Petroleum jelly on leaves experiment

Experiment Design Plan

Plant Transpiration Research Project

VERNIER PLANT TRANSPIRATION RESEARCH PROJECT

Plant Transpiration Research Project

Project Guide

Introduction from Vernier Water is transported in plants, from the roots to the leaves, following a decreasing water potential gradient. Transpiration, or loss of water from the leaves, helps to create a lower osmotic potential in the leaf. The resulting transpirational pull is responsible for the movement of water from the xylem to the mesophyll cells into the air spaces in the leaves. The rate of evaporation of water from the air spaces of the leaf to the outside air depends on the water potential gradient between the leaf and the outside air. Various environmental factors, including those conditions which directly influence the opening and closing of the stomata, will affect a plants transpiration rate. This experiment will measure the transpiration rates under different conditions. You will choose to study the impact of light, humidity, temperature, species or air movement and the impact it has on transpiration.

After reading through the direction make sure to watch the video showing the procedure in action.

Safety Precautions Make sure to use good lab work practices and handle and dispose of sharps appropriately. Keep a close

eye on your pressures and make sure your gas sensor does not get wet (this will ruin the sensor)

Plant Transpiration Research Project

Lab Materials Vernier LabQuest Vernier Gas pressure sensor w/ tubing set Plastic syringe from Vernier kit Vernier Logger Pro (installed on computer) plant cutting (stem must fit within gas sensor tubing plants that work well are tomato, strawberry, bean, geranium, cyclamen etc.) utility clamps, clothes pins, tape or string razor blade or scalpel Tap water Large bowl or container to submerge gas tubing and plant Pipette (HOL kit) Ruler (HOL kit) Something to function as a stand to clamp the plant and tubing onto (chair leg or back, legos, railing etc ) Petroleum jelly (optional but very helpful) Depending on your treatment you may need: Small Lamp Fan with a slow speed Heater (small electric) large plastic bag & water spray bottle A second plant species

Variables: You can modify this lab to test the effect of light, humidity, air movement, species, and temperature on

the rate of transpiration. Choose 1 independent variable to test. Below are lists of variables and some ideas on how to test them:

Light: Test the plant transpiration at different light levels. Run the experiment with the plant under dark

conditions, normal daylight and/or under bright light (have a small lamp shine directly on the leaves) Temperature: Subject the plant to 2 different temperature settings. You can use a small heater to

increase the temperature nearby the plant. DO NOT use a hair drier. The hair drier also changes air movement thus you cannot isolate the effect of heat alone.

Plant Transpiration Research Project

Humidity: You can change the humidity by filling a large plastic bag with water vapor and cover and seal

the plant sample within the bag.

Air Movement: Place a fan with a low speed setting near your plant. Slight air movement should blow

across the surface of the leaves. Too much air movement can damage the leaves. Species: Choose 2 different plant species. Evaluate and compare the rate of transpiration of the different

plants. If you have an idea for another variable not on this list that you would like to test, please send me a

message for pre-­‐approval.

The procedure detailed below can be seen in the video link provided in the assignment directions. It is imperative that you have an airtight seal on all the tubing for the experiment to work. You will repeat this procedure using your treatment. Make sure you keep your data organized and separate. Petroleum jelly around the end of the gas tubing where the plant was inserted can help with the air tight seal (See the video link provided for how to use the petroleum jelly)

Plant Transpiration Research Project

Plant Transpiration Research Project

Plant Transpiration Research Project

You will repeat this procedure using your treatment. Make sure you keep your data organized and separate. Petroleum jelly around the end of the gas tubing where the plant was inserted can help with the air tight seal (See the video link provided for how to use the petroleum jelly)

Plant Transpiration Research Project

Plant Transpiration Research Project