春玉米叶面积系数动态特征的密度效应

为进一步明确春玉米不同密度群体叶面积系数(LAI)特征参数的密度效应，以吉单209和郑单958为材料，于2005年和2006年在东北春玉米区(吉林)分别设置4.5~10.5万株 hm^-2 5个密度和3.0~12.0万株 hm^-2 7个密度处理试验，应用作物高产群体相对LAI动态普适模型方程y= (a+bx)/(1+cx+dx²)模拟分析不同密度对LAI动态特征参数的影响。结果表明，春玉米群体最大LAI在3.0~12.0万株hm^-2范围内随密度增加呈近似直线增大趋势，而最大LAI出现的时间随密度增加而提早；将LAI数据相对化处理后，不同密度群体的LAI差异在最大LAI之后较之前表现明显，高密度群体较低密群体LAI衰减迅速。全生育期平均LAI随密度增加呈显著线性增大趋势，而平均LAI与最大LAI的比率则随密度增加呈显著线性减小趋势。密度对模拟方程各参数均有不同程度的影响，相邻密度差异不明显，间隔3.0万株 hm^-2的差异显著；不同参数变化趋势不同，其中参数a接近“0”，受密度影响不大；b、c均随密度的增加而减小，d随密度的增加而增大。全生育期群体LAI变化速率呈“N”形变化趋势，且与群体LAI变化及生育期对应，高密度群体LAI增加及衰减的速率均大于低密度群体，拔节期和大喇叭口期为密度响应敏感期。由此可见，密度对春玉米全生育群体LAI动态具有调节作用，尤其群体LAI变化速率、最大LAI及其到达的时间、平均LAI及其与最大LAI的比率等重要特征参数对密度响应较为敏感，可作为对春玉米群体密度调控的参考指标。

Effect of Plant Density on Dynamic Characteristics of Leaf Area Index in Development of Spring Maize

To provide further evidence for the regulatory effect of plant densities on the important characteristics of leaf area index (LAI), the important feature of the regulation role for the parameters, such as the velocity of LAI change, mean LAI, the maximum LAI and the time to maximum LAI was analyzed quantitatively. A field experiment using two spring-maize cultivars, Jidan 209 and Zhengdan 958, was conducted with five different densities from 4.5×10⁴ to 10.5×10⁴ plants ha^-1 in 2005 and seven different densities from 3×10⁴ to 12×10⁴ plants ha^-1 in 2006 in Jilin province, respectively. An extensively suitable LAIsimulation model for high yield population, y= (a+bx)/(1+cx+dx²) was adopted in the present research to simulate and analyze the effect of different densities on the dynamic characteristics of LAI in development of spring-maize in whole growth duration. The results indicated that maximum LAI was significantly increased with the increase of planting density from 3×10⁴ to 12×10⁴ plants ha^-1 and the time to the maximum LAI advanced with increasing plant densities. The relative LAI of different densities showed large difference between before and after reaching the maximum LAI. LAI of high density decreased more rapidly than that of low density. The mean LAI in whole growth duration increased while the ratio of mean LAI to the maximum LAI declined with increasing densities. The influence of density on each parameter of model equation by applying the relative model was different, that between intervals of 3×10⁴ plants ha^-1 was significant. The trend of changes on different parameters was different. The parameter a approached to 0, therefore, density has little effect on it. The parameters b and c reduced with increasing densities, but d increased with increasing densities. The velocity of LAI change in growing period showed the trend of a curve of N shape with variable speed, and the changed trend of LAI fit into growth at ages. The velocity of LAI change in high-density population increased or decreased larger than that in low-density population. The jointing period and the big flare periods were in response to density sensitively. The results above proved that some important indexes are more sensitive to different densities, such as the changing velocity of group LAI, the maximum LAI, the time to the maximum LAI, mean LAI, and the ratio of mean LAI to the maximum LAI. These characteristic indexes of LAI may serve as the reference for regulating plant density of spring maize population.