In damaged stems and roots , and in those undergoing secondary growth , it is replaced by a secondary layer , the periderm 已损伤的茎和根，以及进行次生生长的根茎中，表皮被次生层即周皮代替。
2.
The results showed that the root transactions had significant differences in periderm , phloem , and xylem between cultivated and wild salvia miltiorrhiza 结果表明，在解剖横切面上，栽培与野生丹参根的周皮、韧皮部、木质部具有显著差异。
3.
In cultivated salvia miltiorrhiza roots , light - colored periderm contained less layers of cells and low ratio of phloem to xylem , compared with those in wild salvia rniltiorrhiza roots 栽培丹参根的周皮细胞层数少、色淡，韧皮部与木质部比值小，而野生丹参根的周皮细胞层数多、颜色重，韧皮部与木质部比值大。
4.
Thickness of upper and lower epidermis of leaves , width of xylem and phloem of annual and biennial branches , ratio of late wood to early wood , periderm thickness of biennial branches , and length of xylem ray present decreasing trends with latitude ascending ; while ratio of palisade tissue to spongy tissue , epidermis thickness of annual branches , and cortex thickness of biennial branches show unobvious variations with latitude increasing 叶的上下表皮厚度、 1和2年生枝木质部及韧皮部宽度、晚材早材比值、 2年生枝的周皮厚度、木射线长等均随纬度升高而呈下降趋势；而叶的栅栏组织和海绵组织比值、 1年生枝表皮厚度、 2年生皮层厚度等解剖结构随纬度变化没有明显规律。
