Each plant tissue has a structure that suits its job. To identify a tissue, read the structure first and the function follows.
This lesson opens the SPM Biology plant organisation and growth chapter.
Which tissue does which job?
Plant tissues fall into three groups: dermal, ground and vascular.
| Tissue | Key structure clue | Main function |
|---|---|---|
| Epidermis | Flat cells in a single layer, usually with a waxy cuticle | Covers and protects, reduces water loss |
| Parenchyma | Thin-walled living cells with large vacuoles | Stores food and fills space; palisade cells do photosynthesis |
| Collenchyma | Walls thickened unevenly at the corners | Supports young stems and leaf stalks while still flexible |
| Sclerenchyma | Thick lignified walls, dead when mature | Gives rigid support |
| Xylem | Long hollow tubes with lignified walls | Carries water and minerals upwards; supports |
| Phloem | Sieve tubes beside companion cells | Carries sucrose and other food substances |
Worked example: identify a tissue from clues
A student studies a stained stem cross-section. One cell type has a large hollow centre, no living cytoplasm and a thick red-stained wall. Another cell type has a living cytoplasm and sits next to a small cell with a large nucleus.
First cell. A hollow centre means a tube can carry a liquid. Thick walls stained for lignin mean strength. This is xylem, which carries water and minerals and helps support the stem.
Second cell. Living cytoplasm in a tube, with a companion cell beside it, means a cell that carries dissolved food. This is a sieve tube of phloem.
The method is to name the structure clue, state what it allows, and only then write the tissue name.
The mistake that costs marks
The common slip is to say “xylem carries food” or “phloem carries water”. The two tissues sit together in the same bundle, so students swap them.
| Wrong | Right | |
|---|---|---|
| Xylem carries | Food | Water and dissolved minerals |
| Phloem carries | Water | Sucrose and other dissolved food |
| Direction | Both move upwards only | Xylem moves water upwards; phloem moves food to where it is needed |
A quick check: xylem has lignin, and lignin is for strength and tubes that stay open.
Check yourself
A potato tuber stores starch. Which tissue is most likely to fill most of the tuber, and what structure clue explains it?
Answer
Parenchyma. It is made of thin-walled living cells with large vacuoles, and these cells can hold stored starch. The thin walls leave room inside each cell for the stored food.
Xylem and sclerenchyma have thick lignified walls, which suit support rather than storage.
What to study next
Growth adds new tissue, so continue with comparing primary and secondary growth. For how xylem and phloem move substances, see transport in plants.
The biological data interpretation trainer gives you practice with diagrams and tables, and the mistake log and paper-error review records which tissues you swapped.
If you want a teacher to go through your labelled diagrams, see online one-to-one Biology tuition.