Hormone Contents in Kernels at Different Positions on an Ear and Their Relationship with Endosperm Development and Kernel Filling in Maize

Abstract

Kernels at the upper position of a maize ear usually show poorer filling and lower weight in contrast to those at the basal position. The mechanism has not been understood. The experiments were conducted using a maize cultivar Denghai 11, grown in both field and greenhouse conditions, to determine number of endosperm cells, kernel filling rate, and contents of zeatin (Z) + zeatin riboside (ZR), indole-3-acetic acid (IAA), abscisic acid (ABA), and gibberellin-3 (GA3) in the kernels at different positions on an ear from silking to maturity. The results indicated that the maximum number of endosperm cells, maximum division rate of endosperm cells, mean endosperm cell division rate, maximum kernel filling rate, mean kernel filling rate and 100-kernel weight for kernels showed an order of basal position > middle position> upper position. During the active endosperm development and the active kernel filling period, contents of Z+ZR, IAA, and ABA in kernels were the greatest at the basal position, the mediate at the middle position, and the least at the upper position on an ear. The two experiments exhibited similar results. The endosperm cell division rate and kernel filling rate were very significantly and positively correlated with contents of Z+ZR, IAA, and ABA in kernels, whereas significantly and negatively correlated with content of GA3. The results suggested that a lower kernel weight at the upper position on a maize ear is mainly due to a smaller division rate of endosperm cells, leading to less number of endosperm cells, which is closely associated with lower contents of Z+ZR, IAA, and ABA, as well as higher content of GA3 in the kernels during kernel filling.