Photochemistry und Photohioloyy. 1975, Vol. ?I. pp. 383 385. Pergarnon Press
Printed i n Great Britain
TECHNICAL NOTE SOLAR-SIMULATING RADIATION SYSTEMS FOR BIOLOGICAL RESEARCH* MICHAELJ. HURDZAN and RICHARDM. KLEIN Department of Botany, Univcrsity of Vermont, Burlington Vt. 05401, U.S.A. (Receivc~l13 Fehruury 1974; uccepted 30 December 1974)
Plants receive solar radiation as direct sunlight, sunlight filtered through and reflected from clouds and Earth features, skylight, and as radiation filtered through vegetation. Gates (1965) and Henderson and Hodgkiss (1963) measured the spectral energy distribution of some of these light environments. For research, filtered carbon arcs and xenon lamps are probably the best simulators of full sunlight, but they are expensive and not easily adapted for use in growth chambers. Biological research usually uses combinations of fluorescent and incandescent lamps (Federer and Tanner, 1965) which provide spectral distributions very different from natural light (Bickford and Dunn, 1972). These conventional lamp systems permit extensive plant growth and development, but none of the readily available combinations have spectral distributions that match sunlight or the various types of shade environment encountered by plants. As part of a study of plant response to different radiation environments (Hurdzan, 1974), lamp systems were developed that emit spectra more closely simulating natural conditions than hitherto have been reported. These systems can be installed in conventional growth chambers without extensive remodelling and at reasonable cost. Filter systems have also been developed to simulate skylight and canopy shade environments in greenhouses or under field conditions. They do not provide illuminances equivalent to full sunlight and they do deviate from natural spectra. We believe that they are as close as can be achieved with current commercially available lamps.
plastic filter sheets were 0.01 in thick. For radiation monitoring of lamp-filter systems, the lamp units were 46 cm from the sensor heads, a distance chosen as a reasonable lamp-to-pot distance in conventional growth chambers.
Growth-chamber lamp systems Figure 1 shows a noon, full-sun-plus-skylight spectrum made in August on a clear day and the spectrum of our sun-equivalent Lamp System I. The luminaire in a conventional growth chamber consists of 7 Sylvania F,,T, ,/B/HO blue fluorescent lamps alternating with 7 Duro-Test F,,T,,/HO Vitalite fluorescent lamps on 7.5 cm centers. Incandescent (200 W reflector flood) lamps were spaced throughout the luminaire, each incandescent lamp spaced 40 cm from each other lamp to give a repeating pattern. The radiation from the luminaire was filtered through one thickness each of Cinemoid No. 50 (Pale Yellow) to remove wavelengths below 400 nm and Cinemoid No. 52 (Pale Gold) plus Cinemoid No. 29 (Heavy Frost) as a diffusing screen. It was impossible to flatten out
-
110-
70
RESULTS
Radiation in natural environments and lamp-filter combinations were monitored with an ISCO Spectroradiometer corrected for photocell response with curves provided by the manufacturer and with a Yellow Springs Instrument Co. Model 65 Radiometer. ‘Cinemoid’ theatrical filters (Kliegl Bros. Long Island City, N.Y.) and near-UV-absorbing Mylar plastics (Zalik and Miller, 1960; Klein, 1965) were used; all
w n
v)
50-
-.I0
-400
I
I
I
I
450
500
550
600
I 650
I
700
7x)
WAVELENGTH lnm)
*University of Vermont Agricultural Experimcnt Station Figure 1. Comparison of visible spectra of full-noon sunJournal Article 326. light plus skylight with output of Lamp System I. 3x3
MICHAEL J. HURDZANand RICHARD M. KLEIN
384
WAVELENOTH Inm)
Figure 2. Comparison of visible spectra of sunlight and skylight filtered through a single bean leaf and a sugar maple canopy with output of Lamp System 11.
