| This experiment was controlled under field conditions from 2008 to 2009 in the growing seasons. Zhengdan 958 was taken as the experimental material which was planted in a large area in henna province, three-factors formed split-split plot design. Different planting densities, different planting ways and different leaving seedling ways were taken to research the community construction of the different group structure on the characteristics of summer corn canopy, canopy microclimate characteristics, photosynthesis characteristics, chlorophyll fluorescence characteristics, matter accumulation and yield . The main results were as follows:Fristly, planting density was filtered in 2008. In order to identified the appropriate community construction, we set six different planting density as treatment. They were 45000, 60000, 75000, 90000, 105000 and 120000 plants per ha. The results showed that canopy photosynthetic rate (CAP) , in general, with the increase of planting density increased first and then decreased, and reached the maximum at 105000 plants per ha; leaf area index from seedling stage to the milky stage were increased with the density increased, 90000 plants per ha was the maximum in maturity stage; plant dry matter decreased as the density increased, groups of dry matter reached the maximum at 90000 plants per ha; malondialdehyde (MDA), with the function of the advancing, the higher density and the faster increased; the grain filling rate decreased with the increase of the density; kernel per ear, ear grain weight and 1000-kernel weight were reduced with the increase of the density, increasing the planting density appropriately, it could offset the reduction of the ear grain weight and 1000-kernel weight in the way of increasing the kernel per ear, it reached the maximum yield at 90000 plants per ha, as the density increased continued, increasing of the ears can not compensate for the reduction of the ear grain weight and 1000-kernel weight, the final performance was the lower yield. Therefore, based on the rustle of the canopy photosynthetic rate, the groups of dry matter accumulation and the yield, we select three planting density 75000, 90000, 105000 plants per ha, to go on the next experiment.Secondly, the experiment in 2009 was on the community construction. Basing on the result of experiment in 2008, three planting density 75000, 90000, 105000 plants per ha, were retained, and increased planting ways ( such as equidistant row and wide and narrow row planting) and leaving seedling ways ( leaving seedling doubly and singly) two factors. Different planting densities, planting ways and leaving seedling ways could construct the different community construction and it could make effect on the characteristics of summer corn canopy: canopy structure in the mean leaf inclination angle (MLIA), transmission coefficient for diffuse penetration (TCDP), transmission coefficient for radiation penetration (TCRP), extinction coefficient, leaf distribution (LD) along with the advance of grain filling were decreased; MLIA and LD were increased with the increase of planting density; TCDP, TCRP and extinction coefficient were decreased with the increase of planting density; in the same planting density and different planting ways, the equidistant row was less than the wide and narrow row in MLIA, TCDP, TCRP and extinction coefficient, while the LD was in the opposite; in the same planting density and the same planting ways, leaving seedling singly was less than leaving seedling doubly in TCDP, TCRP and extinction coefficient, and the LD was in the opposite, wide and narrow row planting and leaving seedling Doubly could make canopy structure significantly improved.Different canopy structure made effect on the canopy microclimate. The higher the planting density was, the more the Canopy intercept photosynthetic active radiation (PAR) was; equidistant row was more than the wide and narrow row in intercept PAR, there were some differences between the two leaving seedling ways, the leaving seedling singly was more than the the leaving seedling doubly at upper to lower canopy and the middle to upper canopy, and the middle to lower canopy was on the contrary. Canopy temperature (CT) decreased, with the increase of planting density in the daytime; the wide and narrow row was more than the equidistant row, and leaving seedling doubly was more than the leaving seedling singly. CT decreased with the decrease of planting density in the night time, the planting ways and the leving seedling ways were opposite to the the daytime. The carbon dioxide concentration in the Canopy at the day time were complex in different planting density , 90000 plants per ha was the minimal 105000 plants per ha was medial and 75000 plants per ha was the maximal during 8:00-10: 00, canopy carbon dioxide concentration reduced with the increase of the density during 12:00-18:00, the wide and narrow row was more than the equidistant row, and leaving seedling doubly was more than the leaving seedling singly; the carbon dioxide concentration in the canopy increased with the increasing of the density at the night time, the planting ways and the the leaving seedling ways were the same in the day time. In the same planting density, wide and narrow row planting and leaving seedling doubly could intercept more PAR in the lower canopy, and increase the flow of air and traverse of the light in whole canopy, it was beneficial to matter and energy