Cattleya walkeriana growth in different micropropagation systems/ Crescimento de Cattleya walkeriana em diferentes sistemas de micropropagacao

The aim of the present research was to verify the in vitro growth of orchids in different systems of micropropagation, being cultivated in a bioreactor, with natural ventilation and conventional systems. Cattleya walkeriana plants were obtained from the germination of seeds in culture medium. After 8 months, seedlings with 1 cm of length were placed in a culture vessel according to the treatments, which counted with two micropropagation systems (conventional and natural ventilation) in three media of culture (liquid, solid with 5 or 6g [L.sup.-1] of agar). Two additional treatments in bioreactor of temporary and continuous immersion were performed. The design was entirely randomized (ERD), consisting of a 2x3 factorial with two additional treatments, totaling 8 treatments with three repetitions. The temporary immersion bioreactor promoted a bigger growth of the aerial part and of the root system, bigger accumulation of dry mass and better control of water loss by the plants. The temporary immersion bioreactor is the best micropropagation system for the C. walkeriana growth in vitro. Key words: bioreactor, temporary immersion, liquid medium, natural ventilation, in vitro culture. O objetivo do presente trabalho foi verificar o crescimento in vitro de orquideas em diferentes sistemas de micropropagacao, sendo cultivado em biorreator, sistema de ventilacao natural e convencional. Plantas de Cattleya walkeriana foram obtidas a partir da germinacao de sementes em meio de cultura. Apos o a germinacao, as plantas foram uniformizadas com aproximadamente 1,0cm de comprimento e inoculadas nos diferentes tratamentos. Os tratamentos contaram dois sistema de micropropagacao (convencional e ventilacao natural) e tres meios de cultura (liquido, solido com 5 e 6g [L.sup.-1] de agar). Foram realizados dois tratamentos adicionais em biorreator de imersao temporaria e continua. O delineamento foi o inteiramente casualizado, consistindo de um fatorial 2x3 com dois tratamentos adicionais, totalizando oito tratamentos com tres repeticoes. O biorreator de imersao temporaria promoveu o maior crescimento da parte aerea e do sistema radicular, maior acumulo de massa seca e melhor controle da perda de agua das plantas. O biorreator de imersao temporaria e o melhor sistema de micropropagacao para o crescimento in vitro de C. walkeriana. Palavras-chave: biorreator, imersao temporaria, meio liquido, ventilacao natural, cultivo in vitro.