White LED light with wide wavelength spectrum promotes high-yielding and energy-saving indoor vegetable production

摘要

Light-emitting diode (LED) lighting systems for agricultural applications are being rapidly developed. Moreover, a great deal of knowledge of the responses of plants to light has been obtained from spectroscopic analysis studies. In this study, the usefulness of white LED lights with broadband spectra extended to wavelengths beyond 700 nm was evaluated by comparative assessment against other conventional white LED light, combinations of monochromatic red and blue LED (R+B-LED) light and fluorescent light. We examined the effects of LED spectral differences on the productivity and power consumption for hydroponically cultivated lettuce plants [Lactuca sativa L. s. van longifolia and L. sativa var. crispa). When fluorescent light was used as a reference for white illumination, the 13 tested LEDs could be divided into two groups based on their productivity. Yield from the illumination of seven LEDs was higher than that from fluorescent light, but the yield was lower from the remaining six LEDs. To understand the relationship between spectral features and productivity, ratios of integrated values of red, blue and far-red photons were used. Significant increases in biomass were observed under red/blue ratios of 2.4-4.5 and under red/far-red ratios of 2.7-7.4. Neither higher nor lower values beyond these ranges resulted in good yield. The electric power consumptions of white LEDs needed for the same weight of vegetable production were clearly less than that of fluorescent light. Morphological variationtypical of spectral properties of white LEDs was observed. It is concluded that lighting systems of broadband white LEDs can promote plant growth and be an economically valuable tool for culturing plants.