogenous MT content in tomato seedlings drastically decreased, with declines in the net photosynthetic rate and photosystem performance indices (PI_total and PI_abs). The OJIP fluorescence curve exhibited distortion, characterized by anomalous K-band and L-band manifestations. Exogenous MT dramatically enhanced the gene (TrpDC, T5H, SNAcT, and AcSNMT) expression of critical enzymes in MT synthesis, therefore boosting the level of endogenous MT. The application of MT enhanced the photosynthetic parameters. MT treatment decreased the fluorescence intensities of the J-phase and I-phase in the OJIP curve under salt stress, attenuated the irregularities in the K-band and L-band performance, and concurrently enhanced quantum yield and energy partitioning ratios. It specifically elevated φP_o, φE_o, and ψ_o, while decreasing φD_o. The therapy enhanced parameters of both the membrane model (ABS/RC, DI_o/RC, ET_o/RC, and TR_o/RC) and leaf model (ABS/CS_m, TR_o/CS_m, ET_o/CS_m, and DI_o/CS_m). Conversely, the injection of exogenous p-CPA exacerbated salt stress-related damage to the photosystem of tomato seedlings and diminished the beneficial effects of MT. The findings suggest that exogenous MT mitigates salt stress-induced photoinhibition by (1) modulating endogenous MT concentrations, (2) augmenting PSII reaction center functionality, (3) safeguarding the oxygen-evolving complex (OEC), (4) reinstating PSI redox potential, (5) facilitating photosynthetic electron transport, and (6) optimizing energy absorption and dissipation. As a result, MT markedly enhanced photochemical performance and facilitated development and salt stress resilience in tomato seedlings. Full article

Sargassum is an important primary producer of rocky bottom communities in coastal ecosystems. Like other parts of the planet, benthic populations of S. natans from Ilha Grande Bay (IGB), southeastern Brazil, have been suffering from different forms of natural and anthropogenic disturbances, in particular increasing seawater temperatures. The aim of this study was to understand the effects of temperature on the photosynthetic performance of S. natans using the pulse amplitude modulated (PAM) fluorometry. In the field experiments, the occurrence of photoprotection resulted in a difference between the effective and maximum quantum yields [(ΔF (F’_m − F_s)/F’_m and F_v/F_m, respectively) that was maximized at noon. The stress induced by incubation at 32–35 °C caused a decrease in F_v/F_m by 33% on the first day and approximately 20% on subsequent days. In the laboratory, using two co-occurred species of S. natans and Padina gymnospora, we verified that the photosynthetic apparatus of S. natans collapses at 34 °C. The fate of the energy absorbed by photosystem II (PSII) antenna showed that, in S. natans, photochemical activity and non-photochemical quenching of chlorophyll fluorescence (NPQ) drastically decrease, and only the passive dissipation in the form of heat and fluorescence remains. Our results indicate the disappearance of the NPQ photoprotection at 34 °C before the decline of F_v/F_m as the reason for the collapse of photochemistry of Sargassum. Full article

Perennials improve soil strength and stabilize the slope. However, they are very prone to drought stress (DS). To identify plant health indicators, this study investigated the responses of five tropical perennials commonly grown in Singapore’s slope to DS and re-watering (RW) in the greenhouse. The durations for mild, intermediate, and severe DS defined as T1, T2, and T3, respectively, before RW were based on the extents of reduced F_v/F_m ratio (maximal quantum efficiency of PSII) and the levels of wilting. After RW, soil water content (SWC) increased until field capacity in all DS soil, although they were significantly lower than in well-watered (WW) soil. Overall, the F_v/F_m ratios and leaf water content (LWC) decreased significantly in all DS plants compared to those of WW plants, but all increased to the similar level as WW plants after RW. Nitrogen deficiency did not occur in any plants during DS. There were clear positive correlations of SWC with F_v/F_m ratios, LWC, effective quantum yield of PSII (∆F/F_m’), electron transport rate (ETR), and photochemical quenching (qP) for all species. To monitor plant health, it would recommend using both non-destructive measurements such as SWC and F_v/F_m ratios and destructive parameters like LWC, ∆F/F_m’, ETR, and qP. Full article

