E. Goto, H. Matsumoto, Y. Ishigami, S. Hikosaka, K. Fujiwara, A. Yano
Here, we evaluated the effect of light quality on vegetable growth to determine the efficiency of light energy utilization on photosynthesis in plant factories. Specifi-cally, we measured the gross photosynthetic rate (P) of butterhead lettuce, green perilla, red perilla, and tomato seedlings under a range of different LED peak wave-lengths using the assimilation chamber technique. The light-source system included 6 peak LED wavelength types: 405, 465, 530, 595, 660, and 735 nm. The system produces light composed of different combinations of the 6 wavelength ranges. Photo¬synthetic photon flux (PPF) values of 160 and 320 μmol•m-2•s-1 with 4 peak wavelengths (465, 530, 595, and 660 nm of 40 and 80 μmol•m-2•s-1, respectively) were set as the controls. Then, the PPF conditions of 120 and 240 μmol•m-2•s-1 were determined by turning off 1 of the 4 peak LEDs. By using the difference between P at 120 and 160 μmol•m-2•s-1 and 240 and 320 μmol•m-2•s-1, at a given wavelength, an incremental increase in P at low and high PPF levels was calculated, and expressed as absorbed CO2 per added photon. The results showed that the highest incremental increase was obtained at 660 nm for all 4 vegetables. For red perilla and tomato, a significantly low incremental increase was obtained at 465 and 530 nm. The anthocyanin-rich leaves of these 2 plants are known to absorb large quantities of blue and green light in the epidermis, which led to lower P values at these wavelengths. The difference in the incremental increase was smaller at 320 μmol•m-2•s-1 than at 160 μmol•m-2•s-1 for all 4 vegetables. In conclusion, we suggest that the suitable wavelength to increase P varies depending on crop type, light quality history, and light intensity.
Goto, E., Matsumoto, H., Ishigami, Y., Hikosaka, S., Fujiwara, K. and Yano, A. (2014). MEASUREMENTS OF THE PHOTOSYNTHETIC RATES IN VEGETABLES UNDER VARIOUS QUALITIES OF LIGHT FROM LIGHT-EMITTING DIODES. Acta Hortic. 1037, 261-268
DOI: 10.17660/ActaHortic.2014.1037.30
assimilation chamber, lettuce, light quality, perilla, tomato

Acta Horticulturae