Search Results (45)

This study examined the effects of both nitrogen (N) rate and form on the growth, nutrient uptake, and quality parameters of hydroponically grown purslane (Portulaca oleracea L.) during a spring cultivation cycle. Purslane was cultivated in a floating hydroponic system under either adequate or limiting N conditions. More specifically, under adequate N conditions, plants were supplied with NS where ammonium nitrogen (NH₄-N) accounted for either 7% (Nr7) or 14% (Nr14) of the total-N. The limiting N conditions were achieved through the application of either an NS where 30% of N inputs were compensated with Cl (N30), or an NS where 50% of N inputs were balanced by elevating Cl and S by 30% and 20%, respectively (N50). The results demonstrated that mild N stress enhanced the quality characteristics of purslane without significant yield losses. However, further and more severe N restrictions in the NS resulted in significant yield losses without improving product quality. The highest yield reduction (20%) occurred under high NH₄-N supply (Nr14), compared to Nr7-treated plants, which was strongly associated with impaired N assimilation and reduced biomass production. Both N-limiting treatments (N30 and N50) effectively reduced nitrate accumulation in edible tissues by 10% compared to plants grown under adequate N supply (Nr7 and Nr14); however, nitrate levels remained relatively high across all treatments, even though the environmental conditions of the experiment favored nitrate reduction. All applied N regimes and compensation strategies improved the antioxidant and flavonoid content, with the highest antioxidant activity observed in plants grown under high NH₄-N application, indirectly revealing the susceptibility of purslane to NH₄-N-rich conditions. Overall, the form and rate of N supply significantly influenced both plant performance and biochemical quality. Partial replacement of N with Cl (N30) emerged as the most promising strategy, benefiting quality traits and effectively reducing nitrate content without significantly compromising yield. Full article

Drought stress is a critical abiotic constraint on agricultural productivity, particularly affecting crops like pepper (Capsicum annuum L.), which are highly susceptible to water deficits due to their physiological characteristics. The present study investigated the impact of a 40% reduction in irrigation on yield, macronutrient concentrations, and fruit quality across several pepper genotypes. The cultivars evaluated included two landraces, namely ‘JO109’ and ‘JO204’ (Capsicum annuum var. grossum), as well as the California cultivar ‘Yolo Wonder’ and the commercial F1 hybrid ‘Sammy RZ’, which served as controls. The experiment was conducted at the greenhouse facilities of the Laboratory of Vegetable Production, Agricultural University of Athens. Under reduced irrigation, most of the cultivars studied exhibited a decline in yield, which was attributed to a decrease in fruit number in ‘Yolo Wonder’ and a reduction in fruit weight in both ‘JO204’ and ‘Sammy’. In contrast, the landrace ‘JO109’ exhibited consistent yields under both growing conditions, a response likely attributed to elevated K concentration in the leaves and lower Na accumulation in the fruit, indicating enhanced tolerance to water deficit. A decline in leaf K concentration was observed in response to drought stress, while concomitantly increased concentrations of Na, Ca and Mg were recorded. Among fruit macronutrients, only Ca showed a significant decrease under reduced irrigation. Furthermore, fruit firmness (FF), titratable acidity (TA) and total soluble solids content (TSSC) exhibited higher levels under drought stress, particularly in ‘JO109’, while TA remained unaltered. These findings highlight the potential of landraces such as ‘JO109’ to be utilized in breeding programs aimed at enhancing resilience, while maintaining pepper fruit quality under limited water availability. Full article

Agriculture is presently facing several ecological concerns related to the upsurging request for premium-value food produced in compliance with natural horticultural tools. The use of natural substances, such as biostimulants, principally protein hydrolysates (PHs), could be useful to maximize overall vegetable plant fitness. However, the mode of application (foliar spray or fertigation) could affect biostimulant efficiency. The current research was conducted to evaluate the effect of a Zea mays-derived PH (Surnan^®, SPAA, Pescara, Italy) and its mode of application (foliar spray and/or fertigation) on yield traits, mineral profile, nutritional and functional components, along with NUE of “Florida fortuna” strawberry cultivated under tunnel. The findings showed that the corn-based PH effectively enhanced yield and number of marketable fruits per plant (NMFP) compared with the control (+20.1% and +25.4%, respectively). Fruits from biostimulated plants also showed a higher fruit lightness and ascorbic acid and anthocyanin concentration than fruits from control plots. Furthermore, Surnan^® PH increased nitrogen use efficiency (NUE) of strawberry plants. Captivatingly, plants biostimulated via fertigation showed the highest fruit potassium (K) concentration, while those exposed to the foliar spray had the highest fruit phenolic concentration. Generally, our findings recommended that the application of Zea mays-derived PH via foliar spray could be considered a suitable tool to increase functional traits of strawberry grown under tunnel. Full article

