The role of Ca ions in changes induced by excess Cu2+ in bean plants. Growth parameters

The effect of Ca on Cu toxicity in runner bean plants (Phaseolus coccineus L. cv. Piekny Jas) grown hydroponically in nutrient solution was studied. T he toxic effect of excess Cu on plants depends on their age and Ca content in the medium. Copper applied in excess to the plants at the early phase of leaf development strongly limits the uptake of Ca ions from the nutrient s olution, particularly their translocation to leaves. Increased Ca content l imits the inhibitory effect of Cu on leaf growth and decreases the content of chloroplast pigments to the level approximate to that of control. At thi s growth stage the effect of excess Cu is at least partially connected with limited Ca transport to leaves. At the intermediate leaf phase Cu-treated plants react slightly to changed Ca content. At the end of the primary leaf development increased Ca concentration in th e medium intensifies senescence processes induced by excess Cu. The changes are partially connected with intensified water deficit. Increased Ca conte nt in the nutrient solution limits Cu accumulation in the individual organs of Cu-treated plants. However, Cu accumulation in leaves is not decreased at a high level of Ca. Copper generally decreases Ca content in the younges t plants, whereas in the oldest ones only in the case of a low level of Ca in the nutrient solution.