Abstract: 【Objective】 The field experiment was carried out in 2011-2012 and 2012-2013 wheat growth seasons. Four soil layers (0-20, 0-40, 0-60 and 0-140 cm) were designed to make the supplemental irrigation at jointing stage and anthesis stage (target soil relative moisture content=75%), no irrigation during the whole growth season was used as the control. The objective of this experiment was to study the effects of supplemental irrigation based on the measurement of moisture content in different soil layers at jointing stage and anthesis stage on the chloroplast ultramicrostructure and chlorophyll fluorescence parameters of flag leaves of winter wheat, so as to provide a theoretical basis and technical reference for water-saving and high-yield cultivation of wheat. 【Method】 The research was carried out with wheat cultivar Jimai 22, transmission electron microscopy (TEM) was used to analyze the chloroplas ultramicrostructure of flag leaves, the alcohol extraction method was used to analyze the chlorophyll content of flag leaves and chlorophyll fluorometer was used to analyze the chlorophyll fluorescence parameters of flag leaves. This experiment studied the effects of different treatments on the chlorophyll content, the chloroplas ultramicrostructure and the chlorophyll fluorescence parameters of flag leaves, grain yield, water use efficiency and economic benefit of wheat.【Result】When making supplemental irrigation in 0-40 cm soil layer, the oval chloroplasts of flag leaves with intact membrane closely arranged along the cell membrane on day 22 after anthesis. Clear grana lamellae arranged along the long axis of chloroplasts. And clear stroma lamellaes connected grana lamellas. The obvious damages of chloroplas ultramicrostructure were observed when making supplemental irrigation in 0-20 cm soil layer, and the chloroplas ultramicrostructure was caused more serious damage when no irrigation during the whole growth period. The round chloroplasts of flag leaves with damaged membrane arranged disordered and cell wall had a breakdown. The chloroplast ultramicrostructure had no significant difference between supplemental irrigation in 0-60 cm soil layer and 0-40cm soil layer. When making supplemental irrigation in 0-140 cm soil layer, damages of chloroplast ultramicrostructure were observed. Chloroplasts membranes were intact, membranes of cells was damaged and there were gaps among grana lamellas. There were significantly positive correlation among the numbers of chloroplast, chloroplast grana, grana lamellae of mesophyll cell of flag leaves and chlorophyll content (r＝0.99**, 0.99**, 0.96**). The numbers of chloroplast, chloroplast grana and grana lamellae of mesophyll cell under supplemental irrigation in 0-40 cm soil layer significantly increased than those under supplemental irrigation in 0-20 cm soil layer and no irrigation during the whole growth period, and which was why there was high chlorophyll content under supplemental irrigation in 0-40 cm soil layer. When making supplemental irrigation in 0-60 cm and 0-140 cm soil layers, the numbers of chloroplast, chloroplast grana and grana lamellae of mesophyll cell had no significant increase and so as to chlorophyll content. The maximal quantum yield of PSII (Fv/Fm), actual efficiency of PSII (ΦPSII) and photosynthetic electron transport rate (ETR) of flag leaves, 1000-grain weight, grain yield, water use efficiency and economic benefit of wheat under supplemental irrigation in 0-40 cm soil layer significantly increased than those under supplemental irrigation in 0-20 cm soil layer. When making supplemental irrigation in 0-60 cm and 0-140 cm soil layers, Fv/Fm, ΦPSII and ETR had no significant increase, so as the 1000-grain weight, grain yield, water use efficiency and economic benefit of wheat. 【Conclusion】The most important factor for higher 1 000-grain weight and grain yield was supplemental irrigation based on soil moisture measurement in 0-40 cm soil layer which could maintain better chloroplast ultramicrostructure, higher numbers of chloroplast, chloroplast grana, grana lamellae of mesophyll cell of flag leaves, higher chlorophyll content and higher chlorophyll fluorescence parameters during the middle late grain filling stage. Supplemental irrigation based on soil moisture measurement in 0-40 cm soil layer was the most appropriate irrigation treatment for recommendation by considering grain yield, water use efficiency and economic benefit of wheat.

Key words: wheat , supplemental irrigation based on soil moisture measurement , soil layers , chloroplast ultramicrostructure , chlorophyll fluorescence parameters