Figure 8.

CMT position and dynamics in full-grown root hairs. A, Vertical positioning of an MT over time; transects (x, z) through z-depth of an MT at two different time points (left section = 0 min, middle section = 20 min). The difference image (right section) in lower section shows that the MT did not move in the z-direction. Arrow indicates the z-direction. Height and width of image box is 6 and 14 μm, respectively. B, Maximal projection of (x, y, z) stack at one time point. Scale bar = 8 μm. C, Kymograph of a transect (yellow line in B) through the time sequence of maximal projections. Straight lines indicate no lateral movement of the MTs during the 30-min experiment. Vertical bar = 10 min, horizontal bar = 5 μm. Yellow line indicates position of maximal projection in B. D, Sequence of 14 images from repeated 3-D optical sections over time (x, y, z, t). Numbers indicate the time in minutes. The inverted-grayscale images are maximal projections of 20 optical sections with a separating distance of 1 μm taken at the base of the root hair. Newly formed MT shows lateral movement in the time sequence (MT colored in red). The green box in the extra section reveals the subcortical position of the MT in question and represents a (x, z) cross section taken through the optical sections at time point 15 min (position indicated by the green line in 15-min image). The red arrow shows the position of the single MT colored in red. The black arrow is the axis of increasing z. Scale bar = 5 μm. E, Formation of a new CMT. Sequence of 10 images from repeated 3-D optical sections over time (x, y, z, t) taken every minute. The images are maximal projections of the four upper-optical sections (with a separating distance of 1 μm) taken at the level of the cortex of the root hair. The ellipse indicates a single CMT. Initial growth is followed by complete shortening. Subsequent growth from the same site results in growth in a slightly different direction. This process is repeated several times over 20 min. Scale bar = 5 μm. F, Dynamic instability of CMTs at the base of the root hair. The images are the result of maximal projections of four upper-optical sections at a separating distance of 1 μm repeated over time (every 2 min). Numbers indicate number of section. Dynamics is illustrated by the green (growth)/ red (shortening) difference image. For detailed information concerning this technique, see results section. An individual CMT is indicated by an arrow. The green, red, and white color of the arrow indicates growth, shortening, and pause, respectively. Extra section shows reorientation of CMT after a shortening event and subsequent growth; light-blue line corresponds with time point 3, dark blue with time point 6, and magenta with time point 14. Scale bar = 10 μm. G, Dynamic instability at the root hair tip represented in the way as explained in F. Note that section G7 shows two arrows indicating shortening and subsequent growth in a different direction of the same CMT. Light-blue line in extra section shows CMT position at time point 5, dark blue at time point 9, and magenta at time point 14. All root hairs tips are oriented downwards.