| In 2008, at four ecological regions: Shandong Agricultural University, Wenkou, Yanzhou and Laizhou. ZhengDan958 (ZD958) and DengHai661 (DH661) were used for experimental materials, and planted by five different densities which were 22500, 45000, 67500, 90000 and 112500 plant?ha-1. In 2009, Denghai 661 as the test material and planted by 8 different densities, which were 30000, 45000, 60000, 75000, 90000, 105000, 120000 and 135000 plant?ha-1, also used Nongda 108 and Danyu 34 as the test material, they were planted by 5 different densities, which were30000, 45000, 60000, 75000 and 90000 plant?ha-1. The experiment was carried out in Shandong Agricultural University experimental farm. The main results and conclusions were as follows:1. Effects of plant density on grain yield and quality of high-yielding summer maize. The responses of increase density about High-yielding summer maize were differents. The Maximum grain yield of DH 661 was 14947.5 kg·ha-1 under the plant density of 120000 plant·ha-1.With the increase of planting density, ND 108 consistent with the DH 661, The maximum grain yield was 12290.5 kg·ha-1 under the plant density of 9 Million plant·ha-1. The Maximum grain yield of DY 34 was 11551.4 kg·ha-1 under the plant density of 9 Million plant·ha-1. Protein content decreased, fat content was a peak curve, soluble sugar content increased significantly with plant density increased. Simultaneously, total starch, amylopectin and amylose content increased significantly too. Amylopectin content was higher than amylose.2. Effects of plant density on dry matter accumulation and partitioning of high-yielding summer maize.Population grain yield and dry matter accumulation increased significantly with the increasing of plant density, while the per plant were decreased. At anthesis and milking stages,the decrease rate of stem dry matter accumulation was greater than that of leaf with increasing plant density, which was on the contrary at maturity stage. So the effects of plant density on stem dry matter accumulation were significantly strenger than that before milking stage, which was on the contrary after milking stage. After milking stage, the transportation efficiency of both stem and leaf reduced significantly with the increasing of plant density, the contribution rate of stem also reduced significantly. The stem dry matter transportation contributed more than leaf's to the grain yield under the density from 30000 to 90000 plant-ha-1, but the leaf dry matter transportation contributed more than stems to the grain yield under the density from 105000 to 135000 plant?ha-1 . 3. Effects of plant density on plant characteristics of high-yielding summer maize. With the increasing of plant density ear traits were significantly reduced but barren ear length, and ear-height became higher, stems were thinner, leaves became into long and narrow, on the contrary, the population grain yield increased. What show that advantages of plant populations were made up the disadvantages of per plant, so appropriate increase plant density is the key to increase yield.4. Effects of plant density on photosynthetic characteristics of high-yielding summer maize.With the increase of plant density both chlorophyll a and chlorophyll b were significantly reduced, net-photosynthetic rate and net-assimilation rate decreased significantly, PEPCase and RuBPCase activity was significantly decreased. With increasing of plant density, mesophyll cell membranes ruptured, the number of chloroplast significantly reduced, the spindle chloroplast became into oval and ellipsoidal, chloroplast membrane structure incompleted gradually. The number of chloroplast grana reduced significantly, the grana layers increased, the grana dissolved finally. Increased plant density, both leaf area index and leaf area duration increased significantly, thereby the population assimilation rate increased to improve grain yield.5. Effects of plant density on source-sink characteristics of high-yielding summer maize.With the increment of plant density, leaf area index was significantly increased, while the leaf area per plant, the maximum number of filaments, the grains per ear and 1000-grain weight were all decreased. At the same time the harvest index was decreased with the increment of plant density, and the grain-leaf ratio was significantly decreased, while there was not significant difference when plant density was above 67500 plant?ha-1. The yield increased with the increasing of plant population. It showed that the higher plant density distinctly increased the ear grain number per area, through improving the sink-capability of population, and obtained higher yield of summer maize. |
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