My Science School

               The ancients called the cotton plant the ‘Daughter of the Sun’. This was because it was only under the powerful rays of the sun that the plant would grow and flourish. The hotter the sun, the whiter and stronger would be the fibres produced. Ideal conditions for cotton growing require sunlight, heat and rain. Due to these reasons cotton is mostly grown in hot and tropical places all over the world.

               The plant grows upto 2 metres and produces seed pods or bolls which contain about 30 seeds each covered with downy hairs. As the bolls ripen, they grow and then burst open to reveal a mass of fibres.

               The cotton fibres provide the most common material used in clothing. The cotton industry is the greatest of the textile industries and gives work to millions of people all over the world. Cotton fibre is the only fibre that does not have to be softened by soaking or subjected to any other expensive treatment. It just requires to be freed from seeds before being used. However, cotton disease (byssinois) are caused by cotton dust which affects the lungs of those working in industries.

               There are about 20 species of cotton plants, only four of which are cultivated. The People’s Republic of China is the leading producer of cotton, followed by the United States. Apart from these countries cotton is also grown in large quantities in India, Peru, Russia, Brazil, Egypt, and Pakistan and in other tropical and sub-tropical regions of the world. Cotton fibres vary in length from less than 2cm to 4 cm or more. However, short and medium length fibres account for about 90% of world production. Cotton fibres are used in textiles, rugs, sheets, bandages and book binding. Cotton seed can be squeezed for oil used in margarine, salad oil and mellorine. This is also used in manufacturing of cosmetics, paints and soaps. The seeds are then processed into cattle cake and fertilizer.

 

               Adaptation is a biological term which means the process by which all living things change or adapt to new and unfavourable conditions for their survival. Thus human beings, plants and all other living things adapt to their environment for survival. 

               In plants, take the example of the oak tree. Since it grows in a moist climate, its green leaves require much water to carry on the process of photosynthesis. On the other hand, since the desert cactus cannot afford large leaves that would lose more water, its leaves are reduced to spines that grow out of a waterproof stem. To come to some animals, the beaks of birds are again adapted to particular ways of feeding. For example, preying birds like woodpeckers and kingfishers have sharp strong beaks to tear their prey.

               There are two kinds of adaptations: individual adaptation and group adaptation. In individual adaptation an individual adapts himself to new conditions automatically in his lifetime. Group adaptation refers to adaptation by a group. It is a slow process and occurs over many generations. For instance if a man’s job is such that he has to work during night time he would have to adapt to such a routine gradually. To begin with, he may have some difficulty in sleeping during the day but when adapted to the changing requirements after sometime, he would sleep easily. 

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               Many animals and creatures rest during the day but become active at night. Similarly there are many plants which bloom at night only. Such plants are called night blooming plants. The flowers of Raat Ki Rani (Queen of the Night) also fall in the same category. Many night flowering plants belong to the honeysuckle and nightshade families. Do you know why do flowers of Queen of the Night bloom at night only? It is quite often in the case of night flowering plants that they resort to the use of scent, thereby attracting high-flying insects and moths.

               When these insects sit on the flower, a few pollen grains get stuck to their tiny feet and wings. When the same insects go to other flowers of the same variety, the pollen grains are deposited on the flower. This process helps pollination, without which a flower cannot mature into a fruit. Thus we can say that flowers of the Queen of the Night bloom at night to attract those insects which help the process of pollination. Flowers produce fruits and fruits produce seeds. The seeds are responsible for producing new plants.

               Most of the flowers blooming at night are those which cannot bear high temperature and light of the day time. Flowers of Raat Ki Rani also avoid extremes of temperature and daylight by blooming at night.

               There is one more fact about the night blooming flowers. Such flowers do not have attractive and pleasing colours as these colours are not visible in the darkness of night. Most of the night blooming flowers are white because this colour is easily visible in the darkness of night and quite effective in attracting the insects for pollination. In fact, all white or cream coloured flowers such as night-scented stock are pollinated by night-flying moths which are attracted by strong perfumes of the flowers.

