Question

Select the correct matching: Column I Column II A. Tracheids -4. 1 . Elongated and tube like cells with thick and lignified wall and tapering ends. B. Vessels \- 2. Tube like structure made up of many cells, each cell with lignified wall and large central cavity. C. Xylem fibre \(-\quad\) 3. Highly thickened walls and obliterated central humans. D. Xylem parenchyma 4\. Living cell with thin cell wall made up of cellulose. (a) A-2, B-1, C-3, D-4 (b) A-3, B-1, C-2, D-4 (c) \(\mathrm{A}-1, \mathrm{~B}-2, \mathrm{C}-3, \mathrm{D}-4\) (d) \(\mathrm{A}-3, \mathrm{~B}-2, \mathrm{C}-1, \mathrm{D}-4\)

Short answer

The correct answer is (c) A-1, B-2, C-3, D-4.

Step-by-step solution

Understand features of each xylem cell

Tracheids are elongated and tube like cells with thick and lignified wall and tapering ends (Description 1). Vessels are tube like structure made up of many cells, each cell with lignified wall and large central cavity (Description 2). Xylem fibres have highly thickened walls and obliterated central lumens (Description 3). Xylem parenchyma are living cells with thin cell walls made up of cellulose (Description 4).

Match features with xylem cells

From the given task, match the descriptions with the correct cell. A. Tracheids (1). B. Vessels (2). C. Xylem fibre (3). D. Xylem parenchyma (4). Therefore, the correct option is (c) A-1, B-2, C-3, D-4.

Key concepts

Tracheids

In the xylem, tracheids play a vital role in water conduction and structural support. They are elongated cells that are tube-like in shape, with thickened and lignified walls. This lignification provides rigidity, allowing the plant to resist various stresses, such as wind pressure or physical impact. One of the unique features of tracheids is their tapering ends, which overlap with neighboring cells to form a continuous column for water transport.
However, Tracheids do not have perforations, meaning water must pass through pit membranes, which slightly hinders their efficiency compared to vessel elements. Even so, these cells are crucial, especially in gymnosperms, where vessels are typically absent. Their simplicity and durability make them essential for plant survival in adverse conditions.

Vessels

Vessels are major components in xylem tissue and are primarily responsible for conducting water and nutrients more efficiently than tracheids. They consist of a series of cells joined end-to-end to form long tubes known as vessel elements. Each vessel element has a lignified cell wall and a large central cavity, or lumen, that minimizes resistance, allowing for rapid water movement.
Unlike tracheids, vessels have perforation plates at the ends, which facilitate unimpeded water flow from cell to cell. This structural adaptation makes them particularly common in angiosperms, where efficient water transport is essential for supporting larger, more complex plant forms. Despite their effectiveness, the vessels' structure makes them more vulnerable to drought and air embolisms, which can disrupt water conduction.

Xylem Fibre

Xylem fibers are specialized cells within the xylem that primarily provide mechanical support to the plant. These fibers have highly thickened secondary cell walls, reinforced with lignin, which gives them great tensile strength. The central cavity of xylem fibers is obliterated, meaning it is much reduced or completely filled with deposits.
This dense structure limits their role in water transport, but excels at supporting the plant's structure, helping to maintain the upright position needed for optimum sunlight absorption and growth. Due to these characteristics, xylem fibers are crucial for plants exposed to mechanical stress, such as high winds or heavy rains.

Xylem Parenchyma

Xylem parenchyma cells are the only living cells in the xylem tissue. Their walls are composed of cellulose rather than lignin, making them thin compared to other xylem cells. These cells contribute to the storage and transport of nutrients and water within the plant.
Xylem parenchyma plays a key role in repairing and maintaining tissue by storing starch and assisting with the lateral transfer of water. Their ability to remain alive allows them to also participate in wound repair and regrowth. The presence of xylem parenchyma is significant for plant's physiological processes, enabling more resilience against damage and contributing to the plant's overall vitality.