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. 

Continue reading "How do living beings adapt to their environment? "

               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. 

 

 

 

 

 

 

 

Continue reading "Which are the largest and smallest flowers? "

               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.