Regulation of Dry Matter Production Process in Response to Changes in Photosynthetic Source-Sink Balance by Plant Density

大豆（Glycine max Merr.cv.）在试验田种植鹤子（Tsurunoko）植株，密度高（20株/m^2），密度小（1.6株/m^2）。随着植物生长的进展，高密度植物被置于深层相互遮荫的条件下，低密度植物被连续地置于独立的个体条件下。(1)高密度植物的上部叶片在上午至中午之后保持较高的光合活性。低密度植物中午前光合活性较高，中午后光合活性明显降低。(2)低密度植株叶片蔗糖含量高于高密度植株。(3)在低密度植物中，RuBPcase的活性随着光合活性的降低而降低。在活化介质中加入CO_2和Mg^<2+>后，活性完全恢复。(4)低密度植株叶片RuBP含量显著高于高密度植株。因此，低密度植物的结果与源库平衡发生改变时大豆叶片源库模式植物的结果一致（Sawada et al., 1986,1987,1989,1990,1992,1995 5a, b）。

Soybean (Glycine max Merr.cv.Tsurunoko) plants were grown in the experimental field with high (20 plants/m^2) and law (1.6 plants/m^2) densitites. With progressing of their growth, high density plants were placed under deep mutual shading condition, although low density plants were continuously placed under independently indivitual conditions.(1) Upper leaves on high density plants kept high photosynthetic activities from morning to after noon. Low density plants showed high photosynthetic activities before noon but largely lowered the activities after noon.(2) Sucrose content in leaves of the low density plants was higher than in the high density plants.(3) In the low density plants, the activity of RuBPcase lowered according to lowering of photosynthetic activity. This lowered activity was perfectly recovered with addition of CO_2 and Mg^<2+> into activation medium.(4) The RuBP content in leaves of the lower density plants was significantly higher than in those of the high density plants.It is concluded that the results obtained from the low density plants are consisitent with the those which were observed in the source-sink model plants made from soybean leaves when the source/sink balance was altered (Sawada et al., 1986,1987,1989,1990,1992,1995a, b).