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Unlock This CourseAfter a flower has been pollinated and fertilisation occurs, something amazing happens - the flower transforms into a fruit containing seeds. This process is crucial for plant reproduction and ensures the next generation of plants can grow. Understanding how seeds and fruits form helps us appreciate the clever ways plants have evolved to spread their offspring.
Key Definitions:
Once fertilisation happens in the ovary, the flower undergoes dramatic changes. The petals usually fall off as they're no longer needed to attract pollinators. The ovary wall begins to swell and develop into the fruit, whilst the fertilised ovules inside develop into seeds.
Seeds are like nature's survival packages - they contain everything a new plant needs to get started in life. Let's explore how they form and what makes them so special.
After fertilisation, the zygote divides many times to form an embryo. This tiny plant already has the beginnings of roots, stems and leaves. Around the embryo, the parent plant stores food (usually starch, oils or proteins) to give the new plant energy when it germinates. Finally, a tough seed coat forms around everything to protect it.
The baby plant inside the seed, complete with a tiny root (radicle) and shoot (plumule).
Energy-rich substances like starch that fuel the plant's early growth before it can photosynthesise.
A protective outer layer that keeps the seed safe from damage and prevents it drying out.
Some seeds can survive for decades before germinating! The oldest viable seeds ever found were lotus seeds from China, which successfully grew after 1,300 years. Seeds are incredibly tough - they can survive freezing temperatures, drought and even being eaten by animals.
Fruits aren't just tasty snacks - they're sophisticated seed-dispersal systems that have evolved to help plants spread their offspring far and wide.
The fruit develops from the flower's ovary after fertilisation. As the seeds grow inside, the ovary wall (called the pericarp) changes dramatically. It might become fleshy and sweet like an apple, or dry and hard like a nut. These changes aren't random - they're perfectly designed to help disperse the seeds inside.
These fruits, like apples, oranges and tomatoes, have soft, often sweet flesh. They're designed to be eaten by animals, who then spread the seeds in their droppings. The seeds usually have tough coats that protect them as they pass through the animal's digestive system.
Fruits like nuts, pods and capsules have dry walls. Some split open to release seeds (like pea pods), whilst others rely on different dispersal methods. Nuts are actually single-seeded fruits with very hard walls.
Plants have evolved brilliant strategies to spread their seeds away from the parent plant. This prevents overcrowding and helps species colonise new areas.
Many plants produce seeds or fruits with special adaptations for wind dispersal. Dandelion seeds have feathery structures that act like parachutes, whilst maple fruits have wing-like extensions that make them spin as they fall.
Some seeds have hooks or spines that stick to animal fur (like burdock), whilst others are inside tasty fruits that animals eat. The seeds pass through unharmed and are deposited elsewhere with a convenient pile of fertiliser!
Coconuts are perfect examples of water dispersal - they can float across oceans and still germinate on distant shores. Their fibrous outer layer traps air, making them buoyant.
Some plants literally explode their seeds away! Gorse pods dry out and suddenly split open with a loud crack, flinging seeds several metres. Squirting cucumber fruits build up pressure and shoot their seeds out when touched.
Apples are perfect examples of successful fruit evolution. The sweet, nutritious flesh attracts animals (including humans!), whilst the tough pips inside contain the seeds. When animals eat apples, they often discard the core or the seeds pass through their digestive system unharmed. This strategy has made apples one of the world's most widespread fruits.
When conditions are right, seeds begin to germinate - the embryo starts growing and breaks out of the seed coat. This process needs water, oxygen and the right temperature.
First, the seed absorbs water and swells. The seed coat splits and the radicle (embryonic root) emerges first, growing downwards to anchor the plant and absorb water. Then the plumule (embryonic shoot) grows upwards towards the light. The stored food in the seed provides energy until the plant develops proper leaves and can photosynthesise.
Essential for activating enzymes and allowing the embryo to grow.
Needed for respiration to release energy for growth.
Must be warm enough for enzymes to work properly.
Seed and fruit formation represents the completion of the plant reproductive cycle. It ensures genetic material is passed to the next generation and allows plants to colonise new habitats. Without effective seed dispersal, plant species would struggle to survive environmental changes or compete with other plants.
Humans have dramatically influenced seed and fruit formation through selective breeding. We've developed seedless fruits like bananas and grapes and created varieties with larger, sweeter fruits. However, this sometimes comes at the cost of the plant's natural ability to reproduce and disperse seeds.