Question

All the xylem elements, when mature are dead except
A. Tracheid
B. Vessels
C. Xylem parenchyma
D. Xylem fiber

Answer 1

Hint: Xylem are the water transporting tissue of plant body. It helps in unidirectional water transport from the root to the stem and leaves. All the xylem elements are dead but the living cell is made up of thin-walled cellulose. The main job of these living elements is the storage of food material and help in the conduction of water.

Complete answer: Xylem tissue is made up of 4 elements – tracheid, vessels, xylem parenchyma and xylem fiber.
1. Xylem parenchyma is the only living component that is present in the xylem tissue. All the other tissues are dead when they are mature.
2. Xylem parenchyma is represented by groups of parenchyma cells that are found in between the vessels of xylem and the xylem fibers.
3. They have the storage function – they reserve food for future use.
4. In wooden plants, xylem parenchyma cells have secondary lignified walls. On the other hand, some plants have thin parenchyma cells in primary walls with plasmodesmata – known as the primary pit fields. By these pits, cell-to-cell movement of water, mineral, and nutrients takes place.
5. Mature xylem parenchyma cells in active xylem tissue consist of a functional protoplasm that helps to store carbohydrates (mainly glucose) in the form of starch.
6. These cells also play an important role in wound healing by the formation of callus and it differentiates to regenerate functional xylem cells in the plant body.

Thus, the correct answer is option C. xylem parenchyma.

Note: Both xylem and phloem are complex tissues. Xylem helps in unidirectional water transport but phloem helps in bidirectional food transport in the plant cells.