Thigmomorphogenesis: The Involvement of Auxin and Abscisic Acid in Growth Retardation Due to Mechanical Perturbation

When young bean plants are mechanically perturbed for up to10 days, they accumulate large amounts of an auxin-like substanceand increased amounts of ABA. Exogenous ethylene, applied inthe form of ethephon, produces the same result. Physiologicallymoderately high amounts of exogenously applied IAA or loweramounts of ABA cause the same sort of retardation of elongationthat is caused by either mechanical perturbation or exogenousethephon. Either mechanical perturbation or applied ethephonsignificantly retards the polar basipetal transport of ¹⁴C-IAAIt is proposed that mechanical perturbation of bean internodesinduces ethylene evolution which, in turn, induces the accumulationof high levels of IAA and the production of ABA, both of whichcontribute to the retardation of elongation of the internodes. (Received December 24, 1981; Accepted May 19, 1982)