Topics · Primary Science · Systems: Plant Parts & Transport
Plant parts and how water moves through them
Four parts, each with a job, and a one-way route for water from the soil to the air. Nearly every question is either “which part does this” or “what happens if this part is blocked”.
- 478 exam papers analysed
- appears in 96% of P6 Science papers
- ~3 min read
01 The four parts and their jobs
Each part earns its place by doing something the plant needs. Learn the job, not just the name — questions ask what a part does far more often than what it is called.
- Roots (W) — anchor the plant in the soil, and take in water and mineral salts.
- Stem (X) — holds the plant up, and carries water up and food around.
- Leaf (Y) — makes food by photosynthesis, and loses water vapour to the air.
- Flower (Z) — makes seeds, so the plant can reproduce.
02 The path water takes
Water moves in one direction only: in at the roots, up the stem, out through the leaves. Knowing the order lets you answer any blockage question.
The water is not pushed from below. It is pulled from above, because water leaving the leaves draws the next water up behind it — which is why a plant in a windy, dry place drinks more.
03 Blockage questions
The standard P5–P6 question removes or blocks one part and asks what happens. Work along the path and say what is cut off after that point.
Roots removed — no water enters at all, so the whole plant wilts and dies.
Stem ringed or blocked — water cannot get past, so everything above the block wilts while the part below stays alive.
Leaves removed or coated — water cannot leave, so the pull stops and less water is drawn up; the plant also stops making food.
Flowers removed — the plant lives perfectly well but cannot make seeds. This one catches people, because the plant is not harmed.
04 Two tubes, not one
The stem carries two things in opposite directions, in two different sets of tubes.
Water tubes carry water and mineral salts upwards, from roots to leaves.
Food tubes carry food made in the leaves to the rest of the plant, including downwards to the roots.
That is why a plant with its leaves removed starves even though its roots are intact: the roots cannot make food, they receive it.
05 How to say them
These are words most children have never said out loud, and a word you cannot say is a word you avoid using. Capitals mark the syllable you lean on. Tap the speaker to hear it.
- rootmore than oneroots
The part below ground that anchors the plant and takes in water and mineral salts.
- stemmore than onestems
The part that holds the plant up and carries water and food through it.
- mineral salts
Substances dissolved in soil water that a plant needs. Taken in through the roots with the water.
- transpirationsaytran-spi-RAY-shuhn
Water leaving the leaves as vapour. It is what pulls more water up the stem.
- water vapoursayVAY-puh
Water as a gas. What leaves the plant through its leaves.
- absorbsayuhb-ZORB
To take in. Roots absorb water from the soil.
06 What each level is tested on
The same topic, asked differently as it goes up. The percentage is the share of papers at that level in which it appears.
- P3
Naming the four parts and their jobs.
Practise P3 Systems: Plant Parts & Transport — 10 questions →74% of P3 papers
- P4
The path water takes, and what each part contributes.
Practise P4 Systems: Plant Parts & Transport — 10 questions →77% of P4 papers
- P5
Transport in the stem, transpiration, and experiments where a part is removed.
Practise P5 Systems: Plant Parts & Transport — 10 questions →74% of P5 papers
- P6
Explaining the effect of a blockage, and plant transport inside fair-test questions.
Practise P6 Systems: Plant Parts & Transport — 9 questions →96% of P6 papers
07 Mistakes worth knowing about
Each of these is wrong. Decide why before you open it.
“The roots push the water up the stem.”
Water leaving the leaves pulls it up. That is why more water moves on a hot, windy day, when the leaves lose water faster.
“The stem has one set of tubes.”
Two, going opposite ways: water up from the roots, food down and out from the leaves.
“Cut the flowers off and the plant dies.”
It lives normally. It just cannot make seeds, so it cannot reproduce.
“The roots make food for the plant.”
The leaves make the food. The roots take in water and mineral salts and receive food from the leaves.
“Block the stem and the whole plant wilts.”
Only the part above the block. Below it, water from the roots still reaches the plant.
Now try it
39 questions across 4 levels, marked as you go with the working shown.