| The concentration of atmospheric carbon dioxide(CO2)is increasing.CO2 is one of the raw material of plant photosynthesis.The increase of the concentration will affect the photosynthetic physiology of plants,thus affecting the carbon cycle of atmosphere-plantsoil.Meanwhile,climate change prediction showed that the water stress would be more frequency,which would also affect plant growth..Up to now,there have been many studies on the physiological effects of increased CO2 concentration on C3 crops,but there are still different debates on the physiological changes of C4 crops under different water deficit after increased CO2 concentration.And some of such debates existed among different cultivars.Explaining the different strategies of different maize cultivars in response to the increase of CO2 concentration and water stress will provide reference for maize cultivar selection under climate change in the future.In this study,maize cultivars released in different years were selected as the research objects.The artificial climate chamber was used to control the carbon dioxide concentration(environment and increase the CO2 concentration),and drip irrigation was used to set three irrigation amounts of high,medium and low.The main research results are as follows:(1)With the increase of CO2 concentration,the stem diameter of Zhengdan 958 at tasseling stage increased significantly.The leaf area at six-leaf stage,jointing stage and flaring stage increased significantly.The leaf area at flaring stage and tasseling stage of Jingke 968 increased significantly.Under the combined effects of CO2 concentration and water treatment,there were significant differences in stem diameter of Jingke 968 at jointing stage and V12 stage,and there were significant differences in plant height of Zhengdan 958 at six-leaf stage,jointing stage and tasseling stage.(2)Under the saturated light,the increase of CO2 concentration significantly increased the leaf water use efficiency of Jingke 968,but had no significant effect on the leaf water use efficiency of Zhengdan 958.The stomatal conductance of Jingke 968 was higher than that of Zhengdan 958 under the CO2 concentration of 400 ppm,while the stomatal conductance of Jingke 968 was lower than that of Zhengdan 958 under the CO2 concentration of 600 ppm.The results showed that different varieties of maize showed different responses to elevated CO2 concentration,and Jingke 968 might have better drought resistance due to its lower stomatal conductance.(3)CO2 concentration significantly affects the fitting parameters of light response curve of gas exchange parameters.Under different water treatments,there was no significant difference in the maximum value of stomatal conductance between the two maize varieties.The maximum value of stomatal conductance(GS-max)decreased significantly with the increase of CO2 concentration,and the decline amplitude was different under each water treatment.With the increase of CO2 concentration,the light saturation point of stomatal conductance,stomatal limiting and water use efficiency of Jingke 968 increased,while those values of Zhengdan 958 decreased,which means that the light intensity required for the maximum parameters of Jingke 968 is higher.Therefore,in order to obtain higher water use efficiency and yield,planting density and other factors should be considered to meet the demand of higher light,when selecting maize cultivars.(4)The results showed that the stomatal parameters would have different responses to the treatments of CO2 concentration and soil water content,and the stomatal parameters of both sides of leaves would also be significantly different.The relationship between stomatal morphological parameters and stomatal conductance was also analyzed.It was found that the correlation between stomatal density and stomatal conductance varied with different CO2 concentration,cultivars and the front and back sides of leaves.There was a significant positive correlation between stomatal density and stomatal conductance of the front leaf side of Zhengdan 958 at 400 ppm CO2,the back leaf side of Zhengdan 958 at600 ppm CO2 and Jingke 968 at 400 ppm CO2;However,there was a significant negative correlation between stomatal density,and stomatal area on the front side of Jingke 968 and on the back side of Zhengdan 958 under two CO2 concentrations. |
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