Transpiration Lab Report
Introduction & Hypothesis
Transpiration is the loss of water by evaporation in terrestrialplants, especially through the stomata(accompanied by a corresponding water uptake from the roots); a process in which the water vapor escapes through the plant via its stomatainto its externalenvironment. According to biology-online.org, transpiration is part of the water cycle and can also be referred to as sweating or hyperhydrosis. Transpiration occurs mainly in the leaf where there are openings called the stomata. Around the border of each stoma, there are guard cells that open and close to allow the passage of CO2 and O2 for photosynthesis. The rate at which a plant transpires depends on the degree of the stomatal opening. In other words, if the stomatal opening is large, the rate of transpiration will be higher. In addition to the opening of the stomata, there are several other factors that also affect the rate of transpiration. These include the number of leaves on the plant, the number of stomata, presence of a plant cuticle, light supply, temperature, humidity and water supply. To test the effect of pollution on plants, we covered four Coleus plants with carbon powder. We hypothesized that applying a thin layer of carbon powder to each leaf will prevent water from leaving the stoma and thus reflect a decrease in water consumption.
Materials & Methods
Four Coleus clippings were obtained with care taken to ensure that the size of each clipping and the amount of leaves were relatively the same. Each plant was inserted in a 50ml graduated cylinder which was then filled with dH2O to the 50ml line. Para film was used to seal the top of the graduated cylinder around the plant stem to prevent evaporation. Carbon powder was gently added to the leaves of each plant. Two additional Coleus clippings were also placed in separate graduated cylinders to serve as the control for the experiment.
Results
Transpiration is the loss of water by evaporation in terrestrialplants, especially through the stomata(accompanied by a corresponding water uptake from the roots); a process in which the water vapor escapes through the plant via its stomatainto its externalenvironment. According to biology-online.org, transpiration is part of the water cycle and can also be referred to as sweating or hyperhydrosis. Transpiration occurs mainly in the leaf where there are openings called the stomata. Around the border of each stoma, there are guard cells that open and close to allow the passage of CO2 and O2 for photosynthesis. The rate at which a plant transpires depends on the degree of the stomatal opening. In other words, if the stomatal opening is large, the rate of transpiration will be higher. In addition to the opening of the stomata, there are several other factors that also affect the rate of transpiration. These include the number of leaves on the plant, the number of stomata, presence of a plant cuticle, light supply, temperature, humidity and water supply. To test the effect of pollution on plants, we covered four Coleus plants with carbon powder. We hypothesized that applying a thin layer of carbon powder to each leaf will prevent water from leaving the stoma and thus reflect a decrease in water consumption.
Materials & Methods
Four Coleus clippings were obtained with care taken to ensure that the size of each clipping and the amount of leaves were relatively the same. Each plant was inserted in a 50ml graduated cylinder which was then filled with dH2O to the 50ml line. Para film was used to seal the top of the graduated cylinder around the plant stem to prevent evaporation. Carbon powder was gently added to the leaves of each plant. Two additional Coleus clippings were also placed in separate graduated cylinders to serve as the control for the experiment.
Results
We found that the polluted plants used more water than the control plants.
Discussion & Analysis
Water consumption is a good indicator of plant transpiration. Generally, a plant with a higher rate of transpiration will consume more water than a plant that is not transpiring much. The data obtained in this experiment does not support our original hypothesis that polluted plants would have a decreased rate of transpiration. Transpiration can be compared to sweating; therefore, the polluted plants are transpiring at a greater rate in an effort to compensate for the less than ideal conditions. Repeating the experiment with more Coleus clippings will help provide more data and further test the hypothesis.
References
Biology-Online. Answers to all your Biology Questions. Retrieved May 4, 2012. http://www.biology-online.org/dictionary/Transpiration
Stoma - eNotes.com Reference. (n.d.). eNotes - Literature Study Guides, Lesson Plans, and More.. Retrieved May 6, 2012, from
http://www.enotes.com/topic/Stoma
Discussion & Analysis
Water consumption is a good indicator of plant transpiration. Generally, a plant with a higher rate of transpiration will consume more water than a plant that is not transpiring much. The data obtained in this experiment does not support our original hypothesis that polluted plants would have a decreased rate of transpiration. Transpiration can be compared to sweating; therefore, the polluted plants are transpiring at a greater rate in an effort to compensate for the less than ideal conditions. Repeating the experiment with more Coleus clippings will help provide more data and further test the hypothesis.
References
Biology-Online. Answers to all your Biology Questions. Retrieved May 4, 2012. http://www.biology-online.org/dictionary/Transpiration
Stoma - eNotes.com Reference. (n.d.). eNotes - Literature Study Guides, Lesson Plans, and More.. Retrieved May 6, 2012, from
http://www.enotes.com/topic/Stoma