Basically, we were given 9 different plants (English Ivy, Devil's Ivy, Arrowhead, Coleus, Weeping Fig, Geranium, Rubber Plant, Zebra Plant, and Dieffenbachia) and asked to measure (sorta) the amount of water that was transpired from each plant. We were then given three appliances (a fan, heater, and lamp) that replicate environmental factors (wind, temperature, and light), and were asked to measure the new amount of water transpired under each new condition.
Below is the data table taken from our (the internet's) lab.
Plant
|
Water transpired (mL)
|
With the fan
(mL)
|
With the heater *
(mL)
|
With the lamp
(mL)
|
||
English Ivy
|
1.8
|
5.1
|
3.2
|
2.1
|
||
Arrowhead
|
3.6
|
7.5
|
6.6
|
4.0
|
||
Coleus
|
0.9
|
6.0
|
3.9
|
3.0
|
||
Devil’s Ivy
|
2.9
|
4.9
|
4.1
|
3.0
|
||
Weeping fig
|
3.3
|
6.1
|
4.9
|
2.5
|
||
Geranium
|
1.2
|
4.7
|
5.8
|
2.4
|
||
Rubber Plant
|
4.9
|
8.4
|
6.8
|
4.3
|
||
Zebra Plant
|
4.2
|
7.6
|
6.1
|
3.2
|
||
Dieffenbachia
|
4.1
|
7.7
|
6.0
|
3.9
|
||
*All measurements were taken at 21 degrees Celsius, except for with the heater, where the temperature was 27 degrees Celsius.
From the data we can see a constant increase in transpiration with the fan and heater. This will be explained later. However, we see a difference in the change in transpiration when looking at the effect of light on the plants.
Analysis Questions
1. Describe the process of transpiration in vascular plants.
a. A vascular plant can be defined as a land plant with xylem, for transporting water, and phloem, which transports nutrients and sugars, like sucrose, throughout the plant. In vascular plants, water is absorbed through the roots and up the stem through capillary action, which involved 3 parts: Osmosis, cohesion, and adhesion. First, because there is more water located in the soil then in the roots, the water moves from the higher water potential soil into the lower water potential roots. Here the water is attracted to the stem through adhesion, and then attracts to each other through cohesion and hydrogen bonds. Because carbon dioxide is needed for photosynthesis, a plant will open its stomata, tiny pores that open and close located on the bottom of the leaves of plants, and exchange oxygen for carbon dioxide. Because the pores are open for a long time, the water located in the plant begins to evaporate. This is the process of transpiration. Because the water is connected together through cohesion, as one molecule of water is evaporated, another is absorbed through the roots to take it's place.
2. Describe any experimental controls used in the investigation.
a. The experimental control in this investigation are the first experiments done with all 9 plants without any change in the variables. So the experiments without the heater, fan, or lamp are our experimental controls. These experiments do not change any of our independent variables.
3. What environmental factors that you tested increased the rate of transpiration? Was the rate of transpiration increased for all plants tested?
a. All environmental factors, the fan, heater, and lamp, showed an increase in rate of transpiration. However, only the experiments with the heater and fan showed a constant increase in rate of transpiration for all experiments. The lamp only increased the rate in 5 out of the 9 experiments.
4. Did any of the environmental factors increase the rate more than others? Why?
a. The Fan showed the greatest increase in transpiration rate. Because in transpiration, the water evaporates into the air through the stomata. If the area around the openings of the stomata were highly condensed with water vapor, then the water would be equal potential inside the plant and outside. If we introduced a fan, that kept blowing the water vapor away from the areas of the plant, then the air surrounding the plant would constantly be at a lower water potential. The heater, though it also increases transpiration, can not always control humidity, and relies on evaporation, which may take longer than simply blowing.
5. Which species that you tested had the highest transpiration rates? Why do you think different plants had different transpiration rates?
a. The Rubber plant had the highest transpiration rates. When compared to the rates of the Coleus plant, which were much smaller, one can infer that Plant size is directly proportional to rate of transpiration. The bigger a plant's leaves are the greater the amount of stomata on the leaf's surface there are, so there are more chances for transpiration.
6. Suppose you coated the plant with petroleum jelly. How would the plants rate of transpiration be affected?
a. If you coated the plant with petroleum jelly, a high oily substance, the plant's stomata would be blocked. Water may not be able to escape, nor would gases be able to be exchanged. The rate of transpiration for all plants would drop dramatically.
7. Of what value to the plant is the ability to lose water through transpiration?
a. If a plant were not able to lose water through transpiration, then the plant would eventually be "flooded" and die from over watering.
3. What environmental factors that you tested increased the rate of transpiration? Was the rate of transpiration increased for all plants tested?
a. All environmental factors, the fan, heater, and lamp, showed an increase in rate of transpiration. However, only the experiments with the heater and fan showed a constant increase in rate of transpiration for all experiments. The lamp only increased the rate in 5 out of the 9 experiments.
4. Did any of the environmental factors increase the rate more than others? Why?
a. The Fan showed the greatest increase in transpiration rate. Because in transpiration, the water evaporates into the air through the stomata. If the area around the openings of the stomata were highly condensed with water vapor, then the water would be equal potential inside the plant and outside. If we introduced a fan, that kept blowing the water vapor away from the areas of the plant, then the air surrounding the plant would constantly be at a lower water potential. The heater, though it also increases transpiration, can not always control humidity, and relies on evaporation, which may take longer than simply blowing.
5. Which species that you tested had the highest transpiration rates? Why do you think different plants had different transpiration rates?
a. The Rubber plant had the highest transpiration rates. When compared to the rates of the Coleus plant, which were much smaller, one can infer that Plant size is directly proportional to rate of transpiration. The bigger a plant's leaves are the greater the amount of stomata on the leaf's surface there are, so there are more chances for transpiration.
6. Suppose you coated the plant with petroleum jelly. How would the plants rate of transpiration be affected?
a. If you coated the plant with petroleum jelly, a high oily substance, the plant's stomata would be blocked. Water may not be able to escape, nor would gases be able to be exchanged. The rate of transpiration for all plants would drop dramatically.
7. Of what value to the plant is the ability to lose water through transpiration?
a. If a plant were not able to lose water through transpiration, then the plant would eventually be "flooded" and die from over watering.
