DK Science: Plant Products
As well as food and medicines, plants provide other useful products. Many plant cells form NATURAL FIBRES that strengthen and support the plant. The same properties make them perfect for textiles and paper. Timber from trees is used to build boats, houses, and furniture. Palm leaves are woven into baskets, hats, and mats. People also extract perfumed oils and natural dyes from the flowers and leaves of certain plants.
Most paper comes from softwood trees, such as pines. First, machines or chemicals break down the wood chips into fibres. This is called pulping. The fibres are soaked in chemicals, then pressed by heavy rollers into thin, flat sheets. Before pressing, the fibres may be bleached white or dyed different colours. Smoother paper is made by adding starch or clay.
The rubber tree grows naturally in South America, but there are also plantations in Asia. If its bark is cut, the tree produces a milky fluid called latex. People harvest the latex so that it can be turned into rubber, a useful, elastic material. Not all rubber comes from rubber trees. Most is made artificially from petroleum.
Vast farms of lavender are found around the Mediterranean, in Britain, and in the United States. The plant is grown for its scented oil, produced in oil glands on the stems, leaves, and flowers. The harvested flowers may be dried, or pressed to extract the oil. Sometimes the oil is distilled to create a purer, “essential” oil. Lavender oil is used in aromatherapy and as an ingredient for perfumes, soaps, and other cosmetics.
Harvested wood is called timber. Its strength makes it useful in the building trade, especially for creating supporting frameworks. Pine and other softwoods are the most widely used because they grow straight. They also grow fast, which makes their timber cheap and renewable (easily replaced). Hardwood, from flowering trees, grows slowly. It is more costly and is used for furniture.
Henna is a shrub that grows in the Middle East and North Africa. Its leaves are harvested for their reddish-brown pigment. This is used to dye clothes, hair, and even people’s skin. Greenish henna paste, made from powdered leaves, is used to paint the skin. When the paste dries and rubs off, the skin looks tattooed.
Plants produce long groups of cells, called fibres. These can be used to make textiles, such as cotton, as well as other materials such as paper or felt. All plant fibres are strong, because their cell walls contain a tough molecule called cellulose, but to be useful fibres also need other properties, such as flexibility and length. Flax and hemp were two of the earliest fibres used by people.
The cellulose in cotton is arranged as interlocking, coiled strands of fibres. These can be spun into threads called yarn. Yarn is produced on an industrial scale and woven on looms to make textiles. Cotton textiles are hardwearing, “breathable”, and take dyes well. They range from light gauzy fabrics to tough denims.
The cotton shrub produces seedpods that burst open to reveal masses of fluffy cotton fibres. These fibres are harvested to produce cotton yarn and textiles. Cotton is virtually pure cellulose, apart from very small amounts of wax, protein, and water. The plant is cultivated in many parts of the world including China, the United States, and India.