Ganongs Potometer


 
 
Concept Explanation
 

Ganongs Potometer

A potometer is a device, which is used to measure water uptake by shoot during transpiration. It is also known as transpirometer. The Ganongs potometer is used to measure the transpiration rate in a laboratory. With the help of given experiment we can measure water uptake by shoot during transpiration.

Aim of the experiment :- 

To find out the rate of transpiration in a cut twig with the help of Ganongs Potometer.

Requirements :- A freshly cut twig, Ganong's potometer, water, Eosin oil, beaker.

Parts of Ganongs potometer :- 

  • Ganongs potometer is a twice bent glass tube having a wide mouth glass cylinder, a horizontal glass bar with an inserted capillary tube inside and a reservoir attached to the horizontal bar. 
  • Towards the front end of the apparatus a wide mouthed glass cylinder is present. The mouth of the cylinder is fitted with a one holed rubber cork.
  • Freshly cut twig for the experiment is arranged through hoe in the rubber cork. The horizontal bar of this apparatus is a long glass tube inside which a capillary tube is fitted and is having a graduated readings marked above it.
  • This horizontal bar is a having a bent end having a nozzle opening,
  • This bent end is kept inside a beaker containing colored water. Towards the front end of the horizontal bar a vertically arranged reservoir is present connected to the horizontal bar where water can be stored in it.
  • There is a stop or pinch cork is present below the reservoir to allow or stop the flow of water from reservoir to horizontal bar. The whole apparatus stands on flat surface like table with the help of a stand.
  •                                                    

     Procedure :-

  • A few drop of eosin oil is added to water to make it coloured.
  • A freshly cut twig is placed on the mouth of the glass cylinder.
  • A single air bubble has to be kept at the zero reading of the horizontal bar. Lifting the bent end allows the air bubbles to enter and get trapped in the horizontal bar.
  • When  the experiment begins, it is observed that the air bubbles at the zero reading starts to move .
  • Observation :-

    As the transpiration takes place, a transpirational pull is created by the shoot to make up for the loss. Due to this , the horizontal bubble starts moving in the direction of the  twig

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