Increased tolerance of sunflower mutant seedlings to Cd and Zn in hydroponic culture

Plants, animals and humans require adequate amounts of micro-nutrients, but their excessive accumulation, or uptake of non-essential metals can be extremely harmful. Plants with enhanced tolerance to trace elements, such as cadmium and zinc, can be obtained by chemical mutagenesis, in vitro breeding or by genetic engineering. The effects of Cd and Zn on plant growth, chlorophyll content, production of carotenoids and metal accumulation in Sunflower seedlings were investigated in the 5(th) generation of sunflower mutant lines with improved metal extraction traits in hydroponic medium supplemented with 5 mu M Cd and 50 mu M Zn. Root elongation test indicated an increased tolerance of some sunflower mutant lines. Three from six mutant lines with improved growth on the control medium and on the medium with Cd and Zn showed a higher tolerance index than sunflower inbred line. In four sunflower mutant lines a minor effect of cadmium on chlorophyll content was determined. Sunflower mutant lines grown on medium with Cd and Zn showed a similar or an increased carotenoid concentration, as compared to control medium. An enhanced carotenoid content after metal exposure revealed a possible protective mechanism of this mutant line against oxidative stress caused by Cd and excess Zn concentration. Metal concentration in some Sunflower Mutants was higher in both roots and shoots, in others only in roots, as compared to sunflower inbred line.