Effect of low temperature and calcium on survival and membrane properties of isolated winter wheat cells

Isolated cells obtained by enzymic digestion of young primary leaves of cold-hardened, dark-grown Kharkov winter wheat (Triticum aestivum L.) were exposed to various low temperature stresses. The initial uptake of ⁸⁶Rb was generally decreased by increasing concentrations of Ca²⁺, but after longer periods of incubation, the inhibiting effect of high Ca²⁺ levels diminished. Viability of isolated cells suspended in water declined rapidly when ice encased at −1°C, while in the presence of 10 millimolar Ca²⁺ viability declined only gradually over a 5-week period. Ice encasement markedly reduced ⁸⁶Rb uptake prior to a significant decline in cell viability or increased ion efflux. Cell damage increased progressively when the icing temperature was reduced from −1 to −2 and −3°C, but the presence of Ca²⁺ in the suspending medium reduced injury. Cell viability and ion uptake were reduced to a greater extent following slow cooling than after rapid cooling to subfreezing temperatures ranging from −10 to −30°C. The results from this study support the view that an early change in cellular properties due to prolonged ice encasement at −1°C involves the ion transport system, whereas cooling to lower subfreezing temperatures for only a few hours results in more general membrane damage, including loss of semipermeability of the plasma membrane.