               Thus we see that flowers of Raat Ki Rani are not capable of withstanding day temperature, usually white in colour and have a delicious fragrance with which they attract insects. 

               Cocoa originated in Central and South America. It is said that Christopher Columbus introduced cocoa beans in Europe in 1502. The cocoa seeds however were first commercially planted in 1879 in Ghana. Upto 1913 Ghana was the leading cocoa producing country in the world. Even today Ghana is the largest cocoa producer. It is believed that several lakhs of people are associated with the production of cocoa in Ghana.

               The cocoa trees grow to a height of about 7 metre. It is an evergreen plant. Twice a year, small, star like, pink and yellow flowers appear on it. After sometime flowers grow into fruits or pods of the shape of an egg which are about 6-10 inches long and 3-4 inches thick. These pods take about six months to ripe.

               Equatorial regions are most suitable for growing cocoa trees. It needs constant moisture and in some countries watering is also necessary. Regions having a rain fall of 50-100 mm are most suitable for these plants.

               Generally there are two crops of cocoa —first crop from October to March and other crop from May to August. When cocoa tree is five years old it starts bearing fruits. The ripe fruits are cut with sharp knives from branches. Women and girls usually collect these in baskets and take it to another place where cocoa beans are scooped out from these pods. After this, beans are subjected to fermentation. For this purpose, beans are put into perforated boxes and heated at constant temperature. By this process which takes about six days, impurities are removed to bring out the flavour.

               Cocoa is used in many eatables. But it is mainly used in preparing chocolates. Chocolate powder is made from dry cocoa seeds. Cocoa butter is made by extracting fats from cocoa beans. In ice cream it is used for flavour. It is also used in the manufacture of some medicines. 

               In the world of nature we see a great variety of flowers. We have virtually flowers of every conceivable colour. Some are so perfectly symmetrical with vibrant colours that their beauty attracts us immediately. Some others are shaped like insects or lizards.

               Most flowers have fragrance. However, flowers are not just decorative creations but play a great productive role also. They produce fruits by the process of pollination and the fruits in turn produce seeds.

               In this great world of flowers do you know which the biggest flower is and which is the smallest? 

           

 

                The biggest flower in the world is Rafflesia arnoldii. It is found in the Sumatran Jungle and can have a diameter of over a yard. It is about 0.75 inch thick and weighs about 7 kg. The flower can grow to 91 cm. (3 ft) wide. It blooms for five to seven days. It is reddish or orange brown in colour. It has an unpleasant odour which is attractive to flies. These flies carry out the pollination process. Rafflesia is a parasitic plant and feeds on the sap of trees. It does not have any leaves. 

 

 

 

 

 

 

 

 

                The largest recorded chrysanthemum flower was cultivated by Francois Santini of Indre - et - lorie, France. This giant flower was 2.5 m (8ft. 2 inch) tall and had 4041 blooms. 

 

 

 

 

 

 

 

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               On the basis of autumn defoliation (shedding of leaves) trees and plants can be divided into two groups. The first includes those plants and trees which undergo defoliation every year and are called deciduous trees, while the other includes the evergreen plants or trees which defoliate very slowly and remain green throughout the year. Evergreen plants also undergo defoliation but at one time only a small portion of their leaves fall off.

               Every year with the approach of autumn the trees begin to have their period of rest. In autumn the leaves fall and eventually rot down to give the leaf-mould and humus, which are essential to support rich vegetation. During this period gradually their leaves turn yellow and then curl up and fall on the ground. The tree then remains almost completely inactive until the arrival of spring. The denuded or defoliated trees or plants are a sad sight but at the same time very useful to plants because after it plants get a new life and look. Before defoliation the leaves take yellowish, brownish and reddish hues.

