不同时期化控对密植玉米冠层结构及籽粒灌浆特性的影响

Effect of different times of spraying chemical regulator on the canopy structure and grain filling characteristics of high planting densities

合理的冠层结构能够保障作物群体生产功能得到充分发挥,而喷施化学调控物质是塑造作物冠层的重要措施之一,其中化控时期的选择至关重要。本研究以先玉335为供试品种,分别在60,000株hm^(-2)(D_(1))和90,000株hm^(-2)(D_(2))2个种植密度下,设置3个化控处理(化控剂为乙烯利复配剂),T_(10)(十叶期喷施450 L hm^(-2)化控试剂)、T_(15)(十五叶期喷施450 L hm^(-2)化控试剂)、CK(喷施清水作对照),研究了在不同密度下的不同时期化控处理对玉米冠层结构的调控,分析了冠层结构改变对籽粒灌浆特性和产量的影响。结果表明,在D_(1)密度下,化控处理对产量影响不显著,而在D_(2)密度下,T_(15)较CK两年平均增产7.3%,穗粒数和千粒重分别增加2.6%和3.6%,T_(10)处理穗粒数和千粒重均降低。T_(15)处理吐丝期上部叶夹角降低17.5%,十四至十七叶位的叶面积减小,使穗位层光能截获率增加11.5%,在乳熟期净光合速率(P_(n))仍能维持较高,完熟期群体叶面积指数(LAI)显著提高51.3%,延缓了中下部叶片衰老,增加花后干物质积累及其向籽粒中转移,延长了籽粒灌浆活跃期(P),使得达到最大灌浆速率时天数(T_(max))缩短了0.8 d,灌浆速率最大时生长量(W_(max))和最大灌浆速率(G_(max))分别增加了7.3%和4.0%,平均灌浆速率(V_(max))提高了6.9%。与D_(1)相比,D_(2)条件下喷施化控剂更加显著改善玉米冠层结构,提高玉米群体的光能利用率,增加花后干物质积累量,促进产量增加。相关分析表明,在D_(2)密度下,上部叶片(十四至十七)的叶面积与冠层中部光能截获率、穗粒数、千粒重、产量呈负相关,同时产量与千粒重、穗粒数、净光合速率、花后干物质积累量、灌浆速率最大时的生长量、灌浆速率均呈正相关。综上所述,在高密度下十五叶期喷施化控剂能够有效改善玉米群体上部冠层结构,使其叶面积和叶夹角减小,优化群体的光照条件,增强灌浆后期光合能力,提高籽粒灌浆速率,实现光资源利用和产量的协同提高。

A proper canopy structure ensures that the productive functions of the crop community are fully utilized,the spraying chemical regulator is one of the most important measures to shape the crop canopy,among which the selection of chemical control period is very crucial.The maize variety Xianyu 335 was used as the experimental material,field experiments were conducted with three treatments with two planting densities at 60,000 plants hm^(-2)(D_(1))and 90,000 plants hm^(-2)(D_(2))(chemical regulator made of ethephon),T_(10)(spray chemical regulator at the 10-leaf),T_(15)(spray chemical regulator at the 15-leaf),and CK(spray water as control).Therefore,it is important to explore the regulation of maize canopy structure and analyze the effect of changing canopy structure on grain-filling characteristics and yield.The results showed that at D_(1) density,the chemical regulator treatment had no significant effect on yield;at D_(2) density,compared with the CK,yield of T_(15) increased by 7.3% on average in two years,the number of kernel and the 1000-kernel weight increased by 2.6% and 3.3%,respectively,the number of kernels and the 1000-kernel weight decreased in T_(10).The upper leaf angle was reduced by 17.5% at T_(15) and the leaf area at the 14-17 leaf position was reduced,increased the light energy interception at the ear position leaf at 11.5%,and maintained a high net photosynthetic rate(P_(n))at milk stage,a significant increase of 51.3% in leaf area index(LAI)at the physiological maturity,delayed the senescence of the lower and middle leaves,increased dry matter accumulation of post anthesis and the transfer amount of dry matter,extended active grain filling period(P),reduced the days of maximum grain filling(T_(max))by 0.8 d,increased the weight of maximum grain filling rate(W_(max))and maximum grain-filling rate(G_(max))by 7.3% and 4.0% respectively and increased average grain-filling rate(V_(max))by 6.9%.Compared with D_(1),D_(2) significantly improved maize canopy structure,increased light energy utilization in maize populations,increased post-flowering dry matter accumulation,and promoted yield.After the chemical regulator treatment,leaf area of the upper leaves(14-17)was negatively correlated with light energy interception in the middle of the canopy,kernel number,1000-kernel weight,and yield,and the yield was positively correlated with 1000-kernel weight,kernel number,net photosynthetic rate,post-flowering dry matter accumulation,the weight of maximum grain filling rate and the grain-filling rate.In summary,the spraying of the chemical regulator at the 15-leaf stage of high density was effective in improving the upper canopy structure of the population,resulting in a reduction in leaf area and leaf angle to optimize the light conditions of the population,and enhanced photosynthetic capacity at the late of grain filling,increased grain-filling rate,and it can achieve efficient utilization of light energy and synergistic increase in yield.