Auxin Transport in Leaf Epinasty

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Abstract
Epinastic curvatures appeared in the leaves of Coleus blumei, Euphorbia pulcherrima and Lycopersicum esculentum when the plants were rotated on horizontal clinostats. The angles of curvature were measured on superimposed shadowgraphs and found to be about 40[degree] for the 1st day and 55[degree] at the end of the 2nd day. Similar epinasty was induced in debladed petioles of Coleus by applying 1% IAA in lanolin paste. Evidence for lateral, upward transport of IAA in these petioles was obtained from the development of epinastic curvature regardless of the point of application of the IAA to the distal end of the petiole. The blocking effect of triiodobenzoic acid on auxin transport was used to confirm the lateral transport. When a lanolin paste of 1% IAA-2-C14 was spread thinly on the under epidermis of the leaf blades of the 3 species, excess radiocarbon could be extracted from the convex half of the epinastic curvature in the petiole, with part of the radioactivity still in unaltered IAA. The mechanism for the lateral transport of auxin is unknown. The result has beneficial effects on the life of the plant, comparable to those provided by a similar unknown process previously shown to provide the basis for branch epinasty.