Study On Water Physiology Of Wheat Based On Carbon Stable Isotope

This study was conducted at the Yuanziqu experimental station of Bayannur Institute of Agricultural and Animal Husbandry Sciences in 2022.Three wheat varieties with different drought tolerance,Nongmai 482,Neimai 17 and Ningchun 55,were used as experimental materials.Under four irrigation modes:conventional irrigation（three times in the whole growth period,tillering to jointing stage+heading flowering stage+filling stage）,early stress（heading flowering stage+filling stage）,late stress（tillering to jointing stage+heading flowering stage）,and whole growth period stress（no irrigation）.The changes of biomass,yield,water use efficiency,photosynthetic parameters,chlorophyll content,soluble sugar content,proline content and carbon isotope resolution（?）of different wheat varieties at different stages were studied.The main results are as follows:1.The biomass and yield of each wheat variety were the highest under the conventional irrigation mode,and the yield difference between the middle and late stress mode and the conventional irrigation was the smallest,which was the best irrigation mode for both high yield and water saving.The biomass and yield under limited irrigation（early stress）mode were lower than those under limited irrigation（late stress）mode.The order of wheat biomass and yield under different irrigation treatments was conventional irrigation>late stress>early stress>no irrigation.The biomass and yield of wheat varieties were Nongmai 482>Neimai 17>Ningchun 55.Water use efficiency（WUE）at biomass level(WUE _biomass)and water use efficiency(WUE_yield)at yield level(WUE_yield)were higher under late stress than under conventional irrigation conditions,and there were significant differences in water use efficiency at each level among different wheat varieties.The WUE _biomassand WUE_yieldof the three wheat varieties at flowering stage and maturity stage were Nongmai 482>Neimai 17>Ningchun 55.2.With the deepening of water stress,the?values showed different degrees of decline,and the?values under the four irrigation modes ranged from 18.25‰to20.29‰.There were significant differences in?values among the three wheat varieties,and the?values of leaves and grains showed the same arrangement trend:Nongmai 482>Neimai 17>Ningchun 55.With the continuous extension of water stress time,the?values of the four irrigation modes were as follows:conventional irrigation>late stress>early stress>no irrigation,which showed the same arrangement trend with biomass,yield,WUE_biomassand WUE_yieldat mature stage.There was a very significant positive correlation between theΔ_leafandΔ_grainunder the four irrigation treatments at the mature stage,and the correlation coefficient reached 0.880.The correlation betweenΔ_leafandΔ_grainat tillering stage and flowering stage was not significant.3.With the deepening of water stress,the photosynthetic rate,stomatal conductance and transpiration rate of the three wheat varieties decreased slightly under the late stress mode,and the parameters of the early stress and no irrigation treatment decreased significantly.There were significant differences in photosynthetic parameters among the three wheat varieties under different irrigation modes,and the overall order was the same as that of?:Nongmai 482>Neimai 17>Ningchun 55.There was a significant positive correlation between?_flagleaf and?_grainand photosynthetic rate,transpiration rate and stomatal conductance at maturity stage of wheat varieties.The correlation coefficient between?_flagleaf and photosynthetic rate,stomatal conductance and transpiration rate was higher than that of?_grain.4.In the early stress,late stress and no irrigation treatment,the soluble sugar content of Nongmai 482 at flowering stage was higher than that of Neimai 17 and Ningchun 55,and the increase of soluble sugar content of Nongmai 482 was higher than that of Neimai17 and Ningchun 55.The drought resistance of the three varieties of wheat under each irrigation treatment showed a trend of arrangement:Nongmai 482>Neimai 17>Ningchun 55.5.Under different irrigation modes,there was a significant positive correlation between the flag leaf at anthesis and maturity and the grain at maturity and biomass,yield and water use efficiency at each level.The correlation coefficient between the flag leaf at maturity and biomass,yield and WUE_biomassand WUE_yieldwas higher than that at anthesis.Under the two treatments of early stress and late stress,the correlation coefficients between?and biomass,yield and water use efficiency of different organs were higher than those between?and biomass,yield and water use efficiency of different organs under conventional irrigation and no irrigation.Therefore,the flag leaf?value at maturity can be used as a reliable index for high water use efficiency and high-yield variety breeding.