Background: Drought is a major determinant for growth and productivity of all crops, including cereals, and the drought-induced detrimental effects are anticipated to jeopardize world food security under the ongoing global warming scenario. Biostimulants such as humic acid (HA) can improve drought tolerance in many cereals, including maize and sorghum. These two plant species are genetically related; however, maize is more susceptible to drought than sorghum. The physiological and biochemical mechanisms underlying such differential responses to water shortage in the absence and presence of HA, particularly under field conditions, are not fully understood. Results: Herein, the effects of priming maize and sorghum seeds in 100 mg L⁻¹ HA on their vegetative growth and physiological responses under increased levels of drought (100%, 80%, and 60% field capacity) were simultaneously monitored in the field. In the absence of HA, drought caused 37.0 and 58.7% reductions in biomass accumulation in maize compared to 21.2 and 32.3% in sorghum under low and high drought levels, respectively. These responses were associated with differential retardation in overall growth, relative water content (RWC), photosynthetic pigments and CO₂ assimilation in both plants. In contrast, drought increased root traits as well as H₂O₂, malondialdehyde, and electrolyte leakage in both species. HA treatment significantly improved the growth of both plant species under well-watered and drought conditions, with maize being more responsive than sorghum. HA induced a 29.2% increase in the photosynthetic assimilation rate in maize compared to 15.0% in sorghum under high drought level. The HA-promotive effects were also associated with higher total chlorophyll, stomatal conductance, RWC, sucrose, total soluble sugars, total carbohydrates, proline, and total soluble proteins. HA also reduced the drought-induced oxidative stress via induction of non-enzymic and enzymic antioxidants at significantly different extents in maize and sorghum. Conclusion: The current results identify significant quantitative differences in a set of critical physiological biomarkers underlying the differential responses of field-grown maize and sorghum plants against drought. They also reveal the potential of HA priming as a drought-alleviating biostimulant and as an effective approach for sustainable maize and sorghum production and possibly other crops in drought-affected lands.

Soil salinity is a major threat hindering the optimum growth, yield, and nutritional value of potato. The application of organic composts and micronutrients can effectively ameliorate the salinity-deleterious effects on potato growth and productivity. Herein, the combined effect of banana and soybean composts (BCo and SCo) application alongside foliar supplementation of boron (B), selenium (Se), cobalt (Co), and titanium (Ti) were investigated for improving growth, physiology, and agronomical attributes of potato plants grown in saline alluvial soil. Salinity stress significantly reduced biomass accumulation, chlorophyll content, NPK concentrations, yield attributes, and tuber quality, while inducing malondialdehyde and antioxidant enzymes. Co-application of either BCo or SCo with trace elements markedly alleviated salinity-adverse effects on potato growth and productivity. These promotive effects were also associated with a significant reduction in malondialdehyde content and activities of peroxidase and superoxide dismutase enzymes. The co-application of BCo and B/Se was the most effective among other treatments. Principle component analysis and heatmap also highlighted the efficacy of the co-application of organic composts and micronutrients in improving the salinity tolerance of potato plants. In essence, the co-application of BCo with B and Se can be adopted as a promising strategy for enhancing the productivity of potato crops in salt-affected soils.

Background: Salinity is a major threat to rice growth and productivity. Utilizing wild rice-derived genes and biostimulants with high growth promoting- and stress-alleviating potential can significantly improve salinity tolerance in cultivated rice. Herein, we investigated the vegetative growth and physiological responses of Giza 177 (Oryza sativa, salinity sensitive, high-yielding cultivar) and a promising introgression salt tolerant line (sativa/glaberrima; SG 65) from a population of Giza 177 × African rice (Oryza glaberrima) under low (2.75 mS/cm) and high (5.5 mS/cm) salinity stress. The possible ameliorative effects of priming rice seeds in moringa leaf extract (MLE) on these responses were also tested. Results: The two salinity levels induced differential reduction in plant growth in both cultivars. In the MLE-unprimed plants, salinity induced 34–54% and 30–45% reductions in biomass accumulation in Giza 177 and SG 65, respectively. These responses were associated with significant differential reductions in relative water content, chlorophylls, carotenoids, and gas exchange parameters (transpiration rate, net photosynthetic rate, stomatal conductance, and intercellular CO₂ concentration), ascorbic acid, and total protein. Conversely, salinity induced the accumulation of H₂O₂, malondialdehyde, proline, carbohydrate fractions, and membrane injury. MLE treatment mitigated the above salinity-induced adverse effects in both cultivars via reducing the salt-induced oxidative stress through the induction of non-enzymic (total phenols, and flavonoids) and enzymic antioxidants including ascorbate peroxidase, catalase, peroxidase, and polyphenol oxidase in both cultivars. SG 65 plants exhibited consistently higher salt tolerance and responsiveness to MLE than Giza 177. Conclusions: This study reports significant differences in an array of critical physiological and biochemical indices that underpin the divergent responses between the two salinized cultivars. It demonstrates the potential of African rice-derived genomic fragments and MLE priming in mitigating salinity stress, highlighting their use as a sustainable strategy for increasing rice production in salt-affected soils.

