Year 8 · Science · Ecosystems and photosynthesis · Lesson 3

Leaves and plant minerals

The structure of a leaf and how it's adapted for photosynthesis, the minerals plants need from the soil, fertilisers, and how to test a leaf for starch.

24-minute video lesson

Teaching, worked examples and 20 practice questions solved step by step.

Watch free for a month

What your child will learn

Describe the layers of a leaf
Explain how leaves are adapted for photosynthesis
Describe the role of stomata and guard cells
Name the minerals plants need and what they do
Describe the test for starch in a leaf

The method

Leaves are broad, flat and thin, with lots of chlorophyll, stomata and veins.
The palisade layer has most chloroplasts; stomata (opened by guard cells) let gases in and out.
Minerals: nitrates for growth, phosphates for roots, potassium for flowers and fruit, magnesium for chlorophyll.
Starch test: boil in water, warm in ethanol (water bath), rinse, add iodine: blue-black shows starch.

Key words: palisade, spongy layer, stomata, guard cells, cuticle, nitrates, magnesium, fertiliser, starch test.

Worked examples

The first three practice questions from the lesson, with every step.

Question 1

Why do plants need magnesium? What happens if they don't get enough?

Step 1: Magnesium: make chlorophyll
Step 2: Too little: yellow leaves

Answer: For make chlorophyll; too little gives yellow leaves

Question 2

Why do plants need phosphates? What happens if they don't get enough?

Step 1: Phosphates: healthy roots
Step 2: Too little: poor root growth, purple leaves

Answer: For healthy roots; too little gives poor root growth, purple leaves

Question 3

Why do plants need potassium? What happens if they don't get enough?

Step 1: Potassium: healthy leaves, flowers and fruit
Step 2: Too little: yellow leaves with dead patches

Answer: For healthy leaves, flowers and fruit; too little gives yellow leaves with dead patches