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 cultivar `Grande Naine' were cultured in a non-controlled natural light environment at the IAEA Laboratories, Austria during summertime. Significantly more shoots were produced by plantlets cultivated in a sunlit room with photosynthetic 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 controlled 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 multiplication 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 loss of turgor occurred. Nevertheless, rooted plantlets showed 100% survival during acclimatisation and normal development. Photoperiods of 12 - 16 h did not affect the multiplication rates.