Problem 56 - Objective Biology for NEET

Question

Following are the features of phloem fibres except (a) Pointed apices (b) More elongated (c) Branched (d) Unbranched

Step-by-Step Solution

Answer

The feature which does not apply to phloem fibres is (c) Branched.

Step 1: Identify the features of Phloem fibres

Let's start by identifying the typical features of Phloem fibres which are part of the phloem, a tissue responsible for transport of food in plants. They are elongated, tapering (pointed at each end) and typically unbranched cells.

Step 2: Evaluate the answer choices

Now, look at the answer choices again. Based on our knowledge of Phloem fibres, markings (a), (b), and (d) align with the features of phloem fibres. They are elongated, have pointed apices and are typically unbranched.

Step 3: Select the correct answer

Therefore, (c) Branched does not fit these features, as phloem fibres are typically unbranched. So, the correct answer is (c).

Key Concepts

Tissue Transport in Plants

Plants have a unique way of distributing essential nutrients and water through distinct vascular tissues. These primary tissues are known as the xylem and the phloem.
While xylem is responsible for moving water and dissolved minerals upward from the roots to different parts of the plant, phloem focuses on distributing the food produced via photosynthesis. This particular food, primarily sugars, is transported from the leaves to other parts of the plant that cannot produce their own energy, such as roots or growing seeds.

• Xylem: Transports water and minerals.
• Phloem: Transports synthesized nutrients like sugars.

The phloem achieves this through a process called translocation, which involves a complex interaction of pressure differences, facilitated by energy (ATP), which pushes the nutrients to areas of the plant where they are either used or stored. Understanding this active transport mechanism is crucial to grasping how plants sustain themselves and continue to grow.

Plant Anatomy

Plant anatomy is the study of the physical structure of plants. It involves understanding how various parts of a plant are organized and how they function together. This knowledge is crucial to appreciate how plants survive, adapt, and thrive in their environments.
Plants have two basic systems that form the entire organism: the root system and the shoot system.

• Root System: Anchors the plant and absorbs water and nutrients from the soil.
• Shoot System: Includes the stem, leaves, and flowers. It is responsible for photosynthesis, reproduction, and support.

Within these systems, vascular tissues like xylem and phloem play essential roles. In particular, the phloem—central to the original problem—consists of various components such as phloem fibres, sieve tubes, companion cells, and phloem parenchyma. Each part of the phloem contributes uniquely to its overall function of nutrient transport.

Phloem Features

Phloem, as a vital plant tissue, contains several distinct components that have adapted to fulfill its role in nutrient transport. Phloem fibres are one such element, providing structural support. Understanding the characteristics of these fibres helps identify their role and significance.

• They are typically elongated, which allows them to insert seamlessly into plant structures.
• The fibres have pointed apices, meaning they taper at both ends, facilitating effective integration.
• Generally, they remain unbranched, which helps maintain strength and effectiveness in support.

These features enable the phloem fibres to support the delicate sieve tubes that transport nutrients. Despite their supportive role, they don't interfere with the transport functions of the phloem but rather provide the rigidity needed for optimal plant functioning. Their specific features, as recognized in the original exercise, highlight their importance in the complex system of plant anatomy.