The following points highlight the top eight plant products of industrial value. The plant products are: 1. Fibres and Fibre-Yielding Plants 2. Wood and Cork 3. Tannins and Dyes 4. Rubber 5. Fatty Oils and Vegetable Fats 6. Sugars and Starches 7. Pulp and Paper 8. Gums and Resins.
Plant Product # 1. Fibres and Fibre-Yielding Plants:
The fibre-yielding plants rank second only to food plants in their usefulness to human kind. The utilization of fibres is directly related to the advancement of civilization. As civilization advanced, the use of vegetable fibres increased greatly. They are of enormous value in our daily life. About two thousand species of the plants yield various fibres all over the world.
The chief fibres of commercial importance have been classified in six groups— textile fibres (e.g., cotton, flax, etc.), brush fibres, filling fibres, rough weaving fibres, natural fabrics and paper-making fibres. The most important fibre-yielding plants belong to the families— Malvaceae, Tiliaceae, Linaceae, Leguminosae, Musaceae, Bombacaceae, Liliaceae, Palmae, Gramineae, Amaryllidaceae, Urticaceae, and Bromeliaceae.
Plant Product # 2. Wood and Cork:
In modem days wood is the most widely used commodity outside of food and clothing. It is one of the most versatile of the raw materials of industry. Wood is cheaper, lighter, and more easily worked with tools.
Moreover the wooden structure can be readily altered or rebuilt. Wood is very strong for its weight and unique in strength, elasticity and toughness. It is a bad conductor of heat and electricity and does not rust. The wood is also used in the form of thin sheets or veneers.
The cork consists of the outer bark of the tree. It is used for many purposes. In some cases the natural cork is utilized whereas in others composition cork, made of coarse pieces treated with adhesives and molded. The most important cork made articles are stoppers, hats, floats, mats, tiles, metal tops for sealing bottles, gaskets, inner soles for shoes, etc.
Plant Product # 3. Tannins and Dyes:
Tannins make a heterogeneous group of complex compounds of widespread occurrence in plants. They are organic compounds chiefly glucosidal in nature, which have an acid reaction and are very astringent. It is a colourless solid, dissolves in water to solutions of astringent tastes.
They are of commercial importance because of their property of forming an insoluble colloidal compound (leather) with the hides of animals. They also react with the salts of iron to form dark-blue or greenish-black compounds, the basis of common inks.
The dyes are coloured compounds capable of being fixed to fabrics and which do not wash out with soap and water or fade on exposure to light. Therefore, a coloured organic substance is not necessarily a dye. Natural dyes and stains, obtained from the roots, leaves, bark, fruit or wood of plants, have been used from ancient times.
Plant Product # 4. Rubber:
Rubber is obtained from the latex, of various plants of tropical and sub-tropical regions. Most of the rubber plants belong to the angiospermic families— Euphorbiaceae, Moraceae and Apocynaceae.
The most important rubber plant is Hevea brasiliensis of family Euphorbiaceae. Latex occurs in latex tubes or latex vessels of the plants. Latex is a varying mixture of water, hydrocarbons, resins, oils, proteins, acids, salts, sugar, etc., the substance used as the source of rubber.
The Hevea or Para rubber tree is the source of 95% to 98% of the rubber production of the world. The most important rubber products are tyres and tubes for automobiles and cycles accounting for about 75% of the total rubber consumption, about 6% is used for footwear and about 4% for wire and cable insulations.
Plant Product # 5. Fatty Oils and Vegetable Fats:
The fatty oils are liquid at ordinary temperatures and usually contain oleic acid. Chemically they consist of glycerin in combination with a fatty acid.
The fats are solid at ordinary temperatures and contain stearic or palmitic acid. When a fat is boiled with an alkali, it decomposes and the fatty acid unites with alkali to form soap.
Usually the fatty oils are stored up in seeds of the plants belonging to many angiospermic families sometimes, to a less extent they are also stored in fruits, stems and other plant organs. Several fatty oils are edible and used as cooking media. These edible oils contain both solid and liquid fats.
Plant Product # 6. Sugars and Starches:
The glucose manufactured by the green plant in photosynthesis, is almost universally present in plant cells. This basic material of metabolism, the glucose, has the formula C6H12O6. Fruit sugar or fructose is another product of photosynthesis which has the same formula.
The more complex sugars are built up from these simple sugars. The most important complex sugar is sucrose or cane sugar, which has the formula C12H22O11.This sugar is accumulated in abundance in sugarcane and sugar beets. Today, the sugar industry is the second largest in India, next only to textiles.
Starch occurs in all green plants. It is a complex carbohydrate with the formula (C6H12O5,) n. Like the sugars, they are derived also from glucose and constitute the first visible product k photosynthesis.
This is the commonest type of reserve food in green plants and plays the most important role in their metabolism. Commercial sources of starch are wheat, barley, maize, potatoes and arrowroot. In these plants starch occurs in the form of starch grains which vary in shape and size.
Plant Product # 7. Pulp and Paper:
The paper is a cellulose product. Cellulose is the most complex carbohydrate and is universally present in the cell walls of plants. One of the important uses of cellulose is in the manufacture of paper. Paper can be made from any natural fibrous material.
Plant Product # 8. Gums and Resins:
The true gums are formed as the result of disintegration of internal tissues, for the most part from the decomposition of cellulose. The gums are insoluble in alcohol but soluble in water, readily swell up in it, and form a viscous mass. They are colloidal in nature. They contain a large amount of sugar and are closely allied to the pectins.
The gums are formed in various kinds of plants. Acacia Senegal yields the best gumarabic of commerce. The gums exude naturally from the stems, or in response to wounding. The commercial gums are the dried exudations of the plants.
They represent oxidation products of various essential oils and are very complex and varied in their chemical composition. They are mostly found in the stems of the trees, and occur in abundance in special canals or ducts. They are yellowish solids, insoluble in water but soluble in alcohol, turpentine and spirit. It normally oozes out through the bark and hardens on exposure to the air.