The role of HvSnRK2.7 and HvSnRK2.9 in stomatal regulation of barley

Abstract

This thesis investigated the role of barley SnRK2 kinases HvSnRK2.7 and HvSnRK2.9 in stomatal regulation using two double mutant lines, L15 and L20, and the wild type cultivar Golden Promise. Gas exchange measurements with Licor-6800 showed that mutant plants had higher stomatal conductance and slower stomatal closure in response to reduced relative air humidity compared with wild type plants. Mutants also maintained more stable net CO₂ assimilation under low humidity conditions. No significant differences in stomatal density were detected, indicating that the altered stomatal regulation was caused by changes in stomatal aperture rather than stomatal development. Increased stomatal conductance was also observed in awns and leaf sheaths, suggesting that HvSnRK2.7 and HvSnRK2.9 regulate gas exchange in multiple above-ground organs. Overall, the results demonstrate an important role for these SnRK2 kinases in barley stomatal regulation and responses to atmospheric humidity. Higher stomatal conductance and associated rise in photosynthesis may result in yield gains in well-watered conditions.