Nutritive Role of the Seedcoats during Embryo Development in Pisum sativum L

Structural and metabolic features of the seedcoats of the developing pea seed indicate that events in the cells of the seedcoats are of major importance in controlling the development of the embryo. Information has been obtained on the distribution of N and P constituents of the seedcoats, embryo sac liquid, and the cotyledons of the embryo, in relation to the changes in the activities of several enzymes: aminopeptidases, beta-glucosidase, and acid phosphatase. The liquid contents of the embryo sac are considered to arise as a secretion from the tegmen. High concentrations of amino acids (about 0.3 molar), NH(4) (+) (about 0.1 molar), and orthophosphate (Pi) (up to 4 millimolar) were measured in this fluid. Since Pi was the only form of P present, the data confirm the possible function of some of the seedcoat acid phosphatase activity in the provision of Pi to the embryo.