GANONG’S POTOMETER

To demonstrate transpiration rate and rate of water absorption by a cut shoot under various external conditions. A plant shoot is sealed into a stopper which fits the end tube, central reservoir is attached to the tube by a stopcock. End of tube is connected to a capillary tube graduated in millimeters. One end of which is dipped into a beaker having water. The whole apparatus is filled with water. An air bubble is introduced by lifting the capillary tube out of water, and the rate at which bubble is drawn along the tube is proportional to the rate of water loss by the shoot. The position of an air bubble is adjusted by opening the glass stopcock to admit water from central reservoir. The whole apparatus is mounted on a polished wooden or bakelite base by spring clips.