Problem 155 - Objective Biology for NEET

Question

In dicot root (a) Vascular bundles are scattered and with cambium (b) Vascular bundles are arranged in a ring and have cambium (c) Xylem and phloem are radially arranged (d) Xylem is always endarch

Step-by-Step Solution

Answer

Option (c) - Xylem and phloem are radially arranged is the correct answer.

Step 1: Understand the problem

First, understand what is asked in the exercise. It wants to identify the structural characteristics of a dicot root.

Step 2: Anatomy of a dicot root

Recall that dicots have a central xylem and phloem vascular cylinder, or stele. The xylem and the phloem are arranged in radial strips with the xylem forming an X in the center. Also, the xylem and phloem are separated by a layer of cambium.

Step 3: Select the correct option

In light of the aforementioned information, the correct answer to this exercise will be a statement that accurately describes a dicot root. Option (c) - 'Xylem and phloem are radially arranged' - is the correct answer as this is the typical setup seen in dicot roots.

Key Concepts

Vascular Bundles

In dicot roots, the arrangement of vascular bundles plays a crucial role in their structure and function.
Vascular bundles are complex structures that include both xylem and phloem tissues. These are critical for the transportation of water, minerals, and nutrients. In a dicot root, these bundles are not scattered randomly.
Instead, they are systematically arranged in a circle. This means that xylem and phloem are organized in such a way to maximize efficiency. The arrangement can significantly determine the root's ability to transport substances optimally. For dicots, this radial arrangement of xylem and phloem within the vascular cylinder, or stele, is distinctive.

• Ensures stable and structured transport pathways.
• Helps the root withstand mechanical stresses.
• Promotes efficient absorption of nutrients.

Recall that this radial pattern is a hallmark feature of dicot roots, distinguishing them from other plant structures.

Xylem and Phloem

Xylem and phloem are the two main components of vascular bundles in plants. They are essential for the transportation of essential substances within the plant. In dicot roots, these two tissues are arranged in a unique radial pattern. This means they form alternating radii across the root. Such an arrangement is pivotal for their function.

The xylem is responsible for transporting water and dissolved minerals from the soil to various parts of the plant. Contrastively, the phloem transports the products of photosynthesis, like sugars, from the leaves to other parts of the plant including the roots. The radially arranged xylem and phloem in dicot roots create a precise balance for plant cellular activities:

• Xylem: Drives water upward, vital for photosynthesis and nutrient distribution.
• Phloem: Translocates sugars and metabolic products down, supporting growth and storage.

Understanding their layout helps in learning how plants sustain life efficiently.

Cambium

The cambium is an essential layer of meristematic tissue found in dicot roots. It is located between the xylem and the phloem in the vascular bundles. Cambium is known as a lateral meristem because it plays a major role in increasing the thickness of roots and stems. This is particularly important for dicot roots, which often become woody and require structural support.

In dicots, the cambium is a thin layer of cells that remains active throughout the plant's life, continuously dividing to produce new cells. These new cells subsequently differentiate into either xylem or phloem cells. This ability to grow and differentiate enhances the plant’s ability to adapt to environmental conditions.

• Increases the girth of the plant, enabling strong support.
• Helps in the repair and regeneration of the plant.
• Enables efficient transport of nutrients as it expands.

Understanding the cambium's function reveals how plants grow laterally and how they can strengthen over time.