| Explore | Based on experiences outside of school, we know that plants need water to survive. We have discovered in class that plants undergo both cellular respiration and photosynthesis and have a net primary productivity of chemical energy, which is expressed through amounts of growth through the use of glucose. One main question we have is if there is a salinity that plants perform photosynthesis at optimally. |
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| Research Question | We want to test the salinity that plants complete photosynthesis at most optimally. We came up with this question when we remembered how cells could change in shape with the addition of isotonic, hypertonic, and hypotonic solutions. This fits into the topic of what conditions spurt photosynthesis, as we used different amounts of CO2 to determine the conditions in which spinach leaves completed photosynthesis at. |
| Predictions | Some possible outcomes would be that the plants would perform better in a hypotonic solution, as the turgid structure of plant cells demands more osmotic pressure to function. Thus, with a hypotonic solution, plants would complete both cellular respiration and photosynthesis optimally in a hypotonic solution. |
| Experimental Design | Our plan would be to have 200 ml of water in 5 beakers with 4 of those beakers of water containing its own molarity of NaCl. The molarities would be 0.25M NaCl (hypotonic), 0.5M NaCl (isotonic), 0.75M NaCl (hypertonic), and 1.0M NaCl (hypertonic). Each beaker's water will also have CO2 added to it by way of one's breath through a straw for exactly 10 seconds of constant breathing in each beaker. The independent variable for this lab would be the NaCl molarity, while the dependent variable would be the rate of photosynthesis. The controls would be the beakers used, the plant leaf used, the amount of CO2 added, the source of distilled water, the straws used, and the size of the leaf disks. the control group of leaf disks would be the beaker with no NaCl added. We will record our data by measuring the amount of leaf disks that rise with specific increments. We would measure the time it takes for 3 disks to rise, 5 disks to rise, and 9 to 10 disks to rise. If a certain amount is never met, that increment will be marked as "did not occur." |
| Conclusion | One claim we can make from our experiment is that the leaf disks will rise fastest in the control as plants require a hypotonic solution to remain in a turgid form, where cellular respiration and CO2 are done at an optimal rate. The data will be skewed based off of the osmotic pressure seen in each solution. The data we collected will support our claim, as we believe that hypotonic solutions offer the best environment for plant cells. One future experiment that would expand these results we have would be to measure the pH instead of the salinity, as we could also measure the effects of basic solutions on photosynthesis in plants. |
| Investigation Theme | POS |
| Grade Level | High School Students (Grades 9,10,11,12) |
| School Name | Mountain View High School |
| Session | Fall 2017 |