How water travels from soil to leaf, why transpiration matters, the factors that change its rate, water conservation, and translocation in phloem.
6 narrated scenes. Press play, listen and read along — the points appear as they are explained. Use ‹ Prev / Next › or the scene bar to jump to any scene.
A mango tree lifts water 15 m high with no pump and no heart. How?
Narration uses your device’s built-in voice. No sound? Switch to “Captions only” — the captions advance on their own.
See how guard cells open and close the pore.
Copy these into your notebook in your own words — that is how they stick.
Dead, hollow, lignified vessels with no end walls → continuous water column; strength & support.
Root hairs by osmosis → cortex → xylem → leaf mesophyll → evaporates → stomata.
Loss of water vapour from aerial parts, mainly via stomata.
Transpiration pull moves water and minerals; cooling; turgidity; water for photosynthesis.
Temperature ↑, wind ↑, light ↑ → rate ↑; humidity ↑ → rate ↓.
Thick cuticle, sunken/few stomata, spines, rolled leaves, hairs, succulence, deep roots, leaf fall.
Living sieve tubes with sieve plates + companion cells (energy). Translocation of sucrose from source to sink.
Where sucrose is loaded into phloem (e.g. photosynthesising leaf).
The kind of support a teacher gives after the lesson: worked examples to attempt first, a board illustration, key terms, common misconceptions and memory aids.
Try it in your notebook first, then reveal the solution one step at a time.
| Leaf | Treatment | Mass lost (g) |
|---|---|---|
| A | No jelly | 3.0 |
| B | Jelly on upper surface | 2.6 |
| C | Jelly on lower surface | 0.6 |
| D | Jelly on both surfaces | 0.1 |
Try it in your notebook first, then reveal the solution one step at a time.
| Xylem | Phloem | |
|---|---|---|
| Carries | Water and mineral ions | Sucrose and amino acids (translocation) |
| Direction | Upwards only (roots → leaves) | Both ways — from source (leaves) to sink (roots, fruits, growing tips) |
| Cells | Dead, hollow tubes with no end walls | Living sieve tubes with sieve plates and companion cells |
| Walls | Thickened with lignin (also gives support) | Thin cellulose walls |
| Driven by | Transpiration pull from the leaves | Active processes in living cells (energy needed) |
Xylem: water and minerals, up only, dead cells. Phloem: sugars, both directions, living cells.
Xylem = X-tra water, going up. Phloem = food. Transpiration speeds up with Wind, Warmth, Bright light and Dry air.
Plants on dry Caribbean coasts and islands — such as cacti and the century plant (Agave) — conserve water with thick waxy cuticles, few or sunken stomata and swollen stems or leaves that store water.
Stand a stick of celery or a white flower in water coloured with food dye. After a day, cut across the stem and look for the coloured dots — those are the xylem vessels.
4 quick games on this lesson. Earn XP and badges as you play — your best score for each game is saved. Games are for practice and do not change your exam readiness.
8 items modelled on real CSEC Paper 1 questions. Choose one answer for each, then check. Aim for 80% or better.
Write full answers, then reveal the mark scheme and tick the points you earned (23 marks in total). Your answers are saved on this device.
Question 1 [12 marks]
Transpiration in flowering plants.
(a) Define the term “transpiration”. [1]
(b) State TWO reasons why transpiration is important to plants. [2]
(c) List THREE factors, other than temperature, that affect transpiration, and explain how each affects the rate. [9]
Question 2 [11 marks]
Xylem and phloem are specialised plant tissues.
(a) Define “translocation” and explain TWO ways xylem is suited to transpiration. [5]
(b) Explain why phloem cells, which have very few organelles, can still transport food to all parts of the plant. [2]
(c) Explain TWO ways in which plants conserve water. [4]
Find these in your own past-paper booklets for extra timed practice. The practice above is adapted from them.