My Science School

            Photosynthesis is the process by which green plants make food for themselves and indirectly, for all animals, including human beings.

            In photosynthesis plants combine water and salts in the soil, and carbon dioxide in the air to build up organic compounds, such as sugar starch and proteins. To do this they use the energy of sun light, which is absorbed with the help of the green dye in their leaves called chlorophyll.

            This process of manufacturing food from what they absorb through their roots and leaves make green plants the primary food producers in the world. All animals draw their nourishment from them, either by feeding on plants themselves or by eating other animals that do so. During photosynthesis, which takes place only in daylight, excess oxygen is produced and released into the atmosphere for animals to breathe.

            After the Second World War, the American scientist Melvin Calvin wrote a book about how plants capture the carbon dioxide in the atmosphere. In 1961 he received the Nobel Prize in chemistry in recognition of his work.

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            You would find a Red Giant on the Sierra Nevada Mountains of California in North America. It is a huge redwood tree, called a giant sequoia. These trees, members of the conifer family, are the largest in the world and grow to a height of 300 feet. They have a very hard, reddish brown wood and a thick, very rough bark. The giant sequoias were believed to be the oldest living things in the world. The ring marks on the stumps of the oldest trunks have been carefully counted and it is now known that some of the biggest are about 4,000 years.

              Many of these trees were cut down for their timber, which is resistant to attacks by fungus, and termites and other insects. To preserve the remaining groves of these huge redwoods, a reservation called the Sequoia National park was set up in 1890. The largest tree there is 272 feet high and has a circumference at the base of its trunk of 101(1/2) feet. Its weight has been estimated to be over 6,000 tons.

           Some of the other trees are taller but do not have such large trunks. A tunnel has been cut through the base of one of these giant trees which is big enough to drive a car through.

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The sepals of a flower protect it while it is in bud. The flower is really a kind of shoot, In which the leaves have been altered so that they can take on the task of producing seeds.

    In a simple flower these leaves are arranged in circles, called whorls. The outermost are five green, leaf-shaped sepals. Inside these are five petals, usually heart-shaped, each with a small flap at its base where nectar is produced to attract bees and other insects.

     Both the sepals and the petals are attached at their bases to the “receptacle”, the swollen end of the flower-stalk, which looks like a cone in the middle of the flower.

    Above the sepals and petals are the parts of the flower used in reproduction. These are the stamens, which contain the yellow pollen, and the carpels, which contain the ovules.

   Most flowers are built on this plan but there are wide variations in size, shape and colour, and in the numbers of the different parts of the flowers.

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Many Japanese trees are small because they are dwarfed by the Japanese art of bonsai. This art consists in training and growing dwarf trees as symbols of the Japanese ideal of the immersion of the self in nature. This ideal also finds expression in their poetry, the tea ceremony and flower arranging.

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Fertilizers are used on farms to increase crop yields by ensuring that soils contain the chemical elements required by growing plants. These chemical elements include oxygen, carbon, hydrogen, nitrogen, phosphorus, potassium, sulphur, calcium, magnesium, and iron. If soils are lacking in any of these, the deficiency can be made good by the right fertilizer.

     Until the 119th century, farmers relied mainly on the application of natural fertilizers put “goodness” back into the land. They used manure from the stock-yards and, in the case of coastal areas, seaweed from the shore. Lime was also applied to prevent acidity. This method of soil rejuvenation went a long way to maintain the presence of chemical elements. But it often did little to improve soils already lacking in certain chemicals.

      Nowadays soils are analyzed to find out deficiencies which can be made up by the application of the appropriate chemical fertilizers. Of course, the chemicals alone do not guarantee a successful crop. The continued application of the natural fertilizers, such as manure and humans (decayed vegetables matter) is also essential.

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