The 2010 ASHS Annual Conference

Light quality influences the growth and morphology of plant tissues and plant development. Light-emitting diodes (LEDs) offer precise control of spectral composition and light quality. A comparison of growth under LEDs and white fluorescent lamps was conducted by placing in vitro cultures of anthurium and orchid explants under red LEDs, blue LEDs, and white fluorescent lamps. The objective of this study was to determine the effects of red LEDs and blue LEDs on micropropagation of anthurium ('UH 2357') and orchid (Dendrobium Uniwai Royale 'UH 1081') explants. Anthurium explants were grown in a half-strength Murashige and Skoog medium, supplemented with 15% coconut water, 20 g/L sucrose, and solidified with 2.0 g/L gelrite. The pH was 5.7-5.8. For the orchid, we used a modified Vacin and Went medium plus 17.5 g/L banana powder, 15% coconut water, solidified with 6.5 g/L agar, at a pH 4.8-5.0. Containers with the explants were placed under red LEDs, blue LEDs, and cool white fluorescent lamps at a light level of 69-70 µmoles/m²/s, 12-hr photoperiod, and 25-26°C. The red LEDs and blue LEDS had a higher percentage of alive shoots compared to the fluorescent lamps. The red LEDs resulted in greater shoot height than the other treatments. The fluorescent lamps had a higher callus dry weight than the blue LEDs, with the red LEDs not significantly different from the other treatments. There were no significant differences among the light treatments for the number of alive shoots, total number of shoots, shoot dry weight, root dry weight, and percent partitioning of dry weights for shoots, roots, and callus. With the blue LED treatment, the pigment saturation seemed higher, with darker green leaves and more red/maroon in the shoots. With the red LEDs, the shoots lacked pigmentation in the shoot and leaves. Also, average leaf size was smaller than with the other treatments. For 'UH 1081' orchid, there was no significant difference in total dry weight among the light treatments. In conclusion, LEDs offer a possible means of manipulating the growth of anthurium explants.