Application Of Stable Carbon Isotopes In The Study Of Water Use Efficiency Of Summer Maize With Different Drought Resistance

Shandong province is an important main grain producing area in China,and summer corn is an important grain crop in Shandong Province.Summer maize grows in high temperature season,and sufficient water is an important factor for crop growth and development,as well as a key factor for crops to obtain high yield.Moreover,the annual variability of precipitation in Shandong province is large,uneven seasonal distribution affects the normal growth and development of summer maize.Limited water resources restrict the increase of crop yield,so the utilization and distribution of water resources directly affect the sustainable development of agriculture.It is an important aspect of current agricultural research to select varieties with high and stable yield and to select simple and accurate indicators as indicators of plant water use efficiency（WUE）under rainfed conditions.In this experiment,three summer maize varieties with different drought resistance were selected,namely,tunyu 808（TY808）,Denghai 605（DH605）and Zhengdan 958（ZD958）,which were not drought-resistant.To study the differences of growth and development,WUE and stable carbon isotope resolution(Δ¹³C)of different drought-resistant summer maize varieties,as well as the relationship betweenΔ¹³C value and yield and WUE,preliminarily explore and analyze the relationship betweenΔ¹³C value and plant WUE and yield,and confirm thatΔ¹³C value can be used to indicate WUEy and Y of summer maize.It can provide theoretical basis for selecting varieties with drought resistance and stable yield and high water use efficiency.The test results show that:1.Compared with no drought-resistant varieties TY808,medium drought resistance varieties DH605,relatively drought-resistant varieties ZD958 can increase summer corn aboveground dry matter accumulation,chlorophyll content and leaf area index（LAI）,drought resistance increases the photosynthate of summer maize organs turn grain of traffic volume,so in order to ensure high and stable yield provides a good physical condition.2.Compared with non-drought-resistant variety TY808,medium drought-resistant variety DH605 and relatively drought-resistant variety ZD958 could increase panicle row number.Medium drought-resistant variety DH605 had the highest yield and WUEy,so the yield of DH605 was more stable than the other two varieties.3.Compared with non-drought-resistant cultivar TY808,medium drought-resistant cultivar DH605 and relatively drought-resistant cultivar ZD958 could increase photosynthetic rate（Pn）and transpiration rate（Tr）during the growth period of summer maize.In summer corn main reproductive period,stomatal conductance（Gs）and cell inside and outside the CO₂concentration ratio（Ci/Ca）to present the same trend,that is not TY808 drought-resistant variety,under drought stress,at the early stage of the fertility decreased leaf Gs,into the leaf cells with the decrease of CO₂and the results in the decrease of Ci/Ca,and drought resistance varieties resistant to drought,Increase blade Gs and Ci/Ca value.Therefore,the Gs and Ci/Ca of medium drought-resistant variety DH605 and relatively drought-resistant variety ZD958increased compared with that of non-drought-resistant variety TY808.4.Compared with the non-drought-resistant variety TY808,the carbon isotope resolution(Δ¹³C)of leaves of medium drought-resistant variety DH605 and relatively drought-resistant variety ZD958 was increased,and that of medium drought-resistant variety DH605 was higher than that of relatively drought-resistant variety ZD958.The influence of different drought-resistant varieties on stemΔ¹³C of summer maize was consistent with that of leafΔ¹³C.5.LeafΔ¹³C and stemΔ¹³C showed a significant positive correlation during the main growth period of summer maize,and stable carbon isotope fractionation may not occur between leaf and stem organs.There were significant differences in leafΔ¹³C,stemΔ¹³C and grainΔ¹³C,and leafΔ¹³C and stemΔ¹³C were significantly larger than grainΔ¹³C.6.During the whole growth period,leafΔ¹³C was negatively correlated with WUEi（horizontal leaf water use efficiency）,but there was no significant correlation.Further study is needed to extend leaf water use efficiency to the level of the whole crop growth stage in this experiment.In the mature stage,ΔL（Carbon isotope resolution of leaves at maturity）andΔF（Carbon isotope resolution of mature grains）were negatively correlated with WUEi（P>0.05）,but the correlation betweenΔL and WUEi was better thanΔF,indicating thatΔL could better reflect WUE at leaf level thanΔF.ΔF was negatively correlated with WUEy（water use efficiency at yield level）and Y（yield）（P<0.01）,andΔL was negatively correlated with WUEy and Y（P<0.05）,indicating thatΔF andΔL could better reflect WUE and Y at yield level.According to the experimental results,compared with non-drought-resistant varieties,drought-resistant varieties can increase the transfer of assimilates from various organs to grains of summer maize,but due to the increase of rainfall,there is no significant difference between non-drought-resistant and drought-resistant varieties.The photosynthetic characteristics,WUEy and yield components of DH605 were superior in panicle number,panicle row number and 1000-grain weight,so the yield of DH605 was more stable than the other two varieties.The results showed thatΔF was negatively correlated with WUEy and Y（P<0.01）,andΔL was negatively correlated with WUEy and Y（P<0.05）,indicating thatΔF andΔL could be used as quantitative indexes to accurately evaluate WUEy and Y of summer maize.