Effects of Spectral Quality and Light Quantity of LEDs on In Vitro Shoot Development and Proliferation of Ananas comosus L. Merr.

Light intensity and spectrum have a direct effect on the growth and development of plants and on the qualitative characteristics of their productions. LED technology seems to offer interesting prospects for its possible use in confined environments (growth chambers, bioreactors, greenhouses, etc). On the basis of these considerations, we tested the effects on the in vitro growth and development of micropropagated pineapple (Ananas comosus (L.) Merr.) plantlets using four different light spectra: (1) fluorescence light (FL--control); (2) white LED (WL--blue 20%, green 36%, red 38%, far red 6%, and UV 1%); (3) predominantly red LED (RL--blue 12%, green 19%, red 61%, and far red 8%); (4) Red/Blue LED (RL/BL--67% red and 33% blue) and two light intensities: 80 and 100 ?mol m-2s-1 (16/8 h light/dark photoperiod). A. comosus showed a different morphogenetic response to the light spectra and their intensity and to their interaction. Among the LED lights to date tested, at 80 ?mol m-2s-1 the best results on shoot multiplication were obtained under the RL light and to a lesser extent under the WL. This last treatment resulted also in a significant improvement in shoot quality in terms of secondary shoot dry weight and total chlorophyll concentration when compared to all the other light spectra tested.