Early Flowering Induction in Golden Camellia Seedlings and Effects of Paclobutrazol

Abstract

Camellia chrysantha flowers are in great market demand as a result of their high ornamental and medicinal values. To induce early flowering in 4-year-old juvenile C. chrysantha seedlings, three levels of paclobutrazol (PBZ) concentration (100, 200, and 300 ppm) were applied to the roots. PBZ is a triazole-type cytochrome P450 inhibitor that was found successful in inducing flowering in juvenile C. chrysantha grafted plants in a prior report. The current study shows that all three PBZ concentrations were equally effective in induction of floral buds, resulting in an average of 20 floral buds per treated plant. In comparison, none of the untreated plants flowered. Although the induced flowers were smaller than the ones from mature trees, PBZ treatment did not affect C. chrysantha flowers’ medical values, because there was no significant change in the content of pharmacologically active compounds (polysaccharide, polyphenols, flavonoids, and saponins). None of the PBZ treatments had a negative effect on the current year’s growth in height and basal diameter, photosynthesis, and levels of water-soluble sugars and nutrients [phosphorus (P), nitrogen (N), potassium (K), and carbon (C)]. It is concluded that PBZ is an effective flowering inducer for juvenile C. chrysantha plants. It was also found that PBZ-treated plants experienced defoliation, and there existed a strong correlation between severity of defoliation and PBZ concentration. This might be attributed by the stress induced by PBZ, as demonstrated by the increased activities of some of the stress-related enzymes [ascorbate peroxidase (APX), catalase (CAT), superoxide dismutase (SOD), and peroxidase (POD)], and the level of malondialdehyde (MAD). Considering that severe defoliation can cause stunted or malformed plants and reduce aesthetic value, 100 ppm is the optimal PBZ concentration for flowering induction in C. chrysantha seedlings.