Effects Of Planting Density On Starch Synthesis And Accumulation In Maize Kernels

Starch is a kind of polysaccharide stored in cells during plant growth and development, and it is usually accumulated in seeds or stems and other organs with the form of starch granule. The contents of starch in Maize kernels has a direct influence on the total yield of maize. The plant density of Maize has a great effect on the final yield during the practice of genetics breeding and producing. So, it is very important to study the effects of plant density on the synthesis and accumulation of starch in Maize kernels.In order to elucidate the effects of planting density on the starch synthesis and accumulation in Maize kernels, we selected three compact Maize varieties with strong resistance and different density-tolerance, they are Zheng Dan 958, Xianyu335 and Denghai 618. We studied activities of enzymes related starch synthesis and starch content in maize kernels, agronomic traits and final yield of Maize, photosynthetic rate and grain filling rate under the density of 45000s 60000,70000,90000,105000 and 12000 plants/hm2 respectively. The main results are as follows:1, The enzyme activity of SS and ADPGPPase in grain decreased with the increases of planting density; With the increase of planting density the enzyme activity of SBE in grain increased first and then decrease. The SS activity in grain of Xianyu335 reaches the highest at the 24th day after pollination, while the peak of SS activity in grain of Denghai 618 appears between the 17th and 24th day after pollination, and the SS activity in grain of Zhengdan 958 varies due to the planting density. The ADPGPPase activity in grain of Zhengdan 958 reaches its peak at the 31st day after pollination, it appeares at the 24th day after pollination in xianyu335, and it appeares at the 38th day after pollination in denghai618. The SBE activity in grain of Xianyu335 and Denghai 618 both reaches their peaks at the 24th day after pollination, while it varies due to the planting density in Zheng 958.2, With the increase of planting density, amylose, starch and soluble sugar content increased first and then decrease. Zheng 958 and denghai618 in the density of 75000 plants/hm2 grain amylose and total starch content is highest,while xianyu335 in the density of 75000 plants/hm2 grain amylose and total starch content is highest. Three varieties of grain soluble sugar are the highest content in the density of 75000 plants/hm2. The grain starch and sucrose content gradually reduce with the increase of planting density.3、All varieties per plant yield decreases with planting density increasing, while Denghai 618 has highest per plant yield. The yield of each cultivar groups are increase first and then decrease with the increase of planting density, Zheng dan958 and Denghai 618 in density of 75000 plants/hm2 and the yield is the highest, while Xianyu335 highest yield in density of 60000 plants/hm2. Under the different density, denghai 618 largest yield;Under the high density Zheng dan 958 higher than Xianyu 335, Xianyu 335 under low density is higher than Zheng dan 958.4、All varieties of ear height 、 plant height and ear accounted for the proportion with the increase of planting density, first increase and then decrease. Ear length and ear diameter decreases with the increase of planting density. Zheng Dan 958 yield was not significantly positive correlation with single ear weight and ear length, and the yield was negatively correlated with spike length,while Xianyu 335 and Denghai 618 yield were correlated with ear weight, ear length and ear diameter is positively but not significantly related to the level of relationship.5、 All varieties of 100 grain fresh weight and 100 grain dry weight decrease with the increase of planting density, under the same density Denghai 618 is largest, followed by Zhengdan958, Xianyu335 minimum. The grain moisture content of maize increased with the increase of density. All varieties of grain filling rate decrease with the increase of planting density, both reaches peak at 24 d after pollination, the planting density has great effect on maize grain filling rate under high density. The grain filling rate is positively correlated with 100 grain fresh weight and 100 grain dry weight, Except for a few of the significant correlation levels, the rest are significantly correlated; The grain filling rate is significantly negatively correlated with grain moisture content6、The effect of planting density on the net photosynthetic rate of different leaf positions is different, which have the greatest influence on the third leaf clover, followed by ear lobe, The least influence on the third leaf of ear. With the increase of planting density, silking stage、 filling stage and maturity stage of the third leaf、 ear leaf and the third leaf net photosynthetic rate decreased; The effect of planting density on the photosynthetic rate of the Xianyu335 is the largest, followed by Zheng dan958, Denghai 618 on the minimum.7、Correlation analysis between yield and plant traits under different densities, except Xianyu335 yield and ear height are not significant negative correlation, the other varieties yield shows positive correlation between plant height and ear height, but not significant. Amylose、amylopectin and total starch content are positively correlated with ADPGPPase activity and SBE activity, but not significant; the level is not significant with SS activity.