AMINO ACID AND AMIDE METABOLISM IN THE HULLS AND SEEDS OF DEVELOPING FRUITS OF GARDEN PEA, PISUM SATIVUM L. IV. ALANINE.

Pea plants (Pisum sativum L. cv. Melbourne Market), each with a single developing pod, were pulse-fed [[sup14]C]alanine supplied through the cut stem. The stages of pod development chosen were from 14 to 21 d after full blossom when alanine is one of the principal nitrogenous solutes secreted by the seedcoats into the embryo sac. In addition, [[sup14]C]alanine was supplied to a detached 14 d old pod via the base of the cut peduncle. After 24 h, the peduncles, hulls, seed Components, and where appropriate, parts of the subtending leaf, were separated and frozen for later analysis. The distribution of label in soluble metabolites was determined by paper chromatography and radioautography. Of the total label in metabolites secreted into the embryo sac, only about 4% remained associated with alanine (14 d stage); when [[sup14]C]alanine was fed via the stem, most of this label was in sucrose (60%) and glutamine (27%), but when [[sup14]C]alanine was fed via the peduncle, most of the label entering the embryo sac was in glutamine. The results confirm that most of the alanine secreted into the embryo sac is synthesized in the seedcoats de novo from other solutes, notably asparagine. [ABSTRACT FROM AUTHOR]