Ethylene-induced microtubule reorientations: mediation by helical arrays.

Entire microtubule arrays, within outer cortical and epidermal cells of pea epicotyl and mung-bean hypocotyl, have been visualized by indirect immunofluorescence. In all cells the microtubule arrangement can be interpreted as being a single multistart helix of variable pitch. In control cells the predominant pattern is a tightly compressed helix with the microtubules consequently in a net transverse direction with respect to the cell axis. Occasionally some cells show an oblique helix and rare cells show a longitudinal array which may be interpreted as a steeply pitched helix. By contrast in ethylene treated tissue, many cells show net longitudinal and oblique arrays of microtubules and few show transverse arrays. Similar effects can be induced by high osmolality. It is suggested that the plant cortical cytoskeleton is an integral unit, capable of wholesale reorientation in response to environmental signals.