Photosynthesis Lab Report

Abstract: Photosynthesis is a process that plants use to make food for themselves. Photosynthesis can be influenced by many factors including light intensity, light distance and temperature. In this experiment we used temperature to see how photosynthesis is influenced. During this experiment we took 3 solutions (all three with algae and CO2) and used three different temperatures to analyzed the absorbance rates and pH values of the 3 solutions. The objective of the experiment was to see which temperature absorbs the most light, this would determine which temperature photosynthesis is most efficient in. Three cuvettes with CO2 solution and algae beads at three different temperatures (15°C, 20°C, and 25°C) were placed in front of three lamps. Every five minutes the absorbance value was measured using a spectrometer, and the pH value was recorded using a pH strip, the color of the solution was also noted down for qualitative data. The results concluded that the temperature which absorbs the most light was at 30°C, the absorbance values ranged from 0.396-0.802. At 25°C the absorbance values were 0.343-0.742 and at 15°C it was 0.332-0.683. It can be concluded that in order for photosynthesis to occur the most efficiently and absorb the most light, plants need to placed in a temperature around 30°C. This can be helpful to farmers and other people who grow plants that require photosynthesis to live. This can also be helpful to people who want to help climate change, photosynthesis produces oxygen, by creating an environment where plants can produce more oxygen at one time can be extremely beneficial to our ecosystem. Introduction: Photosynthesis is the process in which light energy is taken from the sun and converted into sugar and oxygen. The equation for photosynthesis is 6CO2 + 6H2O + energy (from light) C6H12O6 + 6O2. Photosynthesis is used by autotrophs, also known as primary producers, and the sugar and oxygen that they produce are beneficial to themselves as well as other heterotrophs, also known as consumers (Upadhyaya, 2020). Other heterotrophs consumed the plants as food and they also breath the oxygen produced by the autotrophs. The process of photosynthesis is practically the reverse of cellular respiration. There are two main phases of photosynthesis: the light reactions and the Calvin cycle (dark reaction). The light reactions take place inside the thylakoids of the chloroplasts, and here solar energy is converted into chemical energy. The molecules that capture the energy from the sun are called pigments, different pigments absorb different wavelengths (Upadhyaya, 2020). The H2O is split and this is how the oxygen is formed. The Calvin Cycle occurs in the stroma of the chloroplasts, this is also known as the dark reactions, and produces glucose with the assistance of an enzyme called RuBisCO - Ribulose Bisphosphate Carboxylase Oxygenase (Upadhyaya, 2020). The different factors that can affect photosynthesis include light intensity, carbon dioxide concentration, light distance, and temperature. In this experiment, we wanted to know in which temperature the solution would absorb the most light. The hypothesis was, if the cuvette was placed at 30°C then the most light would be absorbed. Temperature is an environmental factor that contributes greatly to the way animals and plants live and grow. Aquatic habitats tend to be cooler than terrestrial habitats and therefore the animals and plants that live in aquatic areas adjust and adapt to those specific temperatures. This experiment shows that is difficult for plants to grow is extremely cold environments, for example in places like Antarctica there aren’t many plants that can grow there. The animals there (heterotrophs) cannot rely on plants (autotrophs) to give them food, and therefore find their sources of food from elsewhere. In general, when the temperature is higher certain metabolic processes that occur in an organism function more efficiently. Temperature does affect cellular respiration as well, as temperature increases, the rate of cellular respiration also increases (Banas, 2017). S. Obliquus is an extremely common freshwater algae and are usually found all around the world, it can exist as a unicellular organism, but can also be found in clumps of two or four cells (Lurling, 1999). S. Obliquus is efficient in removing phosphate and ammonia from contaminated water, and can also be used for creating biodiesel and organic fertilizers (Gonzalez, 1997). Materials and Methods: Part 1: Setting Up Cuvettes and Placing Lamps: We took three cuvettes and, in each cuvette, we placed ten algae beads and 2 milliliters of a CO2 solution. We then took another cuvette and added ten algae beads plus distilled water, this is used as a blank (control). We then placed a cuvette in an ice bath at 15°C, one at room temperature 20°C, and one in an incubator at 30°C. We then placed three lamps 25 centimeters away from each cuvette. 