Question

A thick-walled lignified simple mechanical tissue is (a) Parenchyma (b) Collenchymas (c) Sclerenchyma (d) Chlorenchyma

Short answer

The correct answer is (c) Sclerenchyma.

Step-by-step solution

Identifying the properties

Identify the tissue that is thick-walled, lignified, and simple mechanical. These characteristics are crucial in determining the type of tissue.

Comparing with each tissue type

Compare these traits to each option: Parenchyma are usually thin-walled and not lignified. Collenchymas offer support and are often thick-walled, but usually not lignified. Chlorenchyma is a type of parenchyma that contains chloroplasts and usualy is not lignified nor thick-walled.

Making the correct choice

The remaining tissue, Sclerenchyma, fits the given description. It is thick-walled and lignified, and its function is for mechanical support.

Key concepts

Simple mechanical tissue

Simple mechanical tissue refers to a type of plant tissue that provides structural support and strength to various parts of the plant. These tissues are vital as they help plants maintain their shape and withstand various physical stresses, such as wind or the plant's own weight. The term "simple" indicates that these tissues are composed of similar types of cells, unlike complex tissues that consist of different cell types.

One key characteristic of simple mechanical tissue is its uniformity. The cells are of the same shape and size, which allows them to function efficiently as a supportive network within the plant. Simple mechanical tissues can be found in different parts of the plant, like the stem, leaves, and roots.

In general, sclerenchyma is a type of simple mechanical tissue known for its robust function in providing support. Unlike other tissues, sclerenchyma cells are dead at maturity, helping to create a rigid and supporting framework for the plant. This property of being dead yet functional allows these tissues to be very efficient at providing mechanical strength.

Lignified tissue

Lignified tissue refers to plant tissues that have cells with walls strengthened by lignin, a complex organic polymer. Lignin works as a binding agent, giving support and rigidity to the plant's cell walls. This quality is crucial for plants, especially those that grow tall, as it provides the necessary support to withstand gravity and other environmental forces.

Lignification is a process in which lignin is deposited on the cell walls of certain plant tissues, providing several benefits:

• Enhances the strength and stiffness of the plant tissue.
• Improves water conduction within vascular tissues like xylem.
• Provides resistance against decay and pathogens, offering protection.

In sclerenchyma tissues, lignification is particularly significant. The cells of sclerenchyma are heavily lignified, which allows them to serve effectively as supportive structures. The presence of lignin makes these tissues both strong and durable, facilitating the plant's ability to grow and thrive.

Thick-walled tissue

Thick-walled tissues are characterized by their thick cell walls, which play an essential role in providing structural support to plants. These tissues are tailored for support rather than flexibility or metabolic functions. The thickness of the walls is due primarily to layers of cellulose, an important building substance in plant cell walls. In some cases, these walls are also reinforced with lignin, contributing to their rigidity.

The reasons why plants have thick-walled tissues include:

• Enhancing the strength needed to support stems and leaves against environmental forces.
• Protecting the plant from physical harm and pathogen invasion.
• Limiting water loss by providing a barrier against desiccation.

In sclerenchyma, thick-walled cells are a signature feature that provides mechanical support. These thickened walls, along with lignin deposits, ensure that sclerenchyma tissues are capable of offering maximum support. Often associated with woodiness, these tissues are crucial for plants that require more substantial support structures.