Auxin regulates nearly all aspects of plant development and behavior and impinges on a great variety of responses involving cell polarization, expansion, division and differentiation. ~ Chinese botanist Tongda Xu et al
Auxin is a class of hormones that are instrumental in coordinating plant development processes. The local concentration of auxin affects the growth direction of stems, roots, and shoots. Growth goes where auxin flows.
In sensing gravity, plants literally know what’s up. With proper gravitas, auxin directs tree branches to grow at a specific angle.
Auxin also factors in the ripening of fruit, the clinging of climbers, and numerous other behaviors. Auxin works epigenetically in being instrumental to selectively activating genes.