Pollination takes place when pollen lands on the stigma of a plant. It then travels down to the ovary and it’s here that the ovules are fertilised. Most plants have flowers with the male and female parts present in each flower. Mostly, plants rely on insects, such as bees, to take the pollen from the anthers to the stigma.
Pollination by insects
An insect can pollinate flowers accidentally when the pollen is rubbed off the body of the insect. Plants can produce nectar within flowers, a sugary liquid, which many insects feed on. Pollen is a useful source of protein for some insects, such as bees. Insects are attracted to the flower by scent, colours and nectar. They carry pollen from flower to flower, while collecting nectar and pollen for themselves. After pollination, the plant produces a seed, which mostly grows protected inside the plants’ ovaries.
Pollination without insects
It’s not always insects that pollinate the flowers; plants may use the wind, birds or even bats as pollinators! With wind-pollinated plants – such as grasses, cereals and some trees – the flowers are very simple, with no bright colours or nice smells as they don’t need to attract the insects. These plants have both male and female reproductive parts and they make a lot of pollen. This is why a pollen allergy is called ‘hay fever’.
Most plants grow flowers each year, but some take much longer. The century plant or agave grows only one flower after many years and then it dies! Even more amazing is a rare plant called Puya raimondii from the Andes in South America; it doesn’t grow a flower until it is 150 years old – and after that it dies too.
The smallest flowering plant in the world is thought to be a floating duckweed called common watermeal. Its leaves are only 1mm across!
Bamboo plants have amazing flowering habits. There are many different sorts of bamboo, and they have different flowering cycles. A few flower each year, but most wait much longer. What is amazing is that all the bamboos of the same species will flower at exactly the same time, wherever they are growing! Nobody knows how they manage to do this.
The flowers on the European edelweiss are covered with a thick coat of hairs to protect them from the hot sun and the drying winds.
The flowers of the Caucasian lime, which can grow in Britain, are poisonous to bees. They can often be found on the ground underneath the trees.
Hummingbirds hover in front of flowers while they collect nectar. They use so much energy to do this that it would be like you needing to eat 150kg of hamburgers every day!
The white flower of the Amazon water lily is the size of a football and turns purple after it has been pollinated.