G5 Science Reproduction in Plants

Plants reproduce by going through a life cycle:

•A seed develops into a young plant.

•The young plant grows into an adult plant that bears flowers.

•The flowers develop into fruits with seeds.

• State why living things reproduce.

• Identify the male and female parts of a flower.

• Recognise that pollination is the transfer of pollen grains from the anther to the stigma of a flower.

• Identify the agents that help in pollination.

• Describe the processes involved in fertilisation.

• Describe what happens after fertilisation has taken place.

​•Besides insects, birds and wind also help to pollinate flowers.

​•The pollen grains can be transferred within the same flower. This is known as self-pollination.

​•The pollen grains can also be transferred from the anther of one flower to the stigma of another flower of the same species. This is known as cross-pollination.

This stigma has been pollinated.

• Wind pollinated flowers have light-colored petals and do not have a pleasant smell.

• Small, producing a large number of dry pollen grains.

• Examples, rice, barely, corn.

• When a pollen grain lands on the surface of a stigma, it produces a pollen tube.

• The inside of the tip of the tube contains the male reproductive cells of the flower.

• This tube grows downwards through the style to reach the ovules in the ovary.

• Inside each ovule is an egg cell.

• Fertilisation takes place when the male reproductive cell fuses with the egg cell.

After fertilisation, the flower petals wither and fall off.

The ovary starts to swell to form a fruit.

Inside the ovary, the ovules begin to develop into seeds.

The seeds continue to develop inside the fruit and the fruit grows bigger.

After the fruit and seeds are developed, they will need to be scattered in order to grow well.

If fruits and seeds are not scattered away from the parent plants, the seeds will grow too close to one another, leading to overcrowding.

When overcrowding occurs, young plants compete with one another for space, sunlight, water and minerals, leading to poor growth.

To reduce overcrowding, there are several methods of fruit and seed dispersal.

• Wind

• Water

• Explosive action / Splitting

• Animals

Fruits and seeds dispersed by wind are often dry, hairy, light or feathery.
Some of them have wing-like structures.

​Angsana Shorea Dandelion

Fruits dispersed by water usually float and are carried along rivers, streams or seas.
They often have fibrous husks that trap air or waterproof coverings to help them float.

​ Coconut Pong pong Dungun

Some fruits split open when they are ripe. This shoots their seeds away.
These fruit walls have lines of tension that pull and curl up the walls when ripe and dry.

​ Rubber Cotton Saga

Some fruits or seeds dispersed by animals attach themselves to the animal’s body or human clothes or shoes using hooks or stiff hairs.

Lovegrass Mimosa Bur

Some fruits can be eaten by animals.

These fruits are normally fleshy, juicy or brightly coloured.

Big seeds are thrown away.
Smaller seeds are usually swallowed and passed out in the animal’s droppings.

Kiwi Watermelon Papaya

The conditions for germination are:

• Air (oxygen)

• Water

• Warmth (a suitable temperature)

1. A root grows out of the seed.
   During this stage, the seedling cannot make its own food, but gets its energy for growth   from the food stored in its seed leaves.

2. The shoot appears.

The first leaves unfold, so the young plant can make its own food.
The plant grows and bears flowers and its seeds are dispersed.

The cycle repeats.

• Non-flowering plants such as ferns reproduce from spores, which are mainly dispersed by wind.

• Spore bags containing spores can be found on the underside of a fern leaf.

​Flowering plants undergo these processes in order to reproduce and continue the existence of their kind.