Relationship between photomorphogenesis and tree growth in Cryptomeria japonica assessed using light emitting diodes

Abstract

Recently, there has been considerable interest in establishing tree-rearing methods for breeding nursery trees, which are similar to the methods employed in plant factories to produce vegetables. Studies have shown that the efficiency of tree cultivation can be improved by changing the wavelength of the lighting that is used to raise young plants and that light emitting diodes (LEDs) are effective for this purpose. In this study, the effect of blue (450 nm), red (660 nm), and white (combination of blue and yellow (525 nm) LED lights was investigated for rearing Cryptomeria japonica saplings. 7 saplings with each LED were prepared and reared for 52 weeks in a constant environment chamber (Temperature: 23 ± 2 °C, relative humidity 50% ± 10%), and their growth rates and root system morphology were compared. After 52 weeks of breeding, red light induced slightly more stem growth than white light. Blue light was nearly three times more effective in stem growth than white light. Furthermore, the wavelength of light affected the root system morphology. Many root branches were observed in saplings reared under red light, while marked taproot growth was observed in saplings reared under blue light. There was a possibility that saplings could be produced more efficiently by using LED.