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The Effects of Light Intensity on the Rate of Photosynthesis in Sun and Shade Leaves

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The Effects of Light Intensity on the Rate of Photosynthesis in Sun and Shade Leaves In this investigation, I am going to experiment how light intensity affects the rate of photosynthesis. The plant I have chosen that exhibits both sun and shade leaves is Hyptis Emoryi. The very first step of photosynthesis is the process of photophosphorylation. This is where the light absorbed in the thylakoid membrane of the chloroplast is used as energy in synthesis of ATP. The next step is photolysis; here, the molecule of water is split into H+, electrons and oxygen. This stages combined together occur in the light dependent stage. The production of ATP and hydrogen ions is vital for the process of photosynthesis. Hydrogen ions are combine with proton acceptor, NADP. This combination forms Reduced NADP. Reduced NADP is crucial as it helps in the production of glucose, amino acids and lipids. Similarly, the synthesis of ATP is also very important as it provides energy to produce these products. ...read more.


However, in sun leaves, high light intensity will fasten the colour change as they are more adaptable to high light intensity. Whereas in shade leaves, high light intensity will not fasten the rate of photosynthesis, rather it may damage the leaf discs if exposed for long. Therefore, I will predict that for shade leaves, high light intensity will not fasten the rate of photosynthesis. Having said this, light intensity is directly proportional to the rate of photosynthesis (in sun leaves) only to a point. The graph below shows that the line levels off at a point where the optimum level for light intake is reached. At this point, there must be other limiting factor other than light intensity that limits the rate of photosynthesis. These factors could be temperature and carbon dioxide supply. Diagram courtesy of BBC Bitesize My variable will be the light intensity. The light source will be placed at different distances to the sample. My constants will be the same volume and concentration of the indicator. ...read more.


This chemical is hazardous and should be handled carefully. If in contact with skin or eyes, than area of contact must be washed thoroughly with water immediately. If irritation persists, than contact a medical doctor immediately. Apparatus: 1. Hyptis Emoryi plant 2. Straw 3. Six 10ml syringes 4. 0.2moldm-3 NaHCO3 solution 5. Lamp 6. Ruler 7. Stopwatch Method: 1. Using a sun leaf, cut a disc from the leaf with a straw 2. Add 10cm3 of NaHCO3 into an open syringe 3. Place the disc into the syringe and carefully re-install the plunger in the syringe. 4. Get rid of any air spaces inside the syringe by pushing the plunger. 5. then, blocking the nozzle firmly, pull the syringe back until air bubbles from the disc are shown 6. The disc should then sink to the bottom of the syringe as it's denser. I will repeat steps 1-6 for each leaf discs. Then; 7. I will place the syringe 10cm from the lamp and start the stopwatch. 8. I will stop the stopwatch as soon as the colour of the indicator changes from orange to deep purple. I will repeat step 7-8 for distances of 20cm, 30cm, 40cm and 50cm. ...read more.

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