Copper Stress on Photosynthesis of Black Mangle (Avicennia germinans)

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 fluorescence 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 fluorescence 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 in photosynthetic gas exchange and Chlorophyll fluorescence parameters in A. germinans leaves.

Avicennia germinans ; chlorophyll fluorescence; copper; photosystem II; photosynthesis