Problem 26 - Objective Biology for NEET

Question

Growth of pollen tube is measured in terms of (a) Weight (b) Width (c) Volume (d) Length

Step-by-Step Solution

Answer

The correct answer is (d) Length.

Step 1: Identify the nature of the pollen tube

Understand that a pollen tube is an elongated tubular structure. Consider its properties.

Step 2: Analyze the given options

Review each choice – weight, width, volume, and length. Reflect upon which one of these parameters is typically used to gauge the growth of tube-like structures.

Step 3: Select the appropriate parameter

The most logical measure for a tubular structure's growth is its length. Hence, option (d) is the most suited for the given context.

Key Concepts

Plant Reproduction

Plant reproduction is a fascinating process that allows plants to produce offspring, ensuring the survival and diversity of species. It involves several stages, starting from pollen transfer to fertilization and seed formation. Two primary methods of plant reproduction are sexual and asexual reproduction. In sexual reproduction, plants produce seeds through the union of male and female gametes. The male gamete is contained within pollen grains, which are transferred from the anther of a flower to the stigma of another. This transfer can occur through various means such as wind, water, or pollinators like bees.
The pollen grain germinates on the stigma, leading to the growth of a pollen tube that facilitates fertilization.
Asexual reproduction, on the other hand, does not involve gametes. Plants can reproduce through runners, tubers, bulbs, or cuttings from the parent plant, often resulting in offspring genetically identical to the parent. Both methods play crucial roles in the lifecycle and propagation of plant species.

Pollen Tube Structure

A pollen tube is a crucial component of plant reproduction, formed when a pollen grain germinates after landing on a compatible stigma. This structure is essentially a channel that leads sperm cells to the ovule, allowing fertilization to occur. The tube grows down the style towards the ovary, which contains the ovule.
The formation of the pollen tube is highly specialized, involving the elongation of the tube cell as it penetrates the style tissue. This growth is guided by chemical signals released by the ovule. The pollen tube structure primarily consists of a tube cell, which acts as a conduit for the sperm cells, and is surrounded by a tube wall made of pectin and cellulose. The tube wall is strong yet flexible, supporting the tube as it makes its journey.

• The tube cell emerges from the pollen grain tip.
• Cytoskeletal components and secretions regulate its directional growth.
• Sperm cells, carried within, travel through the tube to reach the ovule.

This intricate structure is an excellent example of nature's ingenuity in ensuring successful plant reproduction.

Measurement of Growth

When it comes to measuring the growth of a pollen tube, the most reliable parameter is its length. This is because a pollen tube is an elongated structure, and its primary growth is linear as it extends through the style toward the ovule.
Length measurement is favored over weight, width, or volume for several reasons:

• Weight: The pollen tube is extremely lightweight, making weight an irrelevant measure.
• Width: While width may briefly change with growth, it's typically uniform and not indicative of overall growth.
• Volume: This includes both length and width, but since length is the primary change, it offers more direct insights into growth patterns.

By measuring the length of the pollen tube, researchers can directly assess its growth progress. This measurement provides clear data on how efficiently the pollen can fertilize the ovule, which is crucial for understanding and enhancing plant breeding and reproductive success.