Soybean is one of the most important crops worldwide; however, its production and produced seed quality are challenged by the increasingly reported drought waves because of its relative susceptibility to drought stress conditions. Nitrogen (N) is a major macronutrient that has distinctive influence on soybean, especially if applied in correct rates. Moreover, N has an additive importance under drought stress conditions. An experiment was carried out in Debrecen, Hungary in 2017, 2018, and 2019 to investigate the sole and the combined effects of N application under different irrigation regimes on soybean physiology, yield, and its components in addition to the quality of the produced yield. Results showed that the morpho-physiological traits, in addition to the yield component traits were influenced by both fertilization rates and irrigation regimes. Most importantly, high N rate is not recommended with the absence of drought conditions as, compared to low rate, it decreased flower and pod number per plant, plant height, and seed yield. On the other hand, high N rate enhanced most traits under drought stress conditions. 100-seed weight had the highest correlation with yield, followed by flower and pod number per plant, plant height, and Normalized Difference Vegetation Index (NDVI).

Drought periods are predicted to increase in the future, putting the production of sensitive crops under serious hazards. Soybean, as a legume, is capable of partly achieving its nitrogen demands through the N₂-fixation process; however, this process is inhibited by drought stress conditions. Moreover, N₂-fixation might not fulfill the total N demand for soybean plants, so supplemental N-fertilizer doses might be crucial. A 3-year experiment was carried out in Debrecen, Hungary, to investigate the effects of inoculation and N-fertilizer application on the physiomorphology of soybean (cv. Boglár) under both drought stress and irrigated conditions. Results showed that, regardless of inoculation, drought negatively affected plant height, LAI, SPAD, and, to a smaller extent, NDVI. On average, increasing N-fertilizer enhanced these traits accordingly. Inoculation, on the other hand, resulted in taller plants and higher LAI values, but lower SPAD values. It could be concluded that soybean’s physiomorphology is negatively influenced by drought stress and that N-fertilizer application can enhance it whether soybean plants suffer from drought stress conditions or not.

As a result of global climatic changes, water deficiency is threatening food production for the increasing population worldwide, especially drought-sensitive crops, to which soybean belongs, by suppressing yield potentials. Drought stress can inhibit sown seeds’ germination and manipulate germination parameters. A controlled, two-stage experiment was conducted to investigate the effects of drought stress, induced by PEG (polyethylene glycol), on some germination parameters of two soybean cultivars; ‘ES Mentor’ and ‘Pedro’, in Debrecen, Hungary in 2018. At the first stage, 5 PEG concentrations; 10, 15, 20, 25, and 30%, besides control (0% PEG), were applied to each cultivar in 3 replicates. Results showed that both cultivars could not germinate when 25 and 30% of PEG were applied. Significant differences among PEG concentrations, between cultivars and their interaction were recorded. Based on these results, the second stage consisted of 6 PEG concentrations; 2.5, 5, 7.5, 10, 12.5 and 15% (besides control), also in three replicates. For both cultivars, germination ratio (GR) and root elongation (RE) decreased as the PEG concentration increased. Both germination energy (GE) and ultimate germination (UG) decreased, whereas mean period of altimate germination (MPUG) and percentage inhibition increased with increasing water stress. ‘ES Mentor’ could maintain higher (GR) than ‘Pedro’ under all PEG concentrations except 15%, whereas (RE) was lower under all concentrations. It was concluded that ‘ES Mentor’ can germinate better under different water deficiency levels; however, germinated seeds of ‘Pedro’ can tolerate relative water stress better, as the roots could elongate deeper searching for available water.

The global production of soybean, among other drought-susceptible crops, is reportedly affected by drought periods, putting more pressure on food production worldwide. Drought alters plants’ morphology, physiology and biochemistry. As a response to drought, reactive oxygen species (ROS) concentrations are elevated, causing cellular damage. However, lower concentrations of ROS were reported to have an alleviating role through up-regulating various defensive mechanisms on different levels in drought-stressed plants. This experiment was set up in a controlled environment to monitor the effects of exogenous spray of different (0, 1, 5 and 10 mM) concentrations of H₂O₂ on two soybean genotypes, i.e., Speeda (drought-tolerant), and Coraline (drought-susceptible) under severe drought stress conditions (induced by polyethylene glycol) during flowering stage. Furthermore, each treatment was further divided into two groups, the first group was kept under drought, whereas drought was terminated in the second group at the end of the flowering stage, and the plants were allowed to recover. After 3 days of application, drought stress significantly decreased chlorophyll-a and chlorophyll-b, total carotenoids, stomatal conductance, both optimal and actual photochemical efficiency of PSII (Fv/Fm and Df/Fm, respectively), relative water content, specific leaf area, shoot length and dry weight, and pod number and fresh weight, but significantly increased the leaf concentration of both proline and total soluble sugars, the root length, volume and dry weight of both genotypes. The foliar application of 1 mM and 5 mM H₂O₂ on Speeda and Coraline, respectively enhanced most of the decreased traits measurably, whereas the 10 mM concentration did not. The group of treatments where drought was maintained after flowering failed to produce pods, regardless of H₂O₂ application and concentration, and gradually deteriorated and died 16 and 19 days after drought application on Coraline and Speeda, respectively. Overall, Speeda showed better performance under drought conditions. Low concentrations of foliar H₂O₂ could help the experimented soybean genotypes better overcome the influence of severe drought during even sensitive stages, such as flowering. Furthermore, our findings suggest that chlorophyll fluorescence and the cellular content of proline and soluble sugars in the leaves can provide clear information on the influence of both drought imposition and H₂O₂ application on soybean plants.

