Study On Establishment Of Alfalfa Phosphorus Efficiency Evaluation System And Difference Metabolism In Nitrogen And Phosphorus

In this study,28 main varieties of alfalfa were selected,and the phosphorus efficiency of 28 different varieties of alfalfa was preliminarily screened and tested with2 phosphorus levels of normal phosphorus(1500?mol·L^-1)and low phosphorus(15?mol·L^-1).The phosphorus efficiency indexes were evaluated and Classified.The representative varieties of Alfalfa with different phosphorus efficiency types were selected.We selected 2 phosphorus levels of normal phosphorus(1500?mol·L^-1)and low phosphorus(150?mol·L^-1)to full growth period test of Alfalfa with different phosphorus efficiency types in the outdoor rain proof net for closer to the natural environment.The accuracy and classification of the alfalfa phosphorus rate evaluation system were established through seedling screening test and whole growth period validation test.The photosynthetic characteristics,nitrogen fixation characteristics,enzyme activities of phosphorus and nitrogen metabolism,nitrogen and phosphorus absorption characteristics and the anatomical structure of transport tissue were studied through the full growth period test,and the mechanism of nitrogen and phosphorus nutrient difference was analyzed comprehensively to provide a theoretical basis for scientific and rational fertilization of alfalfa.There are the main conclusions:1.Establishment of phosphorus efficiency evaluation system for Alfalfa.Through the screening test of 28 different varieties of Alfalfa in the seedling stage,combining the analysis of variation characteristics,correlation analysis and principal component analysis,the mathematical method was used to evaluate the related indexes of phosphorus efficiency.The 7 indexes included shoot part of the ground,the accumulation of nitrogen in the underground,the biomass of the above ground,the biomass of the underground,the total root length,the root surface area and the root volume were used as the evaluation indexes of the phosphorus efficiency of alfalfa.According to the comprehensive value of phosphorus efficiency and cluster analysis of the membership function,then were divided into 4 types of phosphorus efficiency,?high efficiency type,II constant effect type,III anti-effective and IV low efficiency type.Through the whole growth period test,the accuracy and scientificity of index in seedling screening test were verified,and the phosphorus efficiency screening and evaluation system of alfalfa was established.The alfalfa highly efficient"Xin mu 1",the constant effect"6010",the anti-effective"Gan Nong 7"and the low efficiency"Longdong"were obtained.2.Mechanisms of phosphorus and nitrogen uptake and metabolism in Alfalfa with different phosphorus efficiency types.Under the normal phosphorus level,the content of chlorophyll in high and normal varieties were significantly higher than anti-effective varieties and low efficiency varieties?P<0.05?.Under the low phosphorus level,the chlorophyll content of the high efficient and normal varieties was lower than reverse and low efficiency type.Under different phosphorus levels,the photosynthetic rate?Pn?,transpiration rate?Tr?and stomatal conductance?Gs?of the high efficiency"Xin mu 1"was significantly higher than that of the low efficiency"Longdong"?P<0.05?,and the CO₂ concentration?Ci?of intercellular CO₂ showed the opposite trend with the other 3 photosynthetic indexes.Under the treatment of normal phosphorus,the area of vascular bundle,xylem area,phloem area and number of ducts were significantly higher than those of low efficiency and anti-effect varieties?P<0.05?.Under low phosphorus treatment,high efficiency and anti-effect varieties were significantly higher than those of low efficiency and normal varieties?P<0.05?.Among them,by increasing the area of vascular bundle,phloem area and xylem area to improve the reutilization of phosphorus in the body and improving the efficiency of phosphorus transport in the body,the reverse type is an important factor in the performance of phosphorus in the deficient phosphorus environment.Under normal phosphorus and low phosphorus treatments,nitrogenase activity of Alfalfa increased first and then decreased,and the activity of nitrogen fixation was strongest at pods.Different phosphorus efficiency types of Alfalfa showed higher nitrogen fixation activity under high normal phosphorus level than those with high efficiency and low efficiency.Under low phosphorus level,the nitrogenase activity of the high-efficiency varieties and the effective varieties is higher than that of the common and low effective varieties.The content of total nitrogen in the aboveground and underground parts of normal phosphorus level was higher than low phosphorus treatment.The activities of NR and GS showed the same trend.In the different growth stages,the acid phosphatase in the shoot part of normal phosphorus and the low phosphorus ground increased first and then increased,and reached the maximum at the flowering stage,and the Poding period decreased.Under low phosphorus treatment,the activities of acid phosphatase and phosphorus in high-efficiency and reactive varieties were all higher than those of the common and low effective varieties.The effect of type varieties,the environment of the phosphorus deficiency induced by improve the activity of acid phosphatase in the body,promote the phosphorus in the body by the aging or mature tissue in phosphatase efficient recycling,to ensure the growth and metabolism site provide sufficient phosphorus.This is the effect type varieties with high phosphorus efficiency in low phosphorus environment of one of the most important factors.