1. Plant Nutrition By Gitika and Mansi

2. What is Photosynthesis? Photosynthesis might be the most important biological process on earth. Photosynthesis is the process in which light energy is converted into chemical energy. Using the energy of light, carbohydrates such as sugars are synthesized from carbon dioxide and water. 3. Why is light so important for photosynthesis ? Plants and trees grow and position themselves to places where they can get the most sunlight. Light is essential to photosynthesis, It is essential for energy generation. Without the energy produced by photosynthesis, the plants will not be able to carry out most metabolic reactions. 4. Photosynthesis investigations 1. Investigations need controls Control plant (or leave) has all substances it needs. Test plant lacks one substance (light/chlorophyll/CO2) 2. Plants must be destarched It is very important that the leaves you are testing should not have any starch in them at the beginning of the experiment. So, first of all, you must destarch the plants. Leave them in the dark for 48 hours. The plants use up all stores of starch in its leaves. 5. Continued.. 3. Starch test with Iodine solution After a few hours, carry out the starch test on both plants: Iodine solution is used; a blue-black color on the leaf is positive. Boil the leaf in water for 30 seconds. This kills the cells in the leaf and break down the membrane and iodine solution gets through cell membrane to reach starch inside the chloroplasts and react with them. 6. Continued Boil the leaf in ethanol in a water bath: to remove chlorophyll it has to be dissolved in ethanol. Leave it until all the chlorophyll has come out of the leaf. Rinse the leaf in water: The water softens it. Spread the leaf out. Add iodine solution to the leaf. If a bluish black colour is seen proves that starch is present. 7. Test if light is needed for photosynthesis The leaf has to be destarched to remove any previously existing starch. When this is done one leaf of the plant is covered and the other is left uncovered. Test the presence of starch with the Iodine test. 8. Conclusion Starch is not present in the covered leaf as it was not exposed to light and starch was not synthesized. This proves that light is necessary for photosynthesis 9. How does light intensity effect photosynthesis? http://www.passmyexams.co.uk/GCSE/biol ogy/factors-affecting-rate-of- photosynthesis.html 10. Conclusion if the light intensity is increased, the rate of photosynthesis increases. This is because light excites chlorophyll molecules, providing the energy for the production of carbohydrates. However, at higher light intensities, the rate of photosynthesis might slow down or stop.