Abstract: The dry-hot wind stresses of high temperature resistant wheat variety of Jimai 22 was conducted with a self-developed portable dry-hot wind generation simulator, the air temperature, humidity and wind speed in the simulation box were controlled by the central control system to simulate the intensity and process of dry-hot wind. According to the Meteorological Industry Standards of QX/T 82-2007 of the People's Republic of China, two stress levels, as severe dry-hot wind (S) and mild dry-hot wind (M) were compared, that were based on the air temperature, relative humidity and wind speed. Two stress stages as the middle filling stage (13 days after flowering) and the later filling stage (23 days after flowering) were all condidered M and L. The distribution characteristics of grain weight at different spikelets and grain positions, and the relations to the stress degrees were all researched under different stages and levels of dry-hot wind stresses, to provide theoretical basis for the prevention and control of dry-hot wind disasters. The results showed that the grain weights at spikelet and grain positions on main stem and tiller in different treatments were changed as a quadratic curve of first rising and then decreasing. A significant decreases were observed under different dry-hot wind stresses. The total grain weights of the lower and upper parts of the spikes were sharply reduced during the middle filling stage, the damages to grain weights were showed as follows: G3 (the third grain position)＞G1 (the first grain position)＞G2 (the second grain position). The grain position of G3, G1 and G2 indicated that the grains were developed from florets of the third, first and second positions respectively. While the grain weights of the lower and middle parts of wheat ear were severely reduced at the later stage stress, and the damage in G3 position was greater than that of the G2 and G1. It was concluded that under such simulation condition, the more significant decrease was observed in the grain weight of the tiller ear in the middle filling stage of dry-hot wind, while the damage to the grain weight of the main stem spike was more serious in the later filling stage. The decrease of the grain weight at the G3 grain position was the most prominent under the middle and later stage stress. The effects of dry-hot wind on grain weights in the middle stage of grain filling were greater than those in the later stage, and the effects of severe dry-hot wind stress were also larger than those of mild stress.

Key words: Dry-hot wind, Winter wheat, Spikelet position, Grain position, Grain weight