greenhouse supplemental light quality forleds.hrt.msu.edu/assets/meeting/lighting-vegetables.pdf ·...
TRANSCRIPT
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Greenhouse Supplemental Light Quality for Vegetable Nurseries
Chieri Kubota and Ricardo Hernández
The University of Arizona
LED Symposium (Feb 20, 2015)
• Supplemental lighting from late fall to early spring• Large commercial greenhouse nurseries are located in Canada (BC and Ontario)
• Typical practices– 18 hour illumination from midnight to 6 pm at around 50‐60 mol m‐2 s‐1 PPF.
– No or limited illumination over pepper seedlings– Overhead HPS lamps
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Photosynthetically Active Radiation (PAR, 400-700 nm)
Plant biologically active radiation (300-800 nm)
UV Blue Green Red Far red
Leaf photosynthesis(quantum efficiency)
After McCree (1972) and Sager (1988)
Plant Growth Rate
Plant Photosynthetic Rate = Leaf Photosynthetic Rate
x Leaf Area
Light quality effect on plant growth can be photosynthetic or
photomorphogenic.
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Supplemental FR Lighting for Baby Leaf Lettuce under Artificial Lighting
• Supplemental far‐red light (700‐800 nm) significantly increased the biomass of baby lettuce plants by 28%.
• This was due to the increased light interception caused by enhanced leaf elongation.
• Similar observation by Stutte et al. (2009).
(Li and Kubota, 2009)28%↑ in dry mass
LED Research Objectives at UA
1. To conduct research necessary for vegetable nurseries to adopt LED lighting technology– Phase I: Light quality requirement for LED lighting
– Phase II: Side‐by‐side comparison with the conventional HPS lighting
2. To explore new LED applications beneficial to vegetable nurseries– Low intensity applications of red and far‐red LEDs for controlling plant morphology
– Pulsed lighting
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Blue vs. Red light
• Red light has the highest quantum efficiency (for single leaf) (e.g., McCree, 1972)
• Blue light increases stomatal opening (conductance) and thereby photosynthetic gas diffusion (e.g., Hogewoning et al., 2010)
• Some species/cultivars (e.g., lettuce) cannot grow under 100% red light (small % of blue light needs to be added) (e.g., Dougher and Bugbee, 2001)
• Blue light reduces leaf size and internode length, making plants more compact. This possibly reduces whole plant photosynthetic rate by reducing the light interception or increases canopy photosynthetic rate by increasing light penetration in the plant canopy.
Phase I: Supplemental LED blue:red photon flux ratios for vegetable transplants
• Objective– To examine different supplemental LED Blue:Redphoton flux ratios for growth and development of vegetable transplants.
• Hypothesis
– Blue photon flux requirement is depending on the background solar DLI (high DLI vs. low DLI).
DLI: daily light integral, moles per sq meter per day (mol m‐2 d‐1)
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Phase I: Materials & MethodsSupplemental PPF: 55 μmol m‐2 s‐1 for 18 hours (2am to 8pm)Supplemental DLI: 3.5 molm‐2 d‐1 by LED light.Plant materials: ‘Cumlaude’ cucumber, ‘Komeett’ and ‘Aloha’ tomato, and ‘Fascinato’ pepper [young seedling stage]
100%
4%
96%
16%
84%
N
NO SUPPLEMENTAL
LIGHT
Side‐by‐side comparisons of supplemental LED lighting under different background solar DLIs• High solar DLI: 16‐23 mol m‐2 d‐1
• Low solar DLI: 5‐9 mol m‐2 d‐1
R100% treatment B4:R96 treatment B16:R84 treatment Control
Peak wavelength: Blue = 455 nm, Red = 661 nm
Minimum DLI for vegetable transplants: 13 mol m‐2 d‐1
Phase I: Materials & Methods
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0.2 0.25 0.3 0.35 0.4 0.45 0.5
0.55 0.6 0.65 0.7
High DLI Low DLI
Shoot dry m
ass (g)
SOLAR DAILY LIGHT INTEGRAL
DRY MASS RESPONSE
control LED supplement
P < 0.0001
P < 0.0001
Effects of supplemental LED light
Phase I: Results
Hernández and Kubota (2014)
Cucumber seedlings shoot dry wt(16 days after seeding)
100%
4%
96%
16%
84%
Growth of tomato and pepper seedlings (both DLIs) & cucumber seedlings (high DLI)
100%
4%
96%
16%
84%
Growth of cucumber seedlings (low DLI)
Under low solar DLI conditions dry mass, leaf count, and leaf area decreased with the increase of blue photon flux for cucumber seedlings.
