Changes in Phosphorus Fractions and Phytase Activity of Rice Seeds during Germination

Abstract

The present experiment provides information on the phosphorus compounds in rice seeds and elucidates the changes they undergo during germination. In ungerminated seeds, the bulk of total‐P appears in phytin (about 76 per cent). It is then dephosphorylated in course of germination with a simultaneous accumulation of large amounts of inorganic‐P. Lipid‐P increases very rapidly from 0 to 24 hours. The increase up to 72 hours is gradual, after which it drops at 96 hours and again rises to a maximum after 120 hours. The ester‐P and RNA‐P, fractions increase in concentration with time of germination (except 120 hours). Protein‐P begins to fall after 48 hours, while DNA‐P remains more or less constant throughout the experiment. The two pH optima recorded for phytase activity at 4.0 and 9.0, suggests that there exist two phytases, one acidic and the other alkaline. Both behave similarly during germination with a continuous increase throughout the course of the experiment. The enzyme with an optimal pH at 4 hydrolyses phytin more actively than the other with the pH optimum at 9.0. Phytase shows maximum activity at a stage when most of the phytin has disappeared; the metabolic significance is uncertain.

Produtividade de plantas de soja provenientes de sementes tratadas com fósforo

“…Segundo, Cohen ( 1975 ), a relação entre fosfato inorgânico e fosfato orgânico reduz à medida que a planta envelhece. Segundo Mukherji et al ( 1971 ), a degradação dos fitatos, realizado por fitases, conduz à um rápido declínio no fósforo ligado ao fitato durante a germinação de sementes de arroz, diminuindo de 2,67 à 0,80 mg de fósforo / g de matéria seca em menos de 72 horas.…”

Changes in the Activity of Some Hydrolases, Peroxidase, and Catalase in the Rice Seed during Germination

“…Phytase activity was assayed by the method of Mukherji et al (15) except that incubation time was only 15 min at 30 C at pH 4.0. The amount of phosphate released was measured by the method of Galanos and Kapoulas (3).…”

“…Many hydrolases have been studied, including a-amylase (2, 19), protease (6,19), phytase (10, 15), phosphatase (24), lipase (26), and RNase (2, 19). Phytase has been shown to be located in the protein bodies of the barley aleurone layers (17).…”

“…The aleurone layer of rice (Oryza sativa L.) is a storage organ for phosphate in the form of phytin (9,15) and for lipids (12); it is richer in hemicellulose than the endosperm (4). It is devoid of starch granules in the mature grain (9).…”

“…To stop the reaction, Na,C03 was added, and the amount of p-nitrophenol released was determined colorimetrically at 420 nm. Activities were expressed in ,tmoles of p-nitrophenol formed per hour per seed.Phytase activity was assayed by the method of Mukherji et al (15) except that incubation time was only 15 min at 30 C at pH 4.0. The amount of phosphate released was measured by the method of Galanos and Kapoulas (3).…”