Crescimento in vitro de Cattleya loddigesii LindI. em diferentes espectros luminosos associado com ácido giberélico

Abstract

The manipulation of the culture medium composition and the conditions of cultivation can optimize the in vitro propagation of orchids, thus consisting in a viable way to increase the quality of micropropagated plants. In order to study the in vitro growth of Cattleya loddigesii, different light spectra (white, yellow, blue, green and red) associated with the concentrations of gibberellic acid (0, 2.5, 5, 10 and 20 mg L-1 GA3 ) were evaluated. Plants measuring approximately 1 cm in length, were inoculated in bottles containing 60 mL of modified WPM medium, according to the treatments. The medium was previously adjusted to pH 5.7 ± 0.1 and autoclaved. After 90 days of inoculation, the number of shoots showed no significant difference between treatments. Number of roots and fresh weight of plants increased in the absence of gibberellin. Best responses for length of shoot and root length were recorded in the absence of GA3 and red cellophane and under cultivation in a growth room (white light), respectively. The highest number of leaves was obtained in plants grown under blue cellophane. Thus we can conclude that the cultivation in a growth room under red cellophane increases the elongation of plants and the presence of GA3 interfere negatively in the growth of in vitro Cattleya loddigesi.