Improving flowering and vegetative growth in Oncidium baueri Lindl. through gibberellic acid application: insights into physiological parameters

Abstract Plant regulators are studied because they can alter commercially significant aspects of plant growth. Gibberellic acid (GA3) exemplifies this, as it plays a crucial role in the growth and flowering processes of various vegetables. Thus, the present study sought to verify the effects caused by the exogenous application of different doses of the plant regulator GA3 on the floral, vegetative, and physiological patterns of the orchid Oncidium baueri. The experimental treatments (T1; T2; T3; T4; and T5) had 10 replicates, each containing one plant, with the respective sprayed doses: 0, 50, 100, 200, and 400 mg L-1 of GA3. The parameters measured were: pseudobulb length (PL) and width (PW), leaf length (LL), leaf width (LW), number of leaves per plant (NL); time for flower spike to sprout (TFSS), time for flowers to open fully (TFOF), and time for flowers to fall (TFF), these measured in days; flower stem length (FSL), number of flowers per stem (NFS), chlorophyll a fluorescence (fv/fm), and stomatal conductance (G s ). Data were compared using the Tukey test at a significance of 5%. The concentration of 200 mg L-1 of GA3 increased PL and LL by 3 cm on average, and NL showed an increasing trend with treatment 4 compared to doses other than 0 mg L-¹. Regarding floral aspects, this same dose showed the lowest TFSS, distinguishing itself from the other treatments. For physiological parameters, this dose also resulted in higher fv/fm (0.826) and G s (65.340 mmol m-2 s-1). Therefore, the use of 200 mg L-1 of GA3 is recommended for O. baueri plants to optimize vegetative and floral promotion.