TIMING OF KERNEL DEVELOPMENT IN WATER-STRESSED MAIZE - WATER POTENTIALS AND ABSCISIC-ACID CONCENTRATIONS

Maize (Zea mays L. cv. Pioneer 3925) subjected to post-anthesis water stress during the first 2 weeks of kernel development had lower leaf-water potentials and higher leaf-ABA concentrations than well-watered controls. There was a concomitant rise in ABA concentration in kernel tissues 3 and 7 d after pollination (DAP), after which the concentration decreased to control levels by 13 DAP. Kernel water potential, however, remained unchanged by the water stress. Radiolabelled ABA, fed to a leaf, was translocated to kernels, where free ABA as well as several ABA metabolites were the major labelled fractions. This suggested that the stress-induced kernel ABA was of maternal origin. Since ABA plays a putative role in seed maturation of several crop species, and applied ABA or water stress often hastens seed development, we expected that a water-stress-induced rise in kernel ABA concentration early in grain development may serve to prematurely induce storage-product accumulation. Zein, starch and several enzymes key to the starch synthesis pathway followed the same course of induction throughout the experiment, with no difference between treatments Hence it was concluded that although water stress increased kernel ABA independent of kernel water status, there was no apparent effect of water stress or ABA on timing of early kernel developmental processes. © 1990 Annals of Botany Company.