Changes in phytic acid and phytase during early development of Phaseolus vulgaris L

Changes in phytic acid, phytase, and inorganic phosphate were examined in the cotyledon of Phaseolus vulgaris L cv. Taylor's Horticultural during embryogeny and germination. Embryogeny normally requires 36 days in this cultivar. Phytic acid is accumulated most rapidly between days 24 and 30. Coincident with this increase, relatively high values of inorganic phosphate were observed in the cotyledon. The inorganic phosphate in the developing cotyledon does not decrease until dehydration phase. This decrease cannot be entirely accounted for by the residual synthesis of phytic acid during this time. These data, along with data from the literature, suggest that close coordination exists between the biochemical systems responsible for the deposition of storage reserves in the cotyledon. Phytase activity remained undetectable during embryogeny. However, a rapid rise in phytase activity was observed commencing after day 2 of germination. The increased activity of phytase was well correlated with the disappearance of its substrate, phytic acid, from the cotyledon. Phosphate levels remained much lower than those observed during embryogeny.