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 leve ls was studied. Changes in chlorophyll and metal content and in photos ynthetic 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 r oot and the chlorophyll content declined sharply. Roots accumulated hi gher amounts of Cu than shoot-leaves at all Cu treatments. High Cu con tents in plant tissues also negatively influenced uptake and transloca tion 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 vari able 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 e fficiency of the reduction of the primary electron acceptor and reflec ts damage to the donor and acceptor side of PSII. An absence of the in termediate transient at the slow part of the fluorescence induction ki netics and a dramatic decrease of the (F(P) - F(S))/F(S) ratio were al so observed under Cu treatments. The photosynthetic function of A. mon tanum seemed to be affected more than root growth and chlorophyll cont ent under Cu stress.