Galactolipase Activity of Chloroplasts in Cadmium-treated Runner Bean Plants

Abstract

The galactolipase activity in chloroplasts of primary leaves of runner bean plants ( Phaseolus coccineus L., cv. Piękny Jaś) grown in Cd-containing nutrient solution was determined and compared with that obtained from plants developed under normal nutrient conditions. A several times higher galactolipase activity was found in Cd-treated plants in comparison with controls. A high galactolipase activity was accompanied by a decrease in all acyl lipid classes (mainly MGDG), components of thylakoid membranes and FFA release. Chloroplasts of Cd-treated plants revealed a lower photosynthetic oxygen evolution than control plants. Decrease of this activity was considerably eliminated in the presence of BSA, used in the chloroplast isolation procedure. In in vitro experiments, inhibition of galactolipase activity due to Cd concentration in the incubation mixture was found. The obtained results are discussed in terms of the indirect effect of long term action of Cd on the decrease of photochemical activity of thylakoids related to thylakoid bound galactolipase activity.