Unraveling the evolutionary history of Brassica L. crops and their wild relatives remains a key challenge in plant evolutionary biology. Brassica cretica is considered the closest living relative of the cultivated B. oleracea. It is mainly distributed in the Aegean Islands and the neighboring mainland regions of Greece and Anatolia, and exhibits extensive phenotypic variability, obscuring its infraspecific classification. In this study, we analyzed five Greek populations of B. cretica and one B. oleracea botanical variety using SSR markers to assess genetic diversity and differentiation. High genetic diversity was detected within natural populations, with a mean of 21.9 alleles per locus and an expected heterozygosity of 0.647. Significant genetic differentiation (Fst = 0.812) revealed the presence of four distinct gene pools, partly supporting the current infraspecific classification of B. cretica. The cultivated plants cluster closely with B. cretica subsp. cretica, supporting the hypothesis of an Eastern Mediterranean origin. Our findings suggest that B. cretica subsp. cretica may have been introduced to suitable habitats or that cultivated plants may have reverted to a feral state in the Peloponnese, given the genetic similarity between populations from Crete and northern Peloponnese. The identified genetic diversity underscores the importance of B. cretica as a genetic resource for breeding programs and highlights the need for conservation, particularly for populations exhibited unique genetic traits. Full article

This study investigates the effects of nitrogen fertilization, irrigation, and biostimulant application on the growth and nutrient composition of Cichorium spinosum L. The experimental design included two nitrogen rates (NR100 and NR30, 100% and 30% of plant requirements), two irrigation levels (WA100 and WA50, 100% and 50% of water availability,), and foliar application of a nitrogen-rich biostimulant (BS and NoBS, biostimulated or not biostimulated). In comparison to NR100, NR30 reduced agronomical parameters leaf number, leaf area, leaf fresh, and dry weight by 13.53%, 24.93%, 20.76%, and 15.00%, respectively, whereas dry matter content was increased by 7.64%. WA50 also resulted in reduction in the agronomical characteristics by 8.62%, 7.19%, 5.53%, and 5.26, respectively, whereas the dry matter content was not affected. BS positively affected the agronomical characteristics by 7.49%, 8.01%, 7.18%, and 5.56, respectively, whereas the dry matter content was not affected. The effects of nitrogen rates and water availability suggest the more pronounced impact of nitrogen compared to water stress on the agronomical characteristics. Biostimulant application partially mitigated the effects of NR30 but was ineffective against WA50. The nutrient content of the leaves was also affected. NR30 reduced leaf nitrate, calcium, and zinc content, but increased iron, manganese, and copper concentrations. WA50 altered magnesium and zinc levels: it increased the former and decreased the latter. The interaction between nitrogen and water stress notably affected the plants’ calcium content, which was higher under the NR100 x WA50 treatment. These findings provide significant insights into the perlite-based cultivation of C. spinosum L., and its resilience against drought stress. Moreover, the beneficial effects of sufficient nitrogen rates on leaf fresh weight of Cichorium spinosum L. outline the importance for improving nutrient solution management schemes. Biostimulant application demonstrated promising results and could, after further research, become a viable solution for maintaining optimal yields under nitrogen stress. Full article

Currently, different strategies, including the application of bio-fertilizers, are used to ameliorate the adverse effects posed by salinity stress as the major global problem in plants. Fish waste is suggested as a novel bio-fertilizer to mitigate the effects of biotic and abiotic stresses. In this investigation, an experiment was conducted to investigate the effects by applying different concentrations (0, 5, 10, and 15% (v/v)) of fish waste bio-fertilizer on stevia plants grown under salt stress conditions (0, 20, 40, and 60 mM of NaCl). Results showed that salinity negatively affected growth parameters, the photosynthetic pigments, the relative water content, and the chlorophyll fluorescence parameters while increased the activity of antioxidant enzymes, total phenol, hydrogen peroxide (H₂O₂), malondialdehyde (MDA), proline, and total carbohydrates compared with control samples. On the other hand, the application of fish waste bio-fertilizer mitigated the effects of salinity stress by enhancing growth and mitigating stress-relative markers, especially at the highest salinity level (60 mM). Overall, fish waste bio-fertilizer could be considered a sustainable, innovative approach for the alleviation of salinity stress effects in plants and, in addition, fish waste bio-fertilizer did not cause more salinity issues, at least with the applied doses and experiment time, which is an imperative aspect. Full article

