COPPER-INDUCED CHANGES ON GROWTH, METAL CONTENT AND PHOTOSYNTHETIC FUNCTION OF ALYSSUM-MONTANUM L PLANTS

The response of root systems of Alyssum montanum to increasing Cu levels was studied. Changes in chlorophyll and metal content and in photosynthetic function were also investigated. Low Cu concentrations in the nutrient solution did not affect root elongation, possibly due to the development of co-tolerance to Cu since the plants are tolerant to Zn and Pb. However, with higher Cu concentrations the extension of the root and the chlorophyll content declined sharply. Roots accumulated higher amounts of Cu than shoot-leaves at all Cu treatments. High Cu contents in plant tissues also negatively influenced uptake and translocation of Ca, Mg, Fe and K in roots and above-ground parts. In addition, excess Cu application was accompanied by a marked decline in the variable fluorescence and a retardation of the electron transfer in PSII, indicating an inhibitory site on the photooxidizing side of PSII. The decreased photochemistry activity of PSII suggests a decrease in the efficiency of the reduction of the primary electron acceptor and reflects damage to the donor and acceptor side of PSII. An absence of the intermediate transient at the slow part of the fluorescence induction kinetics and a dramatic decrease of the (F(P) - F(S))/F(S) ratio were also observed under Cu treatments. The photosynthetic function of A. montanum seemed to be affected more than root growth and chlorophyll content under Cu stress.