> >
Blue photon flux
Cucumber
55 μmol m‐2 s‐1 supplemental lighting, high DLI = 16‐23 and low DLI = 5‐9 molm‐2 d‐1
Effects of B:R ratios of supplemental LED light
Phase I: Results
= =
Hernández and Kubota (2014)
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Conclusion Phase I
• LED supplemental lighting enhanced plant growth even under high background solar DLI conditions.
• 100% red supplemental LED lighting is recommended for cucumber seedlings and is acceptable for tomato and pepper seedlings. [No need to consider including blue light under the range of solar DLI examined (5‐23 mol m‐2 d‐1)].
– Under much lower solar DLI (0 ‐ 5 mol m‐2 d‐1) or when LED lighting contributes to the majority of DLI, addition of blue light is expected to become more critical.
• Responses to LED light quality are species specific.
Phase II: Comparison between LED and HPS supplemental lighting
• Objective
– To find plant responses of vegetable transplants (mature seedlings) grown side‐by‐side under LED and HPS supplemental lighting
– Compared electrical efficiencies between HPS and LED supplemental lighting
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Materials & methods: treatmentsSupplemental PPF: 55‐60 μmol m‐2 s‐1 for 18 hours (2am to 8pm)Supplemental DLI: 3.5‐3.9 molm‐2 d‐1 by LED light.Plant materials: ‘Cumlaude’ cucumber, ‘Komeett’ tomato, and ‘Fascinato’, ‘Orangela’, ‘PP0710’ and ‘Viper’ pepper
100% 100%100%
TreatmentRed‐LED
TreatmentBlue‐LED
Treatment 600W HPS
Blue = 443 nm peakRed = 632 nm peak
53%42%
5%
Background solar DLIs• Low solar DLI: 3.9‐5.2 mol m‐2 d‐1
Phase III: Materials & methods
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Unfair comparison of energy consumption of LEDs vs. HPS
in small scale research settings
LED light
Traditional electric lighting (eg, HPS)
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<
LED vs. HPS supplemental lightingPhase II: Results – Growth and Energy
100% 100%100%53%
42%
5%
HPSRed LEDs Blue LEDs
Supplemental lighting efficiency (plant grams dry mass per kWh used for lighting): 6‐17% increase under HPS
<100% 100%100%53%
42%
5%
HPSRed LEDs Blue LEDs
=
<
Plant growth (biomass) for tomato, cucumber, and pepper (except some cultivars): 20‐30% increase under HPS (due to increase in leaf temperature (+1.0°C)
(Hernandez and Kubota 2014; 2015)
Areal Power Consumption (W m‐2) Fixture Growth Efficiency (g kWh‐1)
Estimation of energy use(LEDs and HPS with reported light conversion efficiency for a 1‐ha commercial scale use at 57 mol m‐2 s‐1)
Hernández and Kubota (2015)
Lamp type Effective photons
(% over total)
PAR conversion efficiency(mol J‐1)
Areal Power Consumptionx
(W m‐2)
Fixture GrowthEfficiency
(Cucumber, sDLI = 4)
(g kWh‐1)
Red LEDs 85% 1.7z 39 3.0
Blue LEDs 85% 1.9z 35 3.3
600 W HPS 81% 1.6y 43 3.5
z Nelson and Bugbee (2014); y Manufacturer catalogue valuex Aldrich and Bartock (1994) with some modifications
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LED vs. HPS supplemental lighting
Phase II: Results ‐Morphology
Hypocotyl length for tomato: significant reduction under blue or red suppl. LEDs
Hypocotyl length for cucumber: 38% reduction under red suppl. LEDs
Hypocotyl length for pepper: Significant reduction under blue suppl. LEDs
Degree of leaf curling was mitigated significantly by blue suppl. LEDs for pepper (four cultivars)
Blue LEDs HPS Red LEDs
Pepper leaf curling index
Hernández et al. (2014); Hernández and Kubota (2015)
Conclusion Phase II
• Growth enhancement under HPS lighting was observed for all species examined, mainly due to the increased radiative heat transfer between the lamp and plants.
