Effect of zinc sulfate stress and its interaction with ascorbic acid on some physiological parameters in Brassica napus

In this investigation, the effect of zinc excess and its interaction with ascorbic acid on some growth parameters (root and shoot, fresh and dry weight, leaf blade area and length of root and stem), proline content, soluble sugars and starch plant were studied on canola. Experimental plants were treated with different concentrations of zinc sulfate ie. 0.7 (control), 50, 100, 250, 500 and 700 mM) and one set with the same zinc concentrations (except control) mixed with 1M of ascorbic acid in Hougland nutrient solution for two weeks. Results indicated that any increase in zinc content leads to considerable decrease in starch level, leaf blade area, stem and root length, but proline and soluble sugars increased significantly in shoot and roots of rape seed. In higher concentrations of zinc sulfate in the presence of 1M ascorbic acid, the above-mentioned effects of zinc sulfate excess on growth parameters were considerably blocked. In the presence of 700 mM of zinc sulfate, chlorosis and necrosis were occurred on the leaves of rape seed, but at the copresence of 1 mM of ascorbic acid, mentioned symptoms was disappeared. It means that at the presence of ascorbic acid the plant could tolerate the toxicity of zinc sulfate excess. In the other word, ascorbic acid could considerably reduce the toxicity of high concentrations of zinc and induce poison durability.