Genotypic variation in tolerance to drought stress is highly coordinated with hydraulic conductivity-photosynthesis interplay and aquaporin expression in field-grown mulberry (Morus spp.)

Hydraulic conductivity quantifies the efficiency of a plant to transport water from root to shoot and is a major constriction on leaf gas exchange physiology. Mulberry (Morus spp.) is the most economically important crop for sericulture industry. In this study, we demonstrate a finely coordinated control of hydraulic dynamics on leaf gas exchange characteristics in 1-year-old field-grown mulberry genotypes (Selection-13 (S13); Kollegal Local (KL) and Kanva-2 (K2)) subjected to water stress by withholding water for 20 days and subsequent recovery for 7 days. Significant variations among three mulberry genotypes have been recorded in net photosynthetic rates (Pn), stomatal conductance and sap flow rate, as well as hydraulic conductivity in stem (KS) and leaf (KL). Among three genotypes, S13 showed significantly high rates of Pn, KS and KL both in control as well as during drought stress (DS) and recovery, providing evidence for superior drought-adaptive strategies. The plant water hydraulics-photosynthesis interplay was finely coordinated with the expression of certain key aquaporins (AQPs) in roots and leaves. Our data clearly demonstrate that expression of certain AQPs play a crucial role in hydraulic dynamics and photosynthetic carbon assimilation during DS and recovery, which could be effectively targeted towards mulberry improvement programs for drought adaptation.