               But why do the trees shed leaves? We know that plants are living organisms which need food to survive. This food is obtained by utilizing the organic substances provided by the leaves. Just like animals, plants also produce waste materials and have to get rid of them, but they do it in a different way. They have to retain waste materials in their tissues until autumn. When the time comes for trees to shed their leaves, the plants extract all the useful products from them, and shake off the waste materials behind. Due to the presence of these waste materials the leaves turn yellow, brown and red. When the leaves are shed a layer of dry needles is left on the tree and it is visible in winter.

               Autumn is thus the period in which the trees get rid of their waste materials.

 

          The age-old maxim, ‘An apple a day keeps the doctor away’ was a polite way of saying that this habit would help to prevent constipation and other related ailments. Since it was believed that the juice of a raw apple aided the fermentation of undigested foods.

          Although one might question such a sweeping statement in the highly advanced modern times, none can deny that apples are good for health because of their high nutritious value. Some people have modified this statement and suggested that ‘it keeps the dentist away more than the doctor’. According to the dentists, biting on a crisp apple is an effective way of removing food particles from between the teeth. Eating an apple after meals and cleaning the teeth in the night and morning is the best way to keep the teeth healthy. 

          Apples contain Vitamins A and C. They are rich in cellulose and carbohydrates. They also contain some minerals. This implies that apples also help in the prevention and cure of several deficiency disorders, e.g. scurvy, night blindness etc. as well as in purifying blood. They also aid in healing, protection against cold and building of healthy bones, teeth and gums.

          The presence of these food sources and their utility in keeping the body fit and healthy justifies the old adage.

          Apples are eaten raw, both for taste as well as its beneficial values. An apple contains about five-sixths water and the remaining one-sixth consists of sugar, ascorbic acid (Vitamin C) and other acids, and rough indigestible matter. Apart from their nutritious value, apples are also used for cooking sweet dishes, and cider is brewed from fermented apples.

          Apples belong to the family of Rosaceae. In the ripen state they are usually red, yellow or green. Apples grow in temperate zones, in relatively cold weather. By the end of 300 A.D, a Roman writer named 37 varieties of apple and today hundreds of varieties are available with varying sweetness. 

          A rain forest is a warm and rainy place with a thick growth of trees. Because of heavy rains, the trees grow tall and close together. The tree tops are so thickly branched that they almost block the passage of the wind. The air is still and uncomfortable. The thick tree top also prevents sunlight from reaching the ground. It is difficult to walk through these areas. Along with a large number of trees, it also has many different kinds of animals. These include noisy birds, hungry crocodiles, lizards, snakes and jaguars. Thousands of insects of different types are also found in the rain forests. There is an ant called ‘army ant’     that eats anything that would not move out of its way. There are certain mosquitoes whose bite is fatal; sweat bees which crawl into people’s ears and noses, and ticks and flies bite their skin.

          Most rain forests are located near the equator. The largest rain forest is the Amazon basin in South America. The temperature ranges from about 20 to 34°C. Thunderstorms occur about every three days. Areas of rain forests experience heavy rains upto 250 cms (100 inches). The tallest trees of rain forest form a covering of leaves called the upper canopy. The upper canopy may be 30 to 46 m above the ground. Smaller trees form lower canopies. The shade from the trees prevents about 99 percent of the sunlight from reaching the ground. Thus there is not much plant life on the forest floor. Dense vegetation close to the ground occurs in clearings and along rivers. These areas are sometimes called jungles.

          There are different kinds of plant and animal life in rain forests. Tropical rain forests contain the greatest variety of wild life including the wealth of insect life. Many of these insects have wonderful forms of camouflage. Also more different species of trees are found in tropical rain forests than in any other kinds of forests in the world. The soil layer in the tropical rain forests is very good for farming. 

