IAA Transport and Georeaction in the Flower Stalk of a Poppy, Papaver Rhoeas L.

The straightening process in the georeaction of the flower stalk(peduncle) of a poppy, Papaver Rhoeas L., was studied in relationto IAA transport in the peduncle and the receptacle. After thepeduncle had been formed, it first nodded. Cutting the flowerbud off at the nodding stage (stage 3–4 if the developmentis divided into 12 stages) caused rapid straightening of thenodding peduncle but the curvature was maintained if IAA wasapplied to the cut end of the decapitated peduncle. Applicationof 2,3,5-triiodobenzoic acid to the upper part of the pedunclejust below the flower bud at various growth stages caused immediatestraightening of the nodding peduncle. The IAA content in thepeduncle was lower at the straightening stages than at the noddingstage. Transport of ¹⁴C-IAA through the receptacle was lessat the straightening stages than at the nodding stage, whilethat through the peduncle was the same at these stages. Theseresults led to the conclusion that the straightening processof the poppy peduncle, which is considered to be a negativegeotropic response, is controlled by a decrease in the basipitaltransport of IAA from the flower bud to the peduncle throughthe receptacle. (Received April 12, 1982; Accepted September 13, 1982)