Changes in Composition during Development and Maturation of Maize Seeds

Abstract

The changes of weight and various chemical constituents, Nfractions, RNA, DNA, fat, soluble sugar, and nucleotides, were determined over a 46-day period after pollination in the endosperm and embryo of developing corn grains. The development of the endosperm was considered in 2 phases. The initial phase, lasting for the first 28 days from pollination, was characterized by an accumulation of soluble constituents (soluble N, amino acids, sugars, and nucleotides) and by the synthesis of protein, RNA, and DNA. During the 2nd phase, from 28 to 46 days, there was a utilization of the soluble constituents, with further increases in protein content. Although DNA content stayed constant, the RNA content decreased and was accompanied by an increase in ribonuclease activity. Further changes occurred during the final maturation of the grain that included an increase in protein and decreases in the nucleic acids and soluble constituents. The embryo developed in a linear manner during the 46 days, and at this stage the development of the embryo was essentially complete. The pattern of endosperm development and the stability of ribonuclease accounted for the high ratio of ribonuclease to RNA observed in this organ during the germination of the mature grain.