Physiological Response Of Coix Lacryma-jobi To Elevated CO₂ Concentration And Nitrogen Application

Since the industrial revolution,a large number of fossil fuels have been burned,resulting in the increasing concentration of CO₂ in the atmosphere.CO₂ is an essential raw material for plant photosynthesis,which will have a profound impact on plant growth and development.The response of plants to elevated CO₂ concentration is closely related to mineral nutrition.Nitrogen(N)is the primary mineral nutrient element for plant growth.Therefore,how will the interaction of CO₂ concentration and N affect plant growth and development and physiological and biochemical processes?Based on this,C.lacryma-jobi,a traditional medicinal and edible homologous plant,was used as the research object in this study The effects of elevated CO₂ concentration and nitrogen application on the growth,biomass accumulation and distribution,osmotic adjustment substances,antioxidant enzymes,nitrogen metabolism enzymes,root activity,root,stem,leaf nutrient elements and coixol element of C.lacryma-jobi were studied in order to provide scientific basis for further understanding the response mechanism of C.lacryma-jobi to elevated CO₂concentration and the effect of nitrogen on it.The main results are as follows,(1)The plant height,stem diameter,root volume,number of first lateral roots and leaf area of C.lacryma jobi increased significantly by 32.86%,16.18%,46.10%,51.52%and 43.75%,while the number of tillers decreased by 40.00%;The tiller number,leaf width,leaf area,leaf number,root volume and primary lateral rooting number of C.lacryma jobi increased by 45.60%,19.27%,35.24%,43.75%,43.45%and 28.57%respectively when nitrogen fertilizer was applied alone;The plant height,stem diameter,tiller number,leaf length,leaf width,leaf area and leaf number of C.lacryma jobi increased by 44.29%,21.68%,100.00%,7.21%,12.46%,26.55%and43.37%under the interaction of elevated CO₂ concentration and nitrogen application.(2)The biomass accumulation of stem and root increased significantly by 92.86%and 65.04%with the increase of CO₂ concentration alone,and the stem biomass ratio increased significantly by 23.08%compared with the root biomass.The leaf biomass ratio increased significantly by 160.87%,the leaf biomass ratio increased significantly by 54.55%,and the root shoot ratio decreased significantly by 17.46%.Under the interaction of elevated CO₂ concentration and nitrogen application,the biomass of leaf,stem and root of C.lacryma jobi increased by 198.55%,153.97%and 68.29%,and the biomass of leaf and stem increased more than that of root,resulting in the biomass ratio of stem and root shoot decreased by 28.21%and 41.27%.(3)The content of SS and SP in the root increased by 57.26%and 30.89%respectively,and the content of SP in the leaf decreased by 70.81%,but there was no significant effect on the content of SS in the leaf.The contents of SS and SP in the leaves increased by 41.20%and 29.58%respectively,while the contents of SP in the roots decreased by 42.78%.Under the interaction of elevated CO₂ concentration and nitrogen application,SS content in leaves and roots of Coix lacryma job I increased by32.40%and 131.69%,while SP content in leaves decreased by 36.98%,while SP content in roots had no significant change.(4)The content of N in leaves and roots of C.lacryma jobi decreased by 8.15%and 8.31%with the increase of CO₂ concentration alone,but there was no significant difference in the content of N in stems,while the content of C in roots increased by15.82%,and there was no significant difference in the content of C in stems and leaves.N content in roots,stems and leaves of C.lacryma jobi increased by 23.29%,28.42%and 19.52%,but no significant effect on C content in roots,stems and leaves.Under the interaction of elevated CO₂ concentration and nitrogen application,the N content in roots and stems increased by 8.99%and 6.79%,while the N content in leaves decreased by 4.22%.There was no significant difference in the C content in roots,stems and leaves.(5)The contents of S,Cu,Zn and Ni in C.lacryma jobi leaves were significantly decreased by 18.06%,54.01%,37.96%and 101.96%with the increase of CO₂concentration alone;The contents of Mn,Cu,Zn and Ni in stems increased significantly by 90.20%,70.55%,46.80%and 149.50%except for Fe;The content of s increased by 16.81%and the content of Fe decreased by 17.21%.The contents of Mg,Fe,Mn and Ni in leaves increased by 99.03%,88.49%,229.94%and 34.95%respectively when nitrogen fertilizer was applied alone;The contents of Mn,Zn and Ni in stems increased by 228.16%,79.17%and 47.17%,respectively;The contents of Mn and Ni in roots increased by 8.21%and 96.62%respectively.The contents of Mg and Mn increased by 54.81%and 107.22%,while the contents of Cu,Fe,Zn and Ni decreased by 67.49%,63.41%,25.25%and 65.14%;The contents of medium and trace elements in stems increased significantly except for Fe;The contents of Mg,S and Zn in roots decreased by 28.18%,13.83%and 38.89%respectively.(6)The content of coixl in the root,stem and leaf of C.lacryma jobi decreased by 31.48%,54.03%and 64.93%with the increase of CO₂ concentration alone.The content of coixl in the root,stem and leaf of C.lacryma jobi increased by 17.49%,243.74%and 9.87%with the application of nitrogen fertilizer alone.Under the interaction of elevated CO₂concentration and nitrogen application,coixl content in root and stem increased by 8.44%and 187.92%,while coixl content in leaf decreased by 29.43%.