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

Uptake of Ca²⁺ by suspension-cultured pear (Pyrus communis L. cv Passe Crassane) cells and protoplasts was significantly enhanced by exposure to 38°C compared to 25°C. The increased uptake was specific for Ca²⁺ and was not due to cell wall binding. Tissues pretreated at 38°C showed increased uptake even upon return to 25°C. Treatment with carbonylcyanide m-chlorophenylhydrazone, salicylhydroxamic acid + KCN, or arsenite also increased Ca²⁺ content of cells. Results are discussed with regard to membrane permeability changes, the cellular control of Ca²⁺, and heat treatments used to inhibit softening of fruit during postharvest storage.