Research Question:
How does the concentration of carbon dioxide affect the rate of photosynthesis in spinach leafs?
Introduction:
Spinach is a eukaryotic photoautotroph, contains plant cells and appears to be green, this suggests that it contains chlorophyll given that chlorophyll reflects green light (Mazia & Tyler, 1963). Photoautotrophs are organisms that use photosynthesis to sustain themselves with nutrients (Cavendish, 2004). In plant cells photosynthesis takes place in the chloroplast, it is a process where photoautotrophs use pigments in order to capture energy from visible light referred to as photons, these autotrophs also need carbon dioxide and water in order to produce glucose and oxygen (Cavendish, 2003).
The general formula of photosynthesis is:
6CO2+ 6H20 + photons → C6H12O6 + 6O2 + ATP (Campbell, 2006).
In chloroplasts photosynthesis occurs in the thylakoid as a light dependent reaction and in the stroma as a light independent reaction (Clegg, 2007). In this experiment by using light we could observe photolysis, which is a light dependent reaction (Clegg, 2007). In photolysis water is broken down into oxygen and hydrogen due to the photons absorbed by chlorophyll in the thylakoid.
(Campbell, 2006) Oxygen is a waste product so in the experiment the oxygen produced was measured by seeing how quick the plant leaf would float up to the surface of the water. (Andersen, 2011) The hydrogen is not a waste product given that it is taken in by a hydrogen acceptor, which causes ATP to be formed through ATP synthase, this action occurs in photophosphorylation which is an action that takes place between photolysis and the calvin cycle. (Clegg, 2007) The calvin cycle is the light independent reaction in photosynthesis and needs the energy from ATP, hydrogen from the photolysis reaction and carbon dioxide to form glucose which is a very useful substance for the organism. (Clegg, 2007)
The significance of the research is that in photosynthesis carbon dioxide is taken in producing oxygen, which is extremely important for all organisms in order to live and function properly. (McGinley, 2010) In photosynthesis glucose is also formed and is vitally needed as an energy source in the photosynthetic organism itself and is therefor the organisms nutrition. (McGinley, 2010)
Aim:
The aim of this lab is to find out how different carbon dioxide concentrations affect the rate of photosynthesis in spinach leafs.
Hypothesis
As the concentration of carbon dioxide is increased, the rate of photosynthesis is going to increase until it reaches a certain point from which the rate of photosynthesis will be constant.
Variables
Independent Variable
Concentration of carbon dioxide
Dependent Variable
Rate of photosynthesis in spinach leafs
Controlled Variable
-Light intensity
-Temperature of the carbon dioxide water solution
-pH of the carbon dioxide water solution
-Concentrations of carbon dioxide in distilled water (0%, 1%, 2%, 2% and 4%) -Volume of distilled water
Control Group:
Test trial using only distilled water without any carbon dioxide
Materials
•200 ml Distilled Water per beaker
•2 Beakers (250ml ±25)
•Baking Soda (20g ±0.1)
•5 Spinach Leafs
•Hole punch
•2 Syringes (20±1.0ml)
•Timer (±0.1s)
•Desk Lamp
•2 Little Bowls (flat bottom, 100 ml)
•pH paper (±1pH)
Pre-test
Method
1.Measure the temperature of the water.
2.Mix 2 g baking soda with 200 ml distilled water making carbon dioxide water solution. 3.Measure the pH.
4.Use the hole punch to punch out 4 pieces of the spinach leaf, make sure you punch out pieces between the veins. 5.Place the spinach pieces in the syringe.
6.Press all the air out of the syringe.
7.Suck in the carbon dioxide water solution with the syringe 8.In order to push out all the air out of the leafs and replace it with water do the following steps: Close the top of the syringe with your finger.
Pull on the bottom of the syringe while shaking the syringe to keep the leafs in the liquid. Push the bottom of the syringe up.
1.Place the leafs in the beaker filled with the carbon dioxide water solution 2.Fill the little bowl with water and place it on top of the beaker containing the carbon dioxide water solution with the leafs in it.
