Transpiration

Transpiration is the loss of water from leaves and stems is a natural and essential process in green plants.

Several factors that can affect the rate of transpiration:

Transpiration is important to plants in maintaining a transpiration stream that draws minerals into plants.
The Rate of transpiration is not necessarily the same as the rate of photosynthesis.

Plants take up water to replace water lost through transpiration.

The amount of water taken up by a plant can be investigated using an instrument using a potometer.
This is essentially a way of connecting a plant to a narrow tube filled with water. As the plant btakes in weater a bubble is drawn along the tube. The speed the bubble moves gives an indication as to the water loss

 

The potometer investigation

The potometer simulation

The potometer investigation generates consistent and realistic results, showing the uptake of water by a photosynthesising plant, from which the rate of transpiration is automatically calculated. A feature draws and print graphs of the data in order to show how transpiration is affected by various environmental factors.

Some tasks you can investigate using the simulation
Turn on the light, the fan and the humidifier. Click on the "Next Result" button. What happens to the bubble in the glass tube? Why does this happen?
Turn off the light, the fan and the humidifier. Click on the "Next Result" button. Turn one of them back on and take another result. What happens when one of them is on?
Does the fan, the light or the humidifier affect the movement of the bubble most?
Why does the bubble move faster when the light is on? What chemical process do plants carry out in light?
Why doesn't the bubble move much when it's dark?
Does the bubble stop completely when it's dark? Why not?
Why would a plant need to take in more water when it is light? What difference does turning the light on make to the mean speed of the bubble?

 

How to use the potometer program

The software is easy to use and provides accurate reliable results for the uptake of water by a plant. There are several buttons, each with a different function.

1. On the right side of the screen are the control toggle buttons: Light, Fan, Humidifier. They turn on and off the devices that control the environmental conditions.

2. On the left side of the screen are the experiment controls:

  • Next Result moves the experiment on by one minute and takes a result.
  • Reset resets the whole experiment and clock.

3. As the simulation takes a result, it is automatically plotted on the graph.


The Potometer simulation has been provided by Actis Ltd, the educational website company. www.actis.co.uk

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