Problem 38 - Objective Biology for NEET

Question

Xylem is composed of how many different elements? (a) 1 (b) 2 (c) 3 (d) 4

Step-by-Step Solution

Answer

The Xylem is composed of 4 different elements

Step 1: Understanding Xylem

Xylem is one of the two types of transport tissues in vascular plants. It transports water and soluble mineral nutrients from the roots throughout the plant. It also helps to replace water lost during transpiration and photosynthesis.

Step 2: Identifying elements of the Xylem

Xylem is mainly composed of four different types of cells: Tracheids, Vessels, Xylem Parenchyma and Xylem Fibres. Tracheids and Vessels are the water conducting cells. Xylem Parenchyma aids in the repair and recovery of these cells while Xylem Fibres provide mechanical support.

Step 3: Choosing the correct option

On the basis of the above observations about the composition of the xylem, it can be inferred that the answer to the question is option (d) 4. Hence, the Xylem is composed of 4 different elements.

Key Concepts

Vascular plants

Vascular plants are a crucial component of the Earth's ecosystem, characterized by the presence of specialized, complex tissues that efficiently conduct water, nutrients, and other substances throughout the plant. These tissues enable vascular plants to survive and thrive in a variety of environments by ensuring that nutrients and water reach all parts of the plant.
The ability to transport nutrients and water differentiates them from non-vascular plants, like mosses and liverworts, which rely on direct contact with water for moisture and nutrient uptake. Vascular plants include a wide variety of species, such as trees, ferns, shrubs, and flowering plants.

• Efficient nutrient transport: Helps plants to grow larger and inhabit diverse habitats.
• Structural support: Vascular tissues provide strength to withstand environmental challenges.

These traits allow vascular plants to play key roles in their ecosystems, from supporting food chains to contributing oxygen and absorbing carbon dioxide.

Transport tissues

Transport tissues are essential for the survival and function of vascular plants. They are specialized structures that carry water, nutrients, and other critical substances to various parts of the plant. These tissues are primarily composed of the xylem and phloem.
The xylem is responsible for the upward movement of water and dissolved minerals from the roots to the leaves and other upper parts of the plant. On the other hand, the phloem distributes the sugars and nutrients produced during photosynthesis to different parts of the plant, including areas of growth and storage.
Here are some important roles of these tissues:

• Support plant growth by transporting nutrients.
• Facilitate repair and healing processes within the plant.
• Maintain effective water and nutrient distribution even in large plants.

By managing the movement of critical substances, transport tissues ensure vascular plants will continue to grow, reproduce, and respond to their environment effectively.

Water conduction

Water conduction is a fundamental process in vascular plants, made possible by the xylem tissues. This process is critical for plant health and survival as it ensures that water and necessary nutrients reach each part of the plant from the roots upwards.
In xylem tissues, water conduction primarily occurs through two types of cells, tracheids and vessels. Tracheids are elongated cells found in all vascular plants, whereas vessels are typically found in angiosperms (flowering plants). Together, they form continuous tubes that efficiently transport water upwards through a process driven by capillary action, root pressure, and transpiration pull.
Key factors in water conduction include:

• Transpiration pull: Loss of water vapor from leaves creates a negative pressure that pulls water upwards.
• Root pressure: Generated by osmotic pressure in the roots, helping push water upwards.
• Capillary action: The adhesion and cohesion of water molecules helps them climb up through the xylem.

This effective water conduction mechanism allows plants to maintain their water balance, produce food through photosynthesis, and adapt to their environments.

Xylem elements

Xylem tissues are intricate systems that consist of various elements, each contributing to its role in water conduction, nutrient transport, and structural support. The four primary components of the xylem are tracheids, vessels, xylem parenchyma, and xylem fibers.
**Tracheids**: These are elongated cells that play a crucial role in both water transport and providing structural support. They are found in all types of vascular plants and function via small pits that allow water to move from cell to cell.
**Vessels**: Predominant in angiosperms, vessel elements are shorter and wider than tracheids and form continuous tubes for efficient water movement. Their presence makes angiosperms more efficient at water transport.
**Xylem Parenchyma**: These cells are living tissues that aid in storage and the lateral transport of water and nutrients, as well as helping in the repair and regeneration of the xylem.
**Xylem Fibres**: They provide mechanical support due to their thickened cell walls, ensuring the structural stability of the plant.

• Each element plays a unique yet interconnected role within the xylem.
• They enable effective water transport and plant stability.

Understanding each element can help us appreciate the complexity and efficiency of plant vascular systems.