Abstract
In plant cultivation, the number of photons is more important than the light energy from the chemical reactions that occur during photosynthesis. In addition, the blue and red photon flux (B/R) ratio is an important parameter for plant cultivation. Here we discuss the effect of the spectral irradiance distribution and the B/R ratio on plant cultivation. We cultivated lettuce seedlings, Lactuca sativa L. Cv. Okayama, using a light-emitting diode illumination system that can precisely control the spectral irradiance distribution and B/R ratio. The B/R ratio varied from 0.36 to 2.06 according to the intensity of the blue light when the photosynthetic photon flux density values were sufficient to ensure the 150 - 200 μmol⋅m−2⋅s−1. High photon flux densities of blue light result in reduced plant length, plant height, and leaf area, thereby suggesting its role in the suppression of leaf growth. Therefore, we conclude that a lower photon flux of blue light (B/R Ratio) is optimal for lettuce cultivation.
Highlights
Plant factories have many advantages, i.e., the plants’ growth environment can be controlled
The number of photons is more important than the light energy due to the chemical reactions that occur during photosynthesis; photons contribute to generating glucose, which determines the rate of photosynthesis
Based on the above results, in this study, we cultivated plants using an light emitting diodes (LEDs) illumination system that could precisely control both the spectral irradiance distribution and the blue and red photon flux (B/R) ratios to examine their effects on plant cultivation
Summary
Plant factories have many advantages, i.e., the plants’ growth environment (e.g., light, temperature, humidity, carbon dioxide concentration, moisture, and nutrients) can be controlled. The use of LEDs in plant cultivation has recently attracted attention due to a number of advantages: (1) it is possible to precisely control the emission wavelength; (2). Their power consumption is smaller than that of other light sources, such as incandescent and fluorescent lamps; and (3) they are capable of pulse irradiation, which is an advantage in plant photosynthesis. The number of photons is more important than the light energy due to the chemical reactions that occur during photosynthesis; photons contribute to generating glucose, which determines the rate of photosynthesis. Based on the above results, in this study, we cultivated plants using an LED illumination system that could precisely control both the spectral irradiance distribution and the B/R ratios to examine their effects on plant cultivation
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