Effect Of Elevated CO₂ On Growth And Photosynthetic Physiology Of Foxtail Millet Under Different Water Conditions

At present,global warming and drought caused by warming in some areas are currently our major environmental problems that we are facing.Foxtail millet is the advantage of traditional crops in arid areas of northern China,and most of the north China region belongs to arid and semi-arid regions.In the case of rising CO2 concentration in today and the future,how the growth and development of foxtail millet and photosynthetic physiology will be changed,is the problems that need to be solved urgently.Previous studies more focus on the single factor's influence,while this study was carried out on the different development stages of the foxtail millet response to high CO2 concentration in different moisture conditions test.We measured the photosynthesis,chlorophyll fluorescence parameters,the physiological and biochemical indexes and morphological index after the mature on jointing stage and milking stage under different water conditions by using the shanxi agricultural university experimental bases Open-top Chamber system(OTC system),and respectively It is intended to provide a certain theoretical basis for how foxtail millet adapts to drought under climate change conditions.The test results are as follows:(1)The interaction between CO2 concentration and water stress had no significant effect on the leaf structure of millet.(2)Under the wet conditions,the high CO2 concentration increased the content of Pn during the jointing stage and grain filling stage in 2015 and during the millet jointing stage in 2016,and the content of WUE was increased during the jointing stage and grain filling stage in 2015 and during the grain filling stage in 2016,and the content of Gs and Tr was decreased during the jointing stage and grain filling stage in 2015 and during the grain filling stage in 2016,while the content of Pn,WUE,Gs and Tr under the drought conditions was increased less than that under the wet conditions,indicating that the drought will affect the positive role of CO2 on photosynthesis.(3)At the jointing stage of millet in 2015,the content of chlorophyll a was significantly decreased,and the content of chlorophyll b was significantly increased,and the content of carotenoid was significantly decreased under the high condition of CO2,while under drought conditions,they all were decreased in different degrees.In 2016,during the grain filling stage,with the increasing concentration of CO2,under the wet conditions,the content of chlorophyll a,chlorophyll b and carotenoid were significantly increased;water stress increased chlorophyll a content and reduced the content of chlorophyll b and carotenoid pigment.The interaction of water stress and elevated CO2 had a significant effect on the content of photosynthetic pigments,which indicated that elevated CO2 could alleviate the adverse factors caused by water stress.(4)With the increasing concentration of CO2,under drought stress,Fv/Fm was concentrated around 0.69-0.75.In 2015,PSII,ETR and qP of leaves at the jointing stage of millet were significantly decreased under different water conditions after increasing CO2 concentration.In 2016,with the increase of CO2 concentration,under different water conditions,the leaf Fv/Fm at the jointing stage of millet was significantly increased,and the leaves Fv'/Fm',phi,PSII,ETR and NPQ in the grain filling stage of millet was significantly increased.The interaction between water stress and elevated CO2 had no significant effect on chlorophyll fluorescence parameters of foxtail millet.(5)With the increase of CO2 concentration,the content of peroxidase(POD)was increased under the drought condition.The interaction between CO2 and water stress did not affect the content of MDA and Pro significantly.The trend of carbohydrate variation in leaves was inconsistent because of the difference in climate conditions and growth stages.(6)With the increase of CO2 concentration,the panicle weight of foxtail millet was significantly increased under different water conditions.Under the interaction of elevated CO2 concentration and water stress,in 2015,panicle length,stem diameter,node number was significantly changed,while no significant change of millet plant height,panicle weight and grain weight was observed;in 2016,there were no significant changes in plant height,stem diameter,number of nodes,plant height,panicle length,spike weight and grain weight.