Connie Wright, age 12, of Monroe, La., for her question:

IS LETTUCE REALLY GOOD FOR YOU?

People usually eat lettuce fresh and uncooked. The popular vegetable is used chiefly in salads, and it is very definitely good for you.

Lots of doctors recommend lettuce in weight control diets because it contains few calories, but it provides large amounts of calcium, iron and vitamin A.

Lettuce farming probably started in Persia, in a location that is now Iran and Afghanistan. It was most likely first cultivated around 550 B.C.

There are three types of lettuce: head, leaf and romaine or cos.

Head lettuce has leaves that curl around the center of the plant, forming a ball shaped head. Crisp head lettuce, often called iceberg lettuce, has a tight head and brittle, juicy leaves. It is this type of lettuce that is the major variety grown commercially in the United States.

Leaf lettuce forms dense, leafy clumps instead of heads. Home gardeners grow more of this variety than any other kind. Most leaf lettuce has light green leaves, but a few red varieties have been developed.

Romaine lettuce, or cos, grows long and upright and its leaves curl inward. It isn't grown commercially too often because the leaves are tender and can be easily damaged in shipment.

Lettuce grown commercially does best with temperatures that stay between 70 degrees and 75 degrees Fahrenheit. Leading in lettuce growing is California where more than half of the country's crop is grown. Other leading lettuce growing states, in order, include Arizona, New Mexico, Colorado and Texas.

Lettuce spoils quickly and must be packed, cooled and shipped immediately after being cut. On most commercial lettuce farms, workers pack and cool the lettuce in the field.

The lettuce usually goes into cardboard boxes and then immediately into refrigerated trucks.

In special refrigerated trucks, the temperatures of the lettuce is dropped to just above freezing.

On some farms, the lettuce is packed between layers of crushed ice in wooden crates. The cartons or crates are then put into refrigerated cars for shipment to market.

The chief diseases of lettuce include bottom rot, downy mildew and lettuce drop. Crop rotation and chemical treatment of the soil help prevent these diseases.

Another disease, tipburn, may be caused by too much heat or humidity. Scientists have developed types of lettuce that resist tipburn.

Such pests as aphids, cabbage loopers and cutworms destroy lettuce leaves and stems, but most of these pests can be controlled with insecticides.