252 1° C C Part 2: Measuring Data Using Spectrometer and Measuring pH After five minutes, we took the cuvette and placed it in a spectrometer to measure the absorbance. We also used a pH strip to measure the pH level of the solution. We also noted the color of the solution to use in our data. After every five minutes until thirty minutes, we took each cuvette (from all three temperatures) and placed them in the spectrometer and measured the pH using a pH strip and noted the color for our qualitative and quantitative data. The results were documented and placed in a table. The first picture below depicts the cuvettes at 0 minutes, 5 minutes, and 10 minutes the second picture shows the cuvettes at 15 minutes, 20 minutes, and 25 minutes, and the last picture demonstrates the cuvettes at 30 minutes. At each increment the pH was measured for the quantitative data and the color was noted for qualitative data. Meausring the pH and noting color of solution at 0 minutes, 5 minutes, and 10 minutes. Meausring the pH and noting color of solution at 15 minutes, 20 minutes, and 25 minutes. At 30 minutes, we are showing how the pH and color of solution was obtained. Results: This experiment was only performed on time. Table 2 shows the pH values and notes the colors. At 25ºC ranged from 7.9-8.1 in the orange color spectrum. At 15°C the color became a medium/dark orange all the way to brown, and the pH ranged from 7.9-8.5, slightly higher than the 25°C. At 30°C the solution started with a medium orange at 0 minutes and became a medium purple at 30 minutes. The initial reaction rates for pH values at 25°C was 4%, at 15°C was also 4%, and at 30°C it was 80%. At 25°C the absorbance values ranged from 0.343-0.742 and in 15°C it was 0.332-0.683. The most light absorbed was in the cuvette in the 30°C, and the absorbance values ranged from 0.396-0.802. The initial reaction rate for the absorbance values at 25°C was 2.58%, at 15°C it was 1.54%, and at 30°C it was 1.4%. Absobance Values 0.9 0.8 0.7 Absorbance 0.6 0.5 0.4 0.3 0.2 0.1 0 0 5 10 15 20 25 ° C (Room Temp) Time (minutes) 15 °C (Ice) 25 30 30 ° C (Water Bath) Graph for Quantitative Value (Absorbance) Table 1: Absorbance Values Time (minutes) 0 5 10 15 20 25 30 25 ° C (Room Temp) 0.343 0.472 0.53 0.594 0.66 0.701 15 °C (Ice) 0.332 0.409 0.472 0.51 0.566 0.601 30 ° C (Water Bath) 0.396 0.466 0.549 0.632 0.702 0.78 0.742 0.683 0.802 Table 2: pH Values and Color of Solution Time (minutes) 25 ° C (Room Temp) 15 °C (Ice) 30 ° C (Water Bath) 0 7.9 (medium orange) 7.9 (medium orange) 7.9 (medium orange) 5 8.1 (dark orange) 8.1 (dark orange) 8.3 (tan) 10 8.1 (dark orange) 8.3 (tan) 8.5 (brown) 15 8.1 (dark orange) 8.3 (tan) 8.5 (brown) 20 8.1 (dark orange) 8.3 (tan) 8.7 (light purple) 25 30 8.1 (dark orange) 8.1 (dark orange) 8.5 (brown) 8.5 (brown) 8.7 (light purple) 8.9 (medium purple) Discussion: The conclusions based off of this experiment include that the solution at 30°C absorbs the most light and therefore photosynthesis is the most efficient at 30°C. Photosynthesis did occur in this experiment because there was carbon dioxide and light energy present, but cellular respiration did not occur because glucose was not present to convert into energy. The hypothesis was correct, we predicted that the solution the 30°C would absorb the most light. In the real world this could be extremely beneficial because scientists can increase the efficiency of photosynthesis so they can improve the number of crops being grown at one time, this can solve the problem of feeding millions of people who can now have access to clean crops and fresh produce (Howe et al, 2015). Michigan State University has created growth chambers where they can manipulate the amount of light, light intensity, and temperature in order to determine what combination of factors can create an environment where photosynthesis can be most efficiently used ((Howe et al, 2015). A potential source of error could have been a miscount in the number of algae beads placed in each solution, a miscount in the amount of carbon dioxide in each solution, spectrometer not being calibrated correctly, switching of the different cuvettes, labeling cuvettes wrong, the lamps not being placed exactly twenty-five centimeters away, timing is not right (measuring at seven minutes instead of five minutes), etc. If I was to design the experiment again, I would have three different spectrometers and have three people assigned to each cuvette measuring the absorbance at exactly 5, 10, 15, 20, 25, 30 minutes. I would also take more pictures, just in case if we miss a small detail, we would have something to rely on. Additional questions that I have on this topic is how do plants like seaweed and coral grow underwater with very little sunlight and varying temperatures. After further research I learned that coral can withstand temperatures from 20°C-32°C and need to live in clear water where sunlight can penetrate the water (Knowlton, 2018).