Water transport in plants. Potometer!

Back to college! After loads of tests and deadlines, there’s some free time, so I can finally type some posts. This year in Biology HL we’re starting with plant biology. One of the experiments we did in order to show in real life what we’re learning from the book used a potometer. A potometer consist in a glass tube with several apertures and it's used to show water uptake from plants and how it is transported in the Xylem through pressure changes. A potometer is shown in the following picture. 

In order to show the water uptake from the plant, the tube was completely filled with water and the plant was introduced into a bung which then was used for sealing the potometer. After that, as the water was absorbed from the tube by the plant, some air would get into the tube on the opposite howl, so then a water cup had to be situated under the opposite hole in order to seal it. A small bubble of air should be then seen inside tube, and as the water is taken up on the right hand side of the potometer, pressure goes down so the bubble moves in that direction. The distance the bubble moves in a fixed amount of time can be used to calculate the rate at which water is absorbed by the plant.

Although a Potometer can be based on a really simple principle and it’s very useful to show water uptake by plants, it can be a bit tricky and tedious to set up. First of all, no air can be getting into the tube apart from the bubble, and in order to seal all holes a substance like vaseline has to be used to cover the space between the plant and the bung. also if there’s some air left in the tube it can separate the water from the roots of the plant, so no water uptake will take place.

Plant biology, although it can look a bit boring at the beginning, becomes really interesting in terms of transport of nutrients through the plants. The point that makes it more interesting for me is that no mechanical procedure can be used to do this and plants still find ways to achieve this without any problems, fact that I find particularly astonishing.