Fig. 5. Parameters of microtubule dynamics in planta. Microtubule dynamic behavior of the plus end was measured in the GFP-TUB6 background. (A) Growth and shrinkage velocities. (B) Transition frequencies among growth (G), shrinkage (S) and pause (P). (C) Total time spent in growth, shrinkage, and pause. Data shown are means ± s.d. Statistical significance (t-test; ^**P<0.005) is obtained between spr2 and the SPR2-overexpressing line. (D) Microtubule dynamicity – a measure of the total tubulin exchange at microtubule plus ends. (E) Time spent in the pause state was classified, depending on the previous history of the microtubule ends. When the microtubules were in the pause state at the start of observation, they were categorized as `undefined'. Sample values were: control, n=23 microtubules and t=38.6 minutes; spr2-2, n=32 microtubules and t=58.8 minutes; spr2-2sp2l-1, n=22 microtubules and t=50.7 minutes; SPR2ox;spr2-2, n=22 microtubules and t=36.8 minutes.