Seed development in Ricinus communis cv. Hale (castor bean). II. Accumulation of phytic acid in the developing endosperm and embryo in relation to the deposition of lipid, protein, and phosphorus

Abstract

The accumulation of phytic acid in the developing endosperm and embryo of the castor bean seed (Ricinus communis L. cv. Hale) has been followed in relation to the deposition of the major lipid and protein reserves. In the endosperm, there is a considerable degree of synchronization in the synthesis and deposition of these reserves, although phytic acid accumulation lags behind that of total protein and lipid. The pattern of reserve deposition within the embryo is documented for the first time. Lipid accumulation commences later than in the endosperm, and the major deposition of phytic acid is also later; protein deposition continues longer in the embryo than in the endosperm. Changes in various phosphorus-containing fractions were followed in both the embryo and endosperm during development, viz total, acid-soluble, inorganic, and lipid phosphorus. While sugar and nucleoside phosphates, and then nucleic acid and protein phosphorus, are predominant in the total phosphorus pool earlier in endosperm development, later there is a large increase in the total pool size, which is attributable particularly to phytic acid formation. This component accounts for over 90% of the total phosphorus content of the mature dry endosperm. A similar pattern of events occurs in the developing embryo.