Charlotte Kingan, of Ardgowen School, asks :-
Why do roses smell?
Nigel Perry, a natural products chemist at Crop and Food Research, responded.
Roses, like many other flowers, use their scent to attract insects. These insects, especially bees, will carry their pollen to other flowers to help them breed and produce seed. In return the bees keep most of the pollen as food, and are also rewarded with specially produced nectar - a sweet sugary liquid. Bees fly towards the flowers attracted by their scent, then see the flowers, some of which have special patterns on their petals visible to insects but not to us.
All of our garden roses are specially bred by people to produce beautiful flowers and fragrance. Modern roses are descended from about nine wild species, with about 5,000 different named types.
The scent of roses is a very valuable ingredient in making perfumes. Damask roses are grown for this, mainly in Europe. Flowers are collected in the early morning hours to prevent loss of the scent compounds as the sun rises. These compounds are extracted from the petals with a liquid called hexane (like petrol, but without much smell of its own). The scent compounds are concentrated further to give a rose oil that is mixed with other ingredients to make many different perfumes.
Hundreds of different chemical compounds have been identified in rose oil, all of them combining to give that lovely smell. Some of these compounds are found in the scent of many flowers. However, the characteristic rose smell is caused by one of the most powerful scent compounds ever discovered, called beta-damascenone after the damask rose. This compound was an important component in the famous perfume 'Poison' by Dior.