Photoperiodic Responses of Two Cestrum Species and Non-Interchangeability of Their Flowering Hormones

Recently Lincoln et al. (2) isolated a fraction from the leaves of induced Xanthium strumarium L. which, when applied to the leaves of noninduced plants of X. pennsylvanicum Wallr., caused formation of flower primordia. With this discovery it becomes more important that we examine various species to determine, if possible, whether a single flowering hormone is present in Angiosperms, or a series of such hormones. This report offers some evidence in this area. Evidence concerning photoperiodic response of Cestrum nocturnum L. has been previously reported by Sachs (4). In his work it was demonstrated that C. nocturnum is a long-short day (LSD) plant; that the hormone is synthesized in mature leaves and is transported through the stem to the potential floral buds both acropetaly and basipetaly. This present investigation gives evidence that C. nocturnlem responds with flower formation to a long day (LD) treatment as well as to a LSD treatment.