The bent peduncle phenomenon in roses is a developmental process involving auxin

In roses, bending of the peduncle during flower development – “bent peduncle phenomenon” (BPP) – results in the production of a series of developmental aberrancies. Detailed characterization of BPP revealed that the typical bending is intrinsically related to developmental features, i.e., the presence of an enlarged sepal appearing as a phylloid structure, floral organ conversions, fasciation of the stem and the higher incidence of BPP in axillary stems developing from BPP stems than from normal stems. The sclerenchymal tissue of BPP stems exhibited larger cells and thinner cell walls than those of normal stems, which may facilitate the bending process. BPP-like bending could be induced by external auxin application and inhibited by auxin transport inhibitors. Thus, in BPP auxin appears to be involved in differential growth, thereby inducing bending. However, there were no differences in endogenous IAA content between the upper and lower sides of bent peduncles, indicating that the asymmetric IAA distribution may be transient. This study strongly suggests that BPP is a developmental process, occurring during the meristematic stage of flower formation, possibly involving auxin distribution, which affects stem bending and fasciation.