The cotton plant belongs to the genus Gossypium of the family Malvaceae (mallow family); the same family as hollyhock, okra and hibiscus. It is generally a shrubby plant having broad three-lobed leaves and seeds in capsules, or bolls; each seed is surrounded with downy fiber, white or creamy in color and easily spun. The fibers flatten and twist naturally as they dry. There are different species of Cotton – Gossypium hirsutum, Gossypium barbadense, Gossypium herbaceum and Gossypium arboreum, the first two species being the most commonly cultivated.
Cotton is of tropical origin but is most successfully cultivated in temperate climates with well-distributed rainfall. All western U.S. cotton and as much as one-third of Southern cotton, however, is grown under irrigation. In the United States, nearly all commercial production comes from varieties of upland cotton (G. hirsutum), but small quantities are obtained from sea-island and American-Egyptian cotton (both belonging to the species G. barbadense). G. arboreum and G. herbaceum are cultivated species in Asia.
Different Parts of the Cotton Plant
Cotton is grown between 37 degrees North at Ukraine and 30 degrees south in Australia in warm, frost-free, sunny climate. Cotton requires a lot of sunshine temperatures between 60 to 95 degrees Fahrenheit (16-35 degrees Celsius). The major cotton producing countries are United States, China, India, Pakistan, Uzbekistan, Brazil, Australia, Egypt, Argentina, Turkey, and Greece.
A cotton plant starts from seeds. The seeds germinate in 5 to 10 days and the cotton plant begins its growth with two cotyledons (the seed leaves that form nodes opposite each other at the base of the main stem) until the plant forms true leaves( leaves produced subsequent to the cotyledons). Cotton has a tap root system and roots go deeper into the soil for search of nutrients. Development of a healthy root system for acquiring soil nutrients is vital to feed the growing plant.
As a cotton plant begins to grow, it develops a series of nodes up the main stem. Beginning with the fifth or sixth node, the plant begins to form fruiting branches, which bear the cotton fruit. Typically, a cotton plant will continue to add nodes and fruiting branches for a total of 16 to 22 nodes, with 12 to 16 fruiting branches. Leaves:
Leaves provide carbohydrate energy supply for adding nodes and branches and for growing bolls. Photosynthesis converts light energy into chemical energy that is stored as sugars in the plant. All plant metabolic reactions are dependent on this energy source.
Cotton has a tap root system and the roots can be as deep as 10 inches in the first 3 weeks. Roots can grow up to 2 inches per day during the early stages of cotton, making them twice as long as the plant height. When plants begin to set bolls, root growth slows abruptly.
Reproductive Stage- Squares, Bolls and Fruits
The flower bud that first appears on the plant when reproductive growth begins is called a ‘square’. The flower bud is enclosed by three bracts. Squares grow for about three weeks before a flower appears. Cream or yellow flowers open during early morning hours. During this time, the male and female flower parts expand rapidly. The flower petals turn pink on the second day and later dry up and drop off and then form a boll. The cotton plant is constantly adding squares to the plant and then aborting squares or young bolls to balance out the demand of the growing boll load. Boll retention should begin near the level of square retention and show a gradual decline throughout the bloom period as the plant reaches its capacity for supplying bolls with carbohydrates.
Species of Cotton
Gossypium hirsutum & Gossypium barbadense
Family: Malvaceae (Mallow)
Plant Height: 4-5 ft
Span Length: 28 to 30 mm
Ginning %: 36 to 37 %
Crop Duration: 130- 225 days
Gossypium herbaceum & Gossypium arboreum
Family: Malvaceae (Mallow)
Plant Height: 5-9 ft
Span Length: 24 to 28 mm
Ginning %: 24 to 36 %
Crop Duration: 135- 250 days