Lactuca sativa (lettuce) is an annual plant belonging to daisy family Asterceae. It is cultivated as leaf vegetable sometimes for its seeds and stem. First it was cultivated by ancient Egyptians who turned it from a weed and seeds were used for producing oil, a food plant which is grown for its succulent leaves. Lettuce is a hardy annual cultivated in low temperatures in order to prevent it from flowering quickly. Native to Mediterranean and Siberia and it is also transported to all areas of world. Generally, the plant measures 6 to 12 inches in height with colorful mainly green leaves. Lettuce varies in shapes and textures from dense head to notched, frilly, scalloped or ruffly leaves. Lettuce plants have main taproot and smaller secondary roots.
Varieties found in Western Europe and US have narrow and long taproots and small set secondary roots. In varieties of Asia, more extensive secondary systems and longer taproots are found. The flower lettuce becomes bitter and unsaleable. Freezing temperatures causes slow growth and might damage to outer leaves. When the plants turn to edible stage, flower stalks measures upto 0.9 meters high having small yellow blossoms. Inflorescences consist of multiple florets having modified calyx known pappus and corolla having five petals fused into strap or ligule and reproductive parts. An ovary is obovate shaped compressed dry fruits which do not open at maturity and measures 3 to 4 mm long. Fruits have 5 to 7 ribs on each side having two rows of small white hairs. Each fruit possess one seed in yellow, white, brown or gray color that depends on lettuce varieties. Lettuce possesses energy, moisture, fat, protein, dietary fiber, carbohydrates and sugars. Vitamins and minerals found in lettuce includes iron, calcium, phosphorus, magnesium, sodium, potassium, zinc and sodium along with vitamins such as riboflavin, thiamin, folate, niacin, Vitamin C, K, A, E and B6. The health benefits provided by lettuce includes prevention of cancer, lowering cholesterol levels, regular sleep, protection of neurons, lower inflammation, control anxiety and wide range of antioxidants.
History
First cultivated in ancient Egypt for producing oil from its seeds. The plant was bred by Egyptians into a plant cultivated for its edible leaves. Evidence shows the cultivation appeared as early as 2680 BC. It is considered as a sacred plant of reproduction god Min and is carried during festivals and placed near his images. The plant is believed to help god to perform sexual act with determination. It is used in creation of many images in wall paintings and tombs. Cultivated variety measures 30 inches long and resemble large version of modern romaine lettuce. Egyptians developed upright lettuce and passed to Greeks who shared with Romans.
In medieval writings, lettuce appeared as medicinal herb. It was mentioned by Hildegard of Bingen on medicinal herbs between 1098 and 1179. Joachim Camerarium provided descriptions in 1586 of romaine or cos lettuce, loose leaf lettuce and head lettuce. From Europe, Christopher Columbus brought it to Americas in late 15th century. In Europe, many varieties were developed in between late 16th century and early 18th century.
In 1900s, the development of new packing, shipping technologies and storage improved lifespan and transportability of lettuce which resulted in increase in availability.
