| Ear photosynthesis makes an important contribution to final grain yield for its better photosynthetic performance and drought-tolerance traits under water stress compared to the flag leaf.It is significant to excavate physiological and biochemical basis,which could provide some theoretical and practical approach for crop production.In our study,pot experiment is conducted to measure the photosynthesis,stomatal traits and yield traits of ear and flag leaf in two wheat cultivars Pubing143 and Zhengyin1 during grain filling.Our main results are as follows:1.Flag leaf Pn decline with grain filling in wheat under water deficit.It showed that the adverse-effect of water deficit on net photosynthetic of wheat flag leaf maily occured throughout whole filling stage,and the plain cultivar was more susceptible to water deficit.However,ear Pn firstly increased with the growth of ear bracts organ and decreased subsequently during grain filling.At 6 DAA,ear Pn decreased by 4.42%(P<0.05)in Pubing143 under water deficit,while Zhengyin1 decreased by 9.89%(P<0.05).At 18 DAA,ear Pn decreased significantly by 55.96%(P<0.01)in Zhengyin1 under water deficit,while Pubing143 decreased by 39.44%(P<0.05).These results showed under water deficit on ear leaf net photosynthetic of two cultivars occured in the mid and late filling stage,and Zhengyin1 was more susceptible to water deficit.At 12 DAA,flag leaf transpiration rate of Zhengyin1 and Pubing143 respectively decreased by 52.61%(P<0.01)and 30.92%(P<0.05)under water deficit.Nevertheless,At 12 DAA,ear transpiration rate of Zhengyin1 and Pubing143 respectively decreased by 27.82%(P<0.01)and 17.12%%(P<0.05)under water deficit.It suggested that transpiration rate and stomatal conductance of ear in wheat were less sensitive to water deficit compared to flag leaf.Besides,chlorophyll content and relative water content in flag leaf and ear of both cultivars had similar change trend.All these results presented that ear of wheat had better photosynthetic capacity and osmotic adjustment ability than flag leaf during grain filling,especially in Pubing143.2.The stomatal frequency and density of flag leaf ventral side in wheat decline under water deficit,and the rate of decline in Zhengyin1 was faster than Pubing143.The stomatal frequency of flag leaf in Zhengyin1 respectively decreased by 31.54% and 34.78%(P<0.05)at 6 DAA and 12 DAA under water deficit.While the decrease of ear was more slowly than flag leaf.The length of stoma increased while the width decreased in wheat under water deficit,which performed significantly in flag leaf,especially in Zhengyin1.It is interesting that we found stoma distributed both in adaxial and abaxial sides of glumes and lemmas.The stomatal frequency in adaxial side of bracts(glumes and lemmas)was quite low compare to other organs,and most of stomas distributed in the bottom of bracts.Moreover,there had gap between the stoma of bracts adaxial side and grain surface.The ear high photosynthetic capacity and water-holding capacity might be related above traits of stoma.3.Under water deficit,grain weight of each ear decline 38.80%(P<0.01)in Zhengyin 1,28.83%(P<0.05)in Pubing 143.The grain yield of Zhengyin 1 and Pubing 143 respectively decreased by 38.80% and 28.83%(P < 0.05).The harvest index(HI)of Zhengyin1 decreased by 21.53%(P<0.05)under water deficit,while HI of Pubing143 did not change obviously.Besides,WUEG of Zhengyin 1 decreased by 5.65%(P<0.05).It indicated that the effects of water deficit on the yield trait and WUE vary from different wheat cultivars.Meanwhile,we also concluded that Pubing143 had advantage of adaptation and water-holding under moderate drought. |
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