甜菜群体冠层光合作用的研究

本试验探讨了甜菜不同密度处理条件下群体各叶层光合速率的变化，生理、生态因子的变化及其各叶层对群体光合作用的贡献。结果表明：不同叶层对整个冠层群体光合作用贡献明显不同，叶丛形成期是中层＞下层＞上层，块根增长期以后则是上层＞中层＞下层。密度过大的处理，中、后期群体光合速率的下降主要与群体中、下位叶层光合速率下降有关，其叶片气孔阻力、相对光照强度和叶面积指数均与低密度处理有明显差异。

A Study on the Canopy Apparent Photosynthesisof Different Leaf Layer in Sugar Beet

A sugar beet cultivar was planted in three populations in a wellcultured field to study the changes of canopy apparent photosynthesis rate and physiological and ecological factors of different leaf layers as well as the contribution of it to canopy apparent photosynthesis(CAP).The results indicated that the contribution of CAP of different leaf layers to Total CAP was different in different growing stages:middle leaf layers'contribution>lower leaf layers'>upper leaf layers'in rossete forming stage;upper leaf layers'contribution>middle leaf layers'>lower leaf layers'in root growing stage and sugar accumulating stage. The decrease of Total CAP with high population in middle and later growing stage was mainly from decrease in middle and lower leaf layers photosynthesis .The main reason was more lower light intensity and higher leaf stomatal resistance in middle and lower leaf layers caused by higher LAI.