Synergistic effects of clove fruit extract and nano-silicon to enhance drought resilience and productivity of soybean through improved plant defense mechanisms

Clove fruit extract (CFE) and nano-silicon particles (Si-NPs) are promising natural and nanotechnological solutions to enhance drought resilience and improve soybean productivity as a crop critically affected by water scarcity. This study specifically focused on how the foliar application of CFE (5%) and/or Si-NPs (1.5 mM), influences plant health and productivity under three irrigation regimes based on crop evapotranspiration (ETc), which were 100% ETc (well-watered), 75% ETc (moderate drought stress), and 50% ETc (high drought stress). The study assessed multiple dimensions including plant development, leaf anatomy, physiological and biochemical responses, antioxidant defense mechanisms, nutrient content, and yield performance. The results revealed that moderate and high drought stress significantly reduced stomatal conductance, transpiration rate, net photosynthetic rate, membrane stability index, photochemical activity, and relative water content. These physiological declines were linked to structural reductions in blade, phloem, spongy, palisade, and xylem thickness, which led to a decrease in leaf area, plant height, chlorophyll content, and nutrient levels, ultimately impairing crop yield. However, the application of CFE and Si-NPs mitigated these adverse effects, with considerable improvements in all measured parameters under drought conditions. These enhancements were associated with increased antioxidant enzyme activities, proline, soluble sugars, total soluble carbohydrates, glutathione, and α-tocopherol. Among the treatments, the combined application of CFE and Si-NPs proved most effective, improving soybean biological yield by 31% under severe drought stress compared to the control. This investigation indicated an environmentally sustainable approach for bolstering soybean resilience and productivity under water-limited conditions.