RATE AND DURATION OF KERNEL GROWTH IN THE DETERMINATION OF MAIZE ( Zea mays L.) KERNEL SIZE

Abstract

At intervals during grain filling, measurements were made of the dry weight of the endosperm, embryo, and pericarp of several inbreds of maize differing in kernel size, and their reciprocal crosses. Differences were observed among genotypes in the growth characteristics of endosperm, embryo and pericarp, i.e., in initial dry weight, length of the lag period, rate and duration of growth and maximum dry weight at physiological maturity. The variability in the latter was mostly a function of rate of growth. For both embryo and endosperm growth, length of the lag period was positively associated with rate of growth while no relationship appeared to exist with duration of growth. An artificially imposed delay of 4 days in date of pollination for the hybrid UN 106 resulted in a less-than-proportional shortening of lag period in basal kernels of treated plants, as compared with control, as well as a lower maximum dry weight (DW). Endosperm, embryo, and pericarp size at physiological maturity, as well as their growth rates, were closely correlated with pericarp DW at 12 days after pollination. Therefore, early pericarp size may represent a determining factor in controlling the subsequent growth of all kernel components, irrespective of their specific genomic and allelic constitution. Possibly because of this pericarp role, a close coordination was evident in the growth and maturation of embryo and endosperm.