Responses of antioxidant enzymes, photosynthetic pigments and carbohydrates in micropropagated Pitcairnia encholirioides L.B. Sm. under ex vitro water deficit and after rehydration/ Respostas de enzimas antioxidantes, pigmentos fotossinteticos e carboidratos em Pitcairnia encholirioides L.B. Sm

In this study, the activities of antioxidant enzymes, photosynthetic pigments, proline and carbohydrate contents in Pitcairnia encholirioides under ex vitro conditions of water deficit were evaluated. Results show that plants under progressive water stress, previously in vitro cultured in media supplemented with 30 g [L.sup.-1] sucrose and GA3, accumulated more proline and increased peroxidase (POD) activity and the contents of photosynthetic pigments and carbohydrates. For plants previously in vitro cultured with 15 g [L.sup.-1] sucrose and NAA, no differences were found for proline content and there were reductions in activities of peroxidase (POD), catalase (CAT) and poliphenoloxidase (PPO), and in contents of carbohydrates, with progress of ex vitro water deficit. After rehydration, plants showed physiological recovery, with enzymatic activities and contents of metabolites similar to those found in the controls not submitted to dehydration, regardless of the previous in vitro culture conditions. These results show that micropropagated P. encholirioides has high tolerance to dehydration once in ex vitro conditions, which can ensure the survival of plants from tissue culture when transferred to its natural environment, emphasizing the importance of such biotechnology for the propagation of endangered species. Keywords: antioxidant enzymes, carbohydrates, photosynthetic pigments, proline, water stress. Neste estudo, foram avaliadas as atividades de enzimas antioxidantes, pigmentos fotossinteticos, conteudo de prolina e carboidratos em Pitcairnia encholirioides sob deficit hidrico em condicoes ex vitro. Os resultados mostraram que as plantas sob estresse hidrico progressivo, previamente cultivadas in vitro em meio de cultura suplementado com 30 g [L.sup.-1] de sacarose e [GA.sub.3] acumularam mais prolina e aumentaram a atividade da peroxidase (POD) e os teores de pigmentos fotossinteticos e carboidratos. Para plantas previamente cultivadas in vitro com 15 g [L.sup.-1] de sacarose e ANA, nao foram encontradas diferencas nos conteudos de prolina e houve reducoes nas atividades da peroxidase (POD), catalase (CAT) e polifenoloxidase (PPO), e no conteudo de carboidratos, com o progresso do deficit hidrico ex vitro. Apos a reidratacao, as plantas apresentaram recuperacao fisiologica, com atividades enzimaticas e conteudo de metabolitos semelhantes aos encontrados nos controles nao sujeitos a desidratacao, independentemente das condicoes de cultivo in vitro. Est