A phosphatase as a potential indicator of the phosphorus status of the glasshouse cucumber (Cucumis sativus)

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Abstract
Phosphoenolpyruvate, which is the substrate for the enzyme for the enzyme pyruvate kinase, is also hydrolysed by a phosphatase when the former enzyme is assayed in unpurified extracts from plant tissues. The activity of this phosphatase has been examined in extracts of cucumber leaves from plants receiving a wide range of N, P, K and Mg treatments. When assayed in the presence of added MgSO4, the phosphatase activity was highly correlated with the P content in the leaves and was not affected by the variation in the N, K or Mg content in the leaves. While the pyruvate kinase activity in extracts of cucumber leaves can be used to indicate the K or Mg status of the plants, the associated phosphatase activity gives an indication of the P status. These enzyme assays which can be completed within 2 h, could offer a rapid means of assessment of the K, Mg and P status of cucumber plants.