Carbohydrates on the growth of Cattleya schilleriana Reichb.f. seedlings / Carboidratos no crescimento de plantulas de Cattleya schilleriana Reichb.f

The aim of the present study was to evaluate the effects of carbohydrate supplementation on the propagation of the orchid Cattleya schilleriana. The 120-d-old seedlings were subcultured in fructose-, glucose-, or sucrose-supplemented (0, 15, 30, and 45g [L.sup.-1]) 1/2 MS culture medium (half-strength macronutrient concentrations), using a completely random design with four repetitions per treatment. After 120d of treatment, root number and length, leaf number and length, and fresh weight were evaluated, and seedling survival was evaluated after 75d of acclimatization in a greenhouse. The in vitro growth data were submitted to regression analysis, whereas the percentage survival data were analyzed using ANOVA and Tukey's test. Both in vitro growth and ex vitro survival were lowest when the plantlets were grown in the absence of a carbohydrate source and highest (>90% survival) when supplemented with glucose. According to our findings, the addition of either glucose (30g [L.sup.-1]) or sucrose (30g [L.sup.-1]) is recommended for mass propagation of C. schilleriana. Key words: in vitro culture; native orchid; glucose; sucrose; acclimatization. O objetivo deste estudo foi avaliar a adicao de doses de carboidratos em meio de cultura 1/2 MS para a propagacao da orquidea Cattleya schilleriana. Plantulas com 120 dias apos semeadura foram recultivadas em 12 tratamentos, onde foram investigadas a adicao de diferentes doses de frutose, glicose e sacarose (0, 15, 30 e 45g [L.sup.-1]). O delineamento utilizado foi inteiramente casualizado com quatro repeticoes por tratamento. Apos 120 dias nos tratamentos, foram mensurados o numero de raizes, comprimento da maior raiz, numero de folhas, comprimento da maior folha e massa fresca total. Depois as plantulas foram aclimatizadas em casa de vegetacao e avaliada a taxa de sobrevivencia apos 75 dias. Os dados obtidos foram submetidos ao teste de Tukey a 5% de probabilidade e ajustadas curvas de regressao. A ausencia de carboidrato reduziu o crescimento das plantulas entre todas as caracteristicas avaliadas in vitro e ex vitro. As doses de glicose promoveram maior eficiencia para o crescimento in vitro e sobrevivencia acima de 90% apos a aclimatizacao. Assim, a adicao de glicose (30g [L.sup.-1]) ou sacarose (30g [L.sup.-1]) sao recomendadas para a propagacao massal de C. schilleriana. Palavras-chave: cultura in vitro; orquidea nativa; glicose; sacarose; aclimatizacao.