b. My predictions for Group II, III, and IV were based on biological and physical processes that effect transpiration and that is why the differences are evident in the graph. Group II was decreased transpiration because water goes from areas of high concentration to low concentration so when the humidity from the air saturates the leaf the rate of transpiration is decreased because there is no need for the plant to use more water. Group III was increased because when there is constant air movement (fan) on the plant the water is constantly being washed away so therefore transpiration is increased since the plant is losing the water from the leaf. Group IV was increased because light promotes photosynthesis which makes the stomata open wide causing the plant to need more water which then causes its transpiration to increase. Now Group I data was right in the middle of he graph because nothing is really making the plant increase or decrease its transpiration so thats why the group of students got the constant rate of transpiration.
c. The concept of water potential is used to account for the movement of water from the plant stem to the atomosphere during transpiration because the concept of water potential is water moving from a high concentration to a low concentration and thats exactly what water does when it goes from the plant stem to the atomosphere. This is because water travels through the plant where there is high concentration and onto the leaf where there is low concentration.
In conclusion there are many factors that affect transpiration; wind, temperature, light, and humidity. The factors can either increase or decrease the the of transpiration but in the end water is always going from a high to low concentration.
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