Abstract

Calcium deficiency caused an increase in alkaline phosphatase activity in cucumber roots [Matsumoto and Yamaya (1981) Plant & Cell Physiol. 22: 1137]. The activities of other hydrolases including acid phosphatase, nucleases and proteases, however, were much less affected by the removal of calcium. Nucleoside di- and triphosphates and inorganic pyrophosphate were effectively hydrolyzed by the induced alkaline phosphatase, whereas nucleoside monophosphate-hydrolyzing activity was basically equal in the roots grown with either complete medium or a medium lacking calcium. The alkaline phosphatase in cucumber roots was found in fractions pelleting at 3,000 × g and in the 100,000 × g supernatant. The calcium-starved roots increased their alkaline phosphatase activity in both fractions. Four isozyme bands of the alkaline phosphatase in the soluble fraction were separated by polyacrylamide gel electrophoresis. One of the isozyme bands showed a prominent increase with the calcium deficiency, but not in the presence of cycloheximide.

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