Pollen Power

Pollen tubes, seen above, from grains of pollen in the rare vine Austrobaileya are providing insight into how flowering plants have evolved.

Research published online this week by the Proceedings of the National Academy of Sciences, show that the ability of flowering plants – known as angiosperms – to quickly and efficiently move sperm from pollen to egg through a part of the plant was the key to their evolutionary diversity.

While previous studies described how fertilization occurred, they didn’t reveal how long it took. This is important because the long it takes for a plant to fertilize by the pollen reaching the egg, the greater that chances are that it will die.

For a seeded plant to fertilize, pollen that lands on the flower must grow a tube to carry sperm to the egg. In non-flowering plants, the pathway is usually short, because the pollen tube must destroy cells in its path, which is a time-consuming process. In flowering plants, though, pollen tubes are able to cover longer distances to the egg by essentially "squeezing" between cells. It is a trait that Joe Williams, from the University of Tennessee, Knoxville, says is vital to their diversification.

When he studied the data he had collected through the years, Williams found that older lineages of flowering plants – those on lower branches of the angiosperms' evolutionary family tree – grew shorter tubes of pollen than those that went on to evolve into the diverse array of flowering plants that exist today.

Williams' research may help explain the amazing diversity in the world's flowering plants, a question that has puzzled scientists from the time of Charles Darwin to today.

-- LiveScience Staff

• Top 10 Poisonous Plants

• How Plants Know When to Flower

• What Is Hay Fever?

Image Credit: Joe Williams, University of Tennessee, Knoxville.