Plant Tissue

A collection of cells performing a specific function is called tissue. Plant tissues can be grouped into plant tissue systems each performing specialized functions. A plant tissue system is defined as a functional unit, connecting all organs of a plant. Plant tissue system is also grouped into various tissues based on their functions.

Plant tissues can be broadly classified based on the ability of the cells to divide into Merismatic tissue and Permanent tissue. Merismatic tissues consist of a group of cells that have the ability to divide. These tissues are small, cuboidal, densely packed cells which keep dividing to form new cells. These tissues are capable of stretching, enlarging and differentiating into other types of tissues as they mature. Meristematic tissues give rise to permanent tissues. Merismatic tissues can be of three types depending on the region where they are present: Apical meristems, lateral meristems, and intercalary meristems. Permanent tissues are derived from the merismatic tissues and have lost their ability to divide. They have attained their mature form. They are further classified into two types: Simple and complex permanent tissues.

The permanent tissues form the major portion of the plant.

Parenchyma- These tissues are found in the soft parts of a plant such the roots, stems, leaves, and flowers. The cells of this tissue are loosely packed and contain large intercellular spaces between them. Each cell has a vacuole at the center. The functions of parenchyma tissues are storage, photosynthesis, and to help the plant float on water.

Collenchyma- Are similar to parenchyma cells with thicker cell walls. They are meant to provide mechanical support to the plant structure in parts such as petiole of the leaf.

Sclerenchyma- The cells of this tissue are dead. They are rigid, contain thick and lignified secondary walls. Their main function is to provide strength and support to parts of the plant.

Unlike simple permanent cells which look the same and are made up of one type of cells, complex permanent tissues are made up of more than one type of cells. These different types of cells coordinate to perform a function. Xylem and Phloem are complex permanent tissues and are found in the vascular bundles in the plants.

Xylem- It consists of tracheids, vessels, xylem parenchyma and xylem fibres.

Tracheids and vessels are hollow tube-like structures that help in conducting water and minerals. The xylem conducts only in one direction i.e vertically. The xylem parenchyma is responsible for storing the prepared food and assists in the conduction of water. Xylem fibres are supportive in function.

Phloem- It consists of four of elements: sieve tubes, companion cells, phloem fibres and the phloem parenchyma. Unlike the xylem, phloem conducts in both directions. It is responsible for transporting food from the leaves to the other parts of the plant. Phloem contains living tissues except for fibres that are dead tissues.

Plant tissues have different functions depending upon their structure and location

Help provide mechanical strength to organs. They help in providing the elasticity and flexibility to the organs. They help the tissues to bend easily in various parts of a plant like- leaf, stem, and branches without damaging the plant

The xylem and phloem tissues help in transportation of material throughout the plants

They divide to produce new cells and help in the growth of the plants. They help in various cellular metabolisms like photosynthesis, regeneration, respiration, etc.

Solved Example for YouQ: Pick the odd one out.

(a) sieve tubes

(b) companion cells

(c) phloem fibres

(d) TracheidsSol.

(e) TracheidsThe odd one out is option

(f) tracheids as they are a part of xylem tissue whereas the other three options are parts of phloem tissue.