The resistance porometer and its application to the study of stomatal movement

Abstract

The porometer is a convenient method of studying the behaviour of stomata since it automatically integrates the effect of a large number of stomata and the same group of stomata remain under continuous observation. The porometer was first described as a method for investigating stomatal movement by Darwin and Pertz (1911). In the apparatus described by these workers a glass chamber bearing a broad flange is cemented with glue to the stomata surface of tire leak; air is sucked through the stomata into the chamber by means of a water column, and the rate of fall of this column is measured at a known average pressure. This rate of fall is then taken as a measure of the degree of opening of the stomata. A modification of the method of direct observation has been described by Maskell (1928).