Transpiration Lab

Transpiration is the movement of water from a plant's roots and into the atmosphere through evaporation. Water is absorbed in the roots of vascular plants and up through the stem to the leaves. This is called "capillary action, a force of attraction between molecules that causes liquids to move up narrow tubes." Stomata are tiny pores on the surface of leaves that intake CO2 and release O2. A plant's transpiration rate can be measured by how much water is taken up by the roots over a period of time. "In a laboratory, a plant's transpiration rate can be measured using a potometer. A potometer can be assembled from standard laboratory materials including: a ring stand, clamps, a 10mL pipette, a 100mL burette, a T-tube, glass tubing, and rubber tubing. To measure transpiration rate, a plant sprig is mounted on the potometer and the burette and pipette are filled with water. Over time the plant will transpire and absorb water through its stem. The potometer is constructed in such a way that the plant's water source is the pipette, therefore the amount of water transpired over time can be determined by reading the water level in the pipette after time has passed. The water supply in the pipette can be replenished from the water supply in the burette by releasing the pinch clamp."

Lab:
First plant: English Ivy- By itself, rate = 1.8 ml per hour.
English Ivy with heater= 3.2.
English Ivy with fan= 5.1.
with lamp= 2.1

2nd plant: Zebra plant- 4.2
with heater- 6.1
with fan- 7.6
with lamp- 3.2

3rd plant: Dieffenbachia- 4.1
with heater- 6.0
with fan- 7.7
with lamp- 3.9

4th plant: Coleus- .9
with heater- 3.9
with fan- 6.0
with lamp- 3.0

Journal Questions
Describe the process of transpiration in vascular plants.
The process of transpiration is the process of water movining through a vascular plant and exiting through stomata in leaves.

Describe any experimental controls used in the Investigation.
Controls: The plant by itself before using the independent variables.

What environmental factors that you tested increased the rate of transpiration? Was the rate of transpiration increased for all plants tested?
Heat, wind and light. All increased: wind the most, heat the second most, and light the least most.

Did any of the environmental factors (heat, light, or wind) increase the transpiration rate more than the others? Why?
Wind increased the most because the wind creates the most energy for the water to move quicker up the stem.

Which species of plants that you tested had the highest transpiration rates? Why do you think different species of plants transpire at different rates?
Zebra plant and Dieffenbachia. Yes.

Suppose you coated the leaves of a plant with petroleum jelly. How would the plant's rate of transpiration be affected?
Transpire less because some of the stomata would be closed.

Of what value to a plant is the ability to lose water through transpiration?
Extreme value so it doesn't drown because of the absorption of water through the roots: it is a cycle.