The Requirement for Organic Nitrogen in Zea mays Embryos

Abstract

Although excised maize embryos showed normal increases in dry matter when cultured with glucose or sucrose, the accumulation of alcohol-soluble and -insoluble N was much inferior. With excision the soluble pools of the neutral and basic amino acids were the 1st components to fall below the control values. Subsequently the increase in protein N failed. Levels of glutamic and aspartic acids and their amides were close to the control values throughout the experimental period. Leachates obtained from detached endosperm pieces were effective in restoring protein synthesis in the excised embryos. Those amino acids which were most severely affected in the detached embryo were the same ones which were most abundantly supplied by the endosperm. In addition a synthetic misture of 1-amino acids with concentrations corresponding to those of the hydrolyzed leachate completely restored the normal levels of total and protein N. These results show that a limited supply of amino acids restricts the accumulation of alcohol insoluble N during the 72 hours following the removal of the endosperm. After this period, the limitation is overcome. It is suggested that the high levels of soluble amino acids normally supplied to the developing embryo by the endosperm restrict their synthesis within the embryo.