LEAF TRANSPIRATION Experiment

Did you know that plants transpire? It’s kind of like people perspiring, but not quite. A simple analogy to help explain the act of transpiration is that a plant transpiring is like a human sweating. Humans sweat by excreting water through pores to cool down. Similarly, a plant goes through transpiration to help carry nutrients throughout the plant and to maintain structure.

 

Objective: To show transpiration by capturing the water that evaporates through the leaves.

 

Materials:
* A plant
* Ziplock bag
* Bread tie or tape

 

Procedure:
1. Place a ziplock bag over some leafs.
2. Secure the bag on the stem with the tape or bread tie.
3. Place the plant in the sunlight for two or three hours. (If you are using a plant from your garden, be sure to choose one that will be in the sunlight for at least three hours.)

 

Explanation:
What is transpiration?
Transpiration is the process by which moisture is carried through plants from roots, then capillary action through the stem and to small pores on the underside of leaves, where it changes to vapor and is released to the atmosphere.

 

Transpiration is essentially evaporation of water from plant leaves. This happens faster when humidity is low, such as on a hot, windy day. Like today for me it was 100F. This causes water to evaporate quickly, so the plant needs to suck up more water from the ground (or from the cup) to catch up!

 

Studies have revealed that about 10 percent of the moisture found in the atmosphere is released by plants through transpiration. The remaining 90 percent is mainly supplied by evaporation from oceans, seas, and other bodies of water (lakes, rivers, streams).

 

How much water do plants transpire?
Plant transpiration is pretty much an invisible process, since the water is evaporating from the leaf surfaces, you don’t just go out and see the leaves “sweating”. Just because you can’t see the water doesn’t mean it is not being put into the air, though. During a growing season, a leaf will transpire many times more water than its own weight. An acre of corn gives off about 3,000-4,000 gallons (11,400-15,100 liters) of water each day, and a large oak tree can transpire 40,000 gallons (151,000 liters) per year.

 

Helpful tips if you are going to try this at home:
– The water from the plants will be a clean source of water
– I used a orange tree
– The best types of plants are those with large, green leaves. Berry bushes also work well. (Avoid toxic plants!)
– Select a plant that receives a good amount of sun. The heat from the sun will speed the transpiration process.

 

Choose a branch that has a large number of healthy leaves; give it a shake to dislodge any insects or debris that might be on the branch. Place your plastic bag over it. Tie it very tightly; you don’t want any water vapor to escape during the process.
– It will take about 3-4 hours in sun to get a decent amount of water from the plant.
– After about 30-60 minutes water will begin to condense on the sides of the bag.
– After another hour or so much larger droplets should form. These will start to run down the sides of the bag and collect in the lowest point.
– You should get at least 1/3 a cup of water after 4 hours.
– Before drinking the water pour it through some fabric like a t-shirt to filter out anything that may have fallen into the water.
– Reattach the bag to another branch and restart the process.

 

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