Potometer precautions setup

Download PDF. Join Now Already a member? Log In. New resources. You could give students guidance on investigating a particular factor affecting the rate of transpiration, or they can choose from a list and develop their own ideas. Use five or six values for each variable tested.

Method 1 : Measure the water uptake by the shoot. Remove a number of leaves from the shoot and measure the rate of water uptake again. Keep removing leaves until all the leaves are off the plant shoot. Label the leaves as you remove them, then estimate their area by placing on squared paper and tracing their outlines. Add together the areas of the leaves to find the total area and multiply by two to get the total surface area, as each leaf has an upper and a lower side.

Add the leaf areas together in the reverse order that they were removed to get figures for the change in the surface area of leaves attached to the plant shoot. Method 2 : Measure the water uptake by the shoot. Use vaseline - or nail varnish, but this could damage the leaves - to cover one or both sides of a leaf. Length of Capillary Tube - A bubble is forced into the capillary. As the water is absorbed by the plants, the bubble starts moving. By spotting regular markings on the tube, it is possible to calculate the amount of water absorbed.

Reservoir — It is generally a funnel with a tap attached to it. Rotating the tap on the reservoir adjusts the bubble. Some other designs make use of a syringe instead.

Tube for Handling the Leafy Shoot - The leafy shoot should be kept in contact with the water. In addition, the surface of the water is not supposed to be exposed to the air. Or else, evaporation will interfere with the calculations. A rubber bung lubricated with petroleum jelly is sufficient for the setup. Transpiration is the mechanism where there is loss of moisture or water in the form of water vapor from the aerial organs of the plants, particularly via the leaves.

In every green plant, the process of transpiration takes place via the stomata of the leaves, in most cases. The rate of transpiration relies on different climatic factors such as temperature, intensity of sunlight, humidity, velocity of wind, availability of water to the plant, atmospheric pressure, and many more. There are various types of transpiration which are:.

Lenticular transpiration. Cuticular transpiration. The plant shoot is held securely in a connected tube. The shoot must be in contact with the water and an air tight seal is essential to ensure the water surface does not come into contact with the surrounding air as evaporation may interfere with the results. Setting up the potometer takes a few simple but essential steps.

If you have instructions for your particular device which contradict these steps, follow them instead. Firstly put the whole unit under water to fill with water ensuring there are no bubbles of air anywhere within the tubing.

Take a cut stem from a plant and insert it into the bung or tube making sure it is secure. The bung may have to be greased with Vaseline in order to get an air tight seal.