Reproduction in Plants – JSS2 Intermediate Science Lesson Note (Second Term)

Reproduction in plants is the process by which plants produce new plants of the same kind, either from one parent or from two.

Behavioural objectives

1. Define reproduction in plants and name its two types.
2. Give examples of plants that reproduce asexually.
3. Name the parts of a flower and state the function of each.
4. Define pollination and state its types and agents.
5. Describe the steps of fertilisation and what the ovule and ovary become.

What are the types of reproduction in plants?

There are two types of reproduction in plants: asexual reproduction and sexual reproduction.

What is asexual reproduction in plants?

Asexual reproduction is the production of a new plant from one parent, without seeds or the joining of male and female cells.

• Number of parents: only one parent is needed.
• Source of the new plant: a part of the parent, such as a stem, root or leaf.
• Result: the new plant is an exact copy (clone) of the parent.

Examples of asexual reproduction:

• Cassava: a cutting of the stem is planted and grows into a new plant.
• Ginger: new shoots grow from the underground stem (rhizome).
• Irish potato: new shoots grow from the “eyes” on the tuber.
• Sugarcane: pieces of stem with buds are planted.
• Bryophyllum (leaf-of-life): tiny plantlets grow at the edges of the leaf.

What is sexual reproduction in plants?

Sexual reproduction is the production of a new plant from the joining of a male cell and a female cell, usually inside a flower.

• Number of parents: two parents, or two parts (male and female).
• Organs used: flowers, which later form fruits and seeds.
• Result: the new plant is a mix of both parents, so it may differ slightly from each one.
• Comparison: you are not an exact copy of your mother or father either.

What is the difference between asexual and sexual reproduction?

What are the parts of a flower?

A flower has four main parts: sepals, petals, stamens (male) and carpel or pistil (female).

The flower is where seeds are made. It is not only for decoration.

What are the sub-parts of the pistil?

• Stigma: the sticky top that catches pollen.
• Style: the tube that joins the stigma to the ovary.
• Ovary: the swollen base that contains the ovules.
• Ovule: the female egg-containing part inside the ovary, which becomes a seed.

What is pollination?

Pollination is the transfer of pollen from the anther to the stigma.

It must happen before a seed can form. Plants cannot walk, so they use agents to carry pollen.

What are the agents of pollination?

• Insects: bees and butterflies visit flowers for nectar, collect pollen on their bodies and legs, and leave it on the next flower.
• Wind: light pollen is blown from flower to flower, as in maize and grasses.
• Other agents: birds and water carry pollen for some plants.

How do insect-pollinated and wind-pollinated flowers differ?

What are the types of pollination?

There are two types of pollination: self-pollination and cross-pollination.

• Self-pollination: pollen moves to the stigma of the same flower, or of another flower on the same plant.
• Cross-pollination: pollen moves to the stigma of a flower on a different plant of the same kind.

What is fertilisation in plants?

Fertilisation is the joining of the male cell from a pollen grain with the female egg cell in the ovule.

What are the steps of fertilisation?

1. A pollen grain lands on the sticky stigma.
2. The pollen grain grows a long pollen tube down through the style.
3. The pollen tube reaches the ovary and enters an ovule.
4. The male cell from the pollen tube joins with the egg cell in the ovule.
5. The ovule becomes a seed.
6. The ovary swells and becomes a fruit.

What happens to the flower after fertilisation?

• Ovule: becomes the seed.
• Ovary: becomes the fruit.
• Petals, stamens and stigma: usually wither and fall off.

What is the order of events from pollination to fruit?

The order is pollination, then fertilisation, then seed and fruit formation.

Evaluation

1. What is the main difference between sexual and asexual reproduction?
2. Name the male part of the flower that produces pollen.
3. Why are petals usually brightly coloured?
4. What does the ovary turn into after fertilisation?
5. State two differences between self-pollination and cross-pollination.

Assignment

Draw a flower in your notebook. Label the sepal, petal, anther, filament, stigma, style and ovary, and write one function beside each.