AP BIOLOGY

Detailed explanation-1: -There are two kinds of conducting elements (i.e., transport tubes) found in the xylem: 1) tracheids and 2) vessels (Figure 6). Tracheids are smaller than vessels in both diameter and length, and taper at each end.

Detailed explanation-2: -Xylem transports water, minerals, and nutrients from the soil to all the plant parts. There are two types of “transport” tissues in plants-xylem and phloem. Water and solutes are transported by the xylem from the roots to the leaves, and food is transported from the leaves to the rest of the plant by the phloem.

Detailed explanation-3: -xylem tracheids. The xylem tracheary elements consist of cells known as tracheids and vessel members, both of which are typically narrow, hollow, and elongated. Tracheids are less specialized than the vessel members and are the only type of water-conducting cells in most gymnosperms and seedless vascular plants.

Detailed explanation-4: -Continuous transpiration occurring in all of the leaves of a plant creates a negative pressure in the water column (xylem). This exerts an upward pull on the water column, called transpiration pull. And thus, the water present in the xylem column transports up to the tip of the stem, leaves, etc.

Detailed explanation-5: -The xylem is also composed of elongated cells. Once the cells are formed, they die. But the cell walls still remain intact, and serve as an excellent pipeline to transport water from the roots to the leaves. A single tree will have many xylem tissues, or elements, extending up through the tree.