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Photosynthesis.In photosynthesis the raw materials are carbon dioxide and water. They react to form the products of the reaction-oxygen and starch (glucose that has been stored).

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Li See Chew Biology Course Work Paul Photosynthesis Photosynthesis is a very important process in nature. It is the production of energy in the form of glucose involving water from the soil, carbon dioxide from the air and light energy from the sun. It takes place in all green plants, which use the green chlorophyll, held in chloroplast in the leaves, to trap light. The main site of photosynthesis is the palisade layer in the leaf of a plant. The cells in the palisade layer contain the green chloroplasts. They are near the upper side of the leaf where they can obtain the maximum amount of light, they are packed very close together and as already mentioned contain green chloroplasts clustered towards the upper side too. Plants photosynthesise to produce food that needed to allow them to grow. The main reaction is to produce glucose and the oxygen is form as the by-product. If the plant does not need to use all the glucose immediately then it is stored which is difficult because glucose is hard to store in water. ...read more.


To show the leaf contains starch, we use iodine solution. If the iodine turns blue black, this shows that the leaf contains starch. Testing a leaf for starch Use a plant kept in light. Detach a leaf, holding it in forceps plunge into boiling water for 5 seconds. This will kill the cells, stop all chemical reactions and make the leaf permeable to alcohol and iodine solution. Push the leaf to the bottom of a boiling tube and cover with ethanol, place in the water bath and leave for 5 minutes. The ethanol will boil and dissolve out the chlorophyll in the leaf. Remove the tube from the bath and carefully tip the ethanol solution into the beaker for waste ethanol. If the leaf is still green add more ethanol and place in water bath for another 5 minutes and drain as before. Fill the tube with cold water and the leaf will probably float to the top, remove the leaf and spread it out onto a white tile, rinse it gently with to remove the ethanol. ...read more.


Discussion In the experiment I found that starch could be found by using the iodine solution. In a healthy plant, most of the starch store at the 'front' of the leaf. If we cover a part of the leaf by aluminium foil, the part that didn't cover will send some of the starch to the part that cover by aluminium foil. The part that covered by aluminium foil also will store the starch when they 'receive' the starch. In the experiment, I also found that photosynthesis can't process when the absent of water, sun light, carbon dioxide or chlorophyll. These factors are important for leaf to photosynthesis and 'make' their own food. Although plant can make their own food by photosynthesis, they do not survive for very long if they are only provided with water, carbon dioxide and light. Plants need minerals and vitamins for healthy growth, so plants need more than simply the products pf photosynthesis to survive. The major requirement for plant are Nitrate, Phosphate and Potassium. Without any of these minerals, the plant will look decidedly sickly. Plant need sun light, water, carbon dioxide and minerals to growth healthy. Leaf : leaf (a) leaf (b) leaf (c) leaf (d) ...read more.

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