The threshold of soil moisture is 15% (account for 60% of the field water holding capacity), at which the leaf-air temperature difference affects illumination intensity and transpiration rate.

• 小麦叶气温差对光照强度的反应以及对叶片蒸腾速率影响的土壤湿度阈值为15%25（占田间持水量的60%25左右）。