Copper Stress on Photosynthesis of Black Mangle (Avicennia germinans Copper Stress on Photosynthesis of Black Mangle (Avicennia germinans Copper Stress on Photosynthesis of Black Mangle ( )

The effects of copper toxicity on the photosynthetic activities of Avicennia germinans was investigated using two CuSO4 concentrations (0.062 and 0.33 M) added in Hoagland's solution in an aerated hydroponic system. Photosynthesis and chlorophyll fl uorescence were measured after 30 h of copper stress. Results obtained in this study show that increasing levels of Cu +2 of 0.062 and 0.33 M Cu +2 resulted in a general reduction of the stomatal conductance (28 and 18%, respectively) and 100% of inhibition of net photosynthesis. Additionally, at these concentrations of Cu +2 , reductions of chlorophyll fl uorescence parameters were also observed. These changes suggested that the photosynthetic apparatus of Avicennia germinans was the primary target of the Cu +2 action. It is concluded that Cu +2 ions causes a drastic decline