密植对玉米叶片下垂特征的影响

Effects of increased plant density on maize leaf drooping characteristic

关键词:  玉米  品种  密度  叶片形态  下垂系数  产量

Key words:  maize  variety  density  leaf morphology  leaf drooping coefficient  yield

摘要:

为构建玉米密植高产群体结构建立评价指标、提供理论依据，以‘先玉335’与‘浚单20’为供试品种，分别设置67 500和97 500株/hm² 2个密度处理，分析3种不同冠层叶片的下垂系数：冠层（a₁），冠层中部（叶长>60 cm，a₂），冠层底部与上部（叶长≤60 cm，a₃）。结果表明：叶片下垂距离与叶长存在显著的线性关系。下垂系数a₁、a₂与穗三叶茎叶夹角，a₁、a₂和a₃与穗位以上叶片之间存在显著负相关关系，下垂系数与千粒重和秃尖长呈显著负相关。‘先玉335’在2个密度间的a₂相差0.13、其他下垂系数相差均<0.04；2个品种的a₃值均<a₁与a₂，说明叶长<60 cm的叶片较易下垂，叶片相对平展；且3种叶片下垂线性回归关系中，R²值（决定系数）均随密度增加相应降低，同一密度下‘先玉335’叶片R²值较‘浚单20’小，说明‘浚单20’叶片形态特征保持能力较‘先玉335’强、下垂关系较稳定，可在密植条件下进一步提高产量。因此，玉米叶片下垂系数能够反映冠层叶片形态结构特征，耐密品种能够通过调节冠层叶片下垂特征以缓解增密对群体带来的不利影响。

Abstract:

In order to establish evaluation indexes of leaf canopy of high yielding maize population and theoretical basis,a field experiment was conducted including two maize hybrids ‘Xianyu 335’ and ‘Xundan 20’ with two planting densities of 67 500 and 97 500 plants/hm²,respectively.Regression analysis method was used to calculate the leaf droop coefficient of three different canopy layer including the whole canopy (a₁),middle canopy (Leave length>60 cm,a₂),and the bottom and the upper of canopy (Leave length ≤ 60 cm,a₃).The results showed that there was a significant linear relationship between the leaf drooping distance and leaf length.The a₁,a₂ of leave regression relationships were negatively and significantly correlated with leaf angles at the middle canopy leaves,and a₁,a₂ and a₃ were negatively and significantly correlated with that of upper canopy leaves.The drooping coefficient is negatively and significantly associated with the thousand kernel weight and bareness.The a₂ of ‘Xianyu 335’ increased by 0.13 with the increasing of planting density,while other drooping coefficient differences were less than 0.04.The a₃ values of two varieties were smaller than a₁ and a₂,indicating leaves with a length less than 60 cm drooped more easily and the leaves that flat.Among the drooping leave linear regression relationships,the coefficient R² (decision coefficient) decreased with the increasing of planting density.At the same planting density,‘Xianyu 335’ had a smaller R² than ‘Xundan 20’ indicating that ‘Xundan 20’ had a high capacity for maintaining leaf morphology,thus increased grain yield.In conclusion,the leaf drooping characteristic could reflect the changes of leaf morphology in space and time as well as the effects of high planting density.Adjusting leaf drooping characteristic is very important for high yielding variety to adapt high planting density.