托福阅读背景材料(358)：植物细胞构成

托福阅读背景知识/材料之植物细胞构成，更多托福阅读背景材料/知识尽在新东方在线托福考试频道！

　　The cells of a plant'are organized into three tissue systems: dermal,vascular, and ground tissue. Each tissue system is continuous throughout theplant's body. The specific characteristics of each tissue, however, are different in the different organs ofthe plant.

　　The dermal tissue system is the "skin" of the plant. The dermal system, or epidermis,is a single layer of cells covering the entire body of the plant. The mailn function of the epidermis is to protect the plant. The epidermis also has specialized characteristics for the particular organs it covers. For example, the epidermis ofleaves and stems has a waxy coating that helps the plant conserve water, and the epidermal cells near the tips of the　plant's roots help the plant absorb water and nutrients from the soil.

　　The second tissue system-the vascular system-is the transportation system for water and nutrients. Vascular tissue also helps to support the plant's structure. The third system- the ground tissue-makes up the bulk of a plant, filling all of the spaces between the dermal and vascular tissue systems. Ground tissue functions in photosynthesis, storage, and support.

　　1、How are the three tissue systems of a piant similar to each other?

　　They all continue throughout the plant's body

　　They all have a protective waxy coating.

　　They all consist of a single layer of cells.

　　They all perform the same bodily functions.

　　2、which ofthe following statements best scribes the plant's epidermis?

　　It helps the plant to stand upright

　　It transports water and nutrients.

　　It covers the plant's entire body.

　　It is found only in young plants.

　　3. Which type of tissue does a plant's body mainly consist of?

　　Dermal

　　Vascular

　　Epidermis

　　Ground