The role of carbohydrates in the responses of chilling-sensitive plants to short- and long-term low-temperature treatments.

The content of particular components of water-soluble carbohydrates and cold tolerance of cucumber ( Cucumis sativus L.) cotyledonary leaves were studied at early developmental stages in dynamics during 6-day-long treatment with a temperature reduced to 12°C at two regimes: short-term cooling (2 h in the end of the night period, DROP) or permanent low-temperature treatment (PLT). PLT cucumber plants were characterized by the accumulation of oligosaccharides, whereas DROP plants contained increased amounts of glucose, fructose, and raffinose, indicating their higher metabolic status. When changes in carbohydrate fractions were compared with the dynamics of cold tolerance, it was found that these changes were synchronous in PLT plants but asynchronous for glucose and oligosaccharides in DROP plants. We suppose that, in cotyledonary leaves of DROP plants, two pools of sugars are produced; one of them used for tolerance development and another one — in active metabolism. This provides for the combination of activated metabolism and high cold tolerance of these plants. In PLT plants, all components of water-soluble carbohydrates are involved in cold tolerance development. [ABSTRACT FROM AUTHOR]