Problem 80 - Objective Biology for NEET

Question

Stem hairs are (a) Unicellular (b) Acellular (c) Multicellular (d) Any of them

Step-by-Step Solution

Answer

The correct answer is (d) Any of them.

Step 1: Understanding the Terms

First, understand what each answer choice means. Unicellular means comprised of one cell. Acellular refers to something not composed of cells. Multicellular means composed of more than one cell.

Step 2: Applying Knowledge

Next, apply knowledge about stem hairs. Stem hairs, also known as trichomes, are hair-like structures on the stem surface. Trichomes can be composed of one cell (making them unicellular) or composed of several cells (making them multicellular). They are never acellular as they are a structure of plant and hence, involve cells.

Step 3: Eliminating the Incorrect Choices

Based on this information, it can be concluded that stem hairs are not acellular. This leaves the options of them being unicellular, multicellular, or any of them.

Step 4: Selecting the Correct Answer

Since stem hairs can be either unicellular or multicellular depending on the plant species, the correct answer would be 'any of them' as this choice considers both possibilities.

Key Concepts

Unicellular

Unicellular structures consist of only a single cell. In the context of plants, unicellular trichomes are fascinating because they perform critical activities with just one cell. These single-celled structures can effectively protect the plant from herbivores and environmental stress.
Additionally, unicellular trichomes can participate in secretion processes, producing essential oils or other substances beneficial to the plant. Such simplicity allows these trichomes to adapt quickly, providing rapid defense on new growths.

• Single-cell structure
• Efficient protection against threats
• Involvement in secretion and defense

This flexibility means some plants may utilize unicellular trichomes, making them an essential feature in many plant species.

Multicellular

On the other hand, multicellular trichomes consist of multiple cells, allowing for a greater variety of functions and more complex structures. These multicellular configurations can be seen in plants that require enhanced protection or need to perform more complex tasks beyond the capacity of a single cell.
Multicellular trichomes can form diverse structures, such as long hairs, glandular types that secrete sticky resins, or elaborate forms that trap moisture. This complexity means that these trichomes can better protect the plant, help in administering chemical warfare against herbivores, or aid in conserving water.

• Composed of multiple cells
• Increased functionality and complexity
• Various roles including protection, secretion, and moisture retention

These characteristics demonstrate the advantages of multicellular trichomes, especially in harsh environments or where advanced defense mechanisms are necessary.

Stem Hairs

Stem hairs, scientifically known as trichomes, are prominent features on plant stems. They are important not just for protection but also for playing roles in regulating temperature and reducing water loss by limiting evaporation.
Trichomes can be found in various shapes and sizes, depending on the plant species and environmental needs. From spiny and threatening to touch, to soft and fluffy, these structures adapt to serve towering roles for the plant’s survival.

• Known as trichomes
• Protect stems from environmental factors
• Limit water evaporation and control plant microclimate

This adaptability speaks volumes about their importance, showing how plants have evolved stem hairs that may be either unicellular or multicellular, adapting specifically to their requirements and habitats.