CHLOROPHYLL FLUORESCENCE AND PHOTOACOUSTIC CHARACTERISTICS IN RELATIONSHIP TO CHANGES IN CHLOROPHYLL AND CA2-TOLERANT SILENE COMPACTA ECOTYPE UNDER CU TREATMENT( CONTENT OF A CU)

The effect of Cu toxicity on photosynthetic function, chlorophyll and Ca2+ content of Cu-tolerant Silene compacta plants grown in nutrient s olution was studied. Since, in plants Brown under 8 mu M Cu, the chlor ophyll and Ca2+ concentration as well as the photosystem II (PSII) pho tochemistry were increased, compared to the control, the development o f an adaptive mechanism of the Cu-tolerant ecotype of S. compacta to 8 mu M Cu is suggested. Increased Cu tolerance of the S. compacta ecoty pe reflects modulation of the photosynthetic apparatus to optimize pho tosynthesis. However, exposure of plants to 160 mu M Cu resulted in a marked increase of the fraction of closed PSII centres and decreased q uantum yield of PSII electron transport (Phi(PSII)) which was accompan ied by a significant decline of relative quantum yield for O-2 evoluti on (A(ox)/A(pt)). The concentration of chlorophyll and Ca2+ in leaves also decreased significantly under 160 mu M Cu treatment. Photochemica l quenching (q(p)) displayed a reduction as a result of perturbation o f the photosynthetic electron transfer chain, while non-photochemical quenching (q(N)) increased. High Cu treatment reduced photosynthetic p roductivity of S. compacta plants which can be attributed, in part, to pertubation of photosynthetic process and photosynthetic pigments as well as to Ca2+ loss.