POTOMETER: ‘H-Type’

POTOMETER: 'H-Type'

• Comprises a glass tube 160mm long x 20mm diameter with an 8mm diameter side-arm connected to a 140mm long piece of 1mm bore capillary tubing to form an  ‘H’.
• A cut shoot is attached to the top of the capillary tubing with a short piece of clear plastic tubing.
• The large diameter glass tubing acts as the reservoir.
• This apparatus is designed for student use.

(Wikipedia excerpt:  .."...A potometer' (from Greek ποτό = drunken, and μέτρο = measure), sometimes known as transpirometer, is a device used for measuring the rate of water uptake of a leafy shoot which is almost equal to the water lost through transpiration. The causes of water uptake are photosynthesis and transpiration.[1] The rate of transpiration can be estimated in two ways: Indirectly - by measuring the distance the water level drops in the graduated tube over a measured length of time. It is assumed that this is due to the cutting taking in water which in turn is necessary to replace an equal volume of water lost by transpiration.

Directly - by measuring the reduction in mass of the potometer over a period of time. Here it is assumed that any loss in mass is due to transpiration. There are two main types of potometers: the bubble potometer (as detailed below), and the mass potometer. The mass potometer consists of a plant with its root submerged in a beaker. This beaker is then placed on a digital balance; readings can be made to determine the amount of water lost by the plant...").

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