大豆叶片停止生长后，叶柄直径持续生长２～３天，叶柄伸长生长持续４～６天，木质部导管数目持续增加５～７天。大豆叶柄长度、叶柄直径和比叶柄重的最大值出现在植株的中上部节位。品种间叶柄直径变化较小，叶柄长度和比叶柄重变化较大。叶柄韧皮部面积、比叶柄重和叶柄长度与叶面积呈正相关（相关系数分别为０．７２，０．７５和０．８６）．新品种单位叶面积的叶柄韧皮部面积有大于老品种的趋势。 After the soybean leaves stopped growing, the diameter of the petiole continued to grow for 2-3 days, the elongation of the petiole continued for 4-6 days, and the number of xylem catheters continued to increase for 5-7 days. The length of petiole, the diameter of petiole and the maximum weight of petioles appeared in the middle and upper nodes of the plant. Varietal petiole diameter changes smaller petiole length and petiole heavier changes. The phloem area of ​​petiole was positively correlated with petiole weight and petiole length and leaf area (correlation coefficients were 0.72, 0.75 and 0.86, respectively). New varieties of leaf area leafy phloem area has a greater trend than the old breed.