Abstract: The problem of rational close planting in soybean was analysed with the method of combining the external morphological character with the internalanatomy in this paper.With the density of 4000 plants per mu,the stems of plants were strong and the seed weightper plant was high.There were a great number of secondary phloem fiber cells and a larger area of the conducting and the mechanical tissue,but a smaller area of the ground tissue on the transverse section of the stems.With the increase in planting density,stems became thinner and tallar,seed weight per plant became lighter,the area of conducting and mechanical tissue became smaller gradually,and the number of secondary phloem fiber cells was reduced greatly,while the area of ground tissue became larger and larger.In the experiment,the density,of 13,000 plants per mu may be the density approaching the ideal population.Although under this density,the stems of plant were comparatively strong,the area of the various tissues were all middle-sized,yet as the relationship between the population and individual plants was well coordinaterd,the highest vield per mu could be obtained.

Key words: Soybean, Density(population), Morphological character, Comparative anatomy