In vitro responses of Dendrobium sp. plantlets to Gibberellic Acid (GA₃) under PEG 6000-induced drought stress

Orchids are among the most economically important ornamental plants, with Dendrobium sp. widely cultivated due to its high diversity and commercial value. However, drought stress remains a major constraint, affecting plant growth at morphological, physiological, and anatomical levels. The application of gibberellic acid (GA₃) at an appropriate concentration is a potential strategy to improve plantlet performance under stress conditions. This study aimed to determine the optimal GA₃ concentration and to evaluate the morphological, physiological, and anatomical responses of Dendrobium sp. plantlets under In vitro drought stress conditions. The experiment was arranged in a Completely Randomized Design (CRD) with a single factor consisting of five GA₃ concentrations (0, 1, 2, 3, and 4 mg/L) in VW medium supplemented with Polyethylene Glycol (PEG 6000). Each treatment consisted of five replicates, with one plantlet per culture bottle. Data were analyzed using analysis of variance (ANOVA) at a 5% significance level, followed by Duncan’s Multiple Range Test (DMRT). The results showed that GA₃ concentration significantly affected stomatal density, while other parameters showed clear trends without significant differences. The optimal GA₃ concentration was 1 mg/L, which resulted in higher plantlet survival, improved morphological performance, increased chlorophyll content, and higher stomatal density. In contrast, higher GA₃ concentrations (≥2 mg/L) tended to reduce plantlet performance, indicating a dose-dependent inhibitory effect under drought stress conditions. These findings demonstrate that GA₃ plays a dose-dependent role in regulating plantlet responses to drought stress and highlight the importance of optimizing plant growth regulator application in orchid tissue culture systems.