LED technology is increasingly used in organ and tissue cultures of ornamental plants due to its ability to adjust the spectral light composition to the physiological and morphological requirements of plants. This chapter presents an overview of studies that have been conducted to investigate the effects of light-emitting diodes (LEDs) on the propagation of different orchids under in vitro condition. Most of the available reports are related to the use of mixed red and blue LEDs. In general, monochromatic red light enhances vegetative growth, whereas blue light usually increases chlorophyll content in the regenerated plantlets. There are some particular species in which beneficial effects of green LED light have been ascertained on the induction of protocorm-like bodies (PLBs). The application of far-red in combination with red light can be effective in the improvement of the quality of micropropagated plantlets. However, the results vary depending on tested spectral composition of light, species, or even cultivar as well as applied environmental conditions. This review also addresses future challenges in the adoption of LED technology for improving the growth and development of plantlets cultivated under ex vitro conditions.