3.Place the desk lamp over the beaker with the bowl on top of it and turn it on. 4.Measure the time until the leafs float up to the top of the carbon dioxide water solution. 5.Repeat the same process 5 times using 0 g, 4 g, 6 g, 8 g and 5g of the baking soda.
Data Collection
Table 1: The effect of different concentrations of carbon dioxide on the rate of photosynthesis CO2 Concentration
(%) ± 0.5pH ±1Temperature (°C) ±0.1Rate of Reaction — Time for leafs to reach the water surface (minutes ±1 second)
Trial 1 Trial 2Trial 3Trial 4
0% (0g ±1)617.60.000.000.000.00
1% (2g ±1)617.68.539.029.0211.02
2% (4g ±1)717.68.568.589.019.32
3% (6g ±1)817.68.068.338.339.47
4% (8g ±1)817.62.022.053.203.42
Observations:
CO2 Concentration 0%
The pH value is 6 and the temperature is at 17.6 °C.
Nothing happens to the leafs or the water, no matter how long you wait.
CO2 Concentration 1%
The pH value is 6 and the temperature is at 17.6 °C.
After some minutes parts of the baking soda are on the ground of the beaker, not dissolved anymore. Tiny bubbles form around the leafs.
Tiny bubbles float up to the water surface.
After 8.5 minutes some leafs start to lift up and then start raising slowly. It takes about 5 seconds for the leaf to reach the water surface after it starts raising.
CO2 Concentration 2%
The pH value is 7 and the temperature is at 17.6 °C.
After some minutes parts of the baking soda are on the ground of the beaker, not dissolved anymore. Tiny bubbles form around the leafs.
Tiny bubbles float up to the water surface.
After 7.5 minutes some leafs start to lift up and then start raising slowly after a certain amount of time. The time it takes to start raising after it lifts up is between 5 seconds and 2 minutes depending on the trial. It takes about 4 seconds for the leaf to reach the water surface after it starts raising.
CO2 Concentration 3%
The pH value is 8 and the temperature is at 17.6 °C.
After some minutes parts of the baking soda are on the ground of the beaker, not dissolved anymore. Tiny bubbles form around the leafs.
Tiny bubbles float up to the water surface.
After 7.5 minutes some leafs start to lift up and then start to raise after some seconds. It takes about 4 seconds for the leaf to reach the water surface after it starts raising.
CO2 Concentration 4%
The pH value is 8 and the temperature is at 17.6 °C.
After some minutes parts of the baking soda are on the ground of the beaker, not dissolved anymore. Tiny bubbles form around the leafs.
Tiny bubbles float up to the water surface.
After 2 minutes some leafs start to lift up and then start raising immediately. It takes about 2 seconds for the leaf to reach the water surface after it starts rising.
Work cited:
Andersen. (2011 October 13th ). Photosynthesis walkthrough. http://www.youtube.com/watch?v=ZnY9_wMZZWI
Campbell, Neil A. (2006). Biology: concepts & connections. Custom ed. San Francisco, Ca.: Pearson Custom Publishing. p. 121
Clegg, C. J. (2007). Biology For the IB diploma: Photosynthesis. London:
Hodder Murray. p. 288-292
McGinley, Mark. (2010) Photosynthesis. The Enclopedia of Earth. http://www.eoearth.org/article/Photosynthesis
Marshall Cavendish. (2003). How It Works: Science and Technology (3rd ed., Vol. 12). New York: Marshall Cavendish. Retrieved from http://www.questiaschool.com
Marshall Cavendish. (2004). Encyclopedia of Life Sciences (2nd ed., Vol. 8). Tarrytown, NY: Marshall Cavendish. Retrieved from http://www.questiaschool.com
Mazia, D., & Tyler, A. (1963). General Physiology of Cell Specialization. New York: McGraw-Hill. Retrieved from http://www.questiaschool.com
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