The effect of zinc excess on photosyntetic pigments, soluble sugar, starch and proline in Brassica napus L.

Zinc is one of the essential micronutrients for the normal growth and development of plants. It is also known as heavy metal which at higher level causes toxicity in most of the plants. Nowadays environmental pollutions especially which caused by heavy metals result from industrial activity.Also the useage of chemical and inorganic fertilizer have non-compensated damage on the agricultural plants. Hence study of plants,</sup> tolerance to heavy metals is significant. The effect of high concentration of zinc on chlorophyll a and b, carotenoid, soluble sugars, starch and prolin in Brassica napus </em>has been studied in this survey. Plants were treated with various Zn concentration (50, 100, 250, 500, 700 µ </strong>M) in nutrient solution for two weeks. All determinations were carried out in triplicate and data were statistically analyzed by using full randomize plots, SPSS v,13, MSTAC (one-way ANOVA) and Duncan test. According to the result chlorophyll a and b significantly decreased in comparison to control by increasing Zn concentration, but content of chlorophyll b was significantly decreased in treatments of 500 and 700 µM Zn. Also carotenoid,</sup>s content significantly decreased in concentration of 500 and 700 µM Zn. Soluble sugar increased in shoots and roots by increase of Zn as well as proline, but starch level were decreased in both.