Low Temperature-Induced GA3 Sensitivity of Wheat: I. Characterization of the Low Temperature Effect on Isolated Aleurone of Kite

Gibberellic acid (GA3) sensitivity (measured as α-amylase production) of the isolated aleurone tissue/deembryonated seed of two wheat (Triticum aestivum L. var Kite and var Aroona) varieties each containing either one of the dwarfing genes, Rht1 and Rht2, was increased significantly as a result of low temperature treatment. The magnitude of the low temperature-induced increase occurred without any change in the lag time of α-amylase production. This low temperature induction of GA3 sensitivity was found to be operative in aleurone tissue of only those varieties having at least one of the three Rht alleles. It is likely, therefore, that the low temperature treatment effect which 'cures' or circumvents the genetic lesions manifest in the Rht1 and Rht2 genotypes is the same as that effective in the Rht3-containing genotype and probably involves an increase in hormone (GA3) receptor sites. Furthermore, this increase appears to be a quantitative temporal one.