Effect of high temperature on calcium uptake by suspension-cultured pear fruit cells

Uptake of Ca(2+) by suspension-cultured pear (Pyrus communis L. cv Passe Crassane) cells and protoplasts was significantly enhanced by exposure to 38 degrees C compared to 25 degrees C. The increased uptake was specific for Ca(2+) and was not due to cell wall binding. Tissues pretreated at 38 degrees C showed increased uptake even upon return to 25 degrees C. Treatment with carbonylcyanide m-chlorophenylhydrazone, salicylhydroxamic acid + KCN, or arsenite also increased Ca(2+) content of cells. Results are discussed with regard to membrane permeability changes, the cellular control of Ca(2+), and heat treatments used to inhibit softening of fruit during postharvest storage.