Responses of strawberry plantlets cultured in vitro under superbright red and blue light-emitting diodes (LEDs)

Unrooted strawberry cv. 'Akihime' shoots with three leaves obtained from standard mixotrophic cultures were cultured in the "Culture Pack''-rockwool system with sugar-free MS medium under CO2-enriched condition. To examine the effect of superbright red and blue light-emitting diodes (LEDs) on in vitro growth of plantlets, these cultures were placed in an incubator, "LED PACK'', with either red LEDs, red LEDs blue LEDs or blue LEDs light source. To clarify the optimum blue and red LED ratio, cultures were placed in "LED PACK 3'' under LED light source with either 100, 90, 80, or 70% red 0, 10, 20, 30% blue, respectively, and also under standard heterotrophic conditions. To determine the effects of irradiation level, cultures were grown under 90% red LEDs+10% blue LEDs at 45, 60 or 75 mumol m(-2) s(-1). Plantlet growth was best at 70% red+30% blue LEDs. The optimal light intensity was 60 mumol m(-2) s(-1). Growth after transfer to soil was also best after in vitro culture with plantlets produced were 70% red LEDs 30% blue LEDs.