Aspirin (Asp) is extensively used in human health as an anti-inflammatory, antipyretic, and anti-thrombotic drug. In this study, we investigated if the foliar application of Asp on tomato plants has comparable beneficial effects on photosynthetic function to that of salicylic acid (SA), with which it shares similar physiological characteristics. We assessed the consequences of foliar Asp-spray on the photosystem II (PSII) efficiency of tomato plants, and we estimated the reactive oxygen species (ROS) generation and the chloroplast ultrastructural changes. Asp acted as an osmoregulator by increasing tomato leaf water content and offering antioxidant protection. This protection kept the redox state of plastoquinone (PQ) pull (qp) more oxidized, increasing the fraction of open PSII reaction centers and enhancing PSII photochemistry (Φ_PSII). In addition, Asp foliar spray decreased reactive oxygen species (ROS) formation, decreasing the excess excitation energy on PSII. This resulted in a lower singlet oxygen (¹O₂) generation and a lower quantum yield for heat dissipation (Φ_NPQ), indicating the photoprotective effect provided by Asp, especially under excess light illumination. Simultaneously, we observed a decrease in stomatal opening by Asp, which reduced the transpiration. Chloroplast ultrastructural data revealed that Asp, by offering a photoprotective effect, decreased the need for the photorespiration process, which reduces photosynthetic performance. It is concluded that Asp shares similar physiological characteristics with SA, having an equivalent beneficial impact to SA by acting as a biostimulant of the photosynthetic function for an enhanced crop yield. Full article

In this study, we present the results of the impact of abiotic environmental (chemical) stressors in the soil environment (salinity, acidification, inorganic elements from industry—red mud waste containing Al) on the content and fluorescence of chlorophyll in the assimilating tissues of Glycine max (L.) Merrill, cv. ES Mentor. Under controlled conditions of a pot experiment during the 2023 growing season, we applied graded doses of these stressors (salinity—doses of 20, 30, and 60 g NaCl per 2 dm³ of water used for plant irrigation; acidity—pH 6, pH 5, and pH 4; red mud—200 g, 400 g, and 600 g per pot) and assessed their impact on the effective and maximum quantum yield of photosystem II (PSII), yield Y(II), or the ratio of variable to maximum fluorescence—the Fv/Fm test. These tests are used to detect plant stress. The Y(II) test yielded values in the range of 0.627–0.800. Significant differences (variance analysis, 95% Least Significant Difference—LSD, post hoc test of analysis of variance—ANOVA) in reducing PSII chlorophyll fluorescence (Y(II)) were found between the medium and high doses of all three stressors compared to the control, indicating plant stress response. The Fv/Fm test yielded values between 0.668 and 0.805 and similarly detected stress responses in plants to all medium and high doses of stressors. The evaluated cultivar showed tolerance to moderately increased salt (NaCl) content and red mud levels. This was also confirmed by the chlorophyll content expressed as the Chlorophyll Content Index (CCI). The highest (significantly confirmed) chlorophyll content was found in the control variant and the variants with lower salt content and a soil pH of 6, with values of 35.633–37.467 CCI, compared to variants with higher red mud content (15.533–18.133 CCI) and higher soil acidity with pH 4 (22.833 CCI). Based on the results obtained, we conclude that the ES Mentor cultivar is tolerant to lower doses of the assessed stressors and can be cultivated in agricultural practice. However, medium to high doses of stressors trigger a strong stress response in plants and, therefore, we do not recommend cultivating this variety in contaminated environments. Full article

1-Methyl cyclopropene (1-MCP) is known as an ethylene antagonist, yet its mechanisms in regulating photosynthetic electron transport and energy dissipation in chrysanthemum under heat stress are not well understood. Here, the chlorophyll a fluorescence and modulated 820 nm reflection transients were analyzed in heat-tolerant and heat-sensitive chrysanthemum plants. This study demonstrates that 1-MCP pre-treatment helps maintain the net photosynthetic rate (P_n) and the reaction center activity of photosystems I and II (PSI and PSII) during heat stress. Specifically, 1-MCP treatment significantly increases the fraction of active oxygen-evolving complex (OEC) centers and reduces relative variable fluorescence intensity at the J step (V_J) as well as the efficiency of electron transfer at the PSI acceptor side (δ_Ro). These effects mitigate damage to the photosynthetic electron transport chain. Additionally, 1-MCP-treated plants exhibit decreased quantum yield of energy dissipation (φ_Do) and reduced energy flux per reaction center (DI_o/RC). Overall, 1-MCP enhances light utilization efficiency and excitation energy dissipation in the PSII antennae, alleviating heat stress-induced damage to PSI and PSII structures and functions. This study not only advances our understanding of 1-MCP’s regulatory role in photosynthetic processes under heat stress but also provides a basis for using exogenous substances to improve chrysanthemum heat resistance. Full article