MECHANOSENSORY MICROTUBULE REORIENTATION IN THE EPIDERMIS OF MAIZE COLEOPTILES SUBJECTED TO BENDING STRESS

Plants respond to mechanical stress by adaptive changes in growth. Alt hough this phenomenon is well established, the mechanism of the percep tion of mechanical forces by plant cells is not yet known. We provide evidence that the cortical microtubules subadjacent to the growth-cont rolling outer epidermal cell wall of maize coleoptiles respond to mech anical extension and compression by rapidly reorientating perpendicula r to the direction of the effective force change. These findings shed new light on many seemingly unrelated observations on microtubule reor ientation by growth factors such as light or phytohormones. Moreover, our results suggest that microtubules associated with the plasma membr ane are causally involved in sensing vectorial forces and provide vect orial information to the cell that can be utilized in the orientation of plant organ expansion.