completely the spike of the 546 nm mercury resonance line emitted by the fluorescent lamps. Direct noon sunlight filtered through a single bean leaf was qualitatively only slightly different from noon sunlight filtered through a canopy of deciduous tree leaves (an Acrr saccharum forest). For simulation of this canopy shade environment, a dual lamp-filter system was developed (Fig. 2). Luminaire A consisted of equal numbers and arrangements of blue and Vitalite fluorescent lamps, as in Lamp System I, with the light filtered through a layer of Cinemoid No. 23 (Light Green) plastic placed directly beneath the fluorescent lamps. General Electric R-40, 150 W green reflector incandescent lamps protruded through the primary Cinemoid filter. Light from the incandescent lamps was filtered through one sheet each of Cinemoid No. 4 (Medium Amber) and Cinemoid No. 29 (Heavy Frost), the latter to diffuse the bright spots characteristic of reflector-flood lamps. Diffuse skylight has the same spectral energy distribution as the natural light on the north side of a building. There is a nearly linear decrease in radiant flux with increasing wavelength (Fig. 3). Lamp System I11 simulated skylight by filtering the light of blue
I
I
400
450
I 500
I
I
I
I
I
550
6W
650
700
750
WAVELENGTH (nm)
Figure 3. Comparison of visible spectra of diffuse skylight with output of Lamp System 111.
and Vitalite fluorescent lamps through one thickness each of Cinemoid No. 36 (Pale Lavander) and Cinemoid No. 50 (Pale Yellow) plastics plus a 1.25cm deep solution of 1.25% CuSO, . 5H20 contained in a Plexiglas box fabricated of 1/4 in thick sheet. Virtually the same spectrum was obtained with a luminaire consisting of 3 blue for every one Cool White fluorescent lamp, the light being filtered through one thickness each of Cinemoid No. 17 (Steel Blue) and Mylar plastic to absorb near-UV radiation (Klein, 1965). Greenhouse or field units
Spectra comparable to those obtained in growth chambers can also be simulated for greenhouse or field studies. Full-sun-plus-sky spectra present no technical problem except for reducing intensities with neutral-density filters (aluminum screening) and elimination of near-UV radiation with Mylar. Deciduous canopy shade was simulated by filtering sunlight through one thickness each of Cinemoid No. 4 (Medium Amber) and Cinemoid No. 61 (Slate Blue). A skylight spectrum was simulated by filtering sunlight through one thickness of Cinemoid No. 17 (Steel
Table I . Comparison of natural light regimes with simulated regimes in a growth chamber and in W/m2 in wavelength band 4 2 s 4 4 0 nm 65&670 nm 720-740 nm (Blue) (Red) (Far Red)
R
greenhouse
Photomorphogenic ratios R/B FR/B R/FR
Noon sunlight Greenhouse simulation Chamber simulation
2.333 0.27 1 0. I20
2,853 0.33 1 0.225
2.303 0,267 0.154
1.17 1.22 1.87
095 0.98 1.28
1.24 1.24 1.46
Noon skylight Greenhouse simulation Chamber simulation
0.565 0,436 0.395
0.255 0.227 0.090
0.164 0.096 0.0 I2
0.45 0.52 0.23
0.29 0.22 0.03
1.55 2.36 7.41
Noon canopy shade Greenhouse simulation Chamber simulation
0,058 0.436 0
0. I27 0-227 0.165
0.926 0.096 0.673
2.19 10.87
16.03 14.40
0.14 0.75 0.24
Technical Note
Blue) plastic plus a 2 c m deep liquid filter of 0.625%
CuS04.5H,0(v/v) in a Plexiglas box fabricated of 1/4 in thick plastic. The copper sulfate solution was stable for 6 months of constant exposure to sunlight. The ratios of blue-red, far red-blue and red-far red radiation (Table I ) provide the plant photobiologist with some measure of the expected photostationary states of phytochrome in plants exposed to the different light regimes (Roodenberg and Askamp, 1960; Mohr, 1972). The sunlight simulations are generally good, but the growth chamber simulation of skylight is only fair, and the simulation of canopy shade, where the radiant flux in the blue region is very low, is least satisfactory. Standard growth chambers are usually fitted with Cool White fluorescent plus incandescent lamps
385
(Friend et al., 1961). These provide cu. 7 W/mZ in the 400-750 nm region with a spectrum very different from solar radiation. This represents about 10 per cent of global radiation in the 400-750 nm wavelength band. The solar-simulating luminaire reported here provide cu. 6.5 W/mZ and thus are directly comparable with those usually installed in growth chambers. Had we used VHO or 1500 ma fluorescent lamps, for which our chamber was not wired, we would have obtained cu. 7 W/mZ. Deutch and Rasmussen (1974) report that radiation beyond 750 nm may play a role in photomorphogenetic efficiency. Their data, although not conclusive, require confirmation and extension and may bear directly on the development of lamp units more closely simulating conditions in nature.
