Graph Justification: As the title states, this graph displays the effect that different conditions have on a plant’s water loss. It seems that as the independent variable, time, increases, the dependent variable, water loss, increases as well. Each condition had a different effect on the plant’s water loss. For example the fan increased the water loss while the mist decreased the water loss. This graph is testing the hypothesis “If a plant is exposed to different conditions, then its rate of transpiration will be affected.”
Analysis (Study Questions):
1. What is the total leaf surface area for the plant?
The total leaf surface area for the plant is 0.00744 m2. To calculate the surface area, one must weigh the leaves (1.116 grams) and a section that is 1 cm2 of a leaf (0.015 grams). Then it must be multiplied by 10,000 to obtain its mass per square meter (150 g/m2). This data must then be put into a formula which divides the weight of the leaves by its mass per meter square. The equation is shown below:
1.116 grams
150 g/m2 = 0.00744 m2
2. Determine the average amount of water loss per milliliter per square meter for each treatment: room, light, fan, and mist.
After doing the experiment, each group recorded the data on a spreadsheet and the average for each condition was calculated. The average for water loss at room temperature was 5.660849 mL/m2. The average for water loss while there was a light was 4.71275 mL/m2. The average for water loss while the fan was on was 10.902 mL/m2. The average for water loss with mist was 2.7725 mL/m2.
3. Explain how each condition affects water loss.
The control of the experiment was the bush bean seedling that was in an environment at room temperature. Since it was a control, it did not have a great effect on its water loss. Light increases a plant’s water loss. This is because once the light hits the leaves, the stomata open and this allows water to be lost at a faster rate. The fan increased water loss because it removed the humid air surrounding the plant and made its environment drier. The plant was then able to release water into the atmosphere. The mist decreased water loss because it makes the air around the plant humid. When the air surrounding the plant is moist, the plant does not release water into the atmosphere.
4. How did these conditions affect the stem to leaf water gradient?
When the plant was exposed to different conditions, like the light or the fan, water traveled up the stem, creating a gradient, and into the leaves which released the water through the stomata. When the plant was exposed to the mist, the gradient decreased because the air surrounding the plant had a high water potential and therefore, water was not moving up the stem. When water is released from the plant, the water potential changes. This change creates a gradient because the water is moving to areas with different water potentials.
5. What is the importance of water potential in controlling the transport of water?
Water potential is important when it comes to transporting water because it influences the direction that the water goes in. If a plant is in an environment that has a low water potential (the atmosphere is dry), then the plant will release water into the atmosphere. This is because the plant had a high water potential and water moves from an area of high water potential to an area of low water potential.
6. Explain several mechanisms by which plants try to minimize water loss.
Plants have several mechanisms that allows them to minimize the amount of water they lose such as opening their stomata at night instead of during the day. This limits the amount of water that is being released into the atmosphere because the sun is not there to increase the rate of transpiration. Also, plants with smaller, thicker leaves have less stomata and a smaller surface area so they are prevented from releasing excess water. The plants can also store water in their stems which they can use during times when it is dry.
Conclusion:
After completing this lab, it was shown that placing the bush bean seedlings in different environments affected the amount of water the plant lost. At room temperature, the rate of transpiration was not affected as much but when it was exposed to the mist, light, and fan, the water loss changed. When the plant was exposed to the fan and light, the plant lost more water because it had a higher water potential than its surrounding environment. When the plant was sprayed with water (the mist), the rate of transpiration decreased because the plant did not release water into a humid atmosphere. This proved that my hypothesis “If a bush bean seedling is exposed to different conditions, then its rate of transpiration will be different in each environment” was correct. Some possible errors could have been that the calculations for water loss were done incorrectly. I noticed that some of the calculations that were inputted into the class spreadsheet were very different from the other calculations and this could have affected the outcome of the graph. Another error could have been that we made a mistake while reading the potometer or that we allowed an air bubble to appear in the tubing. If this experiment were to be repeated, a new condition could be experimented with such as temperature or the plant species could be changed.
