CONTROL OF ARTIFICIAL LIGHT FOR PLANTS

Some instruments of control and measurement of artificial light for plants were made in an attempt to analyze precisely the plant responses to the light.<BR>Measurement of total and spectral irradiances. Two different instruments were used for measurement of light. One kind was a radiometer by which total irradiance in the wavelength range between about 300 nm and 800 nm was measured. The other was a spectroradiometer which was a newly assembled instrument, consisting of an integrating sphere (light receiver), a grating monochrometer, a photomultiplier, an amplifier, and a recorder. This spectroradiometer was able to measure spectral irradiance in the wavelength range between 300 nm and 800 nm, and in the irradiation range between 0.5 μW/cm²⋅nm and 500μW/cm²⋅nm with high resolution and reliable cosine response.<BR>Light control. Six different lamps were used as light sources. They gave specific spectral emissions in the wavelength range between 350 nm and 800 nm. The lamp compartment of the growth cabinet was provided with these lamps. To control the radiant flux (light output) of each lamp, independent controllers corresponding to each lamp were used; the radiant flux control was achieved by SCR element for changing the effective current through the lamp. Both combined spectral and total irradiances were due to the radiant flux of each lamp. This instrument was able to control the total and spectral irradiances by changing the radiant flux of each lamp in the wave-length range between 350 nm and 800 nm and in the range between 0% and 100% of rated capacity.