THE REGULATION OF NITROGEN LOSS FROM MAIZE ENDOSPERM

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Abstract
Maize embryos were grown on agar until the roots were 2–3 cm long, and then were transferred to a nutrient salt solution. The loss of nitrogen from the endosperm was apparent 12 hours after the transfer. When a synthetic mixture of 15 L-amino acids, known to be released by the endosperm, was also included in the medium, the loss of total and alcohol-insoluble nitrogen was delayed for approximately 40 hours. With the omission of leucine, valine, isoleucine, or arginine from the amino acid mixture, this inhibition was still observed. However, when the three branch-chain amino acids were omitted together, or when proline was left out, loss of nitrogen from the endosperm was similar to that observed in the basal medium. These additions and omissions did not significantly affect the loss of dry matter from the endosperm, or the gain in dry matter and alcohol-insoluble nitrogen of the embryo. These results suggest that the degradation of storage protein in the endosperm is a process regulated by the demands of the embryo for amino acids.