Effect Of Elevated CO₂ On Leaves Traits And Yield In Maize Field

As an important raw material for plant photosynthesis,the change of CO₂ concentration in the environment will have a certain effect on the growth process and yield of plants.Maize,as an important grain,feed and economic crop,the yield and economic benefit directly affect the safety of grain and the development of agricultural production.The arid and semi-arid region of the Loess Plateau is an important producing area of maize.Therefore,strengthen research the effects of elevated CO₂ on the growth and yield of maize under different water and fertilizer practices is of great significance to China's corn industry.The research object was spring maize?Zheng dan“958”?in this study.The long-term positioning test was carried out on the Changwu Agricultural and Ecological Experimental Station.The spring maize stomatal characteristics?included density?SD?,area?SA?,perimeter?SP?,width?SW?,length?SL??,leaf area index?LAI?and maize yield were investigated under three different environmental conditions:natural atmosphere CO₂ concentration?as the control,marked as CK?,open-top chamber?OTC?system with CO₂ concentration of 700?mol·mol^-1?marked as OTC+CO₂?,and OTC system with currently atmosphere CO₂concentration?marked as OTC?.And four different water and fertilizer practices were set under each environmental conditions:rainfed and no nitrogen fertilization?marked as RN0?,rainfed with the N rate of 225 kg·hm^-2?marked as RN225?,mulched with the N rate of 225kg·hm^-2?marked as MN225?,mulching with the N rate of 290 kg·hm^-2?marked as MN290?.Plant density was 70,000 plants hm^–2.The results can provide theoretical basis and data support for the research of the effects of elevated CO₂ on maize growth in dry farming on the Loess Plateau.The main conclusions are as follows:?1?The elevated CO₂ had no significant effect on the SD under the conditions of RN0and MN225,spring maize responded to the elevated CO₂ by adjusting the size and shape of stoma,but not SD.Elevated CO₂ increased the SD by 9%?P<0.05?at V6 stage,decreased the SD by 11%?P<0.05?at R3 stage under normal N?N225?.Elevated CO₂ decreased the SD by 10%?P<0.05?at V6 stage under high N?N290?.The elevated CO₂ has positive effects on SD at V6 stage under normal N and has negative effects under high N.?2?The responses of stomatal characteristics of spring maize to the elevated CO₂ were affected by the amount of N application and the applying of film mulching.Elevated CO₂increased the SA,SW,SP,SL by 43%,26%,15%,15%?P<0.05?,respectively,at V6 stage,decreased the SA,SW,SP,SL by 6%,6%;5%,3%;4%,3%;3%,2%?P<0.05?,respectively,at V12 and R5 stages,under RN0.But normal N would change the positive effect of elevated CO₂ on the stomatal characteristics of V6 stage to negative effect.Elevated CO₂ decreased the SA,SW,SP,SL by 14%,10%;5%,2%;7%,7%;3%,4%?P<0.05?,respectively,at V6,V12 stages.Mulched could mitigate this negative effect,even change to positive effect,which showed that SA,SP and SL increased by 8%,5%and 2%?P<0.05?,respectively,at V6 stage,and SW increased by 5%?P<0.05?at V12 stage.High N changed the positive effect of elevated CO₂ on the stomata at V6 stage to negative effect,which showed that SA,SW,SP and SL decreased by 13%,8%,6%and 7%?P<0.05?,respectively,at V6 stage.Elevated CO₂ showed negative effect to the stomatal characteristics of SA,SP,SW,SL at seedling stage under the application of N fertilizer,and showed positive effect under mulched.The effect of elevated CO₂ on the stomatal characteristics was mainly shown at V6stage.?3?The effects of elevated CO₂ on the LAI of spring maize increased gradually with the extension of the field test period.Elevated CO₂ had no significant effect on the LAI under normal and high N in 2016,whereas decreased the LAI by 25%and 9%?P<0.1?,respectively,at V6 and R1 stage,increased the LAI by 18%?P<0.1?at R3 stageunder mulched.Elevated CO₂ increased the LAI by 89%,17%,10%?P<0.1?respectively,at V9,V12,R3 stage under mulched in 2017.High N weakened or counteracted the effect of elevated CO₂ on LAI of spring maize.The elevated CO₂ had the greatest effect on the LAI of spring maize under conditions of MN225.?4?In 2017,elevated CO₂ had no significant effect on the yield of spring maize under normal and high N,whereas increased the yield of spring maize by 17%?P<0.05?under mulched.However,compared with the application of N,film mulching significantly increased the yield of spring maize under elevated CO₂.Therefore,the practice of MN225was the most beneficial to increase the yield of spring maize under elevated CO₂.To some extent,there was a strong positive correlation between maize yield and LAI.To a certain extent,the elevated CO₂ will have a significant impact on the growth and yield of maize in the Loess Plateau in the future,and the field water and fertilizer practice should be adjusted in time to cope with the elevated CO₂.