Science notes, unit 5

Plants

Textbook Science Year 3 (DLP), pages 71–78

What this chapter covers

You can name six ways plants reproduce and give an example of each (5.1.1)
You can explain why plants must keep reproducing (5.1.2)
You can name plants that reproduce in two different ways (5.1.3)
You can describe how tissue culture and marcottage help us grow more plants (5.1.4)

Pupils and teachers planting young mangrove trees in the mud — A mangrove replanting programme. Why do they plant so many young trees?

Picture: Science Year 3 (DLP) textbook, p. 71.

Look at the picture. The pupils are planting young mangrove trees. Old trees die or get cut down. New trees must grow to take their place. In this unit you will learn how plants make new plants.

5.1Ways plants reproduce

To reproduce means to make new young plants of the same kind.

Plants need to reproduce so they do not die out. When a kind of plant dies out completely and is gone forever, we call it extinction.

Plants can reproduce in six ways. Let's meet them one by one.

1. Seeds

Plants that make fruits reproduce through seeds. The seeds are inside the fruit. Plant a seed in soil, water it, and a new plant grows.

A chilli plant and a papaya tree, with their seeds shown in circles — Chilli and papaya have seeds inside their fruits.

More examples: durian, rambutan, watermelon, rice (padi) and the sunflower.

2. Suckers

Suckers are young plants that grow near the bottom of their parent plant.

A sucker can be dug up and planted somewhere else. It grows into a new plant.

A banana plant and a yam plant, each with a small sucker beside it — Banana and yam (keladi) plants grow suckers.

3. Underground stems

Some plants keep a fat stem under the soil. This underground stem stores food. When we plant it, a new plant grows from it.

An onion and a potato growing under the soil — Onions and potatoes are underground stems.

Ginger (halia) and turmeric (kunyit) are underground stems too. Your mother uses them in the kitchen!

4. Spores

Spores are tiny specks, as small as dust. Each spore can grow into a new plant.

Plants that do not have flowers reproduce through spores. Ferns and mushrooms use spores.

Ferns and mushrooms, with their spores shown in circles — Ferns and mushrooms reproduce through spores.

Did you know? Turn over a fern leaf. You may see rows of little brown dots. They are full of spores!

5. Stem cuttings

A stem cutting is a piece of stem cut from a plant. Push it into the soil. Roots and new leaves grow, and soon it is a new plant.

A tapioca plant and a bougainvillea grown from stem cuttings — Tapioca (ubi kayu) and bougainvillea grow from stem cuttings.

Hibiscus (bunga raya) and sweet potato can also grow from stem cuttings.

6. Leaves

A few plants can grow new plants from their leaves. A leaf falls on the soil and tiny new plants grow from it.

A snake plant and a setawar plant, with new plants growing from their leaves — Snake plant and setawar reproduce through leaves.

Did you know? Setawar grows baby plants along the edges of its leaves. They drop off and grow into new setawar plants.

Pictures: Science Year 3 (DLP) textbook, pp. 72–73.

Way	Examples
Seeds	chilli, papaya, durian
Suckers	banana, yam
Underground stems	onion, potato, ginger
Spores	fern, mushroom
Stem cuttings	tapioca, bougainvillea
Leaves	snake plant, setawar

Do not mix up seeds and spores. Seeds come from plants with flowers and fruits. Spores come from plants with no flowers, like ferns and mushrooms.

Pak Ali cuts a piece of stem from his tapioca plant and plants it. What way of reproduction is this?

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Stem cutting.

5.2Why plants must reproduce

Plants reproduce to make more plants of their own kind. This keeps their kind, or species, alive.

A species is a group of living things of the same type. They look alike. For example, all papaya trees are one species.

Why does this matter to us? Plants give living things four important things. A habitat is a home. Oxygen is a gas in the air that we need to breathe.

Animals eating fruits, grass and carrots on a farm — **Food.** Animals and people eat plants: rice, vegetables and fruits.

Monkeys sitting among cut trees in a forest — **Food.** Animals and people eat plants: rice, vegetables and fruits.

Situations 1–4: Science Year 3 (DLP) textbook, pp. 74–75.

If plants stop reproducing, we would lose our food, animals would lose their homes, the air would have less oxygen, and we would have no wood.

Think about it

The nasi lemak at the school canteen comes from plants too! Rice, coconut milk, cucumber, groundnuts and the chilli in the sambal all come from plants. Plants must keep reproducing so we can enjoy it again tomorrow.

Did you know? Mangrove trees protect the beach from big waves. Fish and crabs live among their roots. That is why people replant mangroves.

Name two things that plants give us.

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Any two: food, habitat (a home for animals), oxygen, wood.

5.3One plant, two ways

Some plants can reproduce in two different ways.

Water spinach (kangkung) is one of them. Pupils tested it in two ways.

Water spinach stem cuttings with roots in a jar of water — **Stem cuttings:** put stem cuttings with roots in water.

Hands planting water spinach seeds in soil — **Stem cuttings:** put stem cuttings with roots in water.

Photos: Science Year 3 (DLP) textbook, p. 76.

They looked at the plants every day. New shoots grew in both containers. A shoot is a new young stem with leaves.

Way of reproduction	Did shoots grow?
Stem cutting	Yes
Seeds	Yes

So water spinach can reproduce in more than one way: by stem cuttings and by seeds.

Plant	Two ways it reproduces
Water spinach (kangkung)	Stem cuttings and seeds
Basil (selasih)	Stem cuttings and seeds
Sweet potato (ubi keledek)	Stem cuttings and underground stems

Name one plant that can reproduce in two ways.

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Water spinach, basil or sweet potato.

5.4Technology helps plants reproduce

Scientists and farmers use technology to grow many new plants quickly. Technology means using clever tools and methods. Here are two ways.

Tissue culture

Tissue culture grows new plants from tiny pieces of a parent plant. The pieces are put in a nutrient medium, a special jelly full of plant food.

Three steps: cut a small piece from a plant, place it in a dish of jelly, many small plants grow — Tissue culture: one plant can give many new plants.

Examples: banana plants and orchid plants.

Marcottage

Marcottage (in Malay, tut) makes roots grow on a branch while it is still on the tree. Then the branch is cut off and planted. No seeds are needed.

Examples: mango trees and lime trees.

Pictures: Science Year 3 (DLP) textbook, p. 77.

Did you know? A mango tree from a seed may take many years to give fruit. A marcotted mango tree often fruits much sooner.

Which technology needs a special plant-food jelly: tissue culture or marcottage?

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Tissue culture (the jelly is the nutrient medium).

Try it at home: a hanging garden

Plants growing in cut plastic bottles hung on a wall — Old plastic bottles make a hanging garden (textbook p. 77).

Ask an adult to help you cut an old plastic bottle. Fill it with soil and plant a stem cutting or some seeds. Hang it near a sunny window and water it.

Summary

Topic	Remember this
Six ways plants reproduce	Seeds, suckers, underground stems, spores, stem cuttings, leaves
Why plants reproduce	So there is always food, habitat, oxygen and wood
Plants with two ways	Water spinach, basil, sweet potato
Technology	Tissue culture (banana, orchid) and marcottage (mango, lime)