Elongation of Dendrobium nobile Lindl. plants by gibberellic acid pulverization

The Dendrobium nobile Lindl. (olho-de-boneca) is one of the most popular orchids of Brazil, occupying prominence position in the market of cut plants and pot. However, the very slow development of the family Orchidaceae has been contributing to the high unitary value of the plants, being necessary techniques that promote the fastest way of obtaining plants in the marketed. With the objective of evaluating the effect of the gibberellic acid in the elongation of plants of D. nobile spread by cutting, an entirely randomized experimental design was carried out with five concentrations of GA(3) (0, 50, 100, 200 and 400 mg.L-1) and thirteen replications. They were made four sprays with GA(3) solutions to biweekly intervals and ninety days after beginning of the treatments, the following characteristics were evaluated: height and diameter of the pseudobulbs, number of leaves width and length of the leaves. The GA3 application promoted, in comparison with the control increasings of 64,08% in height and 44,27% in the length of the leaves and decreasing of 50% in the diameter of the pseudobulbs and 56,09% in the width of the leaves. There was no difference among the GA(3) concentrations tested. Therefore, the giberelic acid in the concentrations from 50 to 400 mg. L-1 is efficient in the elongation of D. nobile plants.