            Any plant or animal that occurs in such abundance as to pose a distinct threat to man or his interests is called a pest. And the chemicals used for mitigation, control or elimination of such plants or animals are known as pesticides. Today we have algaecides, defoliants, herbicides, plant growth regulators and fungicides in use to control the growth of undesirable plants which compete with crops or other useful plants. Attractants, insecticides, miticides or acaricides, molluscicides, nematocides, repellents and rodenticides are used to reduce parasitism and disease-transmitting organisms in animals, crops, plants, foods, textiles and human beings.

            Most of the pesticides are chemical compounds and act in a similar fashion, i.e. by blocking some metabolic process. They, however, differ in composition, potency, mode of action, speed of effect. So different pesticides are used at different stages of infection. 

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          Bonsai is the art of developing and growing dwarf trees. The bonsai specimens are ordinary trees and not hereditary dwarfs. They are dwarfed by a system of pruning the roots and branches and training the branches by typing with wire. Any tree or shrub would be called a bonsai if grown in a suitable container and kept dwarf by special horticultural techniques.

          This art originated in China about 1000 years ago, but it was pursued and developed by the Japanese in the 12th century. In fact, bonsai is a Japanese word which means ‘tray planted’.

          The inspiration for bonsai, in fact, comes from the nature itself. The trees grown in rocky crevices of high mountains or overhung from the cliffs remain dwarfed throughout their lives.

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                    Almost every plant and animal in the world has enemies that threaten its existence. So to protect itself every living being has developed some defence mechanism. Sensing the danger some organisms hide, others run, while others just fly away. 

                 Some organisms can even hide without moving. They use ‘camouflage colouring’. That means that their skin colour blends in with the matching colour of the surrounding area so well that the enemies cannot see them. Chameleon has the capacity of changing its body colours. If it is on a green leaf, it turns green; if on a brown twig, it turns brown. Some rabbits change colour with the season. The snowshoe hare is brown in summer and white in winter. The white fur camouflages the rabbit in the snow. Another phenomenon called counter-shading is a common type of camouflage among the fishes. The underside of their body is of lighter shade than the top. This helps the fish to blend in with many shadows it might make. Some other animals have a remarkable ability to take the form and colour of some other object around them. Camouflage also helps some animals catch their food. Since they can blend in with their surroundings, their victims can’t spot them immediately, and thus get caught.

                    Then there are other animals such as antelope who can run very fast. Others may dodge back and forth, like a rabbit. Birds can escape most predators by flying away. 

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          Ever since the evolution of languages different plants and trees have been given names to distinguish one variety from the other. The nomenclature is essential for general use, for a gardener’s catalogue and for botanists. The source of their names is often very interesting and hence worth-knowing.

          Some names have simply been borrowed from other languages, while some others take the name of the places of their origin. Some plants have been named according to their shapes and colours while still others owe their names to some unique features of the plants. Some may have come after the names of their discoverers. Over the time even the names have undergone changes. The origin of names of some important plants and trees are discussed below. 

          The pine tree got its name from the Latin word pinus which means ‘a point’. The spruce tree should really be called the Prussia Tree because it was long thought to be a native of Prussia. The name gradually got corrupted to ‘spruce’.

          A butter cup is a flower which has the shape of a cup and the colour of butter. Lady’s mantle was the name given when ladies wore collars that were pleated and with serrated edges like the leaves of the plant. Honeysuckle has flowers rich in nectar and is, therefore, popular with bees collecting substance for making honey.

          The magnolia has been named after Pierre Magnol of France who was a professor of Botany. The cypress is called so because it was first brought from the island of Cyprus. In Madagascar, there is a tree called, ‘The Travellers Tree’. It has large, fan-shaped leaves that catch the rain water and the passing travellers sometimes quench their thirst with this water.

          The barber plant has been named so because the natives of Orient used to rub its leaves on their faces to check the beard from growing. The names dandelion comes from the French dent de lion because the leaves of this plant resemble the teeth of a lion. Thyme comes from the Latin word Thymus which means to sacrifice and the Romans used to burn this plant on their altars. 

