Abstract:

Wheat grain yield and quality are affected by environmental factors. Temperature is a major component in environmental variations with a marked effect on grain filling in wheat. Short period of heat shock, above 30℃ for a few days, happens frequently during grain filling period in many wheat-growing areas in the world, and becomes an important factor limiting wheat yield and quality. The present study investigated the effects of transient high temperature after anthesis on grain protein content and activities of nitrate reductase(NR) and glutamine synthetase(GS) in wheat(Triticum aestivum L.) to understand the mechanism of heat damage. We arranged daily average temperature 25, 30, 35, and 40℃, respectively in a phytotron, and treated wheat plants during different grain filling periods. The tested wheat cultivars were Yangmai 9 with weak gluten and Yangmai 12 with medium gluten. The results showed that grain protein content under the temperature above 35℃ from anthesis to the 33rd days after anthesis (DAA) was significantly higher than that under normal temperature, and significantly increased with the raise of temperature. There was a little effect of heat stress on protein content after the 33rd DAA. High temperature at different filling stages had different effects on protein content in grains. When heat shock temperature was above 35℃ at the early filling stage, the effect of heat shock from the 6th to 8th DAA was the greatest, followed by that from the 1st to 3rd DAA. Under the same temperature at the middle and late stages, the effect of heat shock from the 19th to 21st DAA was greater, while that from the 36th to 38th DAA was lower. Effects of heat shock at the early filling stage on grain protein content were greater than those at the middle and late stages. At the same stage, the higher the temperature, the lower the NR and GS activities in flag leaves. High temperature stress during grain filling decreased the duration of grain filling and grain weight, which increased grain protein content relatively. Heat damage led to lower quality of grain protein in wheat.

Key words: Transient high temperature after anthesis, Wheat, Grain protein content, NR, GS