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 stalk in a poppy, Papaver Rhoeas L., immediately after its formation was triggered by the weight of its flower bud or by positive georeaction and the following results were obtained.The direction of the nodding was mostly toward the inclined side of the stalk, which was opposite the leaf, for apical flower buds.If the weight of the flower bud at stage 1 was cancelled by applying a load equivalent to the bud weight, the nodding of the stalk was not initiated.The stalk at stages 1 and 2 and the upper part of the stalk (bending zone), as compared with the basal part, at later stages were highly deformable according to measurements by the bending method.The cell wall of highly deformable stalks was rich in hemicelluloses and that of the basal part was abundant in pectic substances.From these results, we concluded that the initiation of the nodding in the flower stalk was caused by the weight of the flower bud and positive geotropic reaction was probably not involved.