A two years field experiment was carried out to analyze the effects of light-enriched treatment and shading on shoot dry matter accumulation and vertical distribution of soybean seed yield or yield components. Light enrichment significantly increased shoot dry matter accumulation per plant to contrast with that of the natural light in 2-years. Under three different density condition, light enrichment averagely increased Hai339 (H339) shoot dry matter accumulation per plant by 43.2%; that of Heinong35 (HN35) by 40.1% and that of Kennong18 (KN18) by 28.7%. Compared with that of the ambient light, shade averagely decreased Hai339 (H339) shoot dry matter accumulation per plant by 33.6%; that of Heinong35 (HN35) by 29.2% and that of Kennong18 (KN18) by 41.7%. Most of yield and pod number was produced in the middle layer of the main stem. Seeds number per pod at middle layer also was more than lower and upper canopy layers. Light sensitivity of lower, middle and upper mainstem part from three soybean cultivars was very different. Compared with the other yield component, seed size was least affected by light treatment. In our experiment, seed size was mostly constant at lower, middle and upper stem layers, although the filling duration of seed produced lowermost node was longer approximate 18 days than that of seed produced uppermost node. Our data indicated that, through redistributing the assimilate at lower, middle and upper canopy layers, soybean plant could showed the mechanism to maintain seed size stable. Clarification of mechanisms responsible for dry matter accumulation and vertical distribution of yield components under different light treatments, may provide some reference for phenotypic improvement and cropping pattern.
Key words: light enrichment, Shading, Vertical distribution, Yield component, Dry matter accumulation
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