A Study on the Mechanism of Nodding Initiation of the Flower Stalk in a Poppy, Papaver Rhoeas L.

A study was made to find whether the nodding of the flower stalkin a poppy, Papaver Rhoeas L., immediately after its formationwas triggered by the weight of its flower bud or by positivegeoreaction and the following results were obtained.

1. The direction of the nodding was mostly toward the inclinedside of the stalk, which was opposite the leaf, for apical flowerbuds.
2. If the weight of the flower bud at stage 1 was cancelledbyapplying a load equivalent to the bud weight, the noddingofthe stalk was not initiated.
3. The stalk at stages 1 and2 and the upper part of the stalk(bending zone), as comparedwith the basal part, at later stageswere highly deformableaccording to measurements by the bendingmethod.
4. The cellwall of highly deformable stalks was rich in hemicellulosesand that of the basal part was abundant in pectic substances.

From these results, we concluded that the initiation of thenodding in the flower stalk was caused by the weight of theflower bud and positive geotropic reaction was probably notinvolved. (Received December 22, 1980; Accepted January 26, 1981)