REFERENCES
Bickford, E. D. and S. Dunn (1972) Liyhtiny fiw Plarit Growth, Kent State Univ. Press. Kent, Ohio. Deutch, B. and 0. Rasmussen (1974) Physiol. Plant. 30, 64-71. Federer, C. A. and C. B. Tanner (1965) Agron. J . 57, 314-315. Friend, D. J. C., V. A. Helson and J. E. Fisher (1961) Can. J . Sci. 41, 418-427. Gates, D. M. (1965) Ecology 46, I - 13. Henderson S. T. and D. Hodgkiss (1963) Brit. J . A p p l . Physics 14, 125-131. Hurdzan, M. J. (1974) Ph.D. Thesis, Dept. of Botany, University of Vermont. Burlington, Vt. Klein, R. M. (1965) Photochem. Photobiol. 4, 625-627. Mohr, H. (1 972) Lectures in Photomorphoqenesis, Springer-Verlag, New York. Roodenberg, J. W. M. and A. A. Askamp (1966) Greenhouse Culture arid ArtiJicial Light, Neth. Tuinbouw voor Lichtingsdienst, Amsterdam. Zalik, S. and R. A. Miller (1960) Plant Physiol. 35, 696-669.
Printed i n Great Britain
TECHNICAL NOTE SOLAR-SIMULATING RADIATION SYSTEMS FOR BIOLOGICAL RESEARCH* MICHAELJ. HURDZAN and RICHARDM. KLEIN Department of Botany, Univcrsity of Vermont, Burlington Vt. 05401, U.S.A. (Receivc~l13 Fehruury 1974; uccepted 30 December 1974)
Plants receive solar radiation as direct sunlight, sunlight filtered through and reflected from clouds and Earth features, skylight, and as radiation filtered through vegetation. Gates (1965) and Henderson and Hodgkiss (1963) measured the spectral energy distribution of some of these light environments. For research, filtered carbon arcs and xenon lamps are probably the best simulators of full sunlight, but they are expensive and not easily adapted for use in growth chambers. Biological research usually uses combinations of fluorescent and incandescent lamps (Federer and Tanner, 1965) which provide spectral distributions very different from natural light (Bickford and Dunn, 1972). These conventional lamp systems permit extensive plant growth and development, but none of the readily available combinations have spectral distributions that match sunlight or the various types of shade environment encountered by plants. As part of a study of plant response to different radiation environments (Hurdzan, 1974), lamp systems were developed that emit spectra more closely simulating natural conditions than hitherto have been reported. These systems can be installed in conventional growth chambers without extensive remodelling and at reasonable cost. Filter systems have also been developed to simulate skylight and canopy shade environments in greenhouses or under field conditions. They do not provide illuminances equivalent to full sunlight and they do deviate from natural spectra. We believe that they are as close as can be achieved with current commercially available lamps.
plastic filter sheets were 0.01 in thick. For radiation monitoring of lamp-filter systems, the lamp units were 46 cm from the sensor heads, a distance chosen as a reasonable lamp-to-pot distance in conventional growth chambers.
