Soil Ni treatment of the plants Hyptis suaveolens (L.) Poit. and Helianthm annuus L. resulted in an increase in Ni content of the leaves causing a disruption in their metabolism. The concentration of soluble nitrogen and protein decreased, whereas reducing sugar and starch contents were markedly higher than the control in both the plants. Catalase activity decreased while peroxidase and polyphenol oxidase activity increased. In sunflower reduction in catalase activity was 5 times and the increase iri peroxidase and polyphenol oxidase was 4 and 8 folds respectively. Decrease in P content was correlated with increase in the activity of acid phosphatase and ATPase.
