17. Introduction to Biotechnology

Correct: Ciliated epithelium is present in respiratory tract. — Its hair-like cilia push mucus and air forward and keep the air passage clear. (Squamous epithelium lines the blood vessels and alveoli.)

Correct: Cuboidal epithelium is present in kidneys. — It lines the tubules of the nephrons and reabsorbs useful materials. (Glandular epithelium is found in the skin and secretes sweat and sebum.)

Correct: Aerenchyma helps the plant to float in water. — It has large air-filled spaces. (Chlorenchyma contains chloroplasts and performs photosynthesis.)

Correct: Striated muscles are also called voluntary muscles. — They move according to our will, as in the arms and legs. (Non-striated muscles are involuntary.)

Correct: Chloroplast is present in chlorenchyma tissue. — Chlorenchyma is the type of parenchyma found in leaves, whose cells contain chloroplasts for photosynthesis. Not all permanent tissues have chloroplasts; xylem and sclerenchyma, for example, are made of dead cells.

Xylem and phloem are complex permanent tissues, and all three terms belong to permanent tissue. Meristematic tissue is made of actively dividing cells that bring about growth; it is not a permanent tissue.

The epidermis (as studied here) is a plant tissue — the outer layer of cells covering the plant. Epithelium, muscle fibre and nerve fibre belong to animal tissues.

Cardiac muscle is a muscular tissue. Cartilage, bone and tendon are connective tissues.

1. Types of cells: a simple tissue is made up of only one type of cells, whereas a complex tissue is made up of more than one type of cells.
2. Function: in a simple tissue all cells together perform the same function; in a complex tissue different types of cells work together to perform a common function.
3. Main work: simple tissues mainly give support, store food, perform photosynthesis and fill spaces; complex tissues conduct water, minerals and food.
4. Living or dead: simple tissues may be living (parenchyma, collenchyma) or dead (sclerenchyma); complex tissues contain both living and dead cells.
5. Examples: simple — parenchyma, collenchyma, sclerenchyma (and meristematic tissue, epidermis); complex — xylem and phloem.

Meristematic tissue is the plant tissue made of actively dividing cells; growth of a plant occurs only in the parts where it is present. Its cells have thick cytoplasm, a conspicuous nucleus and a thin cell wall; they are compactly packed and usually have no vacuoles. Its main function is to bring about plant growth. According to location it is of three types:

• Apical meristem — at the tips of the root and stem; increases their length.
• Intercalary meristem — at the base of the petiole of leaves and of branches; helps the growth of branches and the formation of leaves and flowers.
• Lateral meristem — on the lateral sides of the root and stem; increases their girth (diameter).

New cells formed by meristematic tissue later lose the ability to divide and become permanent tissues.

Xylem is a complex permanent tissue of plants that conducts water and minerals from the roots to all parts of the plant, only in the upward direction. It consists of four types of cells: tracheids, vessels and xylem fibres, which are thick-walled dead cells, and xylem parenchyma, which is living. The tracheids and vessels form interconnected tubes through which water moves. Xylem also gives mechanical strength to the plant; wood is mostly xylem.

Striated muscles are muscles whose cells show alternate dark and light bands (striations) under the microscope. The cells are long, cylindrical, unbranched and multinucleate. As they are attached to bones, they are also called skeletal muscles, and as they move according to our will, they are called voluntary muscles. They bring about movements of the arms and legs, running, speaking and so on. They work by contraction and relaxation of special contractile proteins.

Businesses that are carried on along with agriculture, using the farm, its products and by-products, and that give farmers additional income, are called agro-complementary businesses. Examples:

• Animal husbandry — rearing cows and buffaloes for milk, and bullocks for farm work.
• Poultry farming — rearing chickens for eggs (layers) and meat (broilers).
• Sericulture — rearing silkworms on mulberry leaves for silk.
• Apiculture (bee-keeping) for honey and wax, which also helps pollination of crops.
• Fisheries, goat and sheep rearing, plant nurseries and agritourism.

They make full use of farm resources, give employment and a steady income, and reduce the farmer’s dependence on uncertain crop yields.

Genetic engineering is the technique of bringing about artificial changes in the genetic material (DNA) of an organism, for example by removing a desired gene from one organism and inserting it into the DNA of another. The organism then develops a new, useful characteristic that is not naturally present in it. It is one of the two main techniques of biotechnology.

Examples: BT cotton, in which a gene from a bacterium makes the plant resistant to bollworm pests; Golden Rice, enriched with vitamin A; and bacteria carrying the human insulin gene, which are used to produce insulin for diabetic patients. Genetically modified (GM) crops can resist pests and diseases, withstand environmental stress and give better yield and nutrition.

