Identification And Evaluation Of Nitrogen Efficiency Of Peanut Varieties At Seedling Stage

Nitrogen is one of the essential nutrients for peanut growth and is closely related to peanut yield,quality and physiological metabolism.Traditional planting methods increase yield by applying large amounts of nitrogen fertilizer,resulting in increased planting cost,environmental pollution and low nitrogen use efficiency.Screening peanut varieties with high nitrogen use efficiency is of great significance to improve nitrogen use efficiency and exert nitrogen fixation effect of peanut in later stage.Through the treatment of different nitrogen levels,the suitable low nitrogen level for identification of nitrogen efficiency in peanut seedling stage was determined,and the peanut varieties with high nitrogen efficiency were screened.On this basis,the differences of peanut varieties with different nitrogen efficiency in biomass,root-shoot ratio,root morphology,plant nitrogen accumulation,root absorption kinetic parameters and key enzymes of nitrogen metabolism were discussed.The main research results are as follows:1.Determine the appropriate low nitrogen level for peanut seedling nitrogen efficiency identificationThe biomass,root-shoot ratio,nitrogen accumulation and nitrogen use efficiency of different peanut varieties were significantly different under 0.04 mmol/L Ca（NO₃）₂treatment.Therefore,0.04 mmol/L Ca（NO₃）₂was determined as an appropriate low nitrogen level for identification of nitrogen efficiency of peanut at seedling stage.2.Screening of peanut cultivars with high nitrogen efficiency at seedling stageThe biomass and low nitrogen tolerance coefficient were taken as the key indexes to evaluate the nitrogen efficiency of peanut varieties.The 68 peanut varieties were divided into four types,including 13 cultiv ars with low nitrogen efficiency and high sensitivity,19cultivars with low nitrogen efficiency and high sensitivity,26 cultivars with high nitrogen efficiency and low nitrogen sensitivity,and 10 cultivars with high nitrogen efficiency and low nitrogen sensitivity,respectively.3.Analysis on dominant traits of peanut cultivars with high nitrogen efficiency at seedling stageThe biomass,nitrogen accumulation and the activities of key enzymes in nitrogen metabolism of peanut seedlings were significantly decreased under low nitrogen culture conditions,while the decrease of biomass,nitrate reductase and glutamine synthase activities of nitrogen efficient cultivars was less than that of nitrogen inefficient cultivars.The total root length,root surface area,root volume and root tip number of peanut were significantly decreased under low nitrogen culture,while the average root diameter was significantly increased.The total root length,root surface area and root volume of high nitrogen efficiency cultivars were significantly higher than those of low nitrogen efficiency cultivars.The maximum nitrogen uptake rate（Imax）and critical concentration（Cmin）of peanut decreased,while the Michaelis constant（Km）increased.