Ganongs Potometer

It is possible to utilize a potometer, also called a transpirometer, as a tool for measuring the rate of water uptake by a leafy shoot, which is nearly equal to the rate of water loss by transpiration. The processes of photosynthesis and transpiration are responsible for water uptake.

Ganongs Potometer: An overview

Ganong’s Potometer is a device that is used to measure the amount of water that is taken up by the body during transpiration. It is possible to calculate the transpiration rate by dividing the time period by the number of gaps created by the air bubble in a particular period of time. Multiple readings of the time required are recorded and then repeated by adjusting the air bubble to the reading of 0. The average of these values is used to calculate the transpiration rate. Ganong’s potometer is composed of two pieces of glass: a cylinder with a broad mouth and a tube that has been bent twice.

The following is the Principle that guided the development of Ganong’s Potometer:

Reservoir: A funnel is connected to a reservoir through a tap. The amount of bubbles produced is controlled by twisting the tap on the reservoir.  

Capillary Tube’s length: The length of the capillary tube is measured after a bubble is injected into it. When the water is absorbed by the plants, the bubble begins to move. The amount of water in the tube is estimated by identifying the regular marks on the tube’s wall.

Tube for Handling Leafy Shoot: Water should constantly be present in the tube when handling the leafy shoot and no air should come into contact with the surface of the water since evaporation can cause interference. 

How to Measure Water Uptake in a Laboratory

The rate of transpiration can be estimated in a variety of ways with the use of Ganongs’s Potometer, including the following:

Directly: After some time has passed, the weight of Ganong’s potometer can be determined directly. We assume that any loss occurs as a result of Transpiration.

Indirectly: If the water level drops in the graduated tube and is measured, the amount of time it takes to compute it is determined.

Procedure

An instrument with coloured water is installed on a flat surface in direct sunlight and filled with a variety of colours. A few drops of Eosin oil are added to the coloured water to create the desired effect.

By using a single-holed rubber cork to secure a freshly cut twig to the mouth of a glass cylinder, you may create a beautiful centrepiece.

Before the experiment, a single air bubble is placed in the capillary tube of the horizontal glass rod and maintained at zero reading. The bent side of the horizontal rod is pushed away from the beaker. This will aid in the retention of a couple of air bubbles in the capillary tube. Only a single air bubble should be preserved at the zero reading to ensure accuracy.

In this variation, the cork is removed from the reservoir, allowing water to flow through the horizontal rod and into the reservoir. Using water, the air bubbles are forced to exit through the nozzle. As moisture is lost through transpiration by the aerial parts of the leafy shoot, a pull by transpiration is performed to compensate for the moisture loss through transpiration.

The air bubble is propelled towards the recently cut twig as a result of this force.

In order to compute the amount of water absorption, one must measure the distance travelled by the air bubble in a positive time frame and repeated measurements are recorded by correcting the air bubble to a zero reading.

Potometer’s limitations

1. The process of introducing the air bubble is not straightforward.

2. The twig may not be fully alive for an extended period of time.

3. It is possible that any changes in atmospheric temperature will modify the position of the air bubble within a capillary tube.

4. When a freshly cut twig is immediately placed underwater, a small bit of the twig must be removed underwater to prevent it from rotting. In order to prevent air from entering the xylem vessels, this procedure must be followed.

5. The status of the potometer must not be modified while the experiment is in progress; otherwise, external elements such as temperature and pressure will have an impact on the water absorption. 

6.Water leaks should be avoided at all costs by tightening up everything.

Conclusion

Ganong’s Potometer is a device that is used to measure the amount of water that is taken in during transpiration.

The transpiration charge is computed by taking the gap blanketed by the use of the air bubble in a specific term and dividing it by the number of days in that term.

In Ganong’s potometer, two tumbler tubes are bent twice, one of which has a large mouth and the other of which has a small mouth.

In addition, a horizontal glass bar consistent with a reservoir inserting a capillary tube as well as a pitcher cylinder with a large beginning is fixed to the device’s front stop at the same time that a holed-rubber cork is fixed to the glass cylinder’s establishing is fixed to the device’s front stop.