Metabolic changes in citrullus subjected to zinc stress

Under sand culture conditions, Citrullus vulgaris Schrad. var. fistulosus showed optimal growth at 0.13 ppm zinc supply. Zinc deficiency caused a marked accumulation of reducing sugars and a decrease in non‐reducing sugars. Plants subjected to zinc deficiency also showed an accumulation of non‐protein nitrogen and a decrease in protein nitrogen and nucleic acids. Zinc deficiency resulted in an accumulation of inorganic phosphorus and decrease in organic phosphorus ‐ both acid soluble and insoluble fractions. In plants subjected to zinc stress, activity of carbonic anhydrase was markedly reduced and the activities of acid phosphatase and ribonuclease were significantly stimulated. The changes in the nucleic acids, phosphorus fractions and enzyme activities were largely reversed when zinc stress was overcome by supplying adequate (0.65 ppm) zinc to zinc deficient plants.