Multiplicação “in vitro” de Cattleya x mesquitae pelo método de estiolamento de segmentos caulinares

Abstract

The objective of this study was to stimulate the formation of larger number of shoots and new explants by growth regulators addition to culture medium of in vitro stem segment orchid Cattleya x mesquitae. The stem segments were cut off plants obtained from in vitro seedlings, standardized to 1.0 cm long and grown at temperature of 25C ± 2C, in the dark, for sixty days. The culture medium was MS with reduction of macronutrients by half, containing three concentrations of ANA (0 mg L-1, 0.1 mg L-1, and 2.0 mg L-1) and three concentrations of BAP (0 mg L-1, 0.5 mg L-1, and 2.0 mg L-1). In general, there was a higher shoot production on the base than on the nodes, what indicates a low development of the axillary shoots. With the addition of 0.5 mg L-1 of BAP there was an average production of five shoots per etiolated explant, which represented an increase of up to two shoots as related to the absence of the growth regulator. A higher concentration of BAP in the medium (2.0 mg L-1) revealed to be harmful, causing a 50% reduction in new shoot production. The absence of light was determinant for stem lengthening, whereas the application of growth regulators was unnecessary, although a larger formation of nodes has occurred when 2.0 mg L-1 of ANA was used.