Problem 74 - Objective Biology for NEET

Question

Select \(\mathrm{T} / \mathrm{F}\) (True/False). (a) Epidermis is usually single-layered. (b) Epidermal cells are parenchymatous cell with abundant cytoplasm. (c) Vessel members of xylem are interconnected through perforation in their common walls. (d) Sclerenchyma provides mechanical support to organs. (a) TTTT (b) TFFT (c) TFTT (d) FFTT

Step-by-Step Solution

Answer

Based on the provided explanations, the correct answer option is (d) FFTT.

Step 1: Understanding the Epidermis

The epidermis is indeed usually composed of a single layer of cells. Therefore, statement (a) 'Epidermis is usually single-layered' is 'True'. Therefore, all options with a 'False' in the first position can be eliminated.

Step 2: Understanding the Epidermal Cells

Epidermal cells are not considered parenchymatous cells with abundant cytoplasm. Epidermal cells are specialized for functions such as protection and water resistance. Therefore, the answer to option (b) 'Epidermal cells are parenchymatous cell with abundant cytoplasm' is 'False'. This leaves us with only option (d) as a possible answer.

Step 3: Understanding the Xylem Vessel Members

The xylem's vessel members are interconnected via perforations in their common walls, which is True. This aligns with the third position in option (d). Therefore, statement (c) 'Vessel members of xylem are interconnected through the perforation in their common walls' is 'True'.

Step 4: Understanding the Sclerenchyma

Lastly, sclerenchyma does provide mechanical support to organs, which is also True. This aligns with the fourth position in option (d). Therefore, statement (d) 'Sclerenchyma provides mechanical support to organs' is 'True'.

Key Concepts

Epidermis

The epidermis is the outermost layer of cells that envelopes the body of a plant. It serves as a protective barrier against the external environment, preventing water loss and providing defense against pathogens. Typically, the epidermis is composed of a single layer of closely packed cells.
This one-cell-thick formation is crucial, especially in aerial parts of the plant, like leaves and stems, because it minimizes water loss by transpiration. Additionally, the presence of specialized cells, like guard cells, helps regulate gas exchange and water retention through small openings called stomata.

• Guard cells: Control the opening and closing of stomata.
• Trichomes: Hair-like structures that can protect against herbivory and reduce water loss.

These components make the epidermis a sophisticated layer that balances protection with the essential exchange of gases.

Xylem

Xylem is a crucial tissue in vascular plants, tasked primarily with the conduction of water and dissolved minerals from the roots to the rest of the plant. It provides structural support to the plant as well. The xylem is composed of different types of cells, including tracheids and vessel elements, which are elongated and tubular.
A significant characteristic of vessel elements is their interconnectedness. They are connected end-to-end, forming continuous tubes, with their common walls having perforations that allow for efficient water flow. This vertical alignment of cells not only facilitates upward water movement through capillary action but also contributes to the overall strength and rigidity of the plant.
In addition to conducting water, the xylem also transports some inorganic nutrients and provides support to help hold the plant upright.

Sclerenchyma

Sclerenchyma cells are specialized for providing mechanical support to plants. These cells are characterized by their thick, lignified cell walls which make them strong and durable. Unlike parenchyma cells, sclerenchyma cells are typically dead at maturity, serving a structural purpose rather than a metabolically active one.
Within sclerenchyma, there are two main types of cells: fibers and sclereids.

• Fibers: Long, narrow cells that contribute to the tensile strength of stems and other plant structures.
• Sclereids: Shorter and often found in seed coats and nutshells, providing rigidity and protection.

The presence of sclerenchyma is vital, especially in woody plants and parts of a plant that require strong support, like the cortex and pith.

Parenchyma

Parenchyma is a versatile and fundamental ground tissue found in many parts of the plant. Unlike the specialized tissues such as xylem or sclerenchyma, parenchyma cells are alive at maturity and have thin walls, enabling them to play various roles depending on their location.
These cells are often involved in photosynthesis, storage, and healing, thanks to their ability to divide and regenerate. Their loosely packed structure with large intercellular spaces allows for efficient gas exchange and movement of nutrients.

• Functions: Photosynthesis, storage of nutrients, and helping heal wounds.
• Characteristics: Thin-walled, alive at maturity, and capable of division.

Parenchyma cells can also adapt by developing into more specialized forms when the plant requires it, underscoring their importance in plant growth and regeneration.