研究以先玉335为试验材料,测量了37500株/hm2和67500株/hm2两种密度条件下不同叶位叶片的叶面积和光合有效辐射。对不同叶位叶片光合生产能力的比较发现：从玉米冠层顶部到基部,叶片的光合生产能力呈现单峰不对称曲线分布,最大值出现在顶4~6叶,两种密度表现一致。进一步分析显示,不同叶位叶片的光合生产能力存在较大差别：在种植密度为37500株/hm2和67500株/hm2的条件下,棒三叶(顶7~9)叶面积分别占群体的28.74%和29.11%,其光合生产能力分别占群体的29.60%和29.04%；棒三叶上部的三个叶片(顶4~6)的叶面积分别占群体的25.74%和25.12%,光合生产能力分别占群体的36.27%和40.57%；棒三叶下部的基部叶片分别占群体叶面积32.74%和35.23%,而光合生产能力仅占群体的13.90%和9.79%。研究证实，由于冠层结构的不同造成冠层中光分布的差别,影响了不同叶位叶片光合效率,导致了其光合生产能力的差异；构建合理的群体冠层结构,不仅需要关注叶片的空间分布,更应该重视对冠层功能—光合生产能力的分析。
英文摘要:
By using Xianyu 335 as test material, leaf area and photosynthetically active radiation of leaves at different leaf positions were measured at 37500 plant / hm2 and 67500 plant / hm2. The results showed that the photosynthetic capacity of leaf from the top to the bottom of maize canopy showed a single peak asymmetric curve distribution, the maximum value appeared in the top 4 to 6 leaves under both of the two densities. The further analysis showed that the photosynthetic capacity of leaves at different leaf positions varied greatly. Under the condition of planting densities of 37500 plants / hm2 and 67500 plants / hm2, the leaf areas of leaves around the ear (7 ~ 9) accounted for 28.74% and 29.04%, the photosynthetic capacity accounted for 29.60% and 29.11% respectively. The leaf areas of the top three leaves above the ear (4~6) were 25.74% and 25.12%, respectively, and the photosynthetic capacity accounted for 36.27% and 40.57% of the total population. The leaf areas of the leaves under the ear accounted for 32.74% and 35.23%, respectively, while the photosynthetic capacity only accounted for 13.90% and 9.79% of the total population. The results showed that the photosynthetic efficiency of different leaf positions was affected by the difference of canopy structure, which led to the difference of photosynthetic productivity. The results also showed that to construct the reasonable canopy structure we should not only pay attention to the spatial distribution of leaves, but also pay more attention to the analysis of canopy function - photosynthetic production capacity.
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