Heat balance of cold type wheat field at grain-filling stage under drought stress condition

Through studies on the canopy temperature and some other traits of wheat for more than 20 years, it was verified the presence of cold type wheat, which could maintain over canopy temperature continuously and stably during its grain- filling stage, was discovered with the characteristics of better metabolism and vigor, and stronger tolerance to early senescence, especially for its strong adaptability to stress conditions, which posed an important role of cold type wheat in improving and stabilizing wheat production. With the advent of frequent drought stress, wheat production was affected greatly; therefore gating the heat balance in cold type wheat field under drought condition would benefit the understanding and improvement of formation mechanism of cold type wheat field environment and promote its application in wheat production. The experiments were conducted under rainout shelters for three continuous growth seasons to investigate the differences in canopy temperature, air temperature, air humidity, wind speed, net radiation flux density, latent heat flux, turbulent heat flux, soil heat flux and energy heating leaf blade and stem between cold and warm type wheat materials to investigate the heat balance in cold type wheat field at grain-filling stage under drought stress and to reveal the adaptation mechanism of cold type wheat to drought stress. The results showed that, (1) The net radiation flux density of cold type wheat is 16. 35 -47.57W/m 2 over than that of warm type one, but the difference was not significant. (2) The latent heat flux measured at 0.2 m above ground to 2/3 plant height and 2/3 plant height to the canopy in rows of cold type wheat was 29.09-48.61 W/m 2 and 47.41 -134.89 W/m 2 higher than that of warm type wheat, respectively; but the turbulent heat flux of cold type wheat was 12 48 - 62.57 W/m 2 and 29.37 - 85.81W/m 2 over than that of warm type wheat, respectively. The latent heat flux between the active layer and atmosphere of cold type wheat was 50.30 - 124. 20 W/m 2 higher than that of warm type wheat, but the turbulent heat flux poured into the atmosphere of cold type wheat was 30.50 - 102.40 W/m 2 less than that of warm type wheat. (3) The soil heat flux of cold type wheat was 24.60-65.19 W/m 2 over than that of warm type wheat. (4) The energy heating leaf blade and stem of cold type wheat was 43.70 W/m 2 over than that of warm type wheat. Under drought condition, heat distribution in cold type wheat field created cold and humid microclimate environment through net radiation increased to latent heat and reduced to soil heat and energy heating leaf blade and stem, which benefited the growth and yield improvement of wheat under drought condition and improved its adaptability in stress conditions, especially for those grown in arid and semi-arid areas.