Abstract
The distribution of P1, ester P and acid-insoluble nucleic acid P has been studied in relation to acid phosphatase activity (EC 3. 1. 3. 2) in the component parts of developing pea seeds (Pisum sativum L.). Despite the favourable pH of the liquid contents of the embryo sac (pH 5.5), only very low acid phosphatase activity was detected in this fluid (c. 0.01 units per seed). Potential substrates for phosphatase action were in fact absent from the secretion, the only form of P present being Pi, in concentrations up to 8 mM. The data support the hypothesis that the high acid phosphatase activities which develop in the seed-coats are involved in regulating the supply of P as P1 to the developing embryo.

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