Study On Photosynthesis Regulation Of Winter Wheat/Summer Maize By Nitrogen Applied

A field experiment was carried out in sub-humid areas using Eum-Orthic Anthrosols;, there were two Experimental treatment including CK and fertilizer applied, and on the basis of phosphorus applied, fertilizer applied included 0kg, 45kg, 90kg, 135kg and 180 kg N per hectare that marked as N0, N45, N90, N135, N180. According to the experiment, it studied the vertical distribution patterns of Canopy leaf nitrogen content and SPAD value, the differences of different layer leaves under different nitrogen levels of winter wheat and summer maize in different growth stages, and it researched the rules of fluorescence parameters such as Pn, photosynthetic potential, SPAD value, leaf area, leaf nitrogen content with different treatments of nitrogen applied, then it also studied correlation among them. It wanted to prove whether nitrogen applied had an impact on leaf nitrogen content and Photosynthetic parameters or not, also whether it was the same result using different layer of leaf nitrogen nutrition for nitrogen nutrition diagnosis. From the study conclusion it had a certain value to choose the best layer leaf to nitrogen nutrition diagnosis of winter wheat and summer maize. According to the research, the main conclusions were as below:1. Different growth stages of leaf nitrogen content of winter wheat were significantly reduced by top-down rule, and the nitrogen content in different layers increased as the nitrogen increased in the treatments. As the level of the nitrogen fertilizer increased, the gradient at different layer leaf nitrogen content was relatively stable, but the gradient between middle and lower layer increased in mature stage. The law of Canopy leaf chlorophyll content was similar with the vertical distribution of leaf nitrogen content, upper was 6.50% higher than middle in average, and middle was 27.43% higher than lower. Different layer leaf nitrogen content of summer maize of the upper, middle and lower leaf was obviously the law of diminishing, according to the average data of different leaf layers in the whole growth stages, upper is 6.64% higher than middle, and middle is 5.18% higher than lower. With the increasing of nitrogen applied, the differences between upper and middle was increasing, but the differences between middle and lower was decreasing. The law of canopy leaf chlorophyll relative value was similar with the vertical distribution of nitrogen content.2. In the jointing stage, the filling stage and maturity Pn reached the maximum value in the N135 in the flag leaf of winter wheat, and in the jointing stage Ci reached the minimum value in the N180, which was due to too much nitrogen fertilizer restrained Ci value. There were different N contents of flag leaf significantly in different growth stages of winter wheat, Jointing stage>Booting stage>An thesis stage >Mature stage, and with the nitrogen applied increased, it was increased. Fv/Fm and Fv/F0 had a significant difference in different stages, and they reached a maximum value in N180. N content of upper leaf was significant different, Jointing stage>Grain filling stages >Mature stage. With nitrogen applied increasing, Fv/Fm and Fv/F0 increased, and it reached the maximum value in the N135.3. The correlation analysis among different crops photosynthesis and nitrogen applied indicators showed that: winter wheat leaf nitrogen content, SPAD value and the relevance of the amount of nitrogen in the whole growth period reached a significant positive correlation, photosynthetic potential in mature stage was positively correlated, in other growth stages the correlation was not significant. The correlation analysis between WUE-Leaf and nitrogen applied in the whole stages did not reach significant levels, and the correlation analysis among Fv/Fm, Fv/F0 and nitrogen applied was significant in Jointing and Mature stages. The correlation analysis between leaf N content of summer maize and nitrogen applied was significant, and the correlation analysis between Pn and nitrogen applied was weak. The correlation analysis among Fv/Fm, Fv/F0 and nitrogen applied had a weak positive correlation.4. Overall, the correlation analysis between SPAD value and nitrogen applied in different leaf layers of winter wheat and summer maize was a significant positive correlation, also the correlation analysis between leaf N content and nitrogen applied in different leaf layers of winter wheat and summer maize was a significant positive correlation, and the upper was the closest leaf to reflect the nutrition condition of SPAD value, leaf N content and nitrogen applied. The result revealed that the best nitrogen nutrition diagnosis of winter wheat and summer maize was the upper leaf.