Photosynthesis Lab Report
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Name: -------------------------------------------------
Biology 104
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Lab Section: 14
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TA: Victoria Prescott
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Date: 9/13/2012
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The Effects of Light Intensity and NaHCO3 concentrations on the Rate of Photosynthesis
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Definitions of terms:
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The experiment conducted in class was to determine …show more content…
whether plants photosynthesize fastest under a room light or light from a 120 watt light bulb. This experiment was conducted because plants are the basis of the food chain and the key to life since they are able to convert the energy found in light waves into chemical energy that can be used by other organisms. The following terms were used in this experiment
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1- Photosynthesis: Photosynthesis is the process of converting light energy to chemical energy and storing it in the bonds of sugar.
This process occurs in plants and some algae. Plants need only light energy, CO2, and H2O to make sugar. The process of photosynthesis takes place in the chloroplasts, specifically using chlorophyll, the green pigment involved in photosynthesis.
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http://biology.clc.uc.edu/courses/bio104/photosyn.htm
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2- Chloroplasts: are organelles found in plant cells and other eukaryotic organisms that conduct photosynthesis. Chloroplasts capture light energy, store it in the energy storage molecules ATP and NADPH and use it in the process called photosynthesis to make organic molecules and free oxygen from carbon dioxide and water.
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http://en.wikipedia.org/wiki/Chloroplast …show more content…
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4- stoma, also called Stoma, plural Stomata, or Stomas, any of the microscopic openings or pores in the epidermis of leaves and young stems. Stomates are generally more numerous on the underside of leaves. They provide for the exchange of gases between the outside air and the branched system of interconnecting air canals within the leaf. A stomate opens and closes in response to the internal pressure of two sausage-shaped guard cells that surround it. The inner wall of a guard cell is thicker than the outer wall.
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http://www.britannica.com/EBchecked/topic/567123/stomate
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Hypothesis: Purpose of this experiment is to determine if the light a spinach plant is exposed to affects the rate of its photosynthesis. Hypothesis 1: I believe that the spinach leaves that are only exposed to room light will have a slower rate of photosynthesis, and the spinach plants that are exposed to incandescent light will photosynthesize faster. Hypothesis 2: I believe that an increase in the bicarbonate concentrations increases the rate at which CO2 is incorporated into carbohydrate in the light-independent reaction, and so the rate of photosynthesis generally increases until it’s limited by another factor
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Materials and methods:
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Materials: Bicarbonate, Vacuum (Water aspirator), Large beaker, Spinach Leaves, Drinking straw (Hole puncher), Timer, Lamp (light source), and 3 Petri dishes. There were 3 types of variables involved in the experiment
Independent Variable: The light a plant is exposed to during photosynthesis (room light or light from a 120 watt lamp).
Dependant Variable: The rate of photosynthesis of a plant exposed solely to either room or lamp light. Controlled Variables: Amount of light the plant receives, the intensity of the light, type of light bulb, the amount of time the plant is exposed to one type of light, the type of plant, health of plant, age of plant, amount of oxygen the plants are exposed to, amount of carbon dioxide the plants are exposed to, amount of water the plant receives, amount of water the leaf disks are soaked in, amount of bicarbonate in the water solution, the intensity of the vacuum created.
Method: First, we stack many spinach leaves, and with the straw, we punch 10-15 uniform leaf disks for each Petri dish. After that we prepare 100 ml of bicarbonate solution in the water aspirator. Once the container is ready, we put the leaf disks into it to infiltrate them with the sodium bicarbonate solution. We seal the container and immediately connect it to the faucet, we turn the water on (both hot and cold) and let it run for about a minute. After that we turn the water off and unseal the container. With doing so, the air spaces in the leaf disks are infiltrated causing the disks to sink. At this point, we are ready to transfer the leaf disks into the Petri dishes for the experiment.
We fell the three Petri dishes with ½ inch of the 0.05% solution and transform 10-15 leaf disks into each. Then we place the first Petri dish which is covered under the light source and we put the beaker on top of it, the beaker will be filled with 1L of cold water to act as a heat filter and then we start the timer. At the end of each 10 min, we observe and record the number of floating disks. Continue observing the leaf disks until the end of the 40min. As of the second Petri dish, we cover the dish and keep it at the room light and watch it and keep recording the floating disk every 10 min. Finally the third Petri dish, will not be exposed to light at all, so it will be covered with aluminum foil and will be kept for the whole 40 min. in order to see how many disk floated in that period.
