This MCQ module is based on: Plant Tissues — Meristematic and Permanent
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Plant Tissues — Meristematic and Permanent
🎓 Class 9
Science
CBSE
Theory
Ch 3 — Tissues in Action
⏱ ~13 min
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Plant Tissues — Meristematic and Permanent
Class 9 Science · Chapter 3 · Part 2 — Meristems, Parenchyma, Xylem & Phloem
3.3 Two Big Families of Plant Tissues
Plant tissues fall into two broad groups based on whether the cells are still able to divide. The young, dividing cells form meristematic tissue; once the cells stop dividing and take on a fixed shape and job, they become permanent tissue.
3.3.1 Meristematic Tissue — Where Plants Grow
Meristematic cells are small, thin-walled, packed tightly together with little or no space between them, and have a large nucleus and dense cytoplasm. They divide again and again to produce new cells. Based on where in the plant they are found, three types are recognised.
🌱 Meristem Identifier — Click each yellow zone L1 Remember
Three regions of dividing cells keep a plant growing. Click each yellow patch to reveal which meristem it is and what part of growth it controls.
Click any yellow meristem zone above to reveal what kind of growth it controls.
(i) Apical Meristem
Found at the tips of stems, branches and roots. It is responsible for increasing the length of the plant. Whenever you see a shoot growing taller or a root probing deeper, the apical meristem is at work.
(ii) Lateral Meristem (Cambium)
Lies along the sides of the stem and root. It is responsible for increasing the girth (thickness). The annual rings in the trunk of a tree are produced by the lateral meristem.
(iii) Intercalary Meristem
Located between matured tissues, especially at the bases of leaves or above nodes (as in grasses). It helps the plant regrow after damage — that is why a lawn keeps recovering after every mowing.
Mnemonic: A-L-I — Apical (tips), Lateral (sides), Intercalary (in-between).
3.3.2 Permanent Tissues — Mature Workers
When meristematic cells stop dividing and take a fixed structure, they become permanent tissues. These are sub-grouped into simple permanent tissues (one cell type) and complex permanent tissues (more than one cell type).
A) Simple Permanent Tissues
1. Parenchyma
Living cells with thin walls and large vacuoles. They store food, water and air. When they contain chlorophyll they are called chlorenchyma and carry out photosynthesis. In aquatic plants, parenchyma with large air cavities is called aerenchyma, and it gives buoyancy.
2. Collenchyma
Living cells with corners thickened by extra cellulose and pectin. It provides flexibility — bending without breaking — to young stems and leaf stalks. The string-like part you peel off a celery stalk is collenchyma.
3. Sclerenchyma
Dead cells with very thick walls due to a substance called lignin. There is no space between the cells. Sclerenchyma makes the plant hard and stiff — the husk of a coconut, the rough fibres in jute and the gritty particles in a pear are all sclerenchyma.
| Feature | Parenchyma | Collenchyma | Sclerenchyma |
|---|---|---|---|
| Cells | Living, thin-walled | Living, corner-thickened | Dead, thick-walled (lignin) |
| Function | Storage, photosynthesis | Flexible support | Hardness, rigidity |
| Example | Soft pulp of fruit | Leaf stalk of celery | Coconut husk, jute fibre |
Special simple tissue: Epidermis
The single outer layer of a plant body is the epidermis. It is covered with a waxy cuticle in aerial parts, and it has tiny pores called stomata for gaseous exchange. In roots, some epidermal cells extend out as root hairs to absorb water.
B) Complex Permanent Tissues
Complex tissues are made of more than one cell type that act together. The two main complex tissues form the plant's plumbing system — together called the vascular tissue.
Xylem — water and mineral transport (upward)
Xylem carries water and dissolved minerals from the roots upward to leaves. It is made of four cell types:
- Tracheids — long, tapering, dead cells with pitted walls.
- Vessels — long tube-like dead cells joined end-to-end with cross-walls dissolved.
- Xylem parenchyma — the only living cells in xylem; store food.
- Xylem fibres — dead, thick-walled cells, give support.
Phloem — food transport (in any direction)
Phloem carries food (mainly sucrose) made in the leaves to all other parts of the plant. It also has four cell types:
- Sieve tubes — long living cells joined end to end with sieve plates having pores.
- Companion cells — small living cells beside sieve tubes that keep them alive.
- Phloem parenchyma — for storage.
- Phloem fibres — only dead cells in phloem, give support.
Direction of transport: Xylem moves substances upward only (roots → leaves). Phloem moves food both up and down from the leaves to wherever it is needed (this is called translocation).
Activity 3.2 — Looking for Plant Tissues with Your EyesL3 Apply
Predict first: Take a stalk of celery (or stem of any soft plant). Where do you think the strong fibres lie — on the outside or in the middle?
- Cut a transverse section of a soft stem like balsam (or buy a celery stalk).
- Place the section on a slide and add a drop of safranin or red ink. Wait for two minutes.
- Observe under a lens — the lignified xylem and sclerenchyma will appear deep red.
- Note where the coloured tissue is located.
The xylem and sclerenchyma fibres are arranged in patches just under the epidermis (collenchyma layer) and around the vascular bundles. This is the strong skeletal tissue of the stem.
Competency-Based Questions
A bonsai gardener carefully prunes the tip of every shoot to keep the plant short. He never cuts the base of the stem. Strangely, the plant still becomes thicker year by year.
Q1. Which meristem has been removed by pruning, and which is still active? L3
Pruning removes the apical meristem (so the plant cannot increase length). The lateral meristem (cambium) is still active and continues to make the trunk thicker.
Q2. Why are sclerenchyma cells described as 'dead but useful'? L2
Their cytoplasm dies, but their thick lignified walls remain and provide mechanical strength to the plant — like wooden pillars holding up a roof.
Q3. Identify the tissue: living cells, large air cavities, found in lotus stems.
(b) Aerenchyma — the air cavities provide buoyancy.
Q4. Differentiate between xylem vessels and sieve tubes in two points. L2
(i) Vessels are dead, sieve tubes are living. (ii) Vessels carry water upward; sieve tubes carry food in any direction.
Q5. Why is phloem said to be a 'two-way' transport tissue? L4
Food made in leaves can be sent upward to growing buds and fruits or downward to roots, depending on where it is needed. Hence transport happens in both directions.
Assertion–Reason Questions
Choose: (A) Both A and R true and R explains A. (B) Both true but R does not explain A. (C) A true, R false. (D) A false, R true.
Assertion: Sclerenchyma provides hardness to plant parts.
Reason: Sclerenchyma cells have thick walls deposited with lignin.
(A) — lignin is the substance that makes cell walls hard, hence the rigidity.
Assertion: Companion cells are very important for the working of phloem.
Reason: Sieve tubes have very little cytoplasm and depend on companion cells for life functions.
(A) — sieve tubes lose nuclei and cannot survive alone, so companion cells keep them alive.
Assertion: Cambium is responsible for the increase in girth of a tree.
Reason: Cambium is an apical meristem.
(C) — Assertion is true, but the reason is false. Cambium is a lateral meristem, not apical.
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