Keywords: Trichocentrum stramineum, epiphyte, polyvinyl pyrrolidone.
The objective of the present study was to determine the most suitable culture medium for in vitro propagation of Oncidium stramineum Lindl. Murashige and Skoog (MS) medium was used for germination, and for growth MS (T1) and MS (T2) medium supplemented with organic extracts, coconut milk, peptone and active charcoal, and MS (T3) supplemented with organic extracts, coconut milk, peptone and polyvinyl pyrrolidone were tested. Germination was 47.69 %. During growth seven phenological stages were observed: imbibition in four days, green seeds in eight days, germination in thirteen days, initial protocorm in sixteen days, late protocorm in nineteen days, leaf development in twenty-eight days, production of true roots in thirty-four days, and seedling development. Number of buds, leaf length, leaf width, number of roots, and seedling height were affected by the treatments, but not root length. The Tukey analysis showed significant differences among treatments in number of buds, leaf length, number of roots and seedling height. The evaluated variables showed that culture medium (T3) supplemented with organic extracts, coconut water, peptone and polyvinyl pyrrolidone increased leaf width, leaf length and seedling height. With MS (T3) all the variables evaluated correlated significantly. The best growth of Oncidium stramineum Lindl. seedlings was observed in MS culture medium supplemented with 100 mL·litter-1 coconut milk, 40 g·litter-1 organic extracts from tomato, apple and banana, 2.0 g·litter-1 peptone and 200 mg·litter-1 polyvinyl pyrrolidone .