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The Effects of Fructose and Salt Water on the Rate of PhotosynthesisPhotosynthesis ExperimentRebecca MorraLongwood UniversityThe Effects of Fructose and Salt Water on the Rate of Photosynthesis: Photosynthesis ExperimentIntroductionPhotosynthesis is the process by which solar energy is converted into chemical energy that is necessary to sustain plant life (“BioCoach”). The chemical reactions of photosynthesis are summarized in the following equation (“BioCoach”).6CO2?+ 12H2O → C6H12O6 + 6H2O + 6O2 Photosynthesis occurs in the middle tissue of leaves, specifically in the chloroplasts of mesophyll cells (Raven). The chloroplast contains the thylakoid membrane, which is the internal membrane (Raven). This membrane is organized in stacks called grana (Raven). Light reactions occur in this thylakoid membrane (“Fast”). As the membrane absorbs the light from the sun, the water in the cell is separated into individual hydrogen and oxygen atoms (“Fast”). The light reactions create NADPH, ATP, and oxygen (which is released back into the atmosphere) (“Fast”). The Calvin Cycle also occurs in the chloroplast, but it occurs outside of the thylakoid membranes (“Fast”). The carbon dioxide that the plant absorbs from the atmosphere bonds with the hydrogen atoms that were from the splitting of water (“Fast”). The ATP is converted to ADP and the NADPH is reduced to NAD (“Fast”). The final product is glucose (“Fast”). Photosynthesis can be affected by many factors, including light intensity, carbon dioxide concentration, and temperature (“Photosynthesis”). Another factor that affects the rate of photosynthesis is the salinity of the water used to hydrate the plant (Murad). Because of these factors, this lab was conducted to test whether or not the addition of salt and fructose would affect photosynthetic rate. It was hypothesized that the addition of fructose to the water used to hydrate the plant would increase the rate of photosynthesis, and the addition of salt to the water would decrease the rate of photosynthesis. MethodsAn experiment was conducted to test whether or not the rate of photosynthesis would be affected by the addition of fructose or salt to the water used to hydrate the plant. Three test tubes were cleaned and labeled according to the type of water that would be put into them. Plain tap water was poured into one test tube to serve as the control.?This was used to measure what the regular rate of photosynthesis would be without the addition of compounds into the water. Plain tap water was poured into the second test tube, this time with the addition of 2g of fructose. The test tube was then shaken until the fructose was completely dissolved into the water. Plain tap water was also poured into the third test tube, but with the addition of 2g of salt. The test tube was also shaken until the salt was completely dissolved into the water. Three branches of an Elodea plant were cut into 14.5 cm pieces. A branch was then placed into each test tube, cut side up (see Figure 1). Additional water was added to each test tube to top it off. A stopper was then fitted into each test tube and the solution filled the tube to about ? of the length of the horizontal portion. The meniscus was marked on each tube to note the starting point of photosynthesis. The test tubes were then placed into a rack under a 60-watt lamp. Each test tube received the same amount and type of light, environment, and temperature. The Elodea branches were left under the light for 20 minutes to photosynthesize (see Figure 2). After 20 minutes, the level that the meniscus had risen to was recorded. A ruler was then used to measure the distance between the initial meniscus mark and the final meniscus mark using millimeters. The net photosynthesis was calculated by dividing the millimeters of movement by twenty minutes. The net photosynthesis of the salt and sugar water was then compared to the net photosynthesis of the tap water.30683203721100021272538862000Figure 1 Figure 2ResultsTube #1: Tube #1 was filled with plain tap water. The meniscus rose 12 millimeters (see Figure 3).To calculate the net photosynthesis in mm/min:????????????12 millimeters / 20 minutes = .6 millimeters/minute?Tube #2: Tube #2 was filled with tap water mixed with 2g of fructose. The meniscus rose 6 millimeters (see Figure 3). To calculate the net photosynthesis in mm/min:????????????6 millimeters/ 20 minutes = .3 millimeters/minute?Tube #3: Tube #3 was filled with tap water mixed with 2g of salt. The meniscus remained at the initial marking (see Figure 3). To calculate the net photosynthesis in mm/min:????????????0 millimeters/ 20 minutes = 0 millimeters/minuteThe Elodea plant that was put into tap water had a net photosynthesis double of what the net photosynthesis of sugar water was. The Elodea plant had the best photosynthesis rate in the regular tap water. The addition of salt to the water appeared to have no benefit, and actually inhibited the rate of photosynthesis.center26416000Figure 3center1524000Figure 43771901016000Figure 5DiscussionThe results of the experiment both supported and contradicted the hypothesis. The rate of photosynthesis was inhibited by the addition of salt to the water, but the rate was not increased due to the addition of fructose. In fact, the fructose also inhibited the rate of photosynthesis. Perhaps this is due to osmosis. Osmosis is the process of water moving across a membrane toward a higher solute concentration (Raven). Osmotic concentration is the concentration of all solutes in a solution (Raven). If there are unequal osmotic concentrations between two different solutions, the solution with the higher concentration is considered hypertonic (hyperosmotic), and the solution with the lower concentration is hypotonic (hypoosmotic) (Raven). Solutions are isotonic (isosmotic) when they have equal osmotic concentrations (Raven). When a cell is in a hypotonic solution, the cell swells because the solution diffuses through the cell wall and enlarges the body of the cell (Raven). The pressure from inside the cell causes the entire cell to bulge (Raven). When a cell is in a hypertonic solution, however, water diffuses out of the cell into the surrounding solutions, causing the cell to or shrink (Raven). The control in this experiment (the tap water) was isotonic because the rate of photosynthesis was not inhibited or increased, and the cells therefore remained the same size. Perhaps the salt water in this experiment inhibited the photosynthetic rate because it was a hypertonic solution, causing the plant cell to shrink from the cell wall and therefore decrease the meniscus’s movement (the rate of photosynthesis) (Raven). Perhaps the fructose water also inhibited the photosynthetic rate because it was a hypertonic solution as well, but not as hypertonic as the salt solution (since the movement of the meniscus was inhibited, but not as much as the salt solution). Though the hypothesis of this experiment was not proven completely correct, this experiment did lead to some interesting findings. It would be intriguing to apply these discoveries to the outside world and determine how environmental factors such as drought would affect photosynthetic rate. It would also be interesting to discover how increasing the salinity in water could affect not only the plants themselves, but also the surrounding environment. Works Cited"BioCoach Activity."?Pearson. N.p., n.d. Web. 07 Oct. 2015.Murad, A. M., Molinari, H. C., Magalh?es, B. S., Franco, A. C., Takahashi, F. C., de Oliveira-, N. G., & ... Quirino, B. F. (2014). Physiological and Proteomic Analyses of Saccharum spp. Grown under Salt Stress.?Plos ONE,?9(6), 1. doi:10.1371/journal.pone.0098463"Photosynthesis and Limiting Factors."?Structure and Functioning of Seminatural Meadows Developments in Agricultural and Managed Forest Ecology?(1993): 193-210. Web. 7 Oct. 2015."Photosynthesis Fast and Simple."?YouTube. YouTube, n.d. Web. 07 Oct. 2015.Raven, Peter H., and George B. Johnson.?Biology. Boston: McGraw-Hill, 2002. Print. ................
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