Natural light as an alternative light source for the in vitro culture of banana (Musa acuminata cv. 'Grande Naine')

The concept of using sunlight for micropropagation systems is proposed as a way of reducing tissue culture costs. Shoot tips of Musa acuminata cultiva r `Grande Naine' were cultured in a non-controlled natural light environmen t at the IAEA Laboratories, Austria during summertime. Significantly more s hoots were produced by plantlets cultivated in a sunlit room with photosynt hetic photon flux densities (PPFD) fluctuating up to 570 mu mol m(-2) s(-1) , temperatures between 23 and 30 degrees C and photoperiods of 12 to 16-h, than by plantlets under artificial light in a growth chamber providing cont rolled conditions of a constant PPFD of 65 mu mol m(-2) s(-1), temperatures ranging from 23 to 29 degrees C and a 16-h photoperiod. Highest multiplica tion rates were achieved in a greenhouse with PPFD reaching 860 mu mol m(-2 ) s(-1) and temperatures of 18 - 43 degrees C, but browning of leaves and l oss of turgor occurred. Nevertheless, rooted plantlets showed 100% survival during acclimatisation and normal development. Photoperiods of 12 - 16 h d id not affect the multiplication rates.