Cadmium effect on the chlorophyll fluorescence, chlorophyll pigments and proline contents of Celtis caucasica and Robinia pseudoacacia seedlings leaves

Heavy metals such as cadmium generating by urban activities, industrial and agricultural create abiotic stress in the plants which is one of the most important stress affecting physiological activities of plants. In this study, the effects of Cd was investigated on chlorophyll fluorescence (Fv/Fm, Fo, and Fm), photosynthetic pigments (a and b), and proline in one-year-old seedlings of Celtis caucasica and Robinia pseudoacacia. Saline solution containing Cd was sprayed on the leaves. The seedlings were treated during ten days, two times, with different concentrations of Cd (0 (control), 250, 500, 1000 and 2000 mg/L). Chlorophyll fluorescence was measured every other day during ten days. Chlorophyll and proline contents were measured ten days after Cd treatments. The results indicated that chlorophyll fluorescence of C. caucasica and R. pseudoacaci were affected slightly by high concentrations (1000 and 2000 mg/L) of Cd, so that Fv/Fm in both species decreased. The chlorophyll a of Robinia at 1000 and 2000 mg/L of Cd increased and in Celtis showed no significant difference in all treatments of Cd. The chlorophyll b showed no significant difference in all treatments of cadmium in C. caucasica and R. pseudoacaci. Proline content in the C. caucasica increased at 250, 500, 1000 and 2000 mg/L of Cd. C. caucasica and R. pseudoacaci were affected slightly by Cd. Photosystem II, chlorophyll pigments didn’t damage by Cd stress. Other physiological characteristics should be considered in future studies in order to selecting of tree species for afforestation projects in urban polluted areas.