乙矮合剂对不同密度夏玉米花粒期不同部位叶片衰老特性的影响

为探讨乙矮合剂对密植夏玉米叶片衰老及后期早衰的调控机制, 建立华北夏玉米区密植高产稳产化学调控技术, 以中单909和浚单20为材料, 设置乙矮合剂(ECK)和密度梯度处理, 研究密度梯度对夏玉米花粒期不同部位叶片衰老特性的影响与ECK的调控效应。结果表明, 随密度增加, 两品种花粒期单株叶面积减小且降幅增大; 各叶位叶片的叶绿素相对含量和可溶性蛋白含量呈下降趋势; 超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、过氧化物酶(POD)活性呈降低趋势; 丙二醛(MDA)含量则呈增高趋势; 上述指标在叶位和品种间存在差异。ECK处理显著提高各密度不同部位叶片SOD、CAT、POD活性和叶绿素相对含量及可溶性蛋白含量, 显著降低MDA含量; 单株绿叶面积降幅减小, 叶片衰老进程延缓, 衰老程度减轻。ECK处理后, 较高密度群体下(7.5~10.5万株 hm^-2), 中单909和浚单20较各自对照分别增产5.59%~6.63%和6.73%~8.10%。因此, 采用合理的种植密度结合喷施乙矮合剂可作为华北夏玉米区高产栽培的重要技术措施。

Effects of Ethylene-Chlormequat-Potassium on Characteristics of Leaf Senescence at Different Plant Positionsafter Anthesis under Different Planting Densities

In order to explore the effects of ethylene-chlormequat-potassium(ECK) on leaf aging and early senescence in summer maize, and provide a theoretical basis for high and stable yields of summer maize under high planting density by chemical regulation technology in North China Plain,a field experimentwas conducted using two types of maize hybrids (Zhongdan909 and Xundan20)with treatments of ethylene-chlormequat-potassium under different planting densities. The results showed that the increased planting density significantly decreased leaf area (LA) per plant and increased LA reduction rate. With the increase of planting density decreased SPAD value, soluble protein content, and activities of superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) of ear leaf, the third leaf above ear, and the third leaf below ear,while malondialdehyde (MDA) content increased. The above indexes had differences among varieties andleaf positions. ECK treatment significantly increased activities of superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD), SPAD value and soluble protein content in leaves at different positions, decreased LA reduction rate, delayedand alleviatedleaf senescence. Under the density of ≥7.5×10⁴ plant ha^-1, the yield of Zhongdan909 and Xundan20, compared with their own controls, increased by 5.59%−6.63% and 6.73%−8.10%, respectively. ECK treatment significantly prevented early senescence under higher planting densities, therefore increased yield. Thus, adopting an appropriate planting density combined with ECK application could be an important technique for achieving high grain yield in summer maize production in North China Plain.