Effects Of Different Nitrogen Application On The Spring Wheat Yield Formation Under High Temperature After Anthesis

Ningxia spring wheat cultivars Ningchun 4 and 47 as test materials, using split plot experiment, studied the effects of different nitrogen application on spring wheat physiological and biochemical indexes, starch content and yield under high temperature after anthesis, the main conclusions were as follows:1. Under high temperature after anthesis, appropriate amount of nitrogen nutrition treatments significantly increased spring wheat chlorophyll content, photosynthetic rate (Pn), transpiration rate (Tr) and stomatal conductance (Gs), the chlorophyll fluorescence parameters Fm, Fv/Fm, Fv/Fo varying degrees increased, when the nitrogen application at rate of 120-240kg/hm2, most beneficial plants for photosynthesis. Compared with normal temperature, high temperature stress after anthesis all nitrogen application of chlorophyll content, SPAD value, Pn, Tr, Gs and fluorescence Fm, Fv/Fm, Fv/Fo were lower than normal.2. Under high temperature after anthesis, appropriate amount of nitrogen nutrition treatments significantly improved the activity of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT), and significantly lower the malondialdehyde (MDA) content, reduced the harm of exoxidation. The rate of 240kg/hm2 nitrogen treatment were more conducive to improve the activity of enzymes,the nitrogen application at rate of 120kg/hm2 second. Compared with normal temperature, the activity of enzymes under high temperature stress were lower than normal, while the MDA content was higher than normal temperature.3. Under high temperature after anthesis, appropriate amount of nitrogen application increased the amylose content, amylopectin content and total starch content varying degrees, promoted the synthesis of wheat starch, when nitrogen rate was 120-240kg/hm2, starch content was the highest,the rate of 300 kg/hm2 second. Similarly, right rate of nitrogen application could significantly improve the activities of the enzymes involved in starch synthesis (ADPG-PPase, GBSS, SSS, SBE), while the nitrogen rate of 120-240kg/hm2,the activities of key enzymes involved in starch synthesis were higher than the rate of 300 kg/hm2.The amylose content, amylopectin content and total starch content and the activities of the enzymes involved in starch synthesis (ADPG-PPase, GBSS, SSS, SBE) under high temperature after anthesis were respectively lower than normal.4. Under high temperature after anthesis, appropriate amount of nitrogen application could increase the plants’leaf area, promote the dry matter stored in vegetative organs before flowering transported to grain after anthesis, increase the dry matter after anthesis accumulation to grain contribution rate, increase the spike grains, grain weight and yield. When the nitrogen at rate of 120-240kg/hm2, grain weight increased most significantly, but the nitrogen application at rate of 300 kg/hm2 were not conducive to increase grains per spike, grain weight and biological production.