The Effect Of Temperature On Rate Of Photosynthesis Of Pondweed Plant - Coursework Example

? RATIONALE AND RESEARCH AIM: TO DETERMINE THE EFFECT OF TEMPERATURE ON RATE OF PHOTOSYNTHESIS OF PONDWEED PLANT. Every living organism needs some sort of food material to get energy for growth and development process. Plants and animals differ from each other in a manner that plants prepare their own provision by the process of photosynthesis, while animals consume these plants or other animals as a source of energy. Literal meaning of photosynthesis is “to put together by light”. It is a process that involves capturing sunlight, in the presence of chlorophyll, CO2, water, and then producing starch and oxygen. This starch is then used by the plants either to produce energy, for storage, or to build them into a complex material and then producing starches, oils and proteins. Starch is the best way to store carbohydrates as it is compact and is easily broken down in the body. During the process of photosynthesis plants fix environments CO2 and release oxygen, which is essential for entire living beings for survival. Thus, more than 80% of plant material is synthesized by photosynthesis including respiration process also depends on its byproducts. Chlorophyll is the chemical, which traps light energy and then uses it to synthesize carbohydrates. It acts as catalysts to speed up the process of reaction. Chlorophyll is present in the chloroplasts of the palisade layer of leaves. The equation for photosynthesis is: 6CO2+6H2O => C6H2O6+6O2 +energy Photosynthesis involves trapping of CO2 from the environment in the presence of Chlorophyll and the sunlight. If a light source is placed near the pondweed plant that acts as sunlight, then the plant will release more oxygen due to splitting of water molecule into hydrogen and Oxygen molecule. The Hydrogen molecule that is released in the process will then combine with the CO2 and produces carbohydrates. This process again gives off more oxygen. The whole process needs to be catalyzed by enzymes to speed up the reaction. Photosynthesis is a two phase procedure. Stage one is light reliant and it captures sunlight to manufacture high energy molecule. In the second phases, which are light free reactions, these molecules are used to incarcerate CO2 and convert them into originators of carbohydrates. There are various limiting factors that affect the rate of photosynthesis. Most important factor is the presence of CO2 in the environment i.e., 0.03% to 0.04%. Only at a certain rate can a plant takes up CO2 and proceeds with photosynthesis. Light intensity will also affect the rate as well as temperature. In laboratory experiments, volume of oxygen released per minute is used to determine the rate of the process, and this in turn can be used as the source for determining the effects of limiting factors (Kent, 2000). The law of limiting factor states that, “When a process depends on more than one factor to be favorable then its rate is limited by the factor at its least favorable value. For a process to go at its maximum rate, all factors need to be at an optimum stage.” Measurement of photosynthesis rate is required to determine the limiting factors that can affect productivity of the process as well as its response to environmental stresses. Most of the measurement techniques being used today involve the gaseous exchange of the plants as an indicator for the rate. Chemical pathway of intake of CO2 and water discharge is the same and hence these two pathways are involved in measurement of photosynthesis through stomata conductance and transpiration method (MILLAN, GUEVARA, TORRES, OSORNIO, 2009). These days modified methods are being used to conduct the analysis, which increases the precision and accuracy of the results. The purpose of this experiment is to determine the effect of temperature on the photosynthesis of pondweed plant. Basically, temperature does not pose an enormous effect on the rate of photosynthesis individually; it only affects the speed of the process by affecting the rhythm of chemical responses in the plants. This is because photosynthesis is a light dependant stage and more effect will be produced by presence or absence of light. Although the increase in temperature increases the rate of reactions to an extent, but after a certain limit, photosynthesis slows down due to denaturing of the enzymes that are involved in the process. Very low temperature also slows down the process, under normal CO2 levels (Kent, 2000). Thus, when one of the limiting factor increases, it increases the rate of the process, but to an extent. As the rate of photosynthesis increases with the increase in temperature, Oxygen is more readily given off by the plant. This phenomenon will be used as a marker for the difference in rate of photosynthesis during the experiment. A rise in 50°C to 60°C will slow the process as enzyme will start to break down at that point. Enzymes break down leads to decrease in the rate of photosynthesis, resulting in decreased release of oxygen (Bradfield & Potter, 2009). Hence, between the temperatures of 10°C to 60°C there will an increase and then decrease in the rate of photosynthesis, determining the effect of temperature on the process. Enzymes are important chemical compounds that can alter the rate of a chemical process. Though enzymes have a very narrow range in which they work properly. Increase of temperature increases the reaction until it breaks protein portions of the enzymes. Cross linkages between the enzymes molecule breaks leading to variation in the shape of molecule. ) .They are shaped to hold CO2 and hydrogen molecules and they increase the rate of reaction by increasing collision between the molecules. Increase in temperature provides more energy to the enzyme molecules to