GA₃ and Proline Promote Germination of Wheat Seeds by Stimulating α-Amylase at Unfavorable Temperatures

Abstract

The effects of various constant temperatures(4, 9, 14, 19, 24, 29, 34, and 38°C)on the germination of winter wheat seed(Triticum aestivum L.cv.'Koyuki')in a dark condition were studied. The maximum germinatin percentage was 98% at 24°C. The speed of germination was fastest at 29°C. These results indicate that the most suitable temperature for germination was in the range of 24 to 29°C. α-Amylase expression during germination was also high at higher temperature, and maximum expression occurred at 29°C, although a high temperature of 38°C prevented the synthesis of α-amylase. The close correlation between germination and α-amylase activity at various temperatures indicates that α-amylase is an essential factor for the temperature-dependent germination of wheat seed. In contrast, accumulation of proline increased at a lower temperature, and was the highest at 4°C. We also studied the effects of gibberellin(GA₃) and proline, a compatible osmotica in alleviating the effect of low and high temperature stresses. Pre-soaking treatment with GA₃ and proline was effective in promoting germination and increasing α-amylase expression at a low(4°C)and high(38°C)temperature. These results suggest that GA₃ and proline exhibit positive effects on stress alleviation through the stimulation of α-amylase expression.