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BIOLOGY PROJECT REPORT Name : ANUSHI KOTOKY Class : XII (Science) Roll No. : School : KENDRIYA VIDYALAYA, DULIAJAN ACKNOWLEDGEMENT This project on the subject of biology was successfully carried out under guidance of our Biology teacher, Smti Shubha Krishnamachar and her guidance is greatly acknowledged ********** A Biological Project Work on Photosynthesis CONTENTS I. AIM II. MATERIALS REQUIRED III. INTRODUCTION IV. THEORY V. EXPERIMENTAL PROCEDURE VI. OBSERVATION VII. RESULTS VIII. CONCLUSION IX. BIBLIOGRAPHY LIST OF FIGURES Figure-1: No. of Air bubbles evolved/minute in different wavelength of light. Figure-1a: Average No. of Air bubbles evolved/minute in different wavelength of light. Figure-2: No. of Air bubbles evolved/minute in different concentration of NaHCO3 Figure-2a: Average No. of Air bubbles evolved/minute in different concentration of NaHCO3 Figure-3: No. of Air bubbles evolved/minute in different temperature Figure-3a: Average No. of Air bubbles evolved/minute in different temperature Figure-4: No. of Air bubbles evolved/minute in different times in a day Figure-4a: Average No. of Air bubbles evolved/minute in different times in a day ******************* A Biological Project Work on Photosynthesis I. AIM : TO STUDY THE EFFECTS OF LIGHT, CARBON DIOXIDE CONCENTRATION AND TEMPERATURE ON THE RATE OF PHOTOSYNTHESIS. MATERIALS REQUIRED : Beaker, test tubes, hydrilla plant, thermometer, cardboard box, sodium bicarbonate, ice and coloured paper (red, blue, green & yellow). INTRODUCTION : It is rightly said that photosynthesis is the only process that supports all lives on the earth. It is the only link between solar energy and the Chemical energy by the use of which all living beings maintain their existence. Food and oxygen which are produced by the green plants are the two basic needs of life. Had there been no photosynthesis by green plants, no life would have evolved. II. THEORY : Photosynthesis is the process of food manufacture by green plants by taking water from the soil and carbon dioxide from the atmosphere in the presence of sunlight and chlorophyll. The process of photosynthesis consists of two steps – 1. Light reactions : In these reactions which take place in the presence of light, solar energy is trapped by chlorophyll and store in the form of chemical energy of ATP (ADENOSINE TRIPHOSPHATE), and as reducing power in NADPH (NICOTINAMIDE ADENINE DINUCLEOTIDE PHOSPHATE HORMONE). Splitting of water take place and oxygen gas is evolved. 2. Dark reactions : These reactions take place in dark in which the reducing capacity of NADPH and the energy of ATP are utilized in the conversion of CO2 to carbohydrates. Photosynthesis is regulated by a number of different factors – external and internal. EXTERNAL FACTORS : 1. LIGHT : Light is the basic need for photosynthesis. No photosynthesis is possible without light even if other factors are present. Light through its quality (spectrum of light) and quantity (intensity and duration) affect photosynthesis. As far as the quality of light is concerned, experiments have proved that maximum photosynthesis occurs in red light. No photosynthesis activity has been seen in green light. Under suitable conditions of temperature and concentration of CO2 the rate of photosynthesis is proportional to the product of light intensity and duration of exposure. However, in the intermittent light (i.e. alternating light and dark periods) the rate of photosynthetic activity is much greater than in continuous light. 2. CONCENTRATION OF CARBON DIOXIDE : The concentration of CO2 in the atmosphere is 0.03%. An increase in the concentration up to 3% also increases the rate of photosynthesis provided other factors remain favourable. Any further increase in the concentration of CO2 produces toxic effects lowering the rate of photosynthesis. 3. SUPPLY OF WATER : Water is one of the reactant but the amount of water needed for photosynthesis is very small hence its deficiency rarely affects photosynthesis. The scarcity of water may have secondary affect on closing of stomata and thus reducing the rate of diffusion of CO2 in the leaf. 4. TEMPERATURE : For every reaction there is an optimum, minimum and maximum temperature. The optimum temperature is that temperature at which the reaction occurs at maximum rate. For photosynthesis the average optimum temperature is between 25°C to 40°C provided other factors are favourable. Any further increase beyond 40°C has adverse and declining effect on photosynthesis as a result of inactivation of enzymes. Photosynthesis has been found to occur even at 0°C in some plants of colder regions. INTERNAL FACTORS : 1. CHLOROPHYLL : It is indispensable for photosynthesis. Studies have revealed that more the amount of chlorophyll, greater is the photosynthesis. 