The process of fertilisation in plants

Fertilisation in plants is the joining of male and female reproductive cells to start the development of a new plant. This process happens inside flowers and involves specific structures that ensure successful reproduction.

How fertilisation occurs

1. Pollen grains land on the stigma of a flower, often carried by wind or insects.
2. Each pollen grain grows a pollen tube, which extends down through the style toward the ovary.
3. The pollen tube delivers sperm cells from the pollen grain directly to the ovule inside the ovary.
4. A sperm cell fuses with an egg cell in the ovule, completing fertilisation and creating a zygote that will develop into an embryo.

This sequence allows plants to reproduce sexually, combining genetic material from two parents.

Definitions of seeds and fruits

After fertilisation, plants develop structures that protect and nourish the new plant. These include seeds and fruits, each with specific components and roles in plant reproduction.

Seeds

A seed is a structure that contains an embryo (the young plant) along with stored food to support its early growth. The stored food provides energy until the embryo can make its own through photosynthesis.

Fruits

A fruit is the mature ovary of a flower that develops after fertilisation and encloses one or more seeds. Fruits protect the seeds and often help in their dispersal.

How seeds and fruits form after fertilisation

Fertilisation triggers changes in the flower's ovary, leading to the development of seeds and fruits. This transformation ensures the new plant has what it needs to survive and grow.

Formation process

1. After the sperm fuses with the egg in the ovule, the zygote develops into an embryo.
2. The ovule transforms into a seed, incorporating stored food around the embryo.
3. The ovary wall thickens and changes to form the fruit, which surrounds and protects the seed or seeds.

As a result, the fruit provides a protective layer, while the seed holds the potential for a new plant.

Methods of seed dispersal and their associated structures

Seed dispersal is the spreading of seeds away from the parent plant to reduce competition and increase chances of survival. Plants use different modes of dispersal, each with structures adapted to that method.

Dispersal by wind

• Seeds travel through the air with structures that make them lightweight and easy to carry.
• The seeds often have wing-like extensions or fluffy hairs that catch the wind, allowing seeds to float long distances.

Dispersal by animals

• Animals carry seeds externally or internally, often attracted by the fruit's features.
• The seeds often have hooks or barbs that stick to fur, or fleshy, edible fruits that animals eat, later depositing seeds in droppings.

Dispersal by water

• Seeds float on water currents to new locations, common in plants near rivers or coasts.
• The seeds typically have waterproof coatings or air-filled parts that help seeds stay afloat and travel without damage.