Effect of Plant Growth Regulators on Flowering Traits and Physiological Characteristics of Dendrobium denneanum

In this study, to explore the effects of plant growth regulators 6-benzylaminopurine (BAP), Paclobutrazol (PBZ) and thidiazuron (TDZ) on the ornamental traits and physiology of Dendrobium denneanum Kerr. Different concentrations of BAP (200, 400, 600 mg/L), PBZ (1000, 1500, 2000 mg/L) and TDZ (10, 20, 40 mg/L) were set up to treat D. denneanum, and spraying water served as control (CK). The changes in flowering traits and physiological indexes of D. denneanum were observed and analyzed, while the content of endogenous hormones in its flowering process was determined by liquid chromatography. The results showed that 400 mg/L BAP, 2000 mg/L PBZ and 40 mg/L TDZ are beneficial for the formation of flowering quality in D. denneanum. Their ability to increase the content of photosynthetic pigments in D. denneanum leaves and slow down the loss of soluble sugars and soluble proteins during flowering, as well as increase the activities of superoxide dismutase (SOD) and peroxidase (POD) and reduce the content of malondialdehyde (MDA). Through the analysis of endogenous hormones, it was found that high levels of gibberellin (GA) favored flower bud differentiation and promoted flowering, while low levels of indole acetic acid (IAA) in the early stage favored the induction of flowering, and high levels of IAA in the later stage favored the establishment of flower morphology, compared with high levels of Zeatin (ZT) in the early stage, which induced flowering, and low levels of ZT in the later stage favored the morphology of flower differentiation.