A High A High A High A High- - -Intensity, Variable Intensity, Variable Intensity, Variable Intensity, Variable- - -Spectra LED Spectra LED Spectra LED Spectra LED Array for Plant Production in Challenging Array for Plant Production in Challenging Array for Plant Production in Challenging Array for Plant Production in Challenging Environments Environments Environments Environments David Hawley 1 , Michael Stasiak 1 , Jamie Lawson 1 , Alan Scott 2 , Per Aage Lysaa 3 , Mike A. Dixon 1 . 1 Controlled Environment Systems Research Facility, University of Guelph, Guelph, Ontario, Canada; 2 COM DEV Ltd., Kanata Ontario, Canada; 3 Intravision Group AS, Snaroya Norway. 6 th International AgroSpace Workshop Sperlonga, May 2014
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A HighA HighA HighA High----Intensity, VariableIntensity, VariableIntensity, VariableIntensity, Variable----Spectra LED Spectra LED Spectra LED Spectra LED
Array for Plant Production in Challenging Array for Plant Production in Challenging Array for Plant Production in Challenging Array for Plant Production in Challenging
EnvironmentsEnvironmentsEnvironmentsEnvironments
David Hawley1, Michael Stasiak1, Jamie Lawson1, Alan Scott2, Per Aage Lysaa3, Mike A. Dixon1.
1Controlled Environment Systems Research Facility, University of Guelph, Guelph, Ontario, Canada; 2COM DEV Ltd., Kanata Ontario,
Canada; 3Intravision Group AS, Snaroya Norway.
6th International AgroSpace Workshop
Sperlonga, May 2014
ObjectivesObjectivesObjectivesObjectives
The aim of this study was to develop an array capable of emitting
variable spectra using multi-coloured, narrow-bandwidth LEDs.
The array would then be used to design high-resolution light
“recipes” for eliciting targeted responses.
LED selectionLED selectionLED selectionLED selection
655 nm
627 nm
591 nm
530 nm
505 nm
470 nm
440 nm
AssemblyAssemblyAssemblyAssembly
AssemblyAssemblyAssemblyAssembly
AssemblyAssemblyAssemblyAssembly
Assembly
Wiring and PowerWiring and PowerWiring and PowerWiring and Power
Wiring and PowerWiring and PowerWiring and PowerWiring and Power
• Constant current of 700 mA
• Required forward voltages ranged from 1.8 – 2.55 V,
depending on colour
• Colours outside the visible spectrum required much greater
voltage
• Four channels per ballast
• One ballast per colour
• 12 clusters of one colour in an array
One channel:
(2.55V x (3 clusters of 7 LEDS)) ���� 53.55 V at 700 mA == 37.49 W
Four channels:
37.49 W x 4 channels == 149.96 W.
Intensity CharacterizationIntensity CharacterizationIntensity CharacterizationIntensity Characterization
Intensity CharacterizationIntensity CharacterizationIntensity CharacterizationIntensity Characterization
1
2
3
4
5
A B C D E
1300-14001200-13001100-12001000-1100900-1000800-900
ExperimentsExperimentsExperimentsExperiments
1. Germination
2. Photosynthesis during vegetative growth
3. Adaptation
Experiments Experiments Experiments Experiments ---- GerminationGerminationGerminationGermination
• 8 species � wheat, barley, radish, lettuce, tomato,
soybean, kale, pepper
• 16 h photoperiod
• 7 monochromatic light qualities, HPS, darkness
• 22 °C ± 0.5 °C
• PAR = 280 µmol/m2/s
Experiments Experiments Experiments Experiments –––– GerminationGerminationGerminationGermination
Experiments - Germination
Experiments - Germination
Summarized Results Summarized Results Summarized Results Summarized Results ---- GerminationGerminationGerminationGermination
• Sensitivity to light quality varies between species
• Longer wavelengths favourable to some species while
completely inhibitory to others
• Shorter wavelengths were generally inhibitory to
germination
• Possible competition between photoreceptors in regards
to germination regulation
Experiments Experiments Experiments Experiments ---- PhotosynthesisPhotosynthesisPhotosynthesisPhotosynthesis
• Lettuce, tomato, pepper
• 39 light qualities
• Net CO2 assimilation rates
measured
• Photosynthesis compared on
a leaf area basis
"WHITE"
RB BL CY GN
OFF OFF OFF
RB BL CY DR
OFF OFF OFF
RB CY RD DR
OFF OFF OFF
RB A RD DR
OFF OFF OFF
GN A RD DR
OFF OFF OFF
Photosynthesis Photosynthesis Photosynthesis Photosynthesis ---- LettuceLettuceLettuceLettuce
Photosynthesis Photosynthesis Photosynthesis Photosynthesis ---- LettuceLettuceLettuceLettuce
Lettuce: Code 8-L
DR
-GN
-CY
-GN
RB
A R
D D
RA
RD
DR
RD
DR
0
50
100
150
Light Quality
Rela
tive c
arb
on a
ssim
ilati
on (
whit
e=100%
)
Photosynthesis Photosynthesis Photosynthesis Photosynthesis ---- TomatoTomatoTomatoTomato
Photosynthesis Photosynthesis Photosynthesis Photosynthesis ---- TomatoTomatoTomatoTomatoTomato: Code 8-T
A
-CY
-BL -C
YR
B A
RD
DR
A R
D D
R
RD
DR
0
50
100
150
Light Quality
Rela
tive c
arb
on
assim
ilati
on
(w
hit
