Effects Of Elevated CO₂ Concentration And Temperature On The Physiological And Ecological Characteristics Of Coix Lachryma-job

With global warming and the acceleration of urbanization,the impact of atmospheric CO₂concentration and temperature increase on plant growth and development has become more and more significant.As important climatic factors for plant growth and development,the study of CO₂concentration,temperature increase and their interaction is meaning for obtaining physiological and ecological data of plant response to global climate change and revealing the interaction relationship and response law between CO₂concentration and temperature increase.In this study,a medicinal and edible crop Coix lacryma-jobi L.was selected as the research object with white-shelled Coix in Xingren and black-shelled Coix in Guoan,and two CO₂concentrations were set in a potted manner using an artificial climate box that can precisely control CO₂concentration and temperature.Gradients(400±20μmol·mol^-1and 800±20μmol·mol^-1)and two temperature gradients（25/20℃ and 30/25℃）,the effects of CO₂concentration and temperature increase on white-shell and black-shell Coix were systematically studied on growth form,biomass accumulation and distribution,chlorophyll and osmotic adjustment substances content,plant endogenous hormones,antioxidant system,carbon,nitrogen,phosphorus,potassium content and stoichiometric ratio in leaves,main secondary metabolites（flavonoids,total phenols and coixin）.The main results are as follows:（1）The increase of temperature,the increase of CO₂concentration and their interaction increased the plant height,leaf length,leaf width,leaf thickness and leaf area morphological indicators of white-shelled and black-shelled Coix to varying degrees,and reached the maximum under the interaction.There was no significant change in the number of taproots between white-shelled and black-shelled Coix.Under the increase of CO₂concentration and the interaction of CO₂and temperature,the biomass of each part and total biomass of white-shelled and black-shelled Coix increased,especially the stem biomass and total biomass.When the temperature increased,the total biomass and biomass of each part of white-shelled Coix still showed an increasing trend,while the stem,leaf and total biomass of black-shelled Coix decreased significantly,resulting in a significant increase in the ratio of root biomass and root to shoot ratio.（2）The contents of chlorophyll,soluble sugar and soluble protein in black-shelled Coix showed a decreasing trend when the temperature increased,while only the soluble protein content in white-shelled Coix decreased significantly.The increase of CO₂concentration significantly increased the soluble sugar content of white-shelled Coix,and significantly decreased the soluble protein content of white-shelled and black coix,but had no significant effect on the chlorophyll content of the two.The interactive treatment of CO₂concentration and temperature mainly promoted the photosynthesis of white-shelled and black-shelled Coix by accumulating chlorophyll content,especially to make up for the decrease of chlorophyll content of black-shelled Coix caused by the increase of temperature.（3）Under the single factor treatment of temperature increase or CO₂concentration increase,and the interaction treatment of CO₂concentration and temperature increase,the SOD,POD activity and MDA content of white-shelled and black-shelled Coix showed a trend of decreasing firstly and then increasing.The CAT activities showed different performances.The CAT activity of white shell Coix showed an increasing trend under the increasing temperature,CO₂concentration and the interactive treatment of CO₂concentration and temperature increasing,while the CAT activity of black shell Coix showed a decreasing trend.The highest and lowest values were reached under the interaction treatments of CO₂concentration and temperature increasing,and there were significant differences among the varieties under each treatment.（4）The content of ZA in white-shelled and black-shelled Coix were significantly increased with the increase of temperature,and the content of GA₃in white-shelled Coix was significantly decreased,but there was no significant difference on the content of IAA and ABA in white-shelled and black-shelled Coix.The increase of CO₂concentration significantly increased the contents of GA₃and ZA in white-shelled coix,while the content of IAA in white-shelled and black-shelled Coix significantly decreased.The interactive treatment of CO₂concentration and temperature increasing significantly reduced the contents of GA₃,ZA and ABA in white-shelled Coix,but there was no significant change in IAA content.（5）The increase of CO₂concentration and temperature mainly promoted the accumulation of phosphorus and potassium in white-shelled Coix,but had no significant effect on the contents of carbon,nitrogen and potassium in black-shelled Coix.The interactive treatments of CO₂concentration and temperature increasing significantly increased the carbon accumulation of white-shelled and black-shelled Coix,and reached the maximum value in each treatment,and showed different changes in potassium content,which there was no significant change in the potassium content of white-shelled Coix.While The potassium content of black-shelled Coix was significantly reduced,and there was no significant effect on the nitrogen and phosphorus content.（6）Under the interaction of CO₂concentration and CO₂concentration and temperature increasing,the content of flavonoids in white-shelled Coix showed a decreasing trend.There was no significant change in the contents of flavonoids and total phenols in black-shelled Coix,but the coixin contents of both decreased significantly,and the The coixol content of white-shelled Coix is always significantly higher than that of black-shelled coix.When the temperature was raised,the flavonoid content of black-shelled Coix significantly decreased,while the coixol content of white-shelled Coix significantly increased.（7）To sum up,the adaptability of the two Coix cultivars under the treatment of temperature increasing,CO₂concentration increasing and interaction of CO₂concentration and temperature increasing is that Xingren white-shelled Coix is stronger than Guoan black-shelled Coix.