Effect of Color in Photosynthesis - Essay Example

IDENTIFICATION AND DETERMINATION OF ABSORPTION SPECTRA OF CHLOROPHYLL Photosynthesis is a regulated and a multi-step process. It is the process by which the plants produce energy from the sunlight to produce sugar which in turn is used for cellular respiration to produce ATP, the store of energy of the cells. This conversion of the less used energy into a usable chemical energy is assisted by the green pigment called chlorophyll. The photosynthesis uses the water molecule and releases oxygen molecule. (Tanaka and Makino 2009). The pigment is a substance that absorbs light and the color is produced due to the reflection of the light that is not absorbed. Chlorophyll absorbs all wavelengths of the visible light except the green light, which is reflected out. The chlorophyll is a complex molecule. Being complex it ahs undergone a lot of modifications and as a result chlorophyll a, chlorophyll b, xanthophylls and carotenoids are found in the leaf. Carotenoids and chlorophyll b absorbs some of the green wavelength energy. Chlorophyll a receives it energy from the blue-violet and reddish orange wavelength. As the intensity of the light increases, the increase of the photosynthesis is observed. (Giacometti and Giacometti, 2009). The present study was performed to determine the effect of the color on the photosynthesis rate, the rate of photosynthesis, the rate of oxygen uptake was determined for this experiment. HYPOTHESIS: Chromatography is the process of separation of the solutes. Paper chromatography is the process of separating the pigments that are present in the chlorophyll into fractions based on their molecular weight. The porosity of the paper helps in the separation using petroleum ether –acetone solvent. The plant emits oxygen when the photosynthesis reactions take place. If the intensity of the light is higher, then the rate of photosynthesis is higher. At the same time if the light is kept closer to the leaf, it should also increases the photosynthesis rate because the intensity is directly proportional to the photosynthesis. The action spectra have color of various wavelengths shorter to longer. If the wavelength is small then the intensity of the light should be higher. This indicates that the color with greater intensity will have greater photosynthetic rate. When the red, green , blue light are used as the light source for the photosynthesis reaction, then the light of shorter wavelength should produce maximum intensity , therefore the photosynthesis will be greater. Of the three colors the blue has the shorter wavelength, so it should produce higher photosynthetic rate. PROCEDURE: Fresh Leaf is taken and for 10 grams of leaf, 3 gram of sodium sulfate is added in a small vial to remove the water from the leaves overnight. The dry leaves are then blended with 100 ml water and 0.2 gram of MgO powder. The homogenized solution is then filtered several times with a cheese cloth adding 20 ml of acetone slowly. The extract is then poured into a separator funnel and 200 ml of petroleum ether is added to it and shaked vigorously. Then it was allowed to stand, till it got separated into two layers. Then 10% NaCl is added for the efficient separation of the layers. The chlorophyll and the carotenoids are not soluble in petroleum ether and moves to the top layer. After draining the lower layer, 120 ml of 80% methanol is added to it. The resulting ether phase is washed twice with 60 ml of 10% NaCl to remove the methanol and acetone. The aqueous phase is made redundant. A vial of anhydrous Na2SO4 is added to remove the water form the sample and swirl to mix. The clear green solution visible in the top of the separating funnel is only used to determine the absorption spectrum for chlorophyll. To the spectrophotometer add 5 ml of the suspension and record the absorbance of the mixture at different wavelengths starting from 420-680 nm at an interval of 20 nm. Similarly the pigments chlorophyll a, chlorophyll b, carotenoid and Xanthophylls absorption characteristics are also absorbed at various wavelengths. The healthy Leaf of 5-6 inches long is taken and it is kept inside the 0.1N NaHCO3 solution and a bent glass pipette and a syringe is kept above. The control tube without the plant Leaf is also prepared and kept along with the experimenting test tube. The control tube acts as a control for the temperature and pressure fluctuations. The both the test tubes were kept in the water and a lamp is kept at a distance of 75 cm away from the plant. As the plant is exposed