Changes in growth, pigment content and antioxidants in the root and leaf tissues of wheat plants under the influence of exogenous salicylic acid

the effect of various concentrations of salicylic acid (sa) on the growth, pigment content and the activity of antioxidants was investigated in the laboratory grown wheat plants. the root and shoot growth was affected at higher concentration of sa in early days of growth. the activities of catalase (cat), ascorbate peroxidase (apx) and guaicol-specific peroxidase (pox) declined with the application of sa (50, 500 and 1000 μm), the decrease being more pronounced with the increase in sa concentrations both in the root and leaf tissues. on the other hand superoxide dismutase (sod) activity increased with the application of sa. at low concentrations, sa has no effect on the activities of these enzymes in vitro. salicylic acid at higher concentrations (5- and 10 mm) though inhibited cat activity, the activities of apx and pox remain unchanged. high concentration of sa increased the level of h2o2 and malondialdehyde both in root and leaf tissues. thus, sa though has been reported to be a signal molecule for inducing various physiological and morphological attributes in plants, this study indicated the negative effect of the compound on growth and the activity of major enzymatic antioxidants.