Grape varieties respond to decrease in soil water status by stomatal closure and reduced shoot growth with simultaneous increase in root growth. Most of the water deficit responses are known to be regulated by endogenous hormonal contents like abscissic acid (ABA) and cytokinins. To determine how these endogenous hormones are related to changes in shoot and root morphology, four grape genotypes were grown in pots and subjected to different levels of soil moisture stress for 14 days. None of the genotypes could survive beyond 4 days under 100% stress conditions. There was an increased accumulation of ABA and corresponding decrease in cytokinins at 50% stress compared to control (100% irrigation). Among the genotypes tested Flame Seedless had highest ABA and lowest cytokinin levels and it also had highest root to shoot length ratio and root to shoot dry weight ratio. It is presumed that the reduction in shoot growth and stomatal conductance observed may be due to their ability to synthesize and accumulate ABA with the onset of soil moisture stress.
ABA, cytokinins, grape genotypes, root to shoot length ratio, soil moisture stress, stomatal conductance
