Plants — Class 3 Science (Samacheer Kalvi)
TN State Board (Samacheer Kalvi) Class 3 Science. Parts of a plant, roots, flowers and leaves.
1. The six parts
| Part | What it does |
|---|---|
| Root | Holds the plant in the soil, takes in water and minerals |
| Stem | Holds up the plant and carries water and food |
| Leaf | Makes food, and releases water vapour |
| Flower | The reproductive part, which becomes a fruit |
| Fruit | Protects the seeds inside |
| Seed | Grows into a new plant |
2. The stem is a highway
It is easy to think the stem only holds the plant upright. It does more than that.
Inside the stem are tiny tubes. One set carries water upward from the roots to the leaves. Another carries food downward from the leaves to the rest of the plant.
Cut a stem and stand it in coloured water, and after some hours the colour appears in the leaves. That is the upward tube being caught in the act.
3. Two kinds of root
Tap root: one thick main root growing straight down, with smaller roots branching off it. Carrot, radish, beetroot, mango and neem all have tap roots.
Fibrous root: many thin roots of similar size spreading out. Grass, rice, wheat and onion have fibrous roots.
When you eat a carrot you are eating a tap root, thickened because the plant stored food in it.
4. Parts of a flower
| Part | What it does |
|---|---|
| Petal | Colourful, attracts insects and birds |
| Sepal | Small and green, protects the bud before it opens |
| Stamen | The male part, makes pollen |
| Pistil | The female part, in the centre |
A way to keep the last two apart: stamen contains the letters "men", and it is the male part. The pistil sits in the middle and receives the pollen.
After pollination the flower changes into a fruit, and the seeds form inside it.
5. What leaves do
Leaves have two jobs.
Photosynthesis is the making of food. The leaf takes in sunlight, carbon dioxide from the air and water from the roots, and produces food for the plant. It gives out oxygen as it does so, which is why plants matter to every animal that breathes.
Transpiration is the release of extra water as vapour, through tiny openings in the leaf. Tie a clear plastic bag over a leafy branch on a sunny day and drops will collect inside it.
6. Worked examples
Example 1. A carrot and a blade of grass are pulled up. How do their roots differ?
The carrot has a tap root: one thick main root going straight down. The grass has fibrous roots: many thin ones spreading out.
Example 2. A cut stem is stood in red water and the leaves turn reddish. What does this show?
That the stem carries water upward from its base to the leaves, through tubes inside it.
Example 3. Which part of a flower attracts insects, and which protects the bud?
The petals attract insects with their colour. The sepals, small and green, protect the bud before it opens.
Example 4. Name the three things a leaf needs to make food, and the gas it gives out.
Sunlight, carbon dioxide and water. It gives out oxygen.
7. Practice
- Name the six parts of a plant.
- Give two jobs of the stem.
- Name two plants with tap roots and two with fibrous roots.
- Which part of the flower makes pollen?
- Name the two functions of a leaf.
- Which gas do leaves take in, and which do they give out, when making food?
- What does a flower become after pollination?
8. Answers
- Root, stem, leaf, flower, fruit and seed.
- It holds the plant up, and it carries water upward and food downward.
- Tap roots: carrot and mango. Fibrous roots: grass and onion.
- The stamen, which is the male part.
- Photosynthesis, which makes food, and transpiration, which releases water vapour.
- It takes in carbon dioxide and gives out oxygen.
- A fruit, with seeds inside it.
9. Summary
- The six parts are root, stem, leaf, flower, fruit and seed.
- The stem supports the plant and also carries water up and food down.
- A tap root is one thick main root; fibrous roots are many thin ones.
- A carrot is a tap root that has thickened with stored food.
- Petals attract, sepals protect, the stamen is male and the pistil female.
- Leaves make food by photosynthesis, using sunlight, carbon dioxide and water, and give out oxygen.
- Leaves also release extra water as vapour, which is transpiration.