work at a faster rate. Further increase in temperature can irreversibly change the shape of the molecule so that they won’t be able to hold hydrogen and CO2 and proceed with the reaction. This changed molecule becomes useless as it is unable to bind to the specific substrate for a particular chemical reaction. This whole phenomenon takes place as soon as temperature crosses optimum level. (Gray, Calvin &, Bhattia, 2011) Pondweed plant is used in this experiment so that oxygen given off by an aquatic plant can be easily observed during the experiment. This would have been difficult if any land plant would be taken for the same experiment (Beckett, 1976). PLANNING: The apparatus required for the experiment includes Bunsen burner, Tripod stand, Gauze, 500ml Beaker, a test tube marked at a specific level, Thermometer, Paper clip, Elodea (pondweed) plant, water, sodium bicarbonate, and a lamp at controlled intensity of light. We can either set up a single apparatus with varying temperatures or we can set up four to five similar apparatuses with different temperatures at the same time (Backette, 1976) CONTROL PROCEDURE: We will control the intensity of the light throughout the experiment by placing it at a constant distance from the apparatus so that no variance occurs in the results due to the change in light intensity. Sodium hydro carbonate is used in the experiment to produce CO2 in water, which is required by aquatic plants to carry out photosynthesis. This NaHCO3 is only used at the beginning of the experiment so that its concentration does not affect the process either. Water level in the test tube and the beaker is also kept invariable, so that difference in water quantity does not affect enzyme activity, thus, altering rate of reaction. Length of the pondweed plant can also have an effect on the results so its length will be kept constant at a specific level. Temperature will be the only varying variable throughout the experiment. This will be varied using a Bunsen burner and a thermometer to control the temperature. The results can be more accurate if we use electronic water bath for the purpose, which will make temperature control easier. We will note the temperature on the thermometer as it reaches our specified level and will start counting the numbers of bubbles released per minute. Since the independent variable in the procedure is temperature it will be manipulated by changing the temperature of the water bath using the burner and it will be monitored by thermometer. Dependent variable in the phenomenon is the amount of air that is being released from the plant. POTENTIAL HAZARDS This experiment is basically a safe one. Few precautionary measures can still be taken to avoid any mishaps. Try not to spill the water from test tube or water bath as it will affect the results. Carefully handle Bunsen burner while hot. To reduce this potential hazard use of Bunsen burner can be avoided and water’s temperature can be easily controlled by adding hot water to increase the temperature. Ice can be used to reduce the temperature of the water bath. Take care of the thermometer being used in the experiment and try not to break it as it contains mercury, which is poisonous. Care is needed with electrical lamp as it was placed near the apparatus. Change of its distance can easily affect the results as well as spilling of water at any point can damage the lamp. Wiring of the lamp can also be a potential danger. A trail of the experiment is performed before actually starting the procedure so that functioning of the apparatus can be checked. After checking everything, we switch on the burner to proceed with the experiment. Figure 1: Apparatus of the Experiment PROCEDURE: Place the water beaker on the tripod stand with the gauze. Fill the beaker with water. Cool the water in the beaker to 10°C using ice. Now take a pondweed (Elodea) plant and cut it to 7cm in length. Cut it in a manner that there is larger surface for the release of oxygen. Attach a paper clip with the pondweed so that it does not float to the top of the water in the test tube. If something like that happens, then we won’t be able to observe any release of oxygen during the procedure. Place the plant upside down in the test tube filled with cold, boiled water. The water must not be too cold as pondweed (Elodea) won’t be able to photosynthesize. Too hot water can also kill the plant. Now place the water filled test tube in the water bath with thermometer. Place the lamp 10cm apart from the apparatus and this distance is fixed throughout the process. Set up all the apparatus in an area where you have plenty of area to work. Make sure nothing spills during the experiment making the results variable and hurting people at the same time. 0.6gm of NaHCO3 is added at the start of experiment in the test tube. 2-3 minutes are given to plant to get adapt to the circumstances. As soon as the bubbles have started to release from the plant, we will start recording the results in the column that is already present in our observation portion. The number of bubbles released per minutes will be counted three times at a single temperature point, so that an average of the three readings can be used to get accurate results from the experiments. Inconsistent readings during the experiment are recorded in a separate section, where observations with a larger variance then expected are repeated and then recorded separately so that mean value gives an almost accurate value. The temperature will be increased to another 10°C by switching the Bunsen burner on, now at 20°C record the readings for second observation. Three readings will also be taken at 20°C. Same procedure will be applied after raising the temperature to 30°C, 40°C, 50°C and then at 60°C. Mean values of the experiment are then plotted on the graph to get the clear picture of the effect of temperature during this whole procedure. Throughout the experiment no changing is made in the intensity of light, water level and NaHCO3 amount. The apparatus is appropriate according to the method of experiment. It is suitable to tell us how enzymes respond to the changes in environmental stresses, thus affecting the rate of photosynthesis. This apparatus is used to give the pondweed plant a controlled environment under normal lab conditions, which would have improved with the use of electronic water bath. RECORDING AND OBSERVING DATA: The observation column consists of six columns. 