Organisation of Plant Tissue

A flowering plant is a multicellular organism whose cells are not scattered at random. Similar cells that share a function are grouped into a tissue, and tissues combine to form organs such as the root, stem and leaf. Studying how plant tissue is organised helps us understand how a plant absorbs, transports and manufactures the substances it needs.

Two broad groups of tissue

Plant tissues are first divided by whether their cells can still divide.

• Meristematic tissue — made of small, thin-walled cells that divide actively by mitosis. It is found at growing points and is responsible for producing new cells.
• Permanent tissue — cells that have stopped dividing and have become specialised for a fixed job. Most of the mature plant body is permanent tissue.

Types of permanent tissue

Permanent tissue is grouped by structure and role:

• Epidermis — a protective outer layer, usually one cell thick, often covered by a waxy cuticle that reduces water loss.
• Parenchyma — thin-walled packing cells that store food and, when they contain chloroplasts, carry out photosynthesis.
• Collenchyma and sclerenchyma — cells with thickened walls that give the plant support and strength.
• Vascular tissue — the transport tissue, made of xylem (carries water and mineral salts) and phloem (carries dissolved food).

Why organisation matters

Because each tissue is specialised, the plant works far more efficiently than a loose mass of identical cells would. Xylem forms continuous tubes so water can rise from root to leaf; epidermis with a cuticle keeps the plant from drying out; parenchyma packed with chloroplasts turns sunlight into food. This division of labour is the same principle seen in animals, but the tissues themselves are different.