Chlorophyll fluorescence and photoacoustic characteristics in relationship to changes in chlorophyll and Ca²⁺ content of a Cu‐tolerant Silene compacta ecotype under Cu treatment

The effect of Cu toxicity on photosynthetic function, chlorophyll and Ca 2+ content of Cu‐tolerant Silene compacta plants grown in nutrient solution was studied. Since, in plants grown under 8 μ M Cu, the chlorophyll and Ca 2+ concentration as well as the photosystem II (PSII) photochemistry were increased, compared to the control, the development of an adaptive mechanism of the Cu‐tolerant ecotype of S. compacta to 8 μ M Cu is suggested. Increased Cu tolerance of the S. compacta ecotype reflects modulation of the photosynthetic apparatus to optimize photosynthesis. However, exposure of plants to 160 μ M Cu resulted in a marked increase of the fraction of closed PSII centres and decreased quantum yield of PSII electron transport (Φ PSU ) which was accompanied by a significant decline of relative quantum yield for O 2 evolution (A ox /A pt ). The concentration of chlorophyll and Ca 2+ in leaves also decreased significantly under 160 μ M Cu treatment. Photochemical quenching (q p ) displayed a reduction as a result of perturbation of the photosynthetic electron transfer chain, while non‐photochemical quenching (q N ) increased. High Cu treatment reduced photosynthetic productivity of S. compacta plants which can be attributed, in part, to pertubation of photosynthetic process and photosynthetic pigments as well as to Ca 2+ loss.