Adaptations of wind-pollinated flowers

Maria is out walking with her dog Diva. She walks past an oak tree, and an apple tree. The apple tree has white flowers, apple blossom, that smell wonderful. There are no such flowers on the oak tree, but there are some strange, hanging things growing on it. Maria takes a closer look and sneezes when she gets near the hanging things.

What are these? They are oak flowers! Oak trees, like apple trees, and most other plants, need flowers in order to reproduce. Male flower organs produce pollen, which fertilises the female flower organs. The transfer of pollen between the male and the female organs of the flower is called pollination.

But the apple blossom is so pretty and white, and it smells nice. Oak flowers are just green, and they don’t smell of anything. That’s because the two trees are pollinated in different ways. Apple trees are pollinated by insects and so need flowers that attract insects. But pollen from oak trees is carried from flower to flower by the wind.

This is called wind-pollination. When wind carries the pollen, a lot of it blows away without reaching other flowers. This is why wind-pollinated plants such as oak, birch and grasses, have developed flowers with special features, or adaptations, so that enough pollen ends up where it should. One of the main adaptations is that the wind-pollinated flowers produce millions and millions of pollen grains. Most of the pollen will likely end up on the ground or in someone’s nose, making them sneeze.

But when there’s so much pollen, chances are much higher that at least some of it will reach other flowers. Pollen is very small, smooth, and very light, which makes it easily carried by the wind. It’s produced in the anthers. The anthers are large and they grow at the tip of the long, flexible filaments. This exposes them to the wind and makes it easy for the pollen to be carried away, even by just a light breeze.

For pollination to take place, the pollen must reach the female flower organs: the carpel. The part of the carpel responsible for collecting pollen are the stigmas. The stigmas of wind-pollinated plants are long, feathery and hang outside the flowers. They are well adapted to catching pollen that floats around in the air! Some wind-pollinated plants have only flowers with male organs, or only flowers with female organs, while other plants have both.

The flowers of wind-pollinated plants don’t have pretty colours or sweet scents, but they work just as well for pollination. I think it’s time to go home Diva, wind-pollinated plants make me sneeze way too much...