The effect of local cooling of cucumber and wheat seedlings on various kinds of stress resistance of their leaves and roots

Shoots and roots of wheat (Triticum aestivum L., cold-resistant species) and cucumber (Cucumis sativus L., cold-sensitive species) were chilled at 2 degreesC or 10 degreesC, respectively, for 7 h. The changes in cold, heat, and salt resistance in treated leaf and root cells were recorded. Local cooling of the leaf resulted in an increase of its cold and salt tolerance, but its heat tolerance remained unchanged. At the same time, cold tolerance of the root slightly increased as a result of local cooling, but its heat and salt tolerance decreased. Cooling of the shoot did not affect the cold and heat tolerance of root cells but caused a decrease in their salt tolerance. Finally, in the leaf maintained at a normal temperature, there was an increase in all kinds of stress resistance as a result of root cooling. We discuss the possibility of an unspecific change in stress resistance caused by metabolic shifts. These shifts are induced by a signal, which is transmitted inside the plant into plant organs located at a considerable distance from the chilled ones.