Abstract

In this paper we tested the hypothesis that the leaf growth reduction of salt-stressed maize is regulated by the abscisic acid (ABA) concentrations in the growing zone of the leaf. Leaf elongation rate (LER) of maize (Zea mays L.) was rapidly inhibited by salinity (80 mM NaCl), and the (+)-ABA concentration increased significantly in the growing zone of the leaf. Upon removal of salinity, ABA concentrations decreased rapidly in the growing zone and LER increased to control levels. Four maize genotypes differing in their responses to salinity were compared over a range of leaf ABA concentrations. (+)-ABA concentrations in the growing zone of the leaf were highly correlated with LER inhibition for all four genotypes. However, the sensitivity of LER to leaf ABA concentrations differed amongst the genotypes. Thus, for each genotype, ABA concentrations in the growing zone of the leaf were a good predictor of maize LER response to salinity.