Abstract: 【Objective】To clarify the regulating effect of melatonin treatment on spring wheat yield under water deficit conditions.【Methods】In the experiment,the spring wheat irrigated varieties Nongmai2 and Yongliang4 were used as test materials. Using randomized complete block design,the effects of exogenous melatonin on the main phenotypic traits of spring wheat,such as chlorophyll content,photosynthetic rate,biomass per plant,spike number,grain number per spike,thousand kernel weight and grain yield,were studied under well-watered and water deficit treatments.【Results】Compared with well-watered treatment,water deficit treatment reduced the chlorophyll content and photosynthetic rate of functional leaves of spring wheat,hindered the accumulation of biomass per plant,reduced spike number,grain number per spike,and thousand kernel weight,reduced yield by 19.01%-20.35%. Under water deficit conditions,melatonin treatment could alleviate the damage to leaves caused by water deficit,maintain high chlorophyll content and photosynthetic rate,promote the accumulation of biomass per plant,inhibit the decrease of spike number,grain number per spike and thousand kernel weight,and increase yield by 13.19%-17.27%.【Conclusion】As a green growth regulator,melatonin played an important role in enhancing the adaptability of spring wheat and coping with frequent water deficit.

Key words: Water deficit, Melatonin, Spring wheat, Photosynthetic characteristics, Grain yield