Growth-chamber lamp systems Figure 1 shows a noon, full-sun-plus-skylight spectrum made in August on a clear day and the spectrum of our sun-equivalent Lamp System I. The luminaire in a conventional growth chamber consists of 7 Sylvania F,,T, ,/B/HO blue fluorescent lamps alternating with 7 Duro-Test F,,T,,/HO Vitalite fluorescent lamps on 7.5 cm centers. Incandescent (200 W reflector flood) lamps were spaced throughout the luminaire, each incandescent lamp spaced 40 cm from each other lamp to give a repeating pattern. The radiation from the luminaire was filtered through one thickness each of Cinemoid No. 50 (Pale Yellow) to remove wavelengths below 400 nm and Cinemoid No. 52 (Pale Gold) plus Cinemoid No. 29 (Heavy Frost) as a diffusing screen. It was impossible to flatten out
-
110-
70
RESULTS
Radiation in natural environments and lamp-filter combinations were monitored with an ISCO Spectroradiometer corrected for photocell response with curves provided by the manufacturer and with a Yellow Springs Instrument Co. Model 65 Radiometer. ‘Cinemoid’ theatrical filters (Kliegl Bros. Long Island City, N.Y.) and near-UV-absorbing Mylar plastics (Zalik and Miller, 1960; Klein, 1965) were used; all
w n
v)
50-
-.I0
-400
I
I
I
I
450
500
550
600
I 650
I
700
7x)
WAVELENGTH lnm)
*University of Vermont Agricultural Experimcnt Station Figure 1. Comparison of visible spectra of full-noon sunJournal Article 326. light plus skylight with output of Lamp System I. 3x3
MICHAEL J. HURDZANand RICHARD M. KLEIN
384
WAVELENOTH Inm)
Figure 2. Comparison of visible spectra of sunlight and skylight filtered through a single bean leaf and a sugar maple canopy with output of Lamp System 11.
completely the spike of the 546 nm mercury resonance line emitted by the fluorescent lamps. Direct noon sunlight filtered through a single bean leaf was qualitatively only slightly different from noon sunlight filtered through a canopy of deciduous tree leaves (an Acrr saccharum forest). For simulation of this canopy shade environment, a dual lamp-filter system was developed (Fig. 2). Luminaire A consisted of equal numbers and arrangements of blue and Vitalite fluorescent lamps, as in Lamp System I, with the light filtered through a layer of Cinemoid No. 23 (Light Green) plastic placed directly beneath the fluorescent lamps. General Electric R-40, 150 W green reflector incandescent lamps protruded through the primary Cinemoid filter. Light from the incandescent lamps was filtered through one sheet each of Cinemoid No. 4 (Medium Amber) and Cinemoid No. 29 (Heavy Frost), the latter to diffuse the bright spots characteristic of reflector-flood lamps. Diffuse skylight has the same spectral energy distribution as the natural light on the north side of a building. There is a nearly linear decrease in radiant flux with increasing wavelength (Fig. 3). Lamp System I11 simulated skylight by filtering the light of blue
I
I
400
450
I 500
I
I
I
I
I
550
6W
650
700
750
WAVELENGTH (nm)
Figure 3. Comparison of visible spectra of diffuse skylight with output of Lamp System 111.