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Results: For this experiment, we measured how long it takes for spinach plants to photosynthesize under a room light and also a lamb (light source). We timed how many leaf disks rose in 10/20/30/40 minute duration under a room light, a lamp (light source) and in the dark as well. The results came out positive supporting the hypothesis as shown on the results section of the attached Raw Data Sheet. We then calculated the average amount of time it took the spinach leaves to photosynthesize under each amount of light, graphed these averages in order to show our results. The Y axis on our graph shows the number of floating leaf disks and the X axis represents the average time it took for the leaf disks to rise. (Duration was forty minutes.) According to our data, the leaf disks exposed to lamp light rose faster, as shown in the graph below.
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Discussion: I think that the concentration of Bicarbonate could have affected our results.
While the oxygen is removed from all leaf disks we picked, there was some of them might have been more thoroughly infiltrated than others. For example, when we picked the disks, some of them sank immediately while others took a while. Also possible that when we distributed the leaf disks, we may have put some of the leaf disks that were not infiltrated under the room light. Because they already had some oxygen in them, they could have been more likely to float quicker. Additionally, there are other factors could have influenced our results detrimentally, as well. In addition, although this method is an easy way to measure the rate of photosynthesis, it is not the most accurate. Cellular respiration, a process that uses the oxygen produced during light reactions, could have occurred. If the oxygen produced by the leaf disks was used during cellular respiration, the leaf disks might not have risen even though they did photosynthesize. I think to improve this experiment next time; we have to keep all these factors in mind, also make sure to pick the leaves off the spinach plant ourselves, or at least ascertain the health and age of both the leaves we use and the plant they are from, not to mentioned doing the vacuuming process as well. In general, for future experiments, I would allot more time and have more materials and do the whole process. Conducting such an experiment inspired me
to conduct similar experiments, testing the rate of photosynthesis under even more conditions. I would want to test and see whether photosynthesis occurs faster when plants are exposed to the sun light (outdoor). Overall, this experiment was a good learning experience. It helped me learn how to put together an experiment and pay attention to even the minute details that can significantly alter one’s results.
Name: -------------------------------------------------
Biology 104
-------------------------------------------------
Lab Section: 14
-------------------------------------------------
TA: Victoria Prescott
-------------------------------------------------
Date: 9/13/2012
-------------------------------------------------
-------------------------------------------------
The Effects of Light Intensity and NaHCO3 concentrations on the Rate of Photosynthesis
-------------------------------------------------
-------------------------------------------------
Definitions of terms:
-------------------------------------------------
The experiment conducted in class was to determine …show more content…
whether plants photosynthesize fastest under a room light or light from a 120 watt light bulb. This experiment was conducted because plants are the basis of the food chain and the key to life since they are able to convert the energy found in light waves into chemical energy that can be used by other organisms. The following terms were used in this experiment
-------------------------------------------------
1- Photosynthesis: Photosynthesis is the process of converting light energy to chemical energy and storing it in the bonds of sugar.
This process occurs in plants and some algae. Plants need only light energy, CO2, and H2O to make sugar. The process of photosynthesis takes place in the chloroplasts, specifically using chlorophyll, the green pigment involved in photosynthesis.
-------------------------------------------------
http://biology.clc.uc.edu/courses/bio104/photosyn.htm
-------------------------------------------------
2- Chloroplasts: are organelles found in plant cells and other eukaryotic organisms that conduct photosynthesis. Chloroplasts capture light energy, store it in the energy storage molecules ATP and NADPH and use it in the process called photosynthesis to make organic molecules and free oxygen from carbon dioxide and water.
-------------------------------------------------
http://en.wikipedia.org/wiki/Chloroplast …show more content…
-------------------------------------------------
4- stoma, also called Stoma, plural Stomata, or Stomas, any of the microscopic openings or pores in the epidermis of leaves and young stems. Stomates are generally more numerous on the underside of leaves. They provide for the exchange of gases between the outside air and the branched system of interconnecting air canals within the leaf. A stomate opens and closes in response to the internal pressure of two sausage-shaped guard cells that surround it. The inner wall of a guard cell is thicker than the outer wall.
