An Interferometric Method for Plant Growth Measurements

An interferometric method in connection with a correlation technique for measuring the velocity of moving parts of plants is described. Velocities down to 5-0 mm d_1 can be measured reliably in a minute. Values of stem elongation rates of etiolated seedlings of a variety of species obtained by this method are very similar to those obtained by the application of linear displacement transducers. Since the optical method requires no mechanical coupling to the plant, velocities of sensitive plant organs can be determined, as shown by measurements of leaf motion.