to light it will produce oxygen through photosynthesis. This gas bubbles will replace the water that is present in the pipette. The oxygen production rate for 2 minute interval time is noted for 10 minutes. The experiment is repeated by varying the distance of the light from the plant (50 cm and 25 cm) respectively. A comparative study on the photosynthetic rates will provide the maximum rate of photosynthesis. Another experiment was done with the color lights such as Blue, Green and Red. The rate of oxygen production is observed. The pigments were exposed to the colors at a time interval of 2 minutes up to 10 minutes. RESULTS: The absorption characteristics of the 4 pigments: The Absorption characteristics of the pigments enable us to know that all the chlorophyll pigments show a peak between 440 – 520 nm. The absorption characteristics are more for light of shorter wavelength. The green levels are enabling us to know that green pigment is less absorbed and thus allowing the other colors to be more absorbed enabling us to prove that green color is expressed. DISCUSSIONS: The first part of the experiment was to determine what the leaf extracts mostly possessed and what was the characteristics of absorbance of the pigments. The absorption level was found to be greater in the colors of purple, blue, orange and red. The green levels are enabling us to know that green pigment is less absorbed and thus allowing the other colors to be more absorbed enabling us to prove that green color is expressed. (Hubbart et. al, 2007). The Chlorophyll pigments had a very good range between the 400-520 nm. This resembles that greater the absorbance if shorter is the wavelength. Similarly the pigments showed greater absorbance in the range of the green color thus enabling us to prove that the pigments were green pigments present inside the leaf. The production rate of the oxygen turns out be higher if the light source is closer to the plant. Thus it enables us to prove that if the intensity of the light is greater, then the absorbance of the light will be maximum, In turn the photosynthesis rate will be high. When the specific colors are used as the light source, then the colors of greater intensity must produce greater photosynthesis. When the colors Red, Blue and Green are used as light source, The Blue color of shorter wavelength and greater intensity should produce more oxygen. (Xiaoqin et. al, 2008). But in our Experiment the greater oxygen production rate was found to be higher for the Red color. The green color does not produce any photosynthesis thus proving that green light is not absorbed by the plants. The red and blue rays of the light spectrum are the most important regions of the energy sources for the plants. Various plant pigments help us to use the light for the photosynthesis. The deviation from the hypothesis may be due to the fact that the other pigments absorb the blue color more than the chlorophyll pigments and Xanthophylls that are present in the leaf dissipates the excess energy associated with the blue light. Moreover the blue light is highly absorbed mainly by the xanthophylls and carotenoids of the chlorophyll pigments. These are main reasons for the change from the hypothesis. (Braddock et. al, 2001). New experiments should be carried out to determine in what part of the leaf the excess energy is stored, the total amount of energy absorbed by all the pigments, the percentage of energy absorbed only by the chlorophyll pigments and the net loss of energy to the surroundings. The experiment can be further extended to study the effect of the other spectral lights on the rate of the photosynthesis. REFERENCES: Braddock, B., Mercer, S., Rachelson, C and Sapp, S. (2001). Effect of the blue and red light on the rate of photosynthesis. Fall 2001. Retrieved on June 8, 2010 from http://spot.colorado.edu/~basey/bluer.htm Giacometti, G and Giacometti, GM. (2009). Evolution of photosynthesis and Respiration: Which Came First? Applied Magnetic Resonance. 37 (4): 13-25 Hubbart, S., Peng, S., Horton, P., Chen, Y and Murchiel, E. H. (2007). Trends in leaf photosynthesis in historical rice varieties developed in the Philippines since1966. Journal of Experimental Botany. 58 (12): 3429-3438. Tanaka, A and Makino, A. (2009). Photosynthetic Research in Plant Science. Plant and Cell Physiology. 50 (4): 681–683. Xiaoqin, Yao, Qing LiuI and Chao Han. (2008). Growth and photosynthetic responses of Picea asperata seedlings to enhanced ultraviolet-B and to nitrogen supply. Brazilian Journal of Plant Physiology. 20 (1). Read More