Kim King, age 10, of Orcutt, Calif., for her question:
HOW DO FLOWERS GET THEIR SCENTS?
The beauteous blossoms seem to be designed just for show and surely we should not expect them to perform any useful work. However, Mother Nature has a very different idea. Flowers are designed to perform the all important duty of reproduction. Their pretty petals and even their perfumes are designed to make this work easier.
Everything about a plant is home made, including the fragrant perfume in its petals. A green plant has magic material called chlorophyll, which uses energy from sunlight to build sugary food from water and gaseous carbon dioxide. This manufacturing of basic plant food goes on all day, as long as there is enough light. Meantime, the roots absorb moisture from the ground and certain useful chemicals are dissolved in this ground water. Bundles of little tubes carry sugar from the greenery and minerals from the roots all around among the busy cells.
When the sun goes down the sugar factories close down but other chemical activities do not come to a stop. This is when the plant uses its sugar and its other chemicals to build a vast assortment of molecules. These molecules are of different substances, suitable for building boxy wooden cells, buds and seeds, petals and colored pigments and also perfumes.
The perfumes are oily substances, and their molecules are complicated. They are made so that part of them tends to evaporate when they become warm. And as they evaporate, they spread their fragrance through the air.
The flowery petals are made from fragile living cells, usually tinted with pretty colors. In among these cells are pockets called perfume sacs. This is where the plant stashes its mini droplets of fragrant scent. When the sun shines, some of the scented oil evaporates and spreads its perfume through the air.
Flower scents range from delightful to downright horrible. But they are not designed to please or upset our human noses. Many flowers depend on insects to fertilize their seeds and the scents are meant to attract them from afar. Many shed sweet scents to attract the honeybee types. But some flowers smell like rotting meat because they need to attract the scavanger fly type insects.