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 germination 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.