Figure 12.

Measurements of root shape. A, In each image, lines were drawn through the root's centerline and the diameter of the gel surface reflection (RD), if visible, was measured. Bar represents 200 μ. B, The root centerline was rendered as a time- and root arc length-dependent X-Y vector, r(s,t), measured from the root origin (shown here as an arbitrarily positioned point on the gel surface, but actually located at the point of radicle emergence from the seed coat). s (mm) is the arc length along the root from the root origin. c is the distance from the root origin to the root tip, or root length. The velocity of the root tip is measured as the time derivative of r at the tip. d_h and d_m are the distances from the root tip to the first observable root hairs and to where the root first becomes stationary, respectively. Bar represents 100 μm.