Salinity, one of the major abiotic stresses in plants, significantly hampers germination, photosynthesis, biomass production, nutrient balance, and yield of staple crops. To mitigate the impact of such stress without compromising yield and quality, sustainable agronomic practices are required. Among these practices, seaweed extracts (SWEs) and microbial biostimulants (PGRBs) have emerged as important categories of plant biostimulants (PBs). This research aimed at elucidating the effects on growth, yield, quality, and nutrient status of two Greek tomato landraces (‘Tomataki’ and ‘Thessaloniki’) following treatments with the Ascophyllum nodosum seaweed extract ‘Algastar’ and the PGPB ‘Nitrostim’ formulation. Plants were subjected to bi-weekly applications of biostimulants and supplied with two nutrient solutions: 0.5 mM (control) and 30 mM NaCl. The results revealed that the different mode(s) of action of the two PBs impacted the tolerance of the different landraces, since ‘Tomataki’ was benefited only from the SWE application while ‘Thessaloniki’ showed significant increase in fruit numbers and average fruit weight with the application of both PBs at 0.5 and 30 mM NaCl in the root zone. In conclusion, the stress induced by salinity can be mitigated by increasing tomato tolerance through the application of PBs, a sustainable tool for productivity enhancement, which aligns well with the strategy of the European Green Deal. Full article

Woodland strawberry (Fragaria vesca L.) is an underutilized plant species that could benefit from the use of biostimulants to improve crop productivity and fruit quality. The scope of the present study was to appraise the influence of two biostimulants (Trichoderma atroviride and plant protein hydrolysate)—used either alone or combined—on the plant performance and economic profitability of two woodland strawberry genotypes (‘Alpine’ and ‘Regina delle Valli’). Overall, data showed that ‘Alpine’ had the highest productive performances, whereas ‘Regina delle Valli’ revealed the highest fruit qualitative traits. T. atroviride inoculation and V-PH application significantly boosted plant marketable yield (+20.5% for T. atroviride and +12.9% for V-PH), total sugars (+1.9% for Trichoderma and +1.4% for V-PH) and anthocyanins (+14.1% for T. atroviride and +9.8% for V-PH) compared to non-treated plants. Plants supplied with both biostimulants had a higher marketable yield (+34.8%), mean fruit weight (+6.0%), fruit dry matter (+13.8%), total sugars (+3.5%), ascorbic acid (+12.7%), flavonoid (+26.3%) and anthocyanins (+29.9%) compared to non-treated plants. Furthermore, our study revealed that the highest fruit polyphenol concentration was recorded in both genotypes treated with the combination of biostimulants and in ‘Regina delle Valli’ sprayed with V-PH, whereas the highest antioxidant activity was found in ‘Regina delle Valli’ fruit when plants were supplied with both biostimulants. Our study pointed out that the application of microbial and non-microbial biostimulants, especially in combination, might be a useful strategy for improving the performances of underutilized species and, therefore, encouraging their cultivation, valorization and economic profitability (+6208.3 EUR /ha when plants were exposed to both biostimulants). Full article

The aim of this research is to introduce innovative cultivation practices that result in reduced nitrate levels in baby leaf lettuce grown under vertical farming conditions while maintaining high productivity. For this reason, three experiments were conducted. The first experiment focused on the impact of two “white” light spectra with a blue:green:red:far-red ratio of 14:32:43:10 (B_lowR_high) and 21:34:36:7 (B_highR_low). The second experiment assessed the effects of two nitrogen supply conditions: sufficient total nitrogen (N₁₅) and limited total nitrogen (N₅), and foliar biostimulant application. In the third experiment, the impact of replacing the nutrient solution in the N₁₅ treatment with tap water for an additional 24 h (TW24) on leaf nitrate content was examined. Results from the lighting experiment revealed no significant effects on agronomical parameters or nitrate content between the two light spectra. Reducing nitrogen content in the nutrient solution reduced leaf nitrate content but negatively influenced agronomical characteristics. Biostimulant application and replacing the nutrient solution with water reduced leaf nitrate content compared to the control and positively affected growth. The most favorable outcomes were observed in plants supplied with sufficient nitrogen and foliar biostimulant but also cultivated for an additional 24 h with tap water (Sp-N₁₅-TW24). Full article