1st column is of temperature. And then number of bubbles per minute is recorded in separate column. For accuracy, Inconsistent readings are observed again and then stated in inconsistency section. Mean values of the number of bubbles per minute is calculated and only these are plotted on the graph. The graph shows that the rate of photosynthesis increases drastically around 30°C to 40°C, which is the optimum temperature for the proper functioning of the enzyme. Around 50°C The enzymes start to denature, showing a decline in release of oxygen during the process. Table 1 Temperature (°C) No. of bubbles observed(1) No. of bubbles observed (2) Numbers of bubbles observed (3) Inconsistency Mean 10 09 15 17 16 16 20 25 33 33 31 32 30 39 60 69 59 62 40 99 98 97 98 98 50 50 55 51 52 53 60 1 4 2 10 2 Figure 2: Graph illustrating the effects of temperature on the rate of photosynthesis Six points of mean values are plotted on the graph. The arithmetic mean is the average or central tendency of the data. Appropriateness of the data has to be checked that whether taking mean is more appropriate than mode or median. Here, in this data median and mode could not be used and mean was the better option among the rest. Mean is a descriptive statistical method that summarizes a given data set and measures variability and dispersion. After representing the data in a tubular form, its graphical representation is done to pronounce its result. For this, simple and clear line graphical method is employed so that results are clear for the observer or reader. LIMITATIONS: One basic limitation of the study was that the rate of photosynthesis was being determined on the basis of oxygen volume released from the plant. The oxygen released was also being used at the same time for the respiration process of the plant. This can affect the accuracy of the results. The dissolved oxygen, nitrogen and other gases released by plants are also included in the volume of oxygen being measured (Tootle & Tootle, 2004). Temperature of water cannot be maintained at a constant level for a longer period of time, so for the observation of bubbles release, a bit rushed up course of action needs to be undertaken and even then the results can vary. Electric water baths can control the temperature at a level specified. This would have saved the trouble of rushing up the whole experiment. Since the experiment is conducted manually, there are chances of human errors as well. Care must be taken while counting the number of bubbles being produced so that minimum chances of errors can occur. Volume of air released by Elodea can also be measured by photosynthometer, which is tube like apparatus used to measure the volume of air being released by the object. CONCLUSION: The result of the experiment suggests there is a direct proportionality between temperature and rate of photosynthesis, though in a specific range of temperature. This is because of the enzymes that denatures at above optimum temperature and stop functioning at below favorable level. Enzymes present in the plant cell help chlorophyll to trap water and split it into oxygen and hydrogen molecule. Increased light, concentration of CO2, and temperature all have profound effect on photosynthesis, but even if CO2 and light intensity is increased even then temperature can limit the process of photosynthesis, as it produces irreversible influence on the shape of enzyme. (Kent, 2000) The experiment also shows that 40°C is the optimum temperature for pondweed plant to photosynthesize. EVALUATING THE RESULTS: The method of the trial was adequate according to the hypothesis of the experiment. Under average set of lab conditions, one can easily find out the effects of any of the limiting factors using this procedure. For determination of other factors, temperature can be kept constant and light intensity or CO2 concentration can be easily varied. For increasing the accuracy of the results obtained from this experiment various other important limiting factors also needs to be considered: such as nutrients of soil, sunrays and carbon dioxide from the environment. The evidence obtained from the results of this experiment indicate that related effects on the rate of photosynthesis will occur if any of the other limiting factors are disturbed in the environment. References: Top of Form MILLAN-ALMARAZ J.R., GUEVARA-GONZALEZ R.G., TORRES-PACHECO I., DE JESUS ROMERO-TRONCOSO R., & OSORNIO-RIOS R.A. (2009). Advantages and disadvantages on photosynthesis measurement techniques: A review. African Journal of Biotechnology. 8, 7340-7349. Top of Form BRADFIELD, P., & POTTER, S. (2009). Edexcel IGCSE biology. Student book. Harlow, Pearson. Top of Form GRAY, N., CALVIN, M., & BHATIA, S. C. (2011). Enzymes biotechnology. Singapore, Alkem Company (S) Pte Ltd. Bottom of Form Top of Form KENT, M. (2000). Advanced biology. Oxford, Oxford University Press. Top of Form BECKETT, B. S. (1976). Biology: a modern introduction. Oxford, Oxford University Press. Top of Form TOOLE, G., & TOOLE, S. (2004). Essential A2 biology for OCR. Cheltenham, Nelson Thornes. Bottom of Form Bottom of Form Bottom of Form Bottom of Form Bottom of Form Read More