Plant Transpiration Lab

DATA TABLE:

	normal	with fan	with heater	with lamp
arrowhead	3.6	7.5	6.6	4
coleus	0.9	6	3.9	3
devil's ivy	2.9	4.6	4.1	3
dieffenbachia	4.1	7.7	6	3.9
english ivy	1.8	5.1	3.2	2.1
geranium	1.2	4.7	5.8	2.4
rubber plant	4.9	8.4	6.8	4.3
weeping fig	3.3	6.1	4.9	2.5
zebra plant	4.2	7.6	6.1	3.2

1. Describe the process of vascular transpiration in plants.

First, water is absorbed through the roots of the plant. This happens with the help of three factors, osmosis, cohesion, and adhesion. Cohesion: the water droplets stick together. Adhesion: The water droplets stick to the xylem  Both cohesion and adhesion occur due to the polarity of a water molecule. Osmosis: the water moves from an area of high concentration (ground) to low concentration (up to the plant). Excess water, i.e. water not used in photosynthesis, in the plant leaves can get evaporated through the stomata, which are used for gas exchange.

2. Describe any experimental controls used in this investigation.

One control is to test all the plants rate of transpiration without any added factor, i.e. light, heat, or fan. Another control is the room remaining a constant temperature throughout the experiments. One more is the air, they are all in the same location so the air will be the same for each experiment. Time is also a control, they each sat for the exact same amount of time.

3. What environmental factors that you tested increased the rate of transpiration? Was the rate of transpiration increased for all plants tested?

For each plant, the presence of a fan caused there to be an increase in the rate of transpiration, so in nature this would be the equivalent of wind, or a constant flow of air. A heater also caused an increase in the rate of transpiration, which is the equivalent of high temperatures in nature. In 4/9 plants there was an increase in transpiration with the presence of light, however the other 5/9 had a decrease.

4. Did any of the environmental factors (heat, light, or wind) increase the transpiration rate more than the others? Why?

In all but 1 plant, the rate of transpiration was highest with the presence of wind. I hypothesize that this is because the constant air flow keeps the water concentration in the air relatively low so osmosis causes more water to continue to be evaporated because it is moving to an area of low concentration. If there is no wind, the air will increase its water concentration, and osmosis won't occur anymore.

5. Which species of plants that you tested had the highest transpiration rate? Why do you think different species of plants transpire at different rates?

The rubber plant had the highest rate of transpiration. I think that different species of plants transpire at different rates because based on the different environments they have adapted to, they have different water needs. For example, plants in a very hot, desert-like environment will have lower rates because they need to hold onto as much water as possible. However, plants in a rain forest environment can have higher rates because there is a constant influx of new water from the roots.

6. Suppose you coated the leaves of a plant with petroleum jelly. How would the plant's rate of transpiration be affected?

The petroleum jelly would hinder the plant's ability to transpire, because oil-like products block moisture from leaving the surface. In humans, this occurs in products such as Chapstick and lotion.

7. Of what value to a plant is the ability to lose water through transpiration?

It is very valuable to a plant because having too much water can drown the plant, or flood the leaves and cause them to burst. At the same time, losing too much would cause it to dry out and not be able to perform cell functions, i.e. photosynthesis.