The use of biostimulants consisting of plant growth-promoting rhizobacteria (PGPR) has been rapidly expanding in horticulture in recent years. In the current study, a novel mix of six Bacillus sp. strains (B. subtilis, B. pumilus, B. megaterium, B. amyloliquefaciens, B. velezensis, B. licheniformis) was tested as a PGPR biostimulant in two experiments with zucchini squash (Cucurbita pepo L.). The first experiment took place in greenhouse soil in winter, while the second experiment was conducted in an open field during summer. In both experiments, seeds of the local landrace “Kompokolokytho” and the commercial hybrid “ARO-800” were either inoculated or non-inoculated with the PGPR biostimulant. The application of the six Bacillus sp. strains increased both the vegetative growth and the yield of zucchini squash, and these effects were associated with significantly higher shoot phosphorus levels in both experiments and both genotypes. Furthermore, at the end of the cultivation, the colony-forming units of Bacillus sp. were appreciably higher in plants originating from inoculated compared to non-inoculated seeds, indicating that the tested mix of Bacillus sp. can be successfully applied through seed inoculation. “ARO-800” produced more vegetative and fruit biomass than “Κompokolokytho” under greenhouse cropping conditions, while in the open field crop, both genotypes performed equally. Presumably, this response occurred because “ARO-800” did not express its full yield potential in the open field due to stress imposed by the high summer temperatures, while the local landrace, which is traditionally grown in open fields, may be more resilient to stress conditions frequently encountered in open fields. Full article

Soil salinity caused by climate change is a major global issue, especially in regions like the Mediterranean basin. Most commercially cultivated horticultural species, including pepper, are considered to be salt sensitive. However, some underutilized genotypes exhibit high adaptability to adverse environmental conditions, without compromising yield. This study aimed to investigate the effects of salinity stress on the yield, nutrition, and fruit quality of four pepper landraces: JO 109 (Capsicum annuum var. grossum), JO 204 (Capsicum annuum var. grossum), JO 207 (Capsicum annuum var. grossum), and ‘Florinis’. The California cultivar ‘Yolo Wonder’ and the commercial F₁ hybrid ‘Sammy RZ‘ were used as controls. The experiment was conducted in the greenhouse facilities of the Laboratory of Vegetable Production at the Agricultural University of Athens. Half of the plants were exposed to a nutrient solution containing NaCl at a concentration that could maintain the NaCl level in the rhizosphere at 30 mM (salt-treated plants), while the remaining plants were irrigated with a nutrient solution containing 0.5 mM NaCl (control plants). Yield and yield quality attributes, such as firmness, titratable acidity (TA), total soluble solids content (TSSC), fruit height, and diameter were recorded. The results revealed that the landraces were more tolerant to salinity than the commercial varieties ‘Yolo Wonder’ and ‘Sammy RZ’. Moreover, subjecting pepper plants to increased salinity resulted in increased fruit quality, manifested by an increase in TSSC and TA. Full article

Cabbage is an annual vegetable crop species cultivated throughout the year. The development of high-yielding cabbage hybrids and the optimization of several agronomic management practices such as fertilization and crop rotation have resulted in increased soil fertility, crop yield and product quality. This study aimed to investigate the effects of the farming system (organic and conventional) and the applied rotation scheme on soil nutrient content, head yield and the nutrient content of cabbage. The preceding crops included either pea (P), faba bean (F) or cabbage (C), and thus, the rotation schemes were P-C, F-C and C-C. Sheep manure was applied in the organic farming system, and the inorganic fertilizer 11-15-15 (N-P₂O₅-K₂O) was applied to the conventionally cultivated plants. The results reveal an interaction between the farming system and the preceding crop for the head yield, with the lowest values (57.00 t ha⁻¹ and 53.87 t ha⁻¹ in 2015/2016 and 2016/2017, respectively) recorded in plots where cabbage was cultivated as a preceding crop under the organic farming system. The N, P and K contents in head tissues were affected only by the farming system, with the greatest values recorded in the conventional farming system. Both factors affected the nutrient content in the soil. Specifically, the highest values of NO₃⁻ and total N content in the soil were recorded in the P-C and F-C rotations, and the K content was higher in the continuous cabbage cropping system (C-C). Moreover, the NO₃⁻, P and K contents in the soils were higher in the conventional farming system compared to the organic system. To conclude, combining inorganic fertilization in a crop rotation scheme with legume species such as pea and faba bean as preceding crops for cabbage can result in increased soil fertility and head yield. Full article

