Study On Nitrogen Uptake And Utilization Efficiency Of Sugarcane With Different Genotypes

Sugarcane is the most important sugar-yielding crop in the world,nitrogen(N)plays an important role in the process of sugarcane's growth.The nitrogen-efficient sugarcane genotype TP3,the nitrogen low-efficiency sugarcane genotype Co285 and the control ROC22 were early selected through the field experiments.Through field experiment and pot experiment,the normal and non-nitrogen treatments were set to compare different nitrogen levels.Study the agronomic characteristics of different N efficiency sugarcane under different N treatment by field experiment.Study the difference of root architecture between 3 sugarcane genotypes under different N treatment in 60 days and 150 days of planting by pot experiment.Study the difference of root structure,root-absorbing capacity and the activity of N metabolism by hydroponics experiment.Analysis the differences and reasons of N uptake efficiency and utilization efficiency of 3 sugarcane genotypes under different N treatment.Results showed that as follows.1.Compared with ROC22 and Co285,TP3 has better agronomic characteristics,the difference with Co285 reached significant level.The root biomass,total root length,root volume,root surface area and root tips of TP3 are better than Co285 significantly.By optimizing root morphological index and increasing the proportion of thin root,TP3 could obtain more nitrogen from growth medium.2.The root depth of different sugarcane genotypes under normal nitrogen(NN)treatment is shallow than the low nitrogen(LN)treatment,and root width and root angle from the horizontal under NN treatment is better than LN treatment.The ratio of root width to root depth and root angle from the horizontal of Co285 is better than TP3 significantly.After 60days and 150days planting,the root angle from the horizontal of Co285 are between 5.68°and 8.26°which is higher than TP3 under N-N treatment,between 4.77°and 9.42°which is higher than TP3 under LN treatment.Indicated the root of TP3 could access to nutrients by growing in deep soil.The proportion of root biomass and root length of TP3 is higher than Co285 in the soil under 10 cm,under different N treatment in different treatment time.However,these indexes of Co285 in the soil of 0?10 cm are better than TP3 due to shallower root distribution.3.The root activity and root absorbing area of different N efficiency sugarcane genotypes under NN treatment is better than LN treatment.The root activity and root absorbing area of TP3 is better than Co285 significantly.Compared with Co285,TP3 has higher Vmax value and lower Km value.Indicated that TP3 has more energy to absorb nitrogen.4.With the growth of sugarcane,the leaf Pn,Gs and Tr are presenting a tendency to increase,while Ci is decreasing.These indexes under NN treatment are better than LN treatment.The Pn of TP3 is higher than ROC22 and Co285 significantly under different N treatment.In addition,the Gs,Ci and Tr of TP3 are at relatively high level.TP3 has stronger power of light energy capture and light contract ability,5.The activity of NR,GS,GOGAT and GDH of different N efficiency sugarcane genotypes increase with N level.The activity of NR,GS and GOGAT of TP3 is higher than Co285 under different N treatment,and the difference under LN treatment reached to significant level.However,there is no difference in GDH activity of 3 sugarcane genotypes under different N treatment.TP3 has higher level of nitrogen metabolism.