Abstract: A LED(Light Emitting Diode) lighting tube for tissue culture was developed by using red LEDs(660±20nm) and blue LEDs(450±20nm).The ratio of red light intensity to blue light intensity(R/B ratio) was set at 4,6,8 and 10 respectively with a total PPF(Photosynthetic Photon Flux) of 35 mol·m-2·s-1.The sweet potato plantlets in vitro grown 28 days under four different R/B ratios and the normal fluorescent lamp were used as a control.Effect of the R/B ratio on the growth of sweet potato plantlets in vitro and the energy consumption with different R/B ratios were investigated.The results showed that the combination of red light and blue light could inhibit excessive growth,reduce plant water content and improve the root-shoot ratio.The fresh weight of above ground,leaf water content and height of plantlet were highest under fluorescent lamp conditions,but they also showed excessive growth and low dry matter accumulation.The stem length,root-shoot ratio,fresh weight of shoot and shoot water content were improved by the high R/B treatment.The root fresh weight and the root-top ratio were highest in the R/B treatment at 8.The R/B treatments had not significant influence on the chlorophyll and carotenoid contents.The energy consumption of LED tubes had a linear relationship with the R/B ratios and reduced by 27.6%～48.0% compared to the fluorescent lamp.

Key words: LED, LED, Tissue culture, R/B treatment, Sweet potato, Energy consumption