Cotton

The cotton plant grows to a height of 3–6 ft (0.9–1.8 m), depending on the species and the region where it is grown. The leaves are heart-shaped, lobed, and coarse veined, somewhat resembling a maple leaf. The plant has many branches with one main central stem. Overall, the plant is cone or pyramid shaped.

After a cotton seed has sprouted (about four to five weeks after planting), two "seed" leaves provide food for the plant until additional "true" leaves appear. Flower buds protected by a fringed, leafy covering develop a few weeks after the plant starts to grow, and then bloom a few weeks later. The flower usually blooms in the morning and then withers and turns color within two to three days. The bloom falls off the plant, leaving a ripening seed pod.

Pollination must occur before the flower falls off. Pollen from the stamens (male part) is transferred to the stigma (female part) by insects and wind, and travels down the stigma to the ovary. The ovary contains ovules, which become seeds if fertilized. The ovary swells around the seeds and develops into a boll. The cotton boll is classified as a fruit because it contains seeds. As the bolls develop, the leaves on the plant turn red.

About four months are needed for the boll to ripen and split open. A cotton boll contains 27 to 45 seeds and each seed grows between 10,000 and 20,000 hairs or fibers. Each fiber is a single cell, 3,000 times longer than wide. The fibers develop in two stages. First, the fibers grow to their full length (in about three weeks). For the following three to four weeks, layers of cellulose are deposited Cotton plants in cultivation in North Carolina. JLM Visuals. Reproduced by permission. in a crisscross fashion, building up the wall of the fiber. After the boll matures and bursts open, the fibers dry out and become tiny hollow tubes that twist up, making the fiber very strong. The seed hairs or fibers grow in different lengths. The outer and longer fibers grow to 2.5 in (6.4 cm) and are primarily used for cloth. These fibers are very strong, durable, flexible, and retain dyes well. The biological function of the long seed hairs is to help scatter the seeds around in the wind. The inner, short fibers are called linter.