The role of ABA in the induction of freezing tolerance was investigated in two wheat (T. aestivum L.) cultivars, Glenlea (spring var) and Fredrick (winter var). Exogenous application of ABA (5×10-5 M for 5 days at 24°C) increased the freezing tolerance of intact plants by only 3°C (LT50) in both cultivars. Maximal freezing tolerance (LT50 of -9°C for Glenlea and -17°C for Fredrick) could only be obtained with a low temperature treatment (6/2°C; day/night) for 40 days. These results show that exogenously applied ABA cannot substitute for low temperature requirementto induce freezing tolerance in intact wheat plants. Furthermore, there was no increase in the endogenous ABA level of wheat plants during low temperature acclimation, suggesting the absence of an essential role for ABA in the development of freezing tolerance in intact plants. On the other hand, ABA application (5×10-5 M for 5 days at 24°C) to embryogenic wheat calli resulted in an increase of freezing tolerance similar to that achieved by low temperature. However, as in intact plants, there was no increase in the endogenous ABA level during low temperature acclimation of calli. These results indicate that the induction of freezing tolerance by low temperature is not associated with an increase in ABA content. Using an antibody specific to a protein family associated with the development of freezing tolerance, we demonstrated that the induction of freezing tolerance by ABA in embryogenic wheat calli was correlated with the accumulation of a new 32 kDa protein. This protein is specifically induced by ABA but shares a common antigenicity with those induced by low temperature. These results suggest that ABA induces freezing tolerance in wheat calli via a regulatory mechanism different from that of low temperature.
|Number of pages||9|
|Journal||Plant and Cell Physiology|
|Publication status||Published - 1 Dec 1994|