EARLY DEVELOPMENTS IN RNA, PROTEIN, AND SUGAR LEVELS DURING COLD STRESS IN WINTER RYE (SECALE-CEREALE) LEAVES

Changes in freezing tolerance of winter rye (Secale cereale L. cv. Voima) were determined for leaf tissues during a 1-week cold stress, which was performed by transferring the 7-d-old seedlings from a greenhouse (25-degrees-C, long day) to 3-degrees-C and short day conditions. The development of cold hardening was shown by using an ion leakage test and by determining the amounts of carbohydrates, soluble proteins and RNA. The first evidence of the development of freezing resistance was found after 1 d at low temperature, i.e. an LT50 value increased from -5 to -7-degrees-C. Plants cold treated for 7 d reached an LT50 value of -9-degrees-C. This increase in freezing tolerance was found to be associated with the increased levels of soluble carbohydrates, total RNA and soluble proteins. These metabolic changes indicate the association with adjustment of growth and cell metabolism to low temperatures at the beginning of cold acclimation of winter rye.