Question

In plants, fibers are a type of cell. a. parenchyma c. collenchyma b. sclerenchyma d. mesophyll

Short answer

Fibers in plants are sclerenchyma cells.

Step-by-step solution

Understand the question

The question asks us to identify which type of plant cell among the options provided is known as fibers.

Define plant cell types

Understand the characteristics of each cell type. Parenchyma cells are living cells with thin walls, collenchyma cells provide flexible support with thicker walls, sclerenchyma cells have thick lignified walls and provide mechanical support, and mesophyll cells are involved in photosynthesis.

Identify fiber cells

Fiber cells in plants are a specific type of sclerenchyma cells. They have thick, lignified walls and provide structural support to the plant.

Choose the correct answer

From the analysis, sclerenchyma cells are the ones known as fibers. The correct answer is option **b. sclerenchyma**.

Key concepts

Sclerenchyma

Sclerenchyma cells are a crucial type of plant cell that provide structural support, giving them a pivotal role in the plant's overall integrity. These cells are characterized by their thick, rigid cell walls that are heavily lignified, which means they are reinforced with lignin, a complex organic polymer. This lignification process makes the cell walls tough and hard, allowing the sclerenchyma cells to support the weight of the plant and withstand various environmental stresses.

Unlike other plant cells, sclerenchyma cells are typically non-living at maturity. This is because their extensive lignification leads to the loss of protoplasm – the living part of the cell – so what remains is just the tough wall. There are two main types of sclerenchyma cells: fibers and sclereids.

• **Fibers**: These are elongated cells that commonly form bundles, which are found throughout the plant in stems, roots, and vascular bundles.
• **Sclereids**: These are shorter, variably-shaped cells, providing support and hardness to nutshells and seed coats.

When you think of fibers in plants, you're likely thinking of sclerenchyma cells due to their dense and rigid nature that forms a supportive framework for the plant.

Parenchyma

Parenchyma cells are the most common and versatile type of plant cell, often referred to as the "all-purpose" cells within the plant. These cells are alive at maturity and possess thin, flexible cell walls that enable them to perform a wide range of functions crucial for the plant's growth and metabolism.

The primary role of parenchyma cells is involved in the storage of nutrients, synthesis of organic products, and photosynthesis, especially within the spongy mesophyll of leaves and the cortex of stems and roots. A key characteristic of these cells is their ability to divide and regenerate, which plays a significant role in healing wounds and in the plant's growth. Here are some key features of parenchyma cells:

• **Storage**: They store starch, proteins, and oils.
• **Photosynthesis**: Contain chloroplasts within the mesophyll enabling them to carry out photosynthesis efficiently.
• **Water and Nutrient Transport**: Act like a medium through which water and nutrients move across the plant.

Due to their ability to form various other specialized cells, parenchyma cells are considered essential for providing flexibility and the plant's adaptive capabilities.

Collenchyma

Collenchyma cells serve as a support tissue in living plants, providing both support and flexibility to various plant parts. Unlike sclerenchyma, these cells are alive at maturity and have unevenly thickened cell walls due to the presence of cellulose and pectin. This unique feature allows collenchyma cells to stretch and elongate, accommodating changes in growth and environment without breaking.

Think of collenchyma as akin to a plant's cartilage. They provide flexible structural support while still being capable of growing. This characteristic is particularly beneficial in parts of the plant that are still elongating, like young stems or leaf petioles.

• **Support**: Collenchyma cells are often found under the epidermis, aiding in mechanical support without compromising flexibility.
• **Growth**: Since these cells are capable of growth and expansion, they mainly support still-growing parts of the plant.

Collenchyma is especially important for the plant's resilience, allowing it to bend without breaking, especially in windy environments or under physical pressure. It is an extraordinary adaptation that helps plants survive and sustain various physiological functions.