• Responses to LED light quality were species and cultivar specific.
• 100% red and 100% blue supplemental lighting might have unique applications for controlling morphology of cucumber and pepper, respectively.
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New LED ApplicationEnd‐of‐Day Far‐red Light Treatment
• Classic photobiology (phytochrome response)
• Light quality at the end of day (photoperiod) determines stem elongation during the successive night (dark period) – EOD far‐red light >> taller plants
• Effective at VERY low light intensity
• Responses are light quality dependent (i.e.,Pfr/Ptotal)
• Potential non‐chemical control of stem or hypocotyl elongation
EOD‐FR Application for Vegetable Rootstock• Longer hypocotyls are needed in vegetable grafting (rootstock)– Greater grafting speed
– Keeping grafted unions above the soil line when they are transplanted.
– Suitable for production of grafted cuttings
Adequate hypocotyl length for grafting cucurbit rootstock is ~7 cm.
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End‐of‐day light quality treatment for controlling morphology of vegetable seedlings in greenhouse
Tomato rootstock seedlings
Squash rootstock seedlings
EOD Far‐red Dose (0 – 9000 mol/m2/d)
(Chia and Kubota, 2010; Kubota et al., 2011)
EOD Far‐red Dose (mol/m2/d)
Squash hypocotyl (mm)
EOD Far‐red Dose (0 – 9000 mol/m2/d)
~3 mol/m2/s for 24 min
~3 mol/m2/s for 24 min
Moving Far‐Red LightingNew application method
?? m/s
High power FR LEDs
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Moving Far‐Red LightingNew application method
Average PF was found by the FR photon flux distribution at the horizontal plane 5 cm below the FR LED bar.
LED bar
Under the following conditions: Average PF = 4.5 mol m‐2 s‐1
Effective length = 700 mm The LED bar’s traveling speed must be 0.8 mm/s or slower in order to meet the target dose of 4000 mol m‐2.
Speed =(Target Dose)
(Average PF) x (Effective length)
(Yang et al., 2012)
End‐of‐Day FR Treatment with Moving fixture vs. Stationary
fixture (A proof of concept)
Main factor Hypocotyl (mm)
EOD FR treatment and LED fixture type (dose = 4000 mol/m2/d)
Moving fixture (0.8 mm/s) 82.2 a
Stationary fixture (11 min at 6.2 mol/m2/s)
89.6 a
Non‐treated control 53.0 b
(Yang et al., 2012)
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• Using a similar approach, EOD red light treatment has been evaluated as a non‐chemical means to prevent stem elongation of vegetable seedlings.
• So far, no clear impact on hypocotyls was found.
End of day red lighting?
Acknowledgements
• Jose Pablo Santana
• Polung Chia
• Mark Kroggel
• Neal Barto
• Zhenchao Yang
• Murat Kacira
• CCS, Inc. (Kyoto, Japan)
• ORBITEC (WI, USA)
• Bevo Farms
• USDA SCRI