| In order to select the optimal planting density for big ear winter wheat varieties Pubing176, 32-62-6-2 and Xiaoyan22 , and study the effects of different densities on their growth and development, we use the two factors split design, variety (line) as the main area, density is deputy area, compare the synthesis performance of wheat traits on different densities, the conclusions are listed as follows:(1)Planting density had a certain influence on winter wheat group dynamic and individuals. Secondary roots and tillers number of three winter wheat varieties (lines) was represented decreasely with planting density increasing. Plant height was higher with planting density increasing. During the period of the flowering to the filling stage, Xiaoyan 22 top-three leafs'LAI was maximum in 4.2 million plants per ha. Pubing176 and 32-62-6-2 top-three leafs'LAI was maximum in 3.15million plants per ha.(2)Planting density had a certain influence on the physiological characteristics of winter wheat. Individual fresh weight and dry weight of three winter wheat varieties (lines) were gradually decreased with planting density increasing. The trends of density on net photosynthesis rate (Pn), stomatal conductance (Co), the transpiration rate (Tr) and univalent water use efficiency (WUE) were very similar to each other, the performance was increased at first, but then it was dropped as the planting density increasing. Photosynthetic stomatal limit (Ls) trend on different densities was contrary to the trend of Pn, Co, Tr and WUE. The variance analysis showed that, for Pn, Co, Tr and Ls, there were significant or remarkably significant difference. Through the above analysis, we abtained the best densities on photosynthetic characteristics of Xiaoyan 22, Pubing176 and 32-62-6-2 were 4.2million plants per ha, 3.15 million plants per ha and 3.15 million plants per ha, respectively.(3) Planting density had a significant influence on grain yield traits of winter wheat. The number of valid spike of three winter wheat varieties (lines) was gradually increased with planting density increasing. Grains per spike and 1000-grain weight were reduced with planting density increasing. The grain yield was increased at first, but then it was dropped as the planting density increasing. The highest yield of Xiaoyan22 was on 4.2 million plants per ha , and the highest yield of Pubing176 and 32-62-6-2 was on the density of 3.15 millon plants per ha. There were significant or remarkably significant difference between the number of spikes and grains per spike. While there were little difference among the weight per 1000 grain on different density.(4) From the path analysis of yield and thire components of three winter wheat varieties (lines), we could see the contribution of spike number was the most important on the yield. The contribution of spike number was the largest for Xiaoyan 22, then grains per spike. The contribution of 1000-grain weight was the least for Xiaoyan22. The contribution of spike number was the largest for Pubing176, then grains per spike, too. The contribution of spike number was the largest for32-62-6-2, then 1000-grain weight.(5) Planting density had no significant influence on economic coefficient. Three winter wheat varieties (lines), the maximum economic coefficient of Xiaoyan 22, Pubing176 and 32-62-6-2 were respectively 4.2 million, 3.15 million and 3.15 million plants per ha.(6) Planting density had definently significant influence on quality of different winter wheats. There was no consistence in change of wheats quality index on the same density. Under this test condition, there was higher protein content in 3.15 million and 4.2 million plant per ha to Xiaoyan22. There was higher protein content in 2.1 million plant per ha to Pubing176. And there was higher protein content in 2.1 and 4.2 million plant per ha to 32-62-6-22. Under the same condition, there was highest rigidness in 2.1 million plant per ha to Xiaoyan 22, there was highest rigidness in 3.15 million plant per ha to Pubing176, and there was highest rigidness in 2.1, 3.15 and 5.25 million plant per ha to 32-62-6-2. Seed moisture content of three winter wheat varieties (lines) all met the standards for safe storage (≤12.5%). Precipitation values were highest in 3.15 million plant per ha to Xiaoyan22 and Pubing 176. There was highest precipitation values in 2.1 million plant per ha.In short, grain yield and quality were difficult to make unified on different planting densities. While there was a optimal planting density which was presented both yield and quality in production. Therefore, considering the various traits of comprehensive performance, we had a results that the best planting density for Xiaoyan22, Pubing176 and 32-62-6-2 was 4.20 million , 3.15 million and 3.15 million plants pe ha respectively.
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