Measurement of plant movement in young and mature plants using electronic speckle pattern interferometry

The use of electronic speckle pattern interferometry (ESPI) to monitor and measure the surface movement of plants is presented. We chose to study the gravitropical response of a coleoptile (the shoot from a growing seed) to illustrate the potentials of the technique for botanical measurements. A coleoptile represents a very fast growing translucent biological object, a difficult object to record interferometrically. Traditional holographic interferometry is not suited to the study of objects with such rapid fringe decorrelation. However, ESPI with its short exposure time, fast sampling rate, and high sensitivity makes it possible to obtain fringes even on the very tip of the coleoptile where the microstructure changes most rapidly.