Deciphering silicon-induced resilience to drought and waterlogging stress in Fagopyrum esculentum Moench: Physiological adaptations during stress and recovery

This study explored the mitigating effect of silicon (Si) on drought- and waterlogging-induced stresses in common buckwheat. Twenty-day-old plants were subjected to 15 days of drought or waterlogging followed by a 15-day recovery. Silicon was applied twice via foliar spray. Both stresses significantly reduced plant growth: height, fresh weight, and dry weight decreased by 54–62% under drought and 46–74% under waterlogging. Silicon supplementation significantly mitigated these reductions. During recovery, Si-treated plants exhibited further improvements: with height increasing by 5–7%, fresh weight by 18–34%, and dry weight by 30–33% under drought and waterlogging, respectively. Stress also impaired physiological status. Relative water content (RWC) decreased by 33% (drought) and 37% (waterlogging), while electrolyte leakage (EL) increased by 44% and 39%, respectively. Silicon maintained higher RWC (by 23–25%) and reduced EL (by 23–36%), indicating improved cellular integrity. Gas exchange parameters declined sharply with photosynthetic rate (P n ) decreasing by 84–98%, stomatal conductance (g s ) by 66–75%, and transpiration rate (T r ) by 65–86% under both stresses but improved with Si application during recovery (P n by 4–65%, g s by 60–65%, T r by 96–245%). Fluorescence transients revealed higher PSII disruption under waterlogging (evidenced by positive K-band) than drought. Silicon application suppressed K-band formation and restored PSII efficiency. Overall, Si alleviated drought- and waterlogging-induced stress, accelerated recovery, and enhanced photosynthetic performance in buckwheat. These findings indicate that Si supplementation could serve as a valuable approach for strengthening plant resilience in environments prone to extreme moisture fluctuations. • Silicon improves plants gas exchange, water balance, and photosynthetic efficiency. • Silicon protects photosystem II function and enhances chlorophyll fluorescence. • Silicon supplementation boosts drought and waterlogging stress tolerance in plants. • Silicon-treated plants show faster post-stress recovery and improved growth.