Abstract
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 (86)Rb was generally decreased by increasing concentrations of Ca(2+), but after longer periods of incubation, the inhibiting effect of high Ca(2+) levels diminished. Viability of isolated cells suspended in water declined rapidly when ice encased at -1 degrees C, while in the presence of 10 millimolar Ca(2+) viability declined only gradually over a 5-week period. Ice encasement markedly reduced (86)Rb 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 degrees C, but the presence of Ca(2+) 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 degrees C. The results from this study support the view that an early change in cellular properties due to prolonged ice encasement at -1 degrees 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.