在大田条件下研究了不同时期和不同程度遮荫对夏玉米产量及生长发育的影响.结果表明，遮荫显著降低玉米产量.不同时期遮荫对其影响不同，花粒期（从开花到成熟期）遮荫的影响最显著，农大108（ND108）和掖单13号（YD13）遮荫50%、90%处理分别减产67.5%、79.4%和82.9%和86.7%，其次是穗期（从拔节到开花期）遮荫，ND108和YD13分别减产34.1%、55.3%和47.2%、65.7%，而苗期（从出苗到拔节期）遮荫对其影响相对较小，ND108和YD13分别减产16.9%、24.5%和18.9%、24.3%.遮荫对YD13产量的影响大于ND108.遮荫时期对玉米产量的影响显著地大于遮荫程度.遮荫后两个玉米品种的生育进程都延迟，并随着遮荫程度的增加，对其影响加剧.穗期遮荫显著影响玉米的穗分化，花丝数和雄穗分枝数显著降低，对YD13的影响大于ND108.苗期和穗期遮荫显著抑制玉米叶面积、株高和茎节的生长.
Under field condition,this paper studied the effects of shading on the growth,development,and grain yield of summer maize varieties ND108 and YD13.The results showed that shading decreased maize yield significantly,and the effect was differed with different shading period and intensity.With a shading intensity of 50% and 90%,the grain yield of ND108 and YD13 was decreased by 67.5% and 79.4%,and 82.9% and 86.7% when shading at flowering-maturing stage,and by 34.1% and 55.3%,and 47.2%,65.7% when shading at joining-flowering stage,respectively.Shading at seedling-joining stage had a relatively smaller effect,with the grain yield decreased by 16.9% and 24.5%,and 18.9% and 24.3%,respectively.Shading had a larger effect on YD13 than on ND108,and the effect of shading period was larger than that of shading intensity.Under shading,the growth and development of maize was retarded,and the effect was increased with increasing shading intensity.Shading at joining-flowering stage affected spike differentiation significantly,reflecting in the marked decrease of the numbers of silks and tassels,and the effect was also larger on YD13 than on ND108.The leaf and plant growth was restrained significantly when shading at seedling stage and at flowering-maturing stage.
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