Effects Of Elevated CO₂ On Nitrogen Nitrition And Growth Of Potato

Carbon dioxide fertilizer applied more and more extensively in the protected cultivation, and concentration of CO₂ has been increased year after year. The increase of CO₂ concentration will bring a deep impact on plants growth, which attributed scientists to pay more and more attention on the research. Nevertheless, a little bit work has been done on its effects on nitrogen acclimation of plant. It was well known that excessive nitrogen fertilizer have been applied, especially excessive application of nitrogen fertilizer in the greenhouse. The nitrate content of crop exceeded standard which endanger human health. The amount of residual nitrate-N increased on rise of nitrogen fertilizer. The effect of nitrate on quality of crop and soil has become a main factor of limiting the sustainable development of greenhouse. Potato (Solmanum tuberosum) is the important vegetable and food crop in China. Cultivation area increased gradually because of being the first to occupy market and high cost when potato was planted in plastic greenhouse. Therefore, the paper studied the effects of elevated CO₂ on nitrate accumulation and nitrogen metabolism and growth of potato in greenhouse, in order to further reveal the possible mechanisms of its effects on nitrate content of crop and nitrogen nutrition at different N level.Under both elevated CO₂ (900±30μL·L^-1) and ambient CO₂ (360±10μL·L^-1) concentration, this study focused on several aspects, such as the growth, nitrate content and acclimation, nitrate reductase activity (NRA) and NRA mRNA relative expression, nitrogen and carbon acclimation, soil mineral N (Nmin) and potassium at three nitrogen level. The main achievements of our studies are as following:The results showed that the increasing range of the dry matter of potato was from 13.4% to 27.0% under elevated CO₂. Nitrogen level had influence on effect of elevated CO₂. Elevating CO₂ increased biomass production greatly and accelerated the dry matter accumulated rate at N1 and N2 level, and decreased at N3 level. The economical yields and R/T decreased under elevating CO₂.NH₄⁺ content decreased under elevated CO₂. The change of NO₃^- content was different at different organ. Elevating CO₂ increase NO₃^- of plant at N1 and N2 level, decreased NO₃^- of tuber at N2 and N3 level. NO₃^- content decreased on the rise of nitrogen level under elevated CO₂.NRA and StNR2 mRNA relative expression level at 50d, 70d and 110d all declined compared with the control group under elavted CO₂ in N1 concentration. NRA and StNR2 mRNA relative expression level was showed reverse inclined at 90d. NRA and StNR2 mRNA was showed increased in 130d. The results probably show StNR2 mRNA translatet protein for requirement of potato growth. NRA and StNR2 mRNA relative expression level at 70d, 90d and 110d all showed converse tendency. That is NRA increased and StNR2 declined compared with the control group under elavted CO₂ in N2 concentration. Meanwhile, the NRA declined and StNR2 increased compared with the control group. NRA and StNR2 mRNA was showed increased in 130d. The results probably show consumption of mRNA translate the protein but can not recruite in time and N2 can block NRA.The expression law of NRA and StNR2 mRNA relative expression level can not be summary nder elavted CO₂ in N3 concentration. The results showed the concentration can not bring reasonable applyment.The changes of StNR2 mRNA indicated the role of NRA under elavted CO₂ in low N concentration. The results provide a basement which guide the reasonable using the Nitrate.Nitrogen content of potato plant increased under elevated CO₂. The maximum increment of nitrogen acclimation decreased on the rise of nitrogen level. The nitrogen content of leaves, stem, root and plant increased at N1 and N2 level, and decreased at N3 level under elevated CO₂. Nitrogen acclimation of tuber were inhibited and decreased on the rise of nitrogen level under elevated CO₂. Nitrogen acclimation rate were promoted at N1 and N2 level so that the nitrogen acclimation of plant increased under elevated CO₂. But nitrogen acclimation rate decreased at N3 level under elevated CO₂ because of decreasing of nitrogen acclimation rate. Potassium of tuber and plant increased at 130d under elevated CO₂.Starch of tuber increased at N1 and N2 level at 110d and 130d under elevated CO₂. Elevating CO₂ increased starch of leaves, decreased soluble sugar of leaves. The sucrose of leaves increased at first and then decreased under elevated CO₂. The sucrose and soluble sugar of tuber decreased under elevated CO₂.NO₃^--N content of soil decreased at 130d than before sowing at N1 and N3 level under elevated CO₂. Potassium content of soil decreased than control at N2 level under elevated CO₂.