Inappropriate fertilisation results in the pollution of groundwater with nitrates and phosphates, eutrophication in surface water, emission of greenhouse gasses, and unwanted N deposition in natural environments, thereby harming the whole ecosystem. In greenhouses, the cultivation in closed-loop soilless culture systems (CLSs) allows for the collection and recycling of the drainage solution, thus minimising contamination of water resources by nutrient emissions originating from the fertigation effluents. Recycling of the DS represents an ecologically sound technology as it can reduce water consumption by 20–35% and fertiliser use by 40–50% in greenhouse crops, while minimising or even eliminating losses of nutrients, thereby preventing environmental pollution by NO₃⁻ and P. The nutrient supply in CLSs is largely based on the anticipated ratio between the mass of a nutrient absorbed by the crop and the volume of water, expressed as mmol L⁻¹, commonly referenced to as “uptake concentration” (UC). However, although the UCs exhibit stability over time under optimal climatic conditions, some deviations at different locations and different cropping stages can occur, leading to the accumulation or depletion of nutrients in the root zone. Although these may be small in the short term, they can reach harmful levels when summed up over longer periods, resulting in serious nutrient imbalances and crop damage. To prevent large nutrient imbalances in the root zone, the composition of the supplied nutrient solution must be frequently readjusted, taking into consideration the current nutrient status in the root zone of the crop. The standard practice to estimate the current nutrient status in the root zone is to regularly collect samples of drainage solution and determine the nutrient concentrations through chemical analyses. However, as results from a chemical laboratory are available several days after sample selection, there is currently intensive research activity aiming to develop ion-selective electrodes (ISEs) for online measurement of the DS composition in real-time. Furthermore, innovative decision support systems (DSSs) fed with the analytical results transmitted either offline or online can substantially contribute to timely and appropriate readjustments of the nutrient supply using as feedback information the current nutrient status in the root zone. The purpose of the present paper is to review the currently applied technologies for nutrient and water recycling in CLSs, as well as the new trends based on ISEs and novel DSSs. Furthermore, a specialised DSS named NUTRISENSE, which can contribute to more efficient management of nutrient supply and salt accumulation in closed-loop soilless cultivations, is presented. Full article

Vertical farming is gaining attention for urban agriculture and sustainable food production, but mainstream crops may not be economically viable in this system, prompting a shift to high-value crops. This study explores the potential of Cichorium spinosum L. (spiny chicory), a wild edible green, for vertical farming. When cultivated on open field and greenhouses, spiny chicory tends to flower prior vernalization deeming the flowered plants unsalable, necessitating an investigation on its flowering responses. C. spinosum L. plants were cultivated and for 5 months in peat-filled pots, under low light (100 μmols m² s⁻¹), and two photoperiods (10 and 15 h) with stable temperature (20 °C) and CO₂ level (400 ppm). No flowering occurred at the end of the first experiment, indicating that photoperiod alone did not induce flowering. Next, C. spinosum L. was hydroponically cultivated under a 15 h photoperiod, light intensity of 300 μmols m⁻² s⁻¹, temperature between 25 and 30 °C, CO₂ levels of 350 to 400 ppm, and plant density of 100 plants m⁻². At the end of the one-month cultivation the yield of the salable fresh weight was approximately 1.7–2 kg per m². Moreover, gas exchange measurements were conducted to analyze CO₂ uptake and evapotranspiration. This study aims to enhance understanding of spiny chicory’s flowering response and growth performance, providing valuable insights for cultivating this wild edible vegetable in vertical farming systems. Full article

Switching over to closed-loop soilless culture systems, thus preventing pollution of water resources by nitrates and saving water and fertilizers, requires accurate estimations of the mean nutrient-to-water uptake ratios. To contribute to this objective, three fruit vegetable species (tomato, eggplant, cucumber) were grown hydroponically in a floating system under identical cropping conditions to quantify species differences in nutrient uptake. The composition of the nutrient solution used to feed the crops was identical for all species. The total water consumption and the concentrations of most nutrients (K, Ca, Mg, N, P, Fe, Mn, Zn, Cu, B) in the nutrient solution and the plant tissues were measured at crop establishment and at two different crop developmental stages. The obtained data were used to determine the uptake concentrations (UCs) using two mass balance models, one based on nutrient removal from the nutrient solution and a second based on nutrient recovery in the plant tissues. The experiment was conducted in the spring–summer season. The results revealed that the nutrient uptake concentrations were substantially different between species for all nutrients except for N, while there were also significant interactions between the two methods used for their estimation of some nutrients. Thus, the UCs of N, P, Ca, and some micronutrients were significantly higher when its estimation was based on the removal of nutrients from the nutrient solution compared to recovery from plant tissues, presumably because with the first method, losses due to denitrification or precipitation could not be separated from those of plant uptake. The comparison of the three greenhouse vegetables revealed a similar UC for nitrogen, while cucumber generally showed significantly lower UCs for P and for the micronutrients Fe, Zn, and Cu at both cropping stages compared to the two Solanaceae species. The obtained results can be used to precisely adjust the nutrient supply in closed-loop soilless cultivations to the plant uptake thus avoiding both depletion and accumulation of nutrients in the root environment. Full article