PHYSIOLOGIA PLANTARUM 93' 551-557 1995 Copynghi © Physichgm Planiarum !995 „ . , . , . , „ . , , ISSN OO3l-93t7 Pnntea w Denmark - all righl.i reserved Chlorophyll fluorescence and photoacoustic characteristics in relationship to changes in chlorophyll and Ca^ content of a Cu-tolerant SUene comjmcta ecotype under Cu treatment Georgia Ouzounidou, Michael Moustakas and Robert Lannoye Ouzounidou, G., Moustakas, M. and Lannoye, R. 1995. Chlorophyll fluorescence and photoacoustic characteristics in relationship to changes in chlorophyll and Ca-* content of a Cu-tolerant Silene compacta ecotype under Cu treatment. - Physiol. Plant. 93: 551-557. The effect of Cu toxicity on photosynthetic function, chlorophyll and Ca-* content of Cu-tolerant Silene compacta plants grown in nutrient solution was studied. Since, in plants grown under 8 ^M Cu, the chlorophyll and Ca-* 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 5. compacta to 8 (JLM 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 fiM Cu resulted in a marked increase of the fraction of closed PSII centres and decreased quantum yield of PSII electron transport ("trei,) which was accompanied by a significant decline of relative quantum yield for O; evolution (A,,,/Ap,). Tbe concentration of chlorophyll and Ca-* in leaves also decreased sig- nificantly under 160 ^LM CU treatment. Photochemical quenching (qp) displayed a reduction as a result of perturbation of the photosynthetic electron transfer chain, while non-photochemical quenching (q^) increased. High Cu treatment reduced photosyn- thetic productivity of 5. compacta plants which can be attributed, in part, to pertuhation of photosynihetic process and photosynthetic pigments as well as to Ca-* loss. Key words - Calcium concentration, chlorophyll content, chlorophyll fluorescence, copper toxicity, O; evolution, photochemical quenching, Siiene compacta, thermal emission. G. Ouzounidou (corresponding author} and M. Moustakas, Dept of Botany, Aristotle Univ. of Thessaloniki, G-54006 Thessaloniki, Greece: R. Lannoye, Laboratoire de Physiologie Vegetale, Univ. Libre de Bruxelles, B-1050 Bruxelles, Belgium. J , , al. 1978, Sandmann and Boger 1980, Baszynski et al. For plants there exist optimum conditions for growth and Ouzounidou et al. 1993). The evolution of Cu tolerance in development as well as for individual metabolic path- populations associated with metalliferous soils is a well- ways such as the process of photosynthesis. Many envi- documented phenomenon (Ernst 1974). Silene compacta ronmental and endogenous factors can influence these is one of the pioneer species of metalliferous soils in optimum conditions for plant growth and cell metabolism Greece (Ouzounidou et al, 1993). (Lichtetithaler 1988). Essential heavy metals, as copper. The fluorescence yield of chlorophyll c is dependent interfere with numerous physiological processes and can on the micro-environment in the thylakoid, and is used as be toxic to plants even at low concentrations (Jensen and an indicator of structural or organizational changes of the Adalsteinsson 1989, De Vos et al. 1992, Lanaras et al. chloroplast membranes and of the physiological and bio- 1993). Inhibition of photosynthesis by Cu has been chemical bases for changes in the ability of leaves to studied in higher plants, algae and cyanobacteria (Shioi et assimilate CO, (Walker and Osmond 1986, Lidon et al. Received 13 July, 1994; revised 10 October, 1994 Physiot Planl. 93. 1995 551