Abstract:

High temperature during grain filling is a key climatic factor affecting wheat grain quality in Huanghuaihai and lower reaches of the Yangtze River in China. High temperature during grain filling decreases the duration of grain filling and increases protein content in wheat, but its physiological mechanism is unclear. The experiments were carried out in growth chamber to investigate the effects of high temperature and day/night temperature difference during grain filling on protein components formation and free amino acid content. Two wheat cultivars including Yangmai9 with low grain protein content and Xuzhou 26 with high grain protein content were treated under different temperature conditions during grain filling. Four day/night temperature regimes of 34℃/22℃, 32℃/24℃, 26℃/14℃ and 24℃/16℃ from 7 days after anthesis until maturity were used to obtain two daily average temperatures of 28℃ and 20℃, and two day/night temperature difference treatments of 12℃ and 8℃. The results showed that contents of crude protein, albumin, globulin and gliadin in grains were significantly increased, but gluten content was decreased by high temperature (Fig.1, 2, 3). When the day temperature was 34℃, protein content of Yangmai9 was decreased, but that of Xuzhou26 was increased. Consequently, the ratio of glutenin to gliadin was decreased by high temperature. Compared with optimal temperature treatments, free amino acid content was also increased in vegetative organs during early period of grain filling but significantly reduced in grains by high temperature during later period of grain filling (Fig.4, 5, 6), which indicated that increment of grain protein content under high temperature was associated with increasing free amino acid content in vegetative organs, and accelerating utilization of amino acids in grain. In addition, the optimal temperature difference of day and night favoring the formations of grain protein and protein components differed with wheat genotypes.

Key words: Wheat, Temperature, Protein component, Amino acid