Effects of different nitrogen levels on key enzymes of nitrogen metabolism and contents of related active substances for three sugarcane varieties

【Objective】In order to understand the absorption and accumulation dynamics law of N nutrient in sugarcane to provide references for scientific and rational application of nitrogen fertilizer, the present experiment was conducted to study effects of different nitrogen levels on the activities of key enzyme in nitrogen metabolism and the contents of related active substances at four different growth stages of 3 sugarcane varieties. 【 Method 】 Using 3 sugarcane varieties viz., ROC22, GT11 and GXB9 as materials, the physiological and biochemical indexes related to nitrogen metabolism at different growth stages were determined under 3 levels of urea fertilization(150, 300 and 600 kg/ha) in the field experiment by using split plot design with two factors in 2013(plant cane) and 2014(ratoon cane). 【Result】The results showed that activities of nitrate reductase(NR), glutamine synthetase(GS), glutamate oxaloacetate transaminase(GOT) and glutamate pyruvate transaminase(GPT) increased with the increase of nitrogen levels. The contents of soluble protein and free amino acids increased within a certain range(150-300 kg/ha) with the increase of nitrogen level, which no longer increased beyond a certain range. While the contents of soluble sugar and nitrate nitrogen were decreased with the increase of nitrogen level within a certain range(150-300 kg/ha). 【Conclusion】Under the urea application rates of 150-300 kg/ha,the nitrogen metabolism of sugarcane is significantly enhanced with the increase of nitrogen level. The sugarcane variety GXB9 has stronger regulative and adaptive ability in low nitrogen environment than other two varieties.