Suaeda schimperi, a halophyte native to the Red Sea’s hyper-arid salt marshes, thrives in its extreme conditions (high salinity, minimal rainfall, and elevated temperatures). However, its adaptive tolerance mechanisms to these harsh cond...

Drought severely threatens the growth and productivity of cereals, including maize and sorghum. Despite their genetic relatedness, sorghum exhibits better drought tolerance than maize, and the physiological basis behind such differential response is largely unknown. Humic acid (HA) is a stress-relieving biostimulant that can boost drought resilience in plants; however, its mechanism of action remains vague. Herein, the reproductive growth, physiological responses, yield, and grain quality of maize and sorghum under increased field-drought conditions (100%, 80%, and 60% field capacity) and the ameliorative effects of seed priming in HA (100 mg L ⁻¹ ) were simultaneously investigated. Drought stress significantly reduced biomass, photosynthetic efficiency, yield traits, and grain quality indices in both species, with sorghum consistently demonstrating smaller reductions. Under severe drought, maize exhibited reductions up to 67.3% in stem dry mass, 68.1% in net photosynthesis, and 63.9% in grain yield, compared to 47.4%, 53.6%, and 54.6% reductions in sorghum, respectively. These differences correlated with lower oxidative damage and higher osmolytes, flavonoids, phenols, and polyphenol oxidase (PPO) in sorghum. HA priming mitigated drought-induced damages and enhanced biomass accumulation, photosynthesis, osmolyte production, non-enzymatic and enzymatic antioxidants, yield traits, and grain quality indices such as grain carbohydrates, protein, oil, and fatty acid composition in both species, with maize being generally more responsive than sorghum. These findings highlight the distinct physiological responses of maize and sorghum to drought and demonstrate that HA priming is a sustainable approach to improve drought tolerance, productivity, and grain quality in these and potentially other crops in drought-prone lands. Graphical Abstract

During maize grain filling, effective coordination between a high source capacity and a robust sink significantly enhances yield. These source–sink relationships are primarily influenced by genotype and nitrogen availability, and achieving a balance between them has been a challenge in modern maize hybrids. In this study, three maize hybrids (B73 × Mo17, B73 × Sids7, and B73 × NC358), sharing B73 as the female parent, were produced, field-grown, and maintained till maturity under limited and sufficient soil nitrogen. The impact of the developing reproductive sink on growth, yield, and dynamic changes in ear-leaf physiology was monitored at 0, 5, 10, 15, and 20 days after pollination. Under limited and adequate N conditions, B73 × NC358 outperformed B73 × Mo17 and B73 × Sids7 in yield and most tested traits. The enhanced yield in B73 × NC358 was associated with increased sink-strength traits and improved source capacity-related morpho- physiological characteristics. As grain filling progressed, B73 × NC358 consistently demonstrated higher biomass accumulation, leaf nitrogen, stover nitrogen, chlorophyll content, total soluble proteins, and elevated activities of nitrate reductase (NR) and glutamine synthetase (GS) compared to the other hybrids. Nitrogen limitation curtails grain yield, growth, and leaf metabolites; however, it induces starch accumulation and increased protease and asparaginase (ASNase) activities in all hybrids. Our findings suggest that B73 × NC358 optimizes leaf nitrogen and balances source capacity and sink strength to enhance biomass, nitrogen use efficiency (NUE), and grain yield. The alleles from B73 and NC358 interact effectively to support a stay-green-like phenotype, promoting growth and grain yield across nitrogen conditions.