Online Plant Transpiration Lab

Lab Data Table

Journal Question:
1. Describe the process of transpiration in vascular plants.
In general terms, transpiration is the release of water from plant leaves. More specifically, transpiration is the evaporation of water into the atmosphere from the leaves and stems of plants.

(Evaporation involves the process of any water changing from a liquid to a vapor).

Transpiration is the evaporation process occurring to the water held in the leaves and stems of plants.

In transpiration, water travels from the soil into the roots of plants, and up to the underside of plant leaves, where it is released into the air. This process occurs thanks to small pores in the leaves called stomates. Stomates are small openings on the underside of leaves that are connected to vascular plant tissues. Also, stomates are dotted on leaf and stem surfaces. Interestingly, some dry environment plants have the ability to close their stomata.

Transpiration is considered a passive process from the plants perspective because it is regulated by humidity in the atmosphere and moisture in the soil and is not the result of a conscious choice made by the plant itself. On the other hand, only 1% of the transpired water that passes through a plant is used in the actual growth process. Some of the water that eventually becomes part of the transpiration process is used as a vehicle to deliver nutrients from the soil into the plant. The purpose of transpiration is also to cool the plant. 

*Vascular: relating to, involving, typical of, or having fluid-carrying vessels. 

2. Describe any experimental controls used in the Investigation.
For this lab, experimental control is the timing for the transpiration --- one hour for all experiments. Also, the transpiration rate of plants in an hour under normal condition with standard room temperature, pressure, and without fan, heater or lamp.

3. What environmental factors that you tested increased the rate of transpiration? Was the rate of transpiration increased for all plants tested?
The environmental factors that are being tested in this lab are: the amount of wind, heat (temperature), and light. During the lab, all the factors increased the rate of transpiration at different levels. The amount of wind increased the transpiration rate of all plants the most. However, the amount of light did not increase the rate of transpiration for all plants tested. Also, the amount of light is the factor that affected the overall transpiration rate the least. The amount of light did not affect the rate of transpiration of dieffenbachia, rubber plant, weeping wig and zebra plant.

4.Did any of the environmental factors (heat, light, or wind) increase the transpiration rate more than the others? Why?
Overall, the increasing amount of wind led to the greatest increase in the rate of transpiration for all plants tested. Wind accelerates the movement of water from the leaf surface while reducing the boundary layer of water vapor. Also, wind would accelerate the speed of evaporating. Besides the wind, heat is another factor that increases the rate of transpiration. Higher temperature would cause water molecules to move faster; thus, the rate of transpiration would increase.

5. Which species of plants that you tested had the highest transpiration rates? Why do you think different species of plants transpire at different rates?
The species of plants with the highest transpiration rates are rubber plant, zebra plant, and dieffenbachia (from highest to lowest). Since different species of plants live in different environment; thus, they have different rates of transpiration. Also, different rates of transpiration are caused by different species of plants' abilities to adapt to different environments through evolution.

6. Suppose you coated the leaves of a plant with petroleum jelly. How would the plant's rate of transpiration be affected?
Since the leaves of a plant are covered with petroleum jelly, the rate pf transpiration would decrease. The jelly would close up the stomata on the leaves and prevent water from evaporationg. Also, light could not penetrate through stomata.

7. Of what value to a plant is the ability to lose water through transpiration?
It is essential for plants to lose water because of the ability of cohesion (the water). Evaporating water does not only help carry nutrients up from the roots through xylem (allowing the plants to absorb nutrients), but also helps moderate the surrounding temperature of the plant and the air humidity. Furthermore, losing water through transpiration helps the plant operate metabolism and keep balance of homeostasis.

Here is the link to the lab :)