Change of Polysaccharide Content and Its Relation with Nitrogen Level in Sugarcane Leaves Under Nitrogen-Fixing Bacteria Inoculation and Nitrogen Supply

Abstract

In order to investigate polysaccharide accumulation in sugarcane leaves under azotobacter inoculation and nitrogen supply, a pot culture experiment was conducted in 2012. The plants of sugarcane varieties B8 and ROC22 were inoculated either with or without endogenous nitrogen fixation bacteria at two levels of nitrogen supply, that is, 0 and 1/2 N (5 mM N) application. The polysaccharide and total nitrogen in leaves were determined at different growth stages of sugarcane. The results showed that the polysaccharide content in sugarcane leaves changed in a single-peak curve for the whole growth duration, and reached the peak in September. Azotobacter inoculation and nitrogen fertilizer application resulted in 2 months advanced the polysaccharide peak in variety B8, but not in ROC22 compared to the non-inoculation treatment. For the non-nitrogen treatment, the azotobacter inoculation significantly increased the polysaccharide content in variety B8 from July to September. Treatment with 1/2 N dose showed decreased polysaccharide content by 39.8 and 29.0 %, respectively, in both B8 and ROC22 that were inoculated with azotobacter. The nitrogen fertilizer application increased the total nitrogen content in sugarcane leaf regardless of with or without azotobacter inoculation. The polynomial regression model fitting showed that the polysaccharide content in sugarcane leaf first increased and then decreased with the increasing of total nitrogen level, showing a parabola relationship between them.