Transpiration Process In Plants With A Potometer: How Is It Done?

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Understanding transpiration is arguably the basis of any successful agricultural venture and ensuring fruitful crops for both farmers and manufacturers who rely on nature to work at its optimal best for the sake of their products. While those who work with plants, don’t always have a degree in biology or botany, they still have a grasp on transpiration and can pinpoint how this vital process is in getting beautifully leafy and healthy plants to grow. 

The following are a few points regarding transpiration, how the process works, and exploring the usage of a potometer, which is the device used to measure the phenomenon.

What is Transpiration?

First things first, it might be useful to briefly explain exactly what transpiration is. It is the process of water moving through a plant and its evaporation from aerial parts such as leaves, stems, and flowers. Plants, like nearly every living organism, necessitate water in order to survive, but the majority of it evaporates and a small amount is left in the roots to nurture its growth. Transpiration is the plant’s loss of water through the stomata of the leaves, and the ability to measure this water loss which is crucial to its development.

What is a Potometer?

The next question to answer, naturally, would be what is a potometer and how does it relate to transpiration? Essentially, this funny-sounding device measures the rate at which a plant draws up water. Since a plant usually draws up water from its roots and loses it through transpiration, you can use it to measure the rate at which it does so. In order to provide an accurate reading, a potometer typically requires a plant cutting, a calibrated pipette to measure water loss, a length of clear plastic tubing, and an airtight seal between the plant and the water-filled tubing mechanism. 

To measure, insert the plant stem into the tubing, making sure there are no air bubbles and that you leave a few centimeters of air between the sensor and water. This can be tricky to do, but you can definitely get it right after a few tries. In order to get a full grasp of the finagling you need to do, perusing this useful resource will help a great deal. It elucidates precisely want needs to be done via a helpful diagram, and you can also take a look at the templates for data control. 


While the potometer is a great tool, there are a few issues you need to be on the lookout for, since it is rather fiddly. By changing the surrounding atmospheric conditions, the effect on transpiration of wind, heat, and humidity can be measured. Potometers are notoriously difficult to set up because air bubbles in the xylem of the plant or in the apparatus itself will prevent the device from working properly.

First off, make sure you have a good seal around your plant sample and that the plant sample is slightly wider than the tubing or bung it’s going into. You can also use petroleum jelly to create an extra seal around the plant and the tubing. 

Furthermore, the potometer needs to be completely full of water, and you might find that it is easier to fill and insert the plant under water, depending on the type. The plant needs to be cut at the stem base of around 1-2cm before inserting to get rid of any air bubbles. And if you cut it under water and keep it there, you can nix any. Issues that come up by having the stem in the air. 

Another point to remember, woody stems are best since you can shove them into the tubing or bung, rendering the process a lot easier with a typical privet. If it’s a cold day collect your plants earlier and keep them indoors in a beaker of water, which will mean that the plant will be a bit speedier when used. 

Finally, one trick botanists sometimes use is adding food coloring in the capillary tubing to make it easier to measure the changes in the rate of water uptake – the coloring makes these things a lot easier to see. So, while using a potometer can be fairly difficult, there are quite a few ways to ensure that measuring different factors is rather simple and straightforward. 

While the potomer is a notoriously difficult tool to set up, it is also an incredibly helpful one in not only measuring transpiration and assessing the effects of different environmental factors on plants, but they can be an excellent resource for students wishing to know more about the best ways to ensure a plant’s healthy growth. 

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