Fontes e concentrações de carboidratos no crescimento vegetativo e no enraizamento in vitro de Miltonia flavescens Lindl.

Miltonia flavescens is an epiphytic orchid native to southern Brazil threatened with extinction by extraction and destruction of their habitats. Type and concentration of carbohydrates are important for promoting growth and development of in vitro cultured orchids. This study aimed to evaluate the effect of different carbohydrate sources and concentrations on in vitro growth and rooting of M. flavescens. In vitro seed-derived plants used as explants were cultured in half-strength MS media containing sucrose, maltose and glucose as carbohydrate sources, at concentrations of 0, 15, 30, 45 and 60 g.L-1. After six months in culture, plants were evaluated for aerial part height, root number, leaf number, shoot number and fresh weight. The experiment was arranged in a complete randomized design, with five replications per treatment and experimental unit consisting of ten plants per flask. Leaf number was the only variable that was not significantly affected by the source and concentration of carbohydrates. At the concentrations of 15 and 60 g.L-1 of carbohydrate, no difference was found among sucrose, glucose and maltose for any variable tested. On the other hand, sucrose at concentrations of 30 and 45 g.L-1 promoted in vitro growth of M. flavescens.Miltonia flavescens is an epiphytic orchid native to southern Brazil threatened with extinction by extraction and destruction of their habitats. Type and concentration of carbohydrates are important for promoting growth and development of in vitro cultured orchids. This study aimed to evaluate the effect of different carbohydrate sources and concentrations on in vitro growth and rooting of M. flavescens. In vitro seed-derived plants used as explants were cultured in half-strength MS media containing sucrose, maltose and glucose as carbohydrate sources, at concentrations of 0, 15, 30, 45 and 60 g.L-1. After six months in culture, plants were evaluated for aerial part height, root number, leaf number, shoot number and fresh weight. The experiment was arranged in a complete randomized design, with five replications per treatment and experimental unit consisting of ten plants per flask. Leaf number was the only variable that was not significantly affected by the source and concentration of carbohydrates. At the concentrations of 15 and 60 g.L-1 of carbohydrate, no difference was found among sucrose, glucose and maltose for any variable tested. On the other hand, sucrose at concentrations of 30 and 45 g.L-1 promoted in vitro growth of M. flavescens.Miltonia flavescens é uma orquídea epífita nativa da região sul do Brasil ameaçada de extinção pelo extrativismo e a destruição dos seus habitats. O tipo e a concentração dos carboidratos são importantes para promover o crescimento e o desenvolvimento das plantas das orquídeas in vitro. O presente trabalho teve como objetivo avaliar o efeito de diferentes fontes e concentrações de carboidratos no crescimento e enraizamento in vitro de plantas de M. flavescens. Foi utilizado o meio de cultura MS, modificado pela redução à metade da concentração de sais. Plantas provenientes de sementes estabelecidas in vitro, foram utilizadas como explantes, os quais foram inoculados nos meios de cultura contendo as seguintes fontes de carboidratos: sacarose, maltose e glicose, nas concentrações de 0, 15, 30, 45 e 60 g L-1. Após seis meses de cultivo as plantas foram avaliadas quanto a altura da parte aérea, número de raízes, número de folhas, número de brotos e peso da matéria fresca. O delineamento experimental utilizado foi inteiramente casualizado com cinco repetições por tratamento, sendo a unidade experimental constituída de um frasco com dez plantas. Apenas o número de folhas não foi significativamente afetado pela fonte e concentração de carboidratos. Quando o meio de cultura foi suplementado com 15 e 60 g L-1 de carboidrato, não foi verificada diferença entre a sacarose, a glicose e a maltose para nenhuma variável e, de maneira geral, a sacarose nas concentrações 30 e 45 g L-1 promoveu melhores resultados no crescimento in vitro de M. flavescens.