Physiological Characteristics Of Genotype Sugar Beet With Water-nitrogen Coupling Efficiency

In order to clarify the physiological characteristics of water-nitrogen coupling high-efficiency sugar beet genotype,seven sugar beets with different genotypes were screened for water-nitrogen coupling efficiency by potted soil culture method in the light incubation room.Using the two selected high-efficiency and low-efficiency varieties,liquid culture method and Zhou's micro-potted soil culture method were used to study the different water-nitrogen coupling efficiency.Physiological characteristics such as morphology,photosynthesis,metabolism,stress resistance and nutrient depletion in rhizosphere of sugar beet with coupling effect were studied.(1)Nitrogen dry matter production efficiency,water use efficiency and dry matter yield are usually used as indicators to measure the coupling effect of water and nitrogen in crops,and KUHN4092 and HI0466,which have the highest coupling effect of water and nitrogen,were selected from seven sugar beet materials tested by using the mean of their membership functions.(2)With the increase of nitrogen application,the morphological characteristics of sugar beet improved significantly,but there were significant differences among varieties.The water-nitrogen coupling high-efficiency varieties were significantly higher than the water-nitrogen coupling low-efficiency varieties in plant height,petiole length,root surface area,total root length,root volume and root-shoot ratio.Under the same nitrogen level,the leaf area and the ratio of plant height to inefficient varieties increased significantly under high water potential(W1).(3)The net photosynthetic rate,stomatal conductance and transpiration rate of different varieties were significantly different,and the water-nitrogen coupling high-efficiency varieties were significantly higher than the low-efficiency varieties.The transpiration rates of water-nitrogen coupled high-efficiency varieties were higher in high water potential treatment than in low water potential treatment,the generalsituation is W1 > W2 > W3,and there were significant differences between water treatment.(4)With the decrease of water potential,the MDA and Pro contents of two types of cultivars showed an overall increase trend,but the two resistance indexes of cultivars with high water-nitrogen coupling effect increased less than those of cultivars with low water potential.Mild water stress did not cause disorder of cell membrane function and compensated for nitrogen uptake.(5)Nitrogen metabolic enzymes in sugar beet changed significantly with the degree of nitrogen nutrition and water stress in the growing environment.With the increase of nitrogen content in nutrient solution,the activities of NR and GS in two types of sugar beet increased significantly under three water stress conditions,but the increase ranges of different water-nitrogen coupling effects were different.Among them,the varieties with high water-nitrogen coupling efficiency,regardless of the amount of nitrogen application,increased significantly in three water stress conditions.Under different stress conditions,the activities of nitrogen metabolic enzymes in both varieties were significantly higher than those in low-efficiency cultivars.The effects of water on nitrogen metabolizing enzymes varied with varieties.The activities of two nitrogen metabolizing enzymes increased significantly in water-nitrogen coupled high-efficiency varieties under mild water stress,regardless of the nitrogen nutrition level,and there was a significant difference compared with low-efficiency varieties.(6)The uptake of ammonium nitrogen and potassium in rhizosphere of water-nitrogen coupled high-efficiency genotype sugar beet was more than that of water-nitrogen coupled low-efficiency genotype,but the phosphorus depletion of low-efficiency genotype sugar beet was less under low nitrogen,indicating that the uptake of phosphorus was weaker under low nitrogen than that under high nitrogen.Under the condition of high nitrogen,water-nitrogen coupling high-efficiency varieties can achieve synergistic absorption of nitrogen,phosphorus and potassium.