Sweet corn is highly susceptible to water deprivation, making it crucial to identify effective strategies for enhancing its tolerance to water deficit conditions. This study investigates the novel application of Spermine as a bio-stimulant to improve sweet corn (Zea mays L. var. saccharata) resilience under hydroponic water deficit conditions. Four genotypes (Dessert, Messenger, Tyson, and Royalty) were treated with Spermine (0.2 mM foliar application), polyethylene glycol 6000 (8% and 12%), and their combinations. The impacts on growth parameters, photosynthetic performance, and oxidative stress markers were evaluated. Spermine significantly enhanced biomass parameters, counteracting the severe reductions caused by PEG-induced water deprivation. In the Dessert and Tyson genotypes, total biomass increased by 145%, while it increased by 118% in Messenger and 110% in Royalty when treated with Spermine under severe water deprivation. However, Spermine treatment application did not recorded higher differences compared to control under non water deficit conditions. In the Dessert genotype, root length increased by 36.6% under combined treatment compared to 12% PEG alone. Spermine also mitigated reductions in shoot length, improved by 90.6% and specific leaf area, with a notable 272.6% increase in Tyson under severe water deficit. Photosynthetic performance, including chlorophyll and carotenoid levels, was enhanced, with a 103.1% increase in relative chlorophyll content in Dessert under severe water deprivation. Spermine also reduced oxidative damage, as indicated by a 48.7% decrease in malondialdehyde levels in Tyson, and increased peroxidase activity, enhancing antioxidant defense in Messenger under severe water deprivation. The quantum efficiency of Photosystem II, which was significantly reduced by water deficit, showed substantial improvement with Spermine treatment, with increases of 107.2% in Tyson and 99.4% in Royalty under moderate water deprivation. These results highlight the potential of Spermine as an effective strategy to improve sweet corn resilience under water-limited conditions, offering a novel approach for sustainable crop management.

Water deficits, exacerbated by climate change and unpredictable weather, have become a significant global challenge to agricultural productivity. In this context, exogenous melatonin treatment is well documented as a stress alleviator; however, its effects on various biological processes, particularly in less-explored genotypes, remain understudied. This study aimed to enhance water deficit resilience in sweet corn by applying foliar melatonin to four genotypes-Messenger, Dessert, Royalty, and Tyson under two levels of water deprivation induced by polyethylene glycol at 8% and 12% concentrations in a hydroponic, controlled environment. The melatonin treatments were assessed for their impact on various morphological, physiological, and biochemical parameters under both normal and water-deficit conditions. Under severe water deprivation (12% PEG), melatonin increased root length by 75%, peroxidase activity by 31% while reducing malondialdehyde content by 34% in genotype Dessert indicating enhanced antioxidant defense and reduced oxidative damage. Likewise in genotype Royalty, stomatal conductance increased by 68%, with increasing specific area by 125% on melatonin treatment under severe water deprivation. The treatment also improved chlorophyll-a content by 93% in Royalty and 37% in Tyson, while decrease in malondialdehyde levels by 42% in Tyson, indicating reduced oxidative damage under severe water deprivation. In addition, melatonin increased photosystem II efficiency (Fv/Fm) in all genotypes with 27% increase in Royalty and improved quantum yield across all genotypes, regardless of the water deficit level. Overall, melatonin treatment showed genotype-specific and dose-dependent effects in mitigating water deficit effects, offering a promising strategy to improve crop resilience and productivity in limited water environments. These results suggest the practical application for integrating melatonin treatments into sustainable agricultural practices, such as improving water deficit tolerance in sweet corn and potentially other crops, to maintain productivity under adverse climatic conditions.