Impacts of photoautotrophic and photomixotrophic conditions on in vitro propagated Billbergia zebrina (Bromeliaceae)

Micro-propagation techniques contribute to the multiplication of several bromeliad species. However, micropropagated plantlets often present low survival rate due to anatomical and physiological disorders induced by in vitro conditions. This study aimed to evaluate the sucrose and gas exchange impact on in vitro propagated Billbergia zebrina plants and to check if there is any residual effect of the in vitro conditions on micropropagated plants after acclimatization. Previously in vitro-established B. zebrina plants were transferred to culture media containing 0.0, 15.0, 30.0, 45.0 or 60.0 g L-1 sucrose. Two different culture container sealing systems were tested: lids with a filter (permitting an excellent gas exchange) and a filter covered with PVC (blocking fluent gas exchange). At 45 days in vitro growth, B. zebrina plantlets were transplanted onto plastic pots containing peat and cultivated for 80 days in greenhouse. At 45 days in vitro and 80 days of acclimatization in the greenhouse, the plants were evaluated. High sucrose levels in the in vitro media resulted in reduced growth. Plantlets exposed to aerated containers presented better rooting, being the sugar-free medium the best in vitro condition (photoautotrophic condition). Limited air exchange resulted in plantlets with anatomical and physiological disorders at the end of the in vitro period. The highest growth rate in the greenhouse was observed in plants previously propagated in unlimited gas exchange system and sugar-free medium. The use of photoautotrophic conditions induces B. zebrina plantlets without anatomical and physiological disorders and it interfere positively on ex vitro growth.