exchange between corn canopy and the atmosphere . Different characteristics of canopy microclimate on maize had an impact on the photosynthetic characteristics. CAP increased with the increase of the density at the silking stage, it increased with planting density increased first and then decreased, and maximum at 90000 plants per ha; the wide and narrow row was more than the equidistant row, and the leaving seedling doubly was less than the leaving seedling singly. Photosynthetic rate and stomatal conductance was gradually decreased with the grain filling stage, in addition to the upper leaves were unobvious, leaving seedling doubly was less than the leaving seedling singly in the middle and lower leaves, the photosynthetic rate were decreased with the increase of density in the three parts of leaves, the wide and narrow row was more than the equidistant row, while the intercellular CO2 concentration was opposite. The maximal photochemical efficiency of PS II in the dark and the latency activity of PS II in the dark were decreased with the advance of growth period, upper leaves was the minimal, lower leaves was medial and middle leaves was the maximal; Fv / Fm and Fv / Fo decreased with the increase of planting density, the wide and narrow row was more than the equidistant row, and the leaving seedling doubly was more than the leaving seedling singly. Photochemical quenching coefficients (qP) decreased with the increasing of planting density, the wide and narrow row was more than the equidistant row, and the leaving seedling doubly was more than the leaving seedling singly; lower leaves were the minimal, middle leaves were medial and upper leaves were the maximal at non-photochemical quenching coefficients (NPQ) , and NPQ increased with decreasing of plant density, the wide and narrow row was more than the equidistant row, and the leaving seedling doubly was more than the leaving seedling singly. The Lower leaves has strong capabilities of photosynthesis in early filling stage. The position which they were in , often made it in a "light hunger" state, so the yield could be improved by improving their conditions of light.Dry matter accumulation, and it's transport, nitrogen utilization, yield and its components were laid on the photosynthetic characteristics. Dry matter weight per plant of all organ were increased with the decrease of planting density during silking and maturity stage; the weight of plant dry matter in leaves, stem and leaf sheath showed that lower leaves was the maximal, middle leaves was medial and upper leaves was the minimal, and reduced with the increase of planting density, the wide and narrow row was more than the equidistant row, there were some differences in leaving seedling ways, leaving seedling doubly was less than the leaving seedling singly in the middle and lower leaves , upper leaves was opposite . In the silking stage, the total content of soluble sugar in leaves and stems showed that: lower leaves was the maximal, middle leaves was medial and upper leaves was the minimal; in maturity stage, middle leaves were the maximal, lower leaves were medial and upper leaves were the minimal. The content of soluble sugar content increased with decreasing of planting density of all parts of the leaf, stem and leaf sheath during the two stages, the wide and narrow row was more than the equidistant row, leaving seedling doubly was less than the leaving seedling singly in the upper organs, in the middle and lower organs were opposite. In silking stage, the lower part were the maximal, the upper part were medial and the middle part were the minimal in leaf, stem and leaf sheath of total nitrogen content; in maturity stage , the upper part were the maximal, middle part were medial and the the lower part were the minimal in leaf, the lower part were the maximal, the middle part were medial and the upper part were the minimal in stem and leaf sheath. During the two stages, the total nitrogen content increased with decreasing of planting density; three parts of the leaves, stem and leaf sheath showed the wide and narrow row was less than the equidistant row in silking stage, and it's opposite in maturity stage. During the grain filling period ,crop growth rate (CGR), N- harvest index (N-HI), N uptake efficiency (NUPE) decreased with the increaseing of planting density, the wide and narrow row was more than the equidistant row, leaving seedling doubly was more than the leaving seedling singly, N use efficiency (NUE) was opposite; harvest index (HI) in different planting densities showed that 90000 plants per ha were the maximal, 75000 plants per ha were medial and the 105000 plants per ha were the minimal, the wide and narrow row was more than the equidistant row, leaving seedling doubly was more than the leaving seedling singly; ear length and ear diameter decreased with the increasing of planting density, the wide and narrow row was more than the equidistant row, leaving seedling doubly was more than the leaving seedling singly. Length of bald increased with the increasing of plant density,planting ways and different leaving seedling ways were different with ear length. Ear grain weight and 100-kernel weight decreased with the increasing of plant density , the wide and narrow row was more than the equidistant row, leaving seedling doubly was more than the leaving seedling singly and the highest yield was D4P2R2 treatment .
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