Effects of Exogenous Auxin (IBA or NAA) and Combined Auxin-BA Dipping Treatments on Propagation Performance, Development, and Physiological Responses of Philodendron hederaceum Schott Stem Cuttings

Background and objective: Philodendron hederaceum Schott is a widely cultivated ornamental foliage plant that is commonly propagated by stem cuttings; however, uneven rooting and establishment, along with variability in early growth, can reduce production uniformity. This study aimed to evaluate the effects of exogenous auxin (indole-3-butyric acid; IBA or 1- naphthaleneacetic acid; NAA) dipping, applied either alone or in combination with a low concentration of 6-benzyladenine (BA), on propagation performance and subsequent morphophysiological quality of P. hederaceum stem cuttings.Methods: Single-node stem cuttings (approximately 5 cm) with one leaf were dipped (basal 0.5 cm for 1 min) in ten solutions, including a control (25% ethanol), BA (0.1 g⋅L-1), IBA or NAA (0.5 or 1.0 g⋅L-1), and auxin-BA combinations, and then grown for four months. Survival and rooting rates, growth parameters, biomass components, remote sensing-based vegetation indices (e.g., anthocyanin reflectance index 2 and normalized difference vegetation index), and chlorophyll fluorescence parameters (Fv/Fm and PIABS) were assessed. Data were analyzed using Duncan's multiple range test, and principal component analysis (PCA) was performed to interpret multivariate response patterns.Results: Survival and rooting rates did not differ significantly among treatments, but several growth parameters (e.g., shoot length and width, internode length, and root length) responded to dipping treatments. Leaf-size parameters showed treatment-dependent changes, while leaf number was not significantly affected. Shoot fresh weight showed limited treatment effects, whereas root fresh and dry weights varied among treatments, indicating that the auxin-BA combination (IBA 0.5 g⋅L-1 with BA 0.1 g⋅L-1) was associated with relatively greater post-establishment vigor, particularly in root biomass accumulation. Optical and leaf pigment-related metrics (e.g., SPAD units, CIELAB L* and a*, and selected vegetation indices) differed across treatments, but Fv/Fm and PIABS were not significantly affected. PCA indicated that PC1 (31.2%) represented a morphology/biomass axis and PC2 (18.2%) reflected vegetation-index variation, with cumulative variance reaching 59.6% by PC3.Conclusion: Overall, auxin-only and auxin-BA combined dipping treatments mainly affected post-establishment growth and quality-related traits rather than rooting rate. Within the tested range, IBA at 0.5 g⋅L-1, particularly in combination with BA at 0.1 g⋅L-1, was associated with more favorable growth and root biomass responses, whereas NAA at 1.0 g⋅L-1 tended to show less favorable responses. PCA further supported the interpretation that growth/biomass traits and optical traits represented partly distinct response dimensions.