Problem 82 - Objective Biology for NEET

Question

Select the incorrect statement from the following: (a) Trichomes help in preventing water loss due to transpiration (b) Cuticle prevents loss of water (c) Cuticle is absent in roots (d) Epidermis is made up of elongated, loosely arranged cell, which forms continuous layer

Step-by-Step Solution

Answer

(d) The epidermis is not made up of elongated, loosely arranged cells; they are in fact closely packed.

Step 1: Analyzing Choice (a)

Trichomes do indeed aid in preventing water loss within plants by limiting the rate of transpiration. This statement is therefore correct, meaning it's not our incorrect statement.

Step 2: Analyzing Choice (b)

The cuticle is a waxy layer present on the surface of the leaves and stem. It aids in preventing water loss, thus statement (b) is also correct and cannot be our answer.

Step 3: Analyzing Choice (c)

Roots are generally located underground where the threat of water loss from evaporation is lesser, therefore a cuticle is indeed generally absent in roots. Thus, statement (c) is also correct.

Step 4: Analyzing Choice (d)

The statement of the epidermis being made up of elongated, loosely arranged cells which form a continuous layer is incorrect. The epidermis is made up of closely packed and regularly shaped cells. This is the incorrect statement we were looking for.

Key Concepts

Transpiration

Transpiration is a natural process where water is lost from plant surfaces, mainly through tiny openings called stomata found on leaves. This process is part of the plant's water regulation system. It helps to transport nutrients from the soil to different parts of the plant.
It also plays a crucial role in cooling the plant by releasing water vapor into the air.
While essential, excessive transpiration can lead to water loss. Plants have adapted to manage this by various means:

• Closing stomata during hot parts of the day
• Developing thick cuticles
• Having structures like trichomes to limit water loss

Understanding transpiration teaches us about how plants manage their internal water balance under different environmental conditions.

Cuticle

The cuticle is a protective, waxy covering found on plant surfaces, predominantly leaves and stems. Its primary function is to act as a barrier against water loss, promoting retention within the plant, especially in arid environments.
This waxy layer is crucial because it helps keep the plant hydrated by resisting water evaporation.
Here are a few functions of the cuticle:

• Reduce water loss through evaporation
• Protect against pathogens and harmful microbes
• Provide protection from mechanical damage

The absence of cuticles in roots indicates that water retention is less of a concern below ground.

Epidermis

The epidermis is the thin outermost layer of cells covering leaves, flowers, roots, and stems in plants. It serves as the first defense against physical damage and pathogen invasion.
Characterized by tightly packed cells, it forms a continuous protective layer. Latest studies show:

• Epidermal cells help in reducing water loss
• They support gas exchange through stomata
• The protective feature aligns with the plant's overall defense strategy

The incorrect notion that these cells are elongated and loosely packed contradicts this efficient protective role, highlighting the importance of their true dense arrangement.

Trichomes

Trichomes are tiny hair-like structures on the epidermis of plants. They appear on leaves, stems, and other plant parts, providing various benefits.
One of their primary roles is to help prevent water loss by minimizing air flow over the plant's surface and reducing transpiration.
Additionally, trichomes can:

• Reflect sunlight to prevent overheating
• Deter herbivores by adding an additional layer of protection
• Trap moisture in arid environments, aiding in water retention

These mechanisms illustrate how trichomes contribute significantly to a plant's survival strategies, especially in challenging environments.