Effects Of Water Stress On Leaf Photosynthetic Characteristics And Grain Yield Of Foxtail Millet

Millet is one of the main crops in the northern China.It plays not only an important role in dry-farming and animal-husbandry,but also an important strategic-reserve crop under the severe situation of increasing water shortage.Millet is resistant to drought and barren land,has high water use efficiency,wide adaptability.It is mostly planted on barren and arid soil,where water stress often occurs.The production of millet is inseparable from its harsh water conditions.Excessive drought can reduce the yield and quality of millet,decrease the living standard of residents in millet growing areas,and slow down China’s ecological development strategy.In this experiment,‘Dajinmiao’,a millet variety,was selected as the research object,with two growth stages,namely flowering stage(T1)and filling stage(T2),which used the field test method of controlling water with an awning.Two water stress levels(D1&D2,which the former is lower)were set respectively at each growth stage.Three water stress duration gradients(7,14 and 21 days)were designed.The effects of water stress on leaf photosynthetic characteristics and yield were compared,and the limiting factors of net photosynthetic rate,water use efficiency(WUE)and yield were analyzed.The results showed that:(1)Under water stress,the net photosynthetic rate,light use efficiency(LUE),stomatal conductance,transpiration rate and other growth factors of the millet decreased,while the WUE increased.The more severe and lasting the stress,the more significant the photosynthetic performance decreased.(2)Under water stress for 7 days,the photosynthetic recovery ability of millet at grain filling stage was weaker than that at booting stage.With the further extension of water stress to 14 days,the photosynthetic recovery ability of the high water stress group was significantly higher than that of the light water stress group at the booting and flowering stage,but it was the opposite at the filling stage.When the water stress time was extended to 21 days,the photosynthetic capacity of the two water stress treatment groups could not recover,and the recovery capacity of the high water stress treatment group was worse.(3)Under mild water stress and high water stress within 14 days,the decrease of net photosynthetic rate was mainly due to stomatal limitation;With the increase of water stress degree and duration,the decrease of net photosynthetic rate was mainly due to non stomatal factors.On the premise that the degree and duration of water stress remained constant,the decline of net photosynthetic rate of non stomatal factors caused by water stress in grain filling stage was greater than that in booting and flowering stage.(4)Water stress will lead to the overall decline of Millet Yield and yield composition,which has a significant synergistic relationship with millet net photosynthetic rate,and the yield is more sensitive to water stress at grain filling stage.The yield had a significant positive correlation with productive ear number and an extremely significant positive correlation with total spike number.It also had a negative correlation with 1000-grain weight and empty grain rate,but not significant.