e=
100%
)
Photosynthesis Photosynthesis Photosynthesis Photosynthesis ---- PepperPepperPepperPepper
Photosynthesis Photosynthesis Photosynthesis Photosynthesis ---- PepperPepperPepperPepperPepper: Code 8-P
-DR
-BL -C
YR
B A
RD
DR
GN
A R
D
RB
DR
0
50
100
150
Light Quality
Rela
tive c
arb
on
assim
ilati
on
(w
hit
e=
100%
)
Summarized Results Summarized Results Summarized Results Summarized Results ---- PhotosynthesisPhotosynthesisPhotosynthesisPhotosynthesis
• Longer wavelengths are favourable for lettuce
• Light qualities devoid of longer wavelengths are inhibitory
to tomato
• While some light qualities were more favourable than
others, for pepper there was not a trend favouring any
specific spectra
Adaptation Adaptation Adaptation Adaptation –––– ShortShortShortShort----termtermtermterm
• Alternate between most
favourable and inhibitory light
qualities every 4 hours
Adaptation Adaptation Adaptation Adaptation –––– ShortShortShortShort----termtermtermterm
short term adaptation
GN
/CY
(0-4
h)
DR
(5-8
h)G
N/C
Y (9
-12h
)
DR
(13-
16h)
0.00
0.01
0.02
0.03
0.04
Light Quality
Ph
oto
syn
thesis
(µm
ol/m
2/s
)
Adaptation Adaptation Adaptation Adaptation –––– MidMidMidMid----termtermtermterm
• Measured photosynthesis on day 1 (initial) under
monochromatic light qualities
• Adapted plants for 3 days to a different light quality
• Measured photosynthesis on day 5 (final) under initial light
qualities
• Compared initial and final photosynthetic rates
Adaptation Adaptation Adaptation Adaptation –––– MidMidMidMid----termtermtermterm
Day 1 Day 5Day 2 Day 3 Day 4
measure measureadapt adapt adapt
Day 1 Day 5Day 2 Day 3 Day 4
measure measureadapt adapt adapt
Day 1 Day 5Day 2 Day 3 Day 4
measure measureadapt adapt adapt
Adaptation Adaptation Adaptation Adaptation –––– MidMidMidMid----term term term term –––– white white white white
adaptation - white
pre-a
mber
post-a
mber
pre-g
reen
post-g
reen
pre-d
eep r
edpost
-dee
p red
pre-c
yan
post-c
yan
pre-r
oyal b
lue
post-r
oyal b
lue
pre-r
edpost
-red
pre-b
lue
post-b
lue
pre-R
B G
N D
R
post-R
B G
N D
Rpre
-white
post-w
hite
-0.01
0.00
0.01
0.02
0.03
Light qualities, pre and post adaptation
Ph
oto
syn
thesis
(µ
mo
l/m
2/s
)
adaptation - amber
pre-a
mber
post-a
mber
pre-g
reen
post-g
reen
pre-d
eep r
edpost
-dee
p red
pre-c
yan
post-c
yan
pre-r
oyal b
lue
post-r
oyal b
lue
pre-r
edpost
-red
pre-b
lue
post-b
lue
pre-R
B G
N D
R
post-R
B G
N D
Rpre
-white
post-w
hite
0.00
0.01
0.02
0.03
Light qualities, pre and post adaptation
Ph
oto
syn
thesis
(µ
mo
l/m
2/s
)
Adaptation Adaptation Adaptation Adaptation –––– MidMidMidMid----term term term term –––– amberamberamberamber
Adaptation Adaptation Adaptation Adaptation –––– MidMidMidMid----term term term term –––– royal blueroyal blueroyal blueroyal blue
adaptation - royal blue
pre-a
mber
post-a
mber
pre-g
reen
post-g
reen
pre-d
eep r
edpost
-dee
p red
pre-c
yan
post-c
yan
pre-r
oyal b
lue
post-r
oyal b
lue
pre-r
edpost
-red
pre-b
lue
post-b
lue
pre-R
B G
N D
R
post-R
B G
N D
Rpre
-white
post-w
hite
-0.005
0.000
0.005
0.010
0.015
0.020
Light qualities, pre and post adaptation
Ph
oto
syn
thesis
(µ
mo
l/m
2/s
)
Summarized Results Summarized Results Summarized Results Summarized Results ---- AdaptationAdaptationAdaptationAdaptation
• Plants adapt to different qualities in different ways
• A recovery period may be required before photosynthetic
capacity is restored
• Examining more gradual light transitions in the future is
necessary to potentially reduce plant stress
General ConclusionsGeneral ConclusionsGeneral ConclusionsGeneral Conclusions1. Although darkness was most effective for stimulating
germination there are suggestions of unique light responses from some species.
2. In general, photosynthetic rates during the vegetative growth stages were highest when exposed to longer wavelengths, however some shorter wavelengths were equally effective in some cases.
3. Adaptation to light quality conditions may confound the interpretation of photosynthetic responses, especially if the changes to the light regime are made quickly.
4. We have an excellent experimental tool for investigating plant responses to light quality.
Future DirectionsFuture DirectionsFuture DirectionsFuture Directions
• Experiment with more light qualities, including UV
• Photosynthesis during reproductive development
• Determine photosynthetic recovery period for changing
light qualities
• Quantify synthesis of secondary compounds under varying
light qualities
AcknowledgementsAcknowledgementsAcknowledgementsAcknowledgements
• CESRF group
• Natural Sciences and Engineering Council (NSERC)
• Canadian Space Agency
• COM DEV Ltd.
• Ontario Centres of Excellence
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