Through cell division, banana plants produce leaves that develop into a pseudostem and produce fruit. The bud forms in the bottom part of the plant and grows up through the center of the pseudostem to the top. The arrow-shaped bud pushes through the top of the plant and its weight then causes it to change direction and grow towards the ground.
Bananas go through a unique process known as negative geotropism. Instead of continuing to grow towards the ground, they start to turn towards the sun. The fruit grows against gravity, giving the banana its familiar curved shape.
But why? The answer lies in the botanical history of the banana. It originated in the middle layer of the rainforest, where there is little sunlight. If the fruit were to grow towards the small amount of light that penetrates sideways through the vegetation, the plant could overbalance and topple over.
So bananas developed a way of growing towards the light without destabilizing the plant.