2. LEAF STRUCTURE : It has also a considerable influence on photosynthesis. The size, position, number of stomata and distribution of intercellular spaces determine the amount of CO2 that reaches chloroplasts. 3. END PRODUCT CONCENTRATION : The end product concentration in the photosynthesizing cells has direct bearing on the rate of photosynthesis. Greater concentration has retarding effect on the photosynthesis. III. EXPERIMENTAL PROCEDURE : A known amount of actively photosynthesizing hydrilla plant is taken in a beaker full of water. The amount of hydrilla plant taken must be kept constant throughout the experiment. A funnel is kept inverted over the plant. The plant should be kept in such a way that all the cut ends of the twigs face upwards. A test tube full of water is inverted on the funnel and 4 to 5 experimental sets are prepared. In each set, conditions like amounts of the plant, amount of water in the beaker etc. must be identical. The following experiments were performed. 1. For the wavelength of light : The experimental set is placed in a black painted cardboard box and a bulb of known wattage is fixed in it. A red glass paper is wrapped over the bulb and is the bulb switched on. After sometime air bubbles will start rising and fill the test tube. The number of air bubbles evolved in each minute is counted for 10 minutes and the observations are recorded in an observation table. Similarly, the number of air bubbles by wrapping blue, green and yellow glass papers on the bulb are counted. 2. For carbon dioxide concentration : 0.1%, 0.5%, 1% and 0.2% solutions of sodium bicarbonate are prepared. In the beaker, instead of water, 0.1% sodium bicarbonate solution is taken and the number of air bubbles in each minute is counted for 10 minutes. The set is kept in sunlight. Similarly, the bubbles evolved for 0.5%, 0.2% and 1% solutions are counted. The volumes of the solutions taken should be same for all the strengths of solutions. 3. For temperature : The experimental set is maintained at 5°C by adding ice cold water and then the number of air bubbles evolved in each minute is counted for 10 minutes. Similarly, the reading for 26°C and 40°C are noted down. 4. For different times in a day: The experimental set up is placed in a black painted cardboard box and kept outside at 9.00 AM. After sometime air bubbles will start rising and fill the test tube. The air bubbles evolved in 10 minutes are counted for each minute and recorded in the observation table. Similarly, the number of air bubbles at 11.00 AM and 2.00 PM are also counted. IV. OBSERVATION : TABLE-1 : The number of air bubbles evolved per minute from the hydrilla plant in different wavelength of light. |WAVE LENGTH OF |NUMBER OF AIR BUBBLES EVOLVED/MINUTE | | |LIGHT | | | | | |AVERAGE | | |6TH |7TH | | |6TH |7TH | | |6TH |7TH | |6TH |7TH |8TH |9TH |10TH |11TH |12TH |13TH |14TH |15TH | | |9.00 AM |2 |2 |3 |2 |3 |3 |4 |5 |4 |4 |3.2 | |11.00 AM |4 |4 |5 |4 |5 |6 |6 |7 |9 |8 |5.8 | |2.00 PM |3 |4 |3 |3 |3 |4 |4 |4 |5 |5 |3.8 | | V. RESULTS: 1. For wavelength of light: Avg. No. of air bubbles in red region : 8.4 Avg. No. of air bubbles in blue region : 7.3 Avg. No. of air bubbles in green region : 3.5 Avg. No. of air bubbles in yellow region : 2.9 Thus, photosynthetic rate is maximum in red region (as shown in Figure-1 & 1a). 2. For carbon dioxide concentration: Avg. No. of air bubbles with 0.1% NaHCO3 concentration : 5.9 Avg. No. of air bubbles with 0.5% NaHCO3 concentration : 10.9 Avg. No. of air bubbles with 0.2% NaHCO3 concentration : 7.6 Avg. No. of air bubbles with 1% NaHCO3 concentration : 11.4 Thus, photosynthetic rate is maximum when there is 1% NaHCO3 concentration (as shown in Figure-2 & 2a). 3. For temperature: Avg. No. of air bubbles at 26°C : 5.8 Avg. No. of air bubbles at 5°C : 3.2 Avg. No. of air bubbles at 40°C : 3.8 Thus, photosynthetic rate is maximum at 26°C (as shown in Figure-3 & 3a). 4. For different times in a day: Avg. No. of air bubbles at 9.00 AM : 3.2 Avg. No. of air bubbles at 11.00 AM : 5.8 Avg. No. of air bubbles at 2.00 PM : 3.8 Thus photosynthetic rate is maximum at 11.00 AM (as shown in Figure-4 & 4a). VI. CONCLUSION : The rate of photosynthesis increases with increase in light intensity and carbon dioxide concentration. Photosynthetic activity is maximum in the red region and at room temperature. IX. BIBLIOGRAPHY : Laboratory manual in Biology (Part II) (Aryl Book Depot)