6. Structural and Functional Changes in the Leaves of Lactuca sativa L. and Phaseolus vulgaris L. Grown at Excess of Heavy Metals in the Root Area

Author: Anna Nikolova, Andon Vassilev


Lab experiments with Phaseolus vulgaris L. and Lactuca sativa L. have been carried out with the purpose of studying the responses of young plants to increasing levels of heavy metals (Cd, Zn, Cu) in the root area. Both leaf anatomy and photosynthetic parameters were measured. Different responses of leaf structure to excess heavy metals were detected in the studied species. In the case of lettuce plants, classical xeromorphic changes in the leaf structure have been observed, whereas common bean plants responded by having mesomorphic changes, such as increased size of the epidermal cells and increased thickness of the leaf blade. Both leaf gas exchange and chlorophyll fluorescence parameters, characteristic of the photosynthetic performance, were inhibited similarly by the applied excess heavy metals in both species.

Keywords: heavy metals, Cu, Zn, Cd, leaf structure, mesophyll, epidermis, stomata, photosynthesis.