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               One of the major differences between animals and plants is that animals can move whereas plants cannot. They remain static at one place even though they grow vertically horizontally depending on their growth pattern. But how do these plants spread their seeds to grow at different places? It is interesting to note that nature helps them in this activity and this process is termed as dispersion of seeds. 

               There are mainly four agents responsible for the dispersion of seeds, viz. air, water, birds and animals, and the plants themselves.

               When the dispersion is carried out by the plants themselves the process is called dehiscence. In dehiscence (or dispersion by explosion), a seed-containing structure such as a pod, bursts shooting the seeds into the air. These seeds land up at a distance depending upon the weight of the seed and the force with which they are thrown. Some of the plants that disperse their seeds in this manner include plants of the pea, mustard, and balsam family.

               Air is also an effective dispersing agent for the seeds. Lightweight seeds fly from one place to another along with the wind. Some grass seeds have been detected at heights of more than a thousand metres. Lightweight orchid seeds are carried away by air to great distances from their parent plants. Seeds of some plants, such as dandelion and cattail, have puffy hair that helps them float through the air and land up elsewhere. The seeds of maple, ash and box elder have wing like structures to move like small helicopters in the wind and thus get dispersed. 

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                           The botanists study the internal structure of plants mainly by examining their cross section under a microscope. These thin slices can tell us a lot about the structure of the cells that make up the plant and how they vary in different parts of the plant. In 1665, a scientist named Robert Hooke looked at a piece of cork (a material from the thick outer part of certain trees) under a microscope and saw that it was made up of many tiny compartments. He named them cells and this term has been in use since then. The equipments needed for obtaining the sections include a sharp razor, a small fine brush and a number of watch glasses and microscopic slides. The razor is stroked across the top towards the body, cutting off thin slices as required. Cross-sections as well as the longitudinal pieces are obtained in the same manner. To obtain best results the razor and the material must be kept moist with water in case of fresh material or alcohol if the specimen is a preserved one. To prevent shrinkage the sections shaved off are brushed into water or alcohol. For quick examination the sections are placed on a slide with a drop of glycerine. The thin ones that show the cells clearly can be stained for permanent use. In fact staining is a process of adding dyes to show the different tissues in different colours. Many stains are dissolved in alcohol and before staining the sections must be placed in alcohol. After a certain period in the stain(s) the section is transferred to a series of watch glasses full of alcohol. This removes water and the excess stain. The alcohol is removed by dipping the sections in clove oil or benzene. The section is then placed on a clean glass slide with a drop of Canada Balsam (a resinous glue). A thin glass is added as a cover-slip and sealed by warming the balsam to harden it. The slide, properly labelled, can then be kept and examined whenever necessary. Details of time exposure for staining varies with the stain and material used. The information can be collected from a text-book or worked out by practice. In laboratory analysis many modern techniques are being adopted for in-depth studies on the subject.

 

     

              When Darwin propounded his theory of ‘Survival of the fittest’, it created a great deal of controversy during those days. But gradually it started receiving a wider acceptance as many species were found to be either extinct or facing extinction for the reasons best explained by Darwin. Since the evolution of plant and animal lives, quite a few of them have faced complete extinction and others are facing the dangers of extinction. Hence the conservation of certain species that face extinction has drawn the worldwide attention. These species have been categorized as ‘endangered species’. 

                    Factors responsible for endangering the existence of these species are both natural and man-made. Firstly, the increasing human population is encroaching more and more land, and thus creating a scarcity of land for the wildlife to survive. Forests and heaths have been removed to make way for farming. Large-scale deforestation for wood and industrialization is another cause of the loss of wildlife. Secondly, man has hunted down many animals to extinction — auk and dodo are distinct examples of it. Pollution is also affecting the lives of many animals. Every year millions of sea-birds die unpleasant deaths as their feathers get covered with sticky, black oil waste. The natural causes are the unsuitable conditions of temperature and pressure, lack of proper food material, natural calamities etc. 

 

 

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