Kevin Walsh, age 11, of Phoenix, Ariz. for his question:

HOW DO PLANTS TAKE IN FOOD?

A plant never shops    for food in the supermarket or sits down to dine in a restaurant. Naturally it stays rooted to the spot, where it has no opportunity to catch and cook a meal. True, a few plants catch passing insects, but this is very unusual. The average plant must create its own food from simple chemicals found right within its reach.

Groceries for the plant world include certain gases in the air and special chemicals dissolved in water held in the soil. The preparation of these food ingredients requires warmth plus several hours of daylight. The average plant stays rooted to the spot while it transforms these plentiful raw materials into the multitude of different materials it needs to grow stems, leaves, flowers, fruits and seeds.

A plant's basic food is a simple type of sugar. This is made during the daylight hours by a miraculous process called photosynthesis. The chlorophyll throughout the plant's greenery takes water from the soil and carbon dioxide from the air and uses the energy of sunlight to transform these raw materials into sugar molecules. Photosynthesis starts with dawn and stops when the sun goes down.

Meantime the plant roots absorb underground water which contains an assortment of dissolved chemicals. From here, continuous streams of water must be transported to the topmost twigs‑‑for moisture is needed by all the living cells. Most of this amazing transportation job is done by osmosis, which pushes chemical solutions through the cell walls. This is helped along as moisture evaporates from the greenery upstairs, coaxing up water from cells lower down.  As the water supply    flows through the plant, the busy cells extract the dissolved chemicals they need. These include certain phosphates, nitrates, sulphates, calcium, potassium, iron and several other chemicals usually present in the ground water. The water transportation system distributes these raw materials throughout the entire plant.

At night, the sugar‑making operation stops. Then a multitude of complicated chemical processes take place. Molecules of sugar are used with various chemicals from the soil to build a vast variety of carbohydrates, fats and proteins. These are shuttled around as the plant builds cells to add new growth to stems, roots and leaves. In some cases, the simple raw materials are used to build the complex chemicals that add perfume to the petals.