EFFECT OF WASHING ON THE PLASMA-MEMBRANE AND ON STRESS REACTIONS OF CULTURED ROSE CELLS

Cultured cells of Rosa damascena have been used as a model for studies of responses of plant cells to various stresses, including UV radiati on, protein-synthesis inhibitors, and elicitors from pathogens. Many o f the responses involve reactions at the plasma membrane: efflux of K, changes in the acid balance between cytoplasm and external medium, s ynthesis of H2O2, and inhibition of ferricyanide reduction. In previou s studies, the cells have typically been washed with a solution of low ionic strength. We now show that this washing procedure results in ch anges in the protein composition of the plasma membrane, in the labeli ng of the proteins in the plasma membrane, and in the specific activit y of ATPase in purified plasma membrane vesicles. Also, compared to th e unwashed cells, the washed cells show less net K+ efflux after UV-C and Phytophthora elicitor treatments; more synthesis of H2O2 after UV- C and a pattern of accumulation of H2O2 after elicitor treatment that shows a delayed but higher peak; and more inhibition of ferricyanide r eduction after UV-C, but not after elicitor treatment. The results sug gest that washing has differential effects on the mechanisms by which cultured plant cells perceive or respond to two stresses, UV-C and eli citor.