-------------------------------------------------
http://www.britannica.com/EBchecked/topic/567123/stomate
-------------------------------------------------
-------------------------------------------------
Hypothesis: Purpose of this experiment is to determine if the light a spinach plant is exposed to affects the rate of its photosynthesis. Hypothesis 1: I believe that the spinach leaves that are only exposed to room light will have a slower rate of photosynthesis, and the spinach plants that are exposed to incandescent light will photosynthesize faster. Hypothesis 2: I believe that an increase in the bicarbonate concentrations increases the rate at which CO2 is incorporated into carbohydrate in the light-independent reaction, and so the rate of photosynthesis generally increases until it’s limited by another factor
-------------------------------------------------
Materials and methods:
-------------------------------------------------
Materials: Bicarbonate, Vacuum (Water aspirator), Large beaker, Spinach Leaves, Drinking straw (Hole puncher), Timer, Lamp (light source), and 3 Petri dishes. There were 3 types of variables involved in the experiment
Independent Variable: The light a plant is exposed to during photosynthesis (room light or light from a 120 watt lamp).
Dependant Variable: The rate of photosynthesis of a plant exposed solely to either room or lamp light. Controlled Variables: Amount of light the plant receives, the intensity of the light, type of light bulb, the amount of time the plant is exposed to one type of light, the type of plant, health of plant, age of plant, amount of oxygen the plants are exposed to, amount of carbon dioxide the plants are exposed to, amount of water the plant receives, amount of water the leaf disks are soaked in, amount of bicarbonate in the water solution, the intensity of the vacuum created.
Method: First, we stack many spinach leaves, and with the straw, we punch 10-15 uniform leaf disks for each Petri dish. After that we prepare 100 ml of bicarbonate solution in the water aspirator. Once the container is ready, we put the leaf disks into it to infiltrate them with the sodium bicarbonate solution. We seal the container and immediately connect it to the faucet, we turn the water on (both hot and cold) and let it run for about a minute. After that we turn the water off and unseal the container. With doing so, the air spaces in the leaf disks are infiltrated causing the disks to sink. At this point, we are ready to transfer the leaf disks into the Petri dishes for the experiment.
We fell the three Petri dishes with ½ inch of the 0.05% solution and transform 10-15 leaf disks into each. Then we place the first Petri dish which is covered under the light source and we put the beaker on top of it, the beaker will be filled with 1L of cold water to act as a heat filter and then we start the timer. At the end of each 10 min, we observe and record the number of floating disks. Continue observing the leaf disks until the end of the 40min. As of the second Petri dish, we cover the dish and keep it at the room light and watch it and keep recording the floating disk every 10 min. Finally the third Petri dish, will not be exposed to light at all, so it will be covered with aluminum foil and will be kept for the whole 40 min. in order to see how many disk floated in that period.
-------------------------------------------------
Results: For this experiment, we measured how long it takes for spinach plants to photosynthesize under a room light and also a lamb (light source). We timed how many leaf disks rose in 10/20/30/40 minute duration under a room light, a lamp (light source) and in the dark as well. The results came out positive supporting the hypothesis as shown on the results section of the attached Raw Data Sheet. We then calculated the average amount of time it took the spinach leaves to photosynthesize under each amount of light, graphed these averages in order to show our results. The Y axis on our graph shows the number of floating leaf disks and the X axis represents the average time it took for the leaf disks to rise. (Duration was forty minutes.) According to our data, the leaf disks exposed to lamp light rose faster, as shown in the graph below.
-------------------------------------------------
-------------------------------------------------
-------------------------------------------------
-------------------------------------------------
Discussion: I think that the concentration of Bicarbonate could have affected our results.
While the oxygen is removed from all leaf disks we picked, there was some of them might have been more thoroughly infiltrated than others. For example, when we picked the disks, some of them sank immediately while others took a while. Also possible that when we distributed the leaf disks, we may have put some of the leaf disks that were not infiltrated under the room light. Because they already had some oxygen in them, they could have been more likely to float quicker. Additionally, there are other factors could have influenced our results detrimentally, as well. In addition, although this method is an easy way to measure the rate of photosynthesis, it is not the most accurate. Cellular respiration, a process that uses the oxygen produced during light reactions, could have occurred. If the oxygen produced by the leaf disks was used during cellular respiration, the leaf disks might not have risen even though they did photosynthesize. I think to improve this experiment next time; we have to keep all these factors in mind, also make sure to pick the leaves off the spinach plant ourselves, or at least ascertain the health and age of both the leaves we use and the plant they are from, not to mentioned doing the vacuuming process as well. In general, for future experiments, I would allot more time and have more materials and do the whole process. Conducting such an experiment inspired me
to conduct similar experiments, testing the rate of photosynthesis under even more conditions. I would want to test and see whether photosynthesis occurs faster when plants are exposed to the sun light (outdoor). Overall, this experiment was a good learning experience. It helped me learn how to put together an experiment and pay attention to even the minute details that can significantly alter one’s results.