Abstract: We present a method or botanical growth analysis of plant roots in physiological coordinates which is necessary for the evaluation of growth mechanisms in roots. The here presented framework can be used on long image sequences up to several days. First the displacement vector field is estimated by the structure tensor method. Secondly the physiological coordinates of the root are determined by active contours fitted to the root boundary. Then the middle line as the object coordinate axis of the root is calculated. In the third step the displacement field is sampled and projected on the middle line. This yields an array of tangential displacements along the root which is used to calculate the spatially resolved expansion rate of the root along its length. The performance of the presented framework is demonstrated on both synthetic and real data.