Form 5 · Common mistakes

Organisation of Plant Tissues and Growth, common mistakes

The mistakes SPM students make on Organisation of Plant Tissues and Growth, why each one loses marks, and the correct version.

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The mistakes, why they lose marks, and the fix

Common mistake	Why it loses marks	What earns the mark
Saying all plant cells keep dividing.	Only meristematic tissue divides; permanent tissue has stopped dividing and is specialised.	State that only meristematic tissue divides, while permanent tissue is specialised and no longer divides.
Confusing xylem and phloem.	Xylem carries water and minerals upward; phloem carries sugars to where they are needed.	State that xylem transports water and minerals and phloem transports sugars (translocation).
Placing cell division in the wrong zone of the root.	Cell division is nearest the tip, then elongation, then differentiation further back.	State the order from the tip outward: root cap, cell division, elongation, differentiation.
Calling the epidermis a dividing tissue.	The epidermis is a permanent protective tissue, not a meristem.	State that the epidermis is a permanent protective tissue and only meristems divide.
Confusing collenchyma and sclerenchyma.	Both give support, but collenchyma cells are living with uneven cellulose walls and sclerenchyma cells are dead with lignified walls.	State that collenchyma is living and flexible, while sclerenchyma is dead and rigid.
Thinking secondary growth happens at the tips.	Secondary growth occurs at the vascular cambium along the stem, increasing girth; the tips carry out primary growth.	State that secondary growth at the cambium increases girth, while primary growth at the tips increases length.
Saying growth stops completely in the stationary phase.	Growth slows and levels off because of a limiting factor; it does not stop absolutely.	State that growth levels off in the stationary phase because a limiting factor caps further increase.
Believing a shoot bends because light pulls it.	The bend is caused by auxin building up on the shaded side and making those cells elongate more.	State that uneven auxin distribution and unequal elongation curve the shoot towards the light.
Thinking xylem vessels are living cells.	Xylem vessels are dead at maturity, hollow and lignified; only phloem has living conducting cells.	State that xylem vessels are dead and lignified, while phloem sieve tubes are living.
Confusing the vascular cambium with the cork cambium.	The vascular cambium makes secondary xylem and phloem; the cork cambium makes protective cork (bark).	State that the vascular cambium produces secondary vascular tissue and the cork cambium produces bark.
Measuring wet mass instead of dry mass for a growth curve.	Wet mass changes with water content, so it is less reliable than dry mass as a measure of growth.	State that dry mass is the more reliable measure because it excludes changing water content.
Saying phloem has no living cells because sieve tubes lose their nucleus.	Sieve tube elements are still living and are kept working by companion cells that have a nucleus.	State that phloem sieve tubes are living and are supported by companion cells.

How to avoid these mistakes

List the plant tissues and sort them into meristematic and permanent.
Draw a root tip and label the three zones of growth.
Practise reading and describing a growth curve.
Sort parenchyma, collenchyma and sclerenchyma by whether the cells are living or dead and how each supports the plant.
Sketch a sigmoid growth curve and label the lag, exponential and stationary phases with a reason for each shape.
Explain phototropism and gravitropism in terms of uneven auxin distribution and unequal cell elongation.
Compare the cell structure of a xylem vessel and a phloem sieve tube, noting which is alive and why that matters for its function.

Frequently asked questions

What is the difference between meristematic and permanent tissue?

Meristematic tissue is made of small, thin-walled cells that keep dividing by mitosis to produce new cells, and it is found at the tips of roots and shoots and in the cambium. Permanent tissue is made of cells that have stopped dividing and become specialised for a job, such as the epidermis for protection or xylem for transport. Meristematic tissue makes the plant grow; permanent tissue carries out functions.

What are the zones of growth in a root?

Just behind the root tip there are three zones. In the zone of cell division, meristematic cells divide to make new cells. In the zone of cell elongation, the new cells grow longer, pushing the root through the soil. In the zone of cell differentiation, the cells become specialised, such as into root hair cells or xylem.

What do xylem and phloem transport?

Xylem transports water and dissolved mineral salts from the roots upward to the leaves. Phloem transports the sugars made in photosynthesis from the leaves to other parts of the plant that need energy or storage. The two tissues together form the plant's vascular system.