and Vitalite fluorescent lamps through one thickness each of Cinemoid No. 36 (Pale Lavander) and Cinemoid No. 50 (Pale Yellow) plastics plus a 1.25cm deep solution of 1.25% CuSO, . 5H20 contained in a Plexiglas box fabricated of 1/4 in thick sheet. Virtually the same spectrum was obtained with a luminaire consisting of 3 blue for every one Cool White fluorescent lamp, the light being filtered through one thickness each of Cinemoid No. 17 (Steel Blue) and Mylar plastic to absorb near-UV radiation (Klein, 1965). Greenhouse or field units
Spectra comparable to those obtained in growth chambers can also be simulated for greenhouse or field studies. Full-sun-plus-sky spectra present no technical problem except for reducing intensities with neutral-density filters (aluminum screening) and elimination of near-UV radiation with Mylar. Deciduous canopy shade was simulated by filtering sunlight through one thickness each of Cinemoid No. 4 (Medium Amber) and Cinemoid No. 61 (Slate Blue). A skylight spectrum was simulated by filtering sunlight through one thickness of Cinemoid No. 17 (Steel
Table I . Comparison of natural light regimes with simulated regimes in a growth chamber and in W/m2 in wavelength band 4 2 s 4 4 0 nm 65&670 nm 720-740 nm (Blue) (Red) (Far Red)
R
greenhouse
Photomorphogenic ratios R/B FR/B R/FR
Noon sunlight Greenhouse simulation Chamber simulation
2.333 0.27 1 0. I20
2,853 0.33 1 0.225
2.303 0,267 0.154
1.17 1.22 1.87
095 0.98 1.28
1.24 1.24 1.46
Noon skylight Greenhouse simulation Chamber simulation
0.565 0,436 0.395
0.255 0.227 0.090
0.164 0.096 0.0 I2
0.45 0.52 0.23
0.29 0.22 0.03
1.55 2.36 7.41
Noon canopy shade Greenhouse simulation Chamber simulation
0,058 0.436 0
0. I27 0-227 0.165
0.926 0.096 0.673
2.19 10.87
16.03 14.40
0.14 0.75 0.24
Technical Note
Blue) plastic plus a 2 c m deep liquid filter of 0.625%
CuS04.5H,0(v/v) in a Plexiglas box fabricated of 1/4 in thick plastic. The copper sulfate solution was stable for 6 months of constant exposure to sunlight. The ratios of blue-red, far red-blue and red-far red radiation (Table I ) provide the plant photobiologist with some measure of the expected photostationary states of phytochrome in plants exposed to the different light regimes (Roodenberg and Askamp, 1960; Mohr, 1972). The sunlight simulations are generally good, but the growth chamber simulation of skylight is only fair, and the simulation of canopy shade, where the radiant flux in the blue region is very low, is least satisfactory. Standard growth chambers are usually fitted with Cool White fluorescent plus incandescent lamps
385
(Friend et al., 1961). These provide cu. 7 W/mZ in the 400-750 nm region with a spectrum very different from solar radiation. This represents about 10 per cent of global radiation in the 400-750 nm wavelength band. The solar-simulating luminaire reported here provide cu. 6.5 W/mZ and thus are directly comparable with those usually installed in growth chambers. Had we used VHO or 1500 ma fluorescent lamps, for which our chamber was not wired, we would have obtained cu. 7 W/mZ. Deutch and Rasmussen (1974) report that radiation beyond 750 nm may play a role in photomorphogenetic efficiency. Their data, although not conclusive, require confirmation and extension and may bear directly on the development of lamp units more closely simulating conditions in nature.
REFERENCES
Bickford, E. D. and S. Dunn (1972) Liyhtiny fiw Plarit Growth, Kent State Univ. Press. Kent, Ohio. Deutch, B. and 0. Rasmussen (1974) Physiol. Plant. 30, 64-71. Federer, C. A. and C. B. Tanner (1965) Agron. J . 57, 314-315. Friend, D. J. C., V. A. Helson and J. E. Fisher (1961) Can. J . Sci. 41, 418-427. Gates, D. M. (1965) Ecology 46, I - 13. Henderson S. T. and D. Hodgkiss (1963) Brit. J . A p p l . Physics 14, 125-131. Hurdzan, M. J. (1974) Ph.D. Thesis, Dept. of Botany, University of Vermont. Burlington, Vt. Klein, R. M. (1965) Photochem. Photobiol. 4, 625-627. Mohr, H. (1 972) Lectures in Photomorphoqenesis, Springer-Verlag, New York. Roodenberg, J. W. M. and A. A. Askamp (1966) Greenhouse Culture arid ArtiJicial Light, Neth. Tuinbouw voor Lichtingsdienst, Amsterdam. Zalik, S. and R. A. Miller (1960) Plant Physiol. 35, 696-669.
