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树叶的背面是一个叶脉的网络,植物通过这个网络,完成树液的营养循环。每年,树皮下面都会形成一层新的组织。这一圈一圈的组织构成树的年轮,它会告诉你树木的年龄有多大。
The back of the leaves is a network of veins through which the plants complete the nutrient cycle of the sap. Every year, a new layer of tissue forms under the bark. This circle of organization constitutes the annual rings of the tree. It tells you how old the trees are.