Seed and Fruit Formation: From Flower to Fruit Steps

A seed is a tiny plant embryo packed with food, and a fruit is the mature ovary of a flower that protects the seeds inside. After a flower is pollinated and fertilised, it does not stay a flower forever. It slowly changes into a fruit with seeds that can grow into new plants.

This process matters because almost all the grains, pulses, vegetables and fruits we eat come from seed and fruit formation. Without it, flowering plants could not reproduce, and we would have no rice, wheat, mango, tomato or peas to eat.

Key Concepts

Pollination is the transfer of pollen grains from the anther to the stigma. Fertilisation is the fusion of the male gamete from pollen with the egg cell inside the ovule. After fertilisation, the zygote divides to form the embryo, which has a plumule (future shoot), radicle (future root) and cotyledons (seed leaves). The ovule becomes the seed, its outer layers form the hard seed coat, and the ovary wall becomes the fruit wall called the pericarp. The whole plant world uses this plan.

• True fruit: develops only from the ovary, like mango and coconut.
• False fruit: other parts like the thalamus also become fleshy, like apple and strawberry.
• Parthenocarpy: fruit forms without fertilisation and has no seeds, like banana.

How It Works

1. Pollen lands on the stigma and grows a pollen tube down through the style.
2. The tube reaches the ovule and releases two male gametes.
3. One gamete fuses with the egg to form the zygote. This is syngamy.
4. The second gamete fuses with the polar nuclei to form endosperm, which stores food. This double fertilisation happens only in flowering plants.
5. The zygote divides repeatedly to make the embryo. The ovule hardens into a seed.
6. The ovary wall thickens into pericarp, which may be fleshy in mango or dry in pea pods.
7. Petals, sepals and stamens dry up and fall off as the fruit grows.

Worked Example

Take a pea flower. After self-pollination, each ovule inside the long ovary is fertilised. Suppose the ovary has 8 ovules and all are fertilised. Each ovule becomes one pea seed, so the pod will have 8 seeds. If only 5 are fertilised, the other 3 ovules shrivel and the pod has only 5 peas. Farmers count this to judge yield: more fertilised ovules means more seeds per pod. In a field with 1,000 pods averaging 6 seeds, the harvest is about 6,000 pea seeds from pods alone.

Common Misconceptions

• Misconception: Every fruit has many seeds. Correction: Mango, peach and plum have only one seed because their ovary had effectively one functional ovule.
• Misconception: The fruit is the same as the seed. Correction: The seed is inside the fruit. In a mango, the fleshy part is fruit wall and the hard stone contains the true seed.
• Misconception: Seedless fruits cannot form at all. Correction: Banana and seedless grapes form by parthenocarpy without fertilisation.

Real-World Applications

Farmers use knowledge of fruit formation to increase crop yield by protecting pollinators like bees. Fruit growers spray plant hormones to produce seedless fruits that sell for higher prices. Seed banks store seeds at low temperature to preserve crop varieties for the future. In kitchens, we eat true fruits like tomato as vegetables and false fruits like apple as desserts, all thanks to this process.

In short, fertilisation turns the ovule into a seed with an embryo and the ovary into a protective, often tasty fruit. This change from flower to fruit is how flowering plants spread and how humans get most of their plant food.