Problem 119 - Objective Biology for NEET

Question

The plant body of pteridophyte is (a) Not well-developed (b) Lacks vascular tissue (c) Is thalloid (d) Posses true root, leaves and stem

Step-by-Step Solution

Answer

The correct answer is (d) pteridophytes possess true roots, leaves, and stem.

Step 1: Understanding Pteridophytes

Firstly, know that Pteridophytes are a group of plants consisting of ferns and their allies. They are among the first terrestrial plants to have evolved vascular tissues.

Step 2: Checking Option (a)

The statement states that pteridophyte's body is not well developed. This is not accurate. Pteridophytes have a distinct plant body structure that is differentiated into root, stem, and leaves.

Step 3: Checking Option (b)

This option states that pteridophytes lack vascular tissue. This is also incorrect because pteridophytes were among the first plants to develop vascular tissues including both xylem and phloem.

Step 4: Checking Option (c)

This statement suggests that pteridophytes are thalloid. However, that is incorrect. Thalloid plant bodies are undifferentiated into root, stem, and leaves, while pteridophytes have clearly differentiated plant bodies.

Step 5: Checking Option (d)

The last option states that pteridophytes have a true root, leaves, and stem. This is correct. Pteridophytes have well-defined plant bodies, and they include true leaves, stems, and roots. Therefore, this is the correct answer.

Key Concepts

Vascular Tissues in Plants

Vascular tissues in plants are akin to the circulatory system in animals. They serve as conduits for the transport of water, minerals, and nutrients throughout the plant. In pteridophytes, specifically, the presence of these tissues marks a significant evolutionary advancement compared to their non-vascular predecessors.

The two primary components of vascular tissues are the xylem and phloem. The xylem carries water and dissolved minerals from the roots to all other parts of the plant, a critical process known as transpiration. On the other hand, the phloem transports sucrose and other organic compounds produced by photosynthesis in the leaves to other tissues where needed. This dual system enables pteridophytes to grow larger and survive in a variety of terrestrial habitats.

Plant Body Differentiation

In the plant kingdom, body differentiation refers to the specialization of plant structures into organs with distinct functions – roots, stems, and leaves. Pteridophytes exhibit this complex structure, moving beyond the simpler forms seen in algae and mosses.

Unlike the primitive plants where the body is 'thalloid'— undifferentiated and often flat—pteridophytes have a clear division of labor. The roots anchor the plant and absorb water and nutrients, the stems serve as the main support system and transportation highway connecting the roots and leaves, and the leaves are the primary site for photosynthesis, the process that converts light energy into chemical energy. This advanced differentiation facilitates better survival mechanisms, allowing pteridophytes to thrive in diverse ecosystems.

Fern Anatomy

A keystone example of pteridophytes, the fern, exhibits a specialized anatomy that allows it to flourish in moist environments. Ferns possess rhizomes, which are underground stems that give rise to fronds—the leaves of ferns.

The fronds are typically large and divided into segments called pinnae, which can further divide, displaying a feathery appearance. This elaborate structure maximizes the surface area for photosynthesis and gas exchange. Ferns also have specialized structures like sori, which are clusters of sporangia (spore-producing organs) found on the underside of the fronds, playing a vital role in reproduction.

True Roots, Stems, and Leaves

True roots, stems, and leaves are hallmark features of vascular plants, including pteridophytes. Roots delve into the soil to provide stability and absorb water and nutrients for the plant. Stems, whether above or below ground, support the plant body, bear leaves, and house the vascular tissues that connect the roots and leaves. Leaves are the primary sites of photosynthesis, tailored to capture sunlight efficiently.

In pteridophytes, these organs are not just present but are well-adapted to their environments. The roots may have specialized hairs for better absorption, the stems can be modified to store nutrients or climb, and the leaves can vary greatly in shape and size to optimize light absorption. This organization is not just a structural advantage but also a functional specialization that has allowed pteridophytes to colonize land successfully.