一、教材分析 《茎的作用》是义务教育五年制小学自然第七册的教学内容。它和《根的作用》、《叶的蒸腾作用》、《叶的光合作用》构成本册教材的植物教学单元。学生在低年级时初步认识了根,知道了植物的根是植物茎干下部长在土里的部分,而且还知道根有两种:一种是直根,如向日葵、甜菜;一种是须根,如小麦、水稻。了解叶一般是绿色,叶片的上下表面各由一层排列紧密无色透明的表皮细胞构 First, the textbook analysis “The role of the stem” is the compulsory education five years of primary seventh natural course content. It and the “role of the root”, “leaf transpiration”, “leaf photosynthesis” constitute the teaching materials of the plant teaching unit. Students first learned about roots in their lower grades and learned that the plant's roots are part of the plant under the stalk and are known to have two roots: one is a straight root such as sunflower and sugar beet; one is a fibrous root , Such as wheat, rice. Understand the leaves are generally green, the upper and lower surfaces of the leaves arranged by a layer of closely colorless and transparent epidermal cells