播种密度对冬小麦不同穗位与粒位结实粒数和粒重的影响

利用重穗型小麦品种兰考矮早八和中间型品种周麦18，研究了不同播种密度对结实粒数与粒重的小穗位和粒位效应的影响。结果表明，不同穗型冬小麦品种小穗位结实粒数、小穗重及不同粒位粒重均随着小穗位自基部至顶部呈先增后降的二次曲线变化；不同穗型冬小麦品种穗部籽粒的分布差异显著，主茎穗的结实特性及粒重均优于分蘖穗；随着播种密度的下降，穗部结实特性和粒重有优化的趋势，重穗型品种兰考矮早八对密度的反应更为敏感，中间型品种周麦18小穗位和粒位对播种密度的调节效应较强；不同部位小穗粒重因结实粒数的差异表现出不同的粒位效应，下部和中部小穗位的第2粒位粒重较大，而位于上部和顶部小穗位第1粒位粒重较大，第3粒位粒重次于第1和第2粒位，第4粒位粒重最小。在小麦栽培中，应在保证主茎穗的基础上适当增加分蘖穗的比例。并在保证结实粒数的基础上提高粒重，尤其是下部小穗的结实粒数和粒重。同时，在保证第1、2粒位粒重的前提下最大限度地发挥第3、4粒位的粒重潜力，可以使小麦实现高产稳产。

Effects of Plant Density on Grain Number and Grain Weight at Different Spikelets and Grain Positions in Winter Wheat Cultivars

Seed-setting traits and grain weight are influenced by either genetic factor or cultivation environment in wheat (Triticum aestivum L.), such as plant density. Due to the unbalanced development of a spike, grain number and grain weight at different spikelets and grain positions are largely different. Although their distributions have been described in earlier reports, the effect of plant density is not clear. This study focused on the effect of plant density on the grain number and grain weight of two wheat cultivars (Lankao Aizao 8 of large-spike type and Zhoumai 18 of medium-spike type) at different spikelets and grain positions. The grain number, spikelet weight, and grain weight with the spikelets positions from the bottom to the top increased first and then decreased. The differences of seed-setting traits between two cultivars were significant. Meanwhile, seed-setting traits of main sipke were supeirior than that of tillering spike. Under low sowing density, the seed setting characteristics and grain weight in Lankao Aizao 8 were more superior than those in Zhoumai 18, and those of main stem spike were more superior than those of tillering spike. The effects of spikelet and grain positions on the weight of individual grain varied with the grain number of spikelet. For the basal and middle spikelets, the grain weight was higher at second grain position than at the first one, whereas it was inverse for the upper and top spikelets. The grain weight was lower in the third grain position than in the first and second grain position, and the least in the fourth grain position. In conclusion, appropriate plant density is important for high yield of different spike-type cultivars, and in wheat production we should properly increase the proportion of tillering spike on the basis of ensuring main stem spike number; increase grain weight on the basis of ensuring fertile grain number especially for basal spikelet; and develop the potential of grain weight in the third and fourth grain positions on the basis of ensuring that in the first and second grain positions of spikelet.