Evidence on the effect of priming-induced memory on the mechanisms underlying sugar transport and metabolism in rice plants under salinity

Priming in plants enables them to store information and better prepare for future stress. This study tested the hypothesis that priming rice plants (cv. BRS AG) improves sugar metabolism and transport in the grain-filling stage through memory effects. We investigated physiological changes, including source–sink parameters, carbohydrate metabolism, gene expression, and vascular adjustments. Rice plants were exposed to 150 mM salt stress during either the V5 vegetative and/or R7–R8 reproductive stages, with samples collected after 7 days of stress and after 2 days of recovery. Our findings reveal that primed plants had a more favorable Na⁺/K⁺ ratio in roots, experienced less leaf stress, and showed increased phloem area and reduced metaxylem area under salt stress. Notably, primed plants maintained stable plant height and shoot dry mass during the grain-filling stage. These results support the hypothesis that salt priming in the vegetative stage alters the responses to subsequent salt exposure, improving ionic homeostasis and sucrose transport, which mitigates salt-stress effects. Priming also influenced the expansion of conducting vessels in leaves and roots, contributing to shoot growth. Enhanced vascular characteristics and the regulation of sucrose and triose-phosphate transporters likely facilitated better carbohydrate remobilization to develop grain production potential. These insights into salt stress memory mechanisms highlight strategies to improve rice yield under challenging environmental conditions.