Rearing of silkworms (silk moths) for the production of silk is called sericulture. Bombyx mori is the most commonly used variety. The life cycle of the silk moth has four stages: egg, larva, pupa and adult. Eggs laid by female moths are incubated artificially, and the larvae that hatch are fed on mulberry leaves. The larvae secrete a silk thread from their salivary glands and spin it around themselves to form a cocoon. About ten days before the pupa turns into an adult, the cocoons are put into boiling water; the pupa dies and the silk fibres loosen. The fibres are then unwound, processed and reeled, and silk fabric is woven from them.

Biotechnology: the techniques of bringing about improvements in living organisms by artificial genetic changes and by hybridization, for the welfare of human beings, are together called biotechnology. It includes the techniques of genetic engineering and tissue culture. It makes use of the fact that some cells are ‘totipotent’ — given a proper environment, a whole new organism can grow from them.

Impact on agricultural management:

• GM crops with new characters: by changing the DNA of crops, new varieties not found in nature are produced. Examples: BT cotton (pest-resistant), Golden Rice (rich in vitamin A), maize MON 810, potato Amflora, soybean Vistive Gold.
• Withstanding environmental stress: varieties are developed that can tolerate changes in temperature, drought or excess water, and changing climate.
• Less use of pesticides: crops resistant to insect pests, pathogens and weedicides reduce the need for harmful chemicals.
• Higher yield and nutrition: better-quality seeds improve nutritive value and reduce crop losses, helping a large population get enough food.
• Tissue culture: large numbers of disease-free plantlets of banana, sugarcane, orchids and fruit trees are produced quickly for farms, nurseries, floriculture and forestry. Rare and endangered plants can also be conserved.

The two main techniques of biotechnology are genetic engineering and tissue culture.

• Genetic engineering is used because it allows desired characteristics to be introduced into an organism by artificially changing its DNA — for example, pest resistance in BT cotton, or bacteria that produce human insulin. Such improvements cannot be obtained quickly, or at all, by natural breeding.
• Tissue culture is used because, owing to the totipotency of cells, a complete plant can be grown from a single cell or a small piece of tissue in a nutrient medium. It produces a very large number of identical, disease-free plants in a short time with few resources, even for plants that do not grow easily from seeds, and helps conserve rare species.

Together, these techniques make it possible to produce improved plants, animals and medicines for the welfare of humankind.

Agritourism is a business in which farm land is developed so that people from cities can visit and enjoy rural and farm life. They can relax in natural surroundings, away from crowds and stress, and learn about farming. With the help of tissue culture, plantlets of flowering, medicinal, ornamental and vegetable plants and fruit trees can be produced on a large scale to develop such a centre.

Points to cover in your project on a nearby centre:

• Name, location and area of the centre, and how it was started.
• Attractions: fruit orchards (mango, chikoo, guava, coconut, custard apple), flower and medicinal plant gardens, butterfly garden, organic vegetables, cattle shed, poultry, fish pond, bullock-cart rides, traditional food, village games.
• Facilities for visitors: stay, food, guides.
• Sources of income: entry fees, stay and meals, sale of fruits, vegetables, plantlets, seedlings and farm products.
• Benefits: additional income for farmers, local employment, awareness about agriculture and nature among city people.
• Photographs and an interview with the owner.

Tissue: a group of cells having the same origin, same structure and same function is called a tissue. For example, muscle tissue helps in movement, and conducting tissues of plants transport water and food.

Tissue culture: the growth of cells or tissues outside the body of the organism (ex vivo), in an aseptic and nutrient-rich medium, is called tissue culture. The medium is prepared from agar and may be liquid, solid or gel-like; it supplies the nutrients and energy needed.

The concept is based on totipotency: some cells, if given a proper environment, can develop into a complete new organism. F. C. Steward proved this by growing whole carrot plants from single cells of carrot root. The main steps are:

By tissue culture, a large number of identical, disease-free plantlets can be produced in a short time, even of plants like orchids that are hard to grow from seed, and rare and endangered plants can be saved from extinction.

Livestock means domesticated animals raised on farms for useful products, for work, or for income. Rearing of sheep fits this completely:

• Sheep are domesticated animals reared by farmers and shepherds in large numbers.
• They give many useful products: wool for clothing and blankets, meat, milk, and skin for leather.
• Their dung and urine are used as a good manure in fields.
• Sheep can be sold, so they are a source of income and a form of wealth for the farmer.
• They graze on grasslands and fallow land, and can be reared along with agriculture, so sheep rearing is an agro-complementary business.

Hence, rearing of sheep is a form of livestock farming.

• (1) Butterfly garden in school: find out which butterflies are common in your area. A butterfly garden needs a sunny, sheltered spot. Plant nectar plants (such as lantana, ixora, pentas, marigold and zinnia) for adult butterflies, and host plants on which their caterpillars feed (such as curry leaf and lemon for the lime butterfly, and calotropis for the plain tiger). Keep a shallow wet sand patch for water, avoid pesticides, and keep a record of the butterflies seen.
• (2) Apiculture centre: note the variety of honey bees reared, the design of bee boxes, how honey is extracted, the uses of honey and wax, the flowering plants nearby, how bee-keeping helps pollination of crops, and the income it gives.