Pollution affects flower's fragrance

By Sumana Narayanan
Published: Thursday 15 May 2008

the attractiveness of a flower diminishes when it does not emit fragrance. And not just we human beings, insects also stop taking interest in such a flower. Researchers from University of Virginia, usa, have sounded out a warning that fragrance in flowers may be short-lived. The cause, they say, is air pollution. This is crucial because both colour and fragrance attract insects towards flowers, thus helping pollination.

Their study shows that increasing levels of nitrogen oxides in the air react with and degrade hydrocarbons responsible for fragrance in flowers. Hydrocarbons react easily with nitrogen oxides (no and no2) in the air to form ozone (o3).

This restricts the fragrance from travelling long distances--about 200 metres--thus making it difficult for insects to find flowers. Simulation studies showed that at pre-industrial levels of air pollution, the fragrance of a flower could travel several kilometres. The hydrocarbons break down even before they can be carried away by the wind, the researchers say in the paper published in the March 2008 issue of the Atmospheric Environment. The researchers used mathematical models to understand how common fragrance hydrocarbons--linalool, myrcene and ocimene--disperse in air.

In highly polluted conditions 75 per cent of the fragrance gets killed within 200-300 metres of the source plant. This could mean that insects will take longer to find isolated flower patches and so their efficiency as pollinators could reduce. Besides, the ability of insects to differentiate between scents could also be affected since flower scents are a combination of various hydrocarbons, the researchers said in the paper.

"Pollution affects all aspects of plant biology, so it is not surprising that a flower's fragrance is also altered. This could affect reproductive success in small populations. It could also lead to an increase in loss of genetic variation due to inbreeding," says A K Bhatnagar, head, Department of Botany, Delhi University.

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