by Alexan­der Weitzel — The process I will be dis­cussing is plant grav­it­ro­pism, the abil­ity of higher plants to sense the vec­tor in which grav­ity is act­ing and grow par­al­lel to that vec­tor, ei­ther in the pos­i­tive di­rec­tion (shoots and leaves) or in the neg­a­tive di­rec­tion (roots).