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Photosynthesis lab

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by

Megan McCurley

on 7 January 2013

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Transcript of Photosynthesis lab

Background Step 1 Step 4 Data Methods Materials: The equation for photosynthesis:
2H 0 + CO + light = CH 0 + 0 +H 0
In Spinach leaves there is a cavity which holds the gases released and used during photosynthesis, by removing these gases the leaf will sink in water. It only ascends when photosynthesis has occurred and refilled the cavity with oxygen. However during this time Cellular respiration also occurs using some of the oxygen. So the rate of accent for the spinach leaf is the net rate of photosynthesis. Photosynthesis Prepare 4 Solutions of 300ml H2O with 0.2%, 0.4%, 0.8%, and 1.6% concentration of bicarbonate and one without. These will provide CO2 for the spinach during the photosynthesis process. Cut out 10 discs, from the spinach leaf, for each cup. If the spinach is put in different concentrations of Bicarbonate, which acts as the CO2 for the experiment, then the rate of photosynthesis will increase as the concentration increases until it hits optimum concentration, because the more CO2 available the more can be incorporated into the carbohydrates in the light-independent reaction and the faster photosynthesis can occur. 2 + + = CHO2 + + In order to find the effect of an environmental factor the reactants of the photosynthesis equation must be altered to observe the products, or the effects. In this experiment CO2 Concentrations will be altered, this will alter the amount that can be incorporated into the carbohydrates and take part in the light-independent reaction, which will alter the rate of photosynthesis. Question:
What is the effect of different CO2 concentrations on the floating disks rate of photosynthesis? Spinach
Hole punch
5 clear cups
Dish Detergent
Bicarbonate
Syringes
Measuring tools (tsp and 300ml) Overview: The Concentration of CO2 is changed by adding different amounts of bicarbonate(independent variable) to the H2O, changing the CO2 available and altering the rate of photosynthesis causing the disk to ascend at a different rate(dependent variable). The temperature was held at a constant 18 C, the pressure was held at 0 due to the open cup, and the light source remained at 60W. The beakers were held at a distance of 30cm from the light source. THe lab includes a cup without any added bicarbonate to compare the results with, it is the control. Hypothesis Step 2 Pour the Solutions into individual, labeled cups. Step 3 Add one drop of diluted soap in each cup, this will allow the leaf's hydrophobic surface to absorb the solution. Step 5 Use the syringe to vacuum out the gases from the spongy mesophyll tissue and replace it with the bicarbonate. Place ten disks in the barrel and push in the plunger, suck in the chosen solution of bicarbontate, remove the air from the syringe and then blocking the opening pull the plunger and hold for ten seconds then release and disks should sink. Step 6 Empty solutions and discs into respective cups, place under light source and start the timer. Step 7 Record number of floating disks every minute. # of disks floating each min at different Concentration of CO2 1
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10 Math: Concentration Calculations 0.2% = .002
.002 x 300 =.6ml
.6ml = 1/8 tsp 0.4% = .004
.004 x 300 =1.2ml
1.2ml = 1/4 tsp 0.8% = .008
.008 x 300 =2.4
2.4ml = 1/2 tsp 1.6% = .016
.016 x 300ml =2.4ml
2.4ml = 1 tsp Conclusion Graph 3 Graph 2 Graph 1 By removing the air in the spinach’s mesophyll tissue and replacing it with a solution the plant must photosynthesize before it floats, thereby allowing the rate at which the spinach leaf photosynthesizes to be calculated. In order for the photosynthesis to occur in the water there had to be CO2 formerly retrieved from the air, so bicarbonate was added to provide this. This lab speculated that photosynthesis in spinach had an optimum CO2 concentration. This was tested by placing spinach in different CO2 concentrations as well as in a solution without Bicarbonate, and one of .2%, .4%, .8%, and 1.6%. The data supported this hypothesis. The rate of photosynthesis increased as the CO2 concentration increased, this is shown in graph 3; without the CO2 the spinach disks median was 31 minutes to rise a very slow rate of photosynthesis in comparison to the solution with 0.2% concentration of CO2 which ascended in 14 minutes, almost half the time it took the disks in the solution without CO2. The 0.4% concentration took even less time, filling up the spinach’s cavity through photosynthesis in 4.5 minutes, the rate of photosynthesis further increased at 0.8% concentration, when it took only two minutes, however at the 1.6% concentration the rate of photosynthesis decreased, and it took 2.5 minutes. These results show that 0.8% was the optimum concentration out of the tested concentration as that was when the rate of photosynthesis was the fastest, which supports the hypothesis that there is an optimum CO2 concentration for the photosynthesis of spinach. The Data collected would have been more conclusive if there were more concentrations after the .8% to ensure that it was indeed the optimum CO2 concentration, but also that the decrease in the rate of photosynthesis in the 1.6% solution wasn’t an anomaly. The data might have also been more conclusive had there been absolutely no ambient light. Corrections Expansions Expansions on this lab could explore more possible environmental factors such as light intensities, light wavelengths, temperature, soap dilutions, disk sizes, and pH, all affecting the reactants of photosynthesis. Prezi by: Megan McCurley Special thanks to my
lovely friend Olivia Spaid who allowed me to utilize
her kitchen and also
took the pictures for me. She may or may not kill me for adding this picture, if she does just remember I was a martyr for science.
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