The Next Evolution in Horticulture Lighting—Impact of Using Supplemental UV Dr. Peter Barber Sensor Electronic Technology Inc. June 12, 2018
Wavelength Effects Wavelength (nm) 440 – 470 510 Visible Spectrum
610 640 – 660 740
Effect on Plant Growth Chlorophyll absorption peaks at 439 and 469 nm. The blue spectrum is the most efficiently absorbed spectrum, promoting mainly vegetative growth. Quantum absorption in the green spectrum. Little absorption in the yellow spectrum No chlorophyll benefit, but efficiently absorbed by phycocyanin receptors which initiate light signaling mechanisms for photoperiodism (onset of flowering) Chlorophyll absorption peaks at 642 and 667 nm. Speeds up germination and flower/bud onset. 660 is the most vital wavelength for flowering. Emerson Enhancement Effect—quantum yield of red light and far red light, when shone simultaneously on a plant, increases the rate of photosynthesis.
Over the last 10 years, a significant amount of plant research has been dedicated to studying the harm benefit of UV radiation for plants.
0.06
Power Density (W/m2)
0.05
UV & Solar Spectrum
0.04
0.03
UV LED 5x the Solar output @ sea level
0.02
UV LED 1.25x the Solar output @ 3km elevation
0.01
0.00
275.0280.0285.0290.0295.0300.0305.0310.0315.0
Power Density from Sun between 280 to 300 nm
Applications Seed
Farmer
Consumer
• Treating seedlings for strengthen root systems • Prevention of mold and bacteria
• • • •
Continued Prevention of mold and bacteria Increasing nutritional/medicinal value in plants Increasing aesthetic value in plants (i.e. fresher) Increased shelf-life
• Treating mold spots on produce • Extended shelf-life in conjunction with cold storage
• •
UVB Technology to: prevent/treat powdery mildew, root rot, and spider mites Increase Secondary Plant Metabolites such as: Cannabinoids and Terpenoids
UVA/PCO Technology for Odor Elimination/Control Systems
UVC Technology to Disinfect/Clean Hydroponic Systems
UVB Technology to: Increase post-harvest shelf-life (cold/RT)
Powdery Mildew & Spider Mite Literature
280-300 nm UV used to kill not only female spider mites, but also their eggs** 1 umol/m2s—powdery mildew germination* *A. Suthaparan et al. Journal of Photochemistry & Photobiology B: Biology 156 (2016) p 41-49 **Tanaka et al. Journal of Economic Entomology: 2016, Vol. 109 (4), p.1758
UV &Plants: Secondary Plant Metabolites
Plant Response to UV-B A. MKP1/MPK3/MPK6 Signalling:
• Initiates the plant stress mechanisms to safeguard plant B. UVR8 Pathway*: 280 – 300 nm needs at least 0.1 umol/m2s fluence rate 301 – 310 nm needs at least 1 umol/m2s fluence rate • Main plant signaling pathway for increased secondary plant metabolites…such as flavonoids and THC C. Flavonoid Synthesis: • Initiated through UVR8, responsible for all nutritional and medicinal properties of plants D. Epigenetic Memory: • Initiated through UVR8, responsible for plants memory to environmental stress responses E. ROS and Phytohormons: • Radical Oxygen Scavengers, such as phenolics and vitamin precursors F. DNA Damage and Cell Death
Muller-Xing et al. Front Plant Sci 2014, 5, p. 474
UVR8—Not all UV is Created Equal 285
285
295 300 310
280-290 nm is the most efficient UVB wavelength range to stress the plant the most (Photon Efficiency) 290-300 nm has some impact but needs longer exposure or higher flux to match 280 301-310 nm requires 10x the flux to match effects of 280
Literature Reports on UVB Flavonoids Antioxidants
Essential Oils Stilbenes Anti-cancer
Insecticidal, medicinal, and cosmetic
Phenolics Akaloids
Terpenoids
Anti-cancer
Taxoids for cancer therapy
Hypercium substances
Melatonin
St. John’s wort
Dirurnal rhythmicity
ROS
Isothiocyanates
Cancer therapy
Cannabinoids THC/CBD/CBG
Glucosinolates Deterrents for herbivores, but has a place in medicine now
Vitamin D Antioxidants
UV LEDs Food Treatment Sponsored by
UVB Increases Flavonoids x3 to x4 Emergence = 02/13/11 UV applied = 02/23/11 1st Harvest Half = 03/04/11 Increase UV applied = 03/04/11
UV EXPOSURE TIME: - 1st Harvest = 9 days - 2nd Harvest = 14 days
2nd Harvest = 03/18/11
Chicoric, Quercetin, and Cyanidin show increases after 1st harvest. Chlorogenic response improved on old leaves after 2nd harvest Quercetin showed drastic increases in old leaves in 2nd harvest
Post Harvest Storage ‘Two Star' Green Leaf Lettuce Heads Stored 7 Days Postharvest at 8 deg. C. Chlorophyll A
Chlorophyll B
ug/mg Relative ug/mg Relative 2.18
Chl a+b
Tot Carotenoids
ug/mg
Relative ug/mg Relative
8.41
2.32
Tot Chl/ Tot Carot.
Chl a/ Chl b Relativ e
Relative
Preharvest Controls
6.22
3.63
2.85
Postharvest - Dark
5.52
0.89
2.00
0.92
7.52
0.89
2.16
0.93
3.51
0.97
2.75
0.96
Postharv. UVB Treatment
6.62
1.06
2.30
1.05
8.92
1.06
2.45
1.06
3.64
1.00
2.88
1.01
Postharv. UVA Treatment
5.80
0.93
2.00
0.92
7.80
0.93
2.14
0.93
3.64
1.00
2.90
1.02
Shelf life extension
a
b
Strawberries after 9-days cold storage (a) dark control and (b) illuminated with UVB light
SETi-USDA CRADA Phase 2 Final Report
Cold Storage Experiment —using 295 nm LEDs
CONTROL
UV-B UV-C
Cannabis and UV-B
20% increase in ∆9-THC when greenhouse-grown Nepalese cannabis was given UV 4hrs/day
1
“The potency of high quality marijuana increases in direct ratio to the amount of UVB light it receives.” 2 Concentration of ∆9-THC increased in leaf and flower of UV-B-dosed plants.
1 2 3
Fairbairn, J.W. and J. A. Liebmann. 1974. The cannabinoid content of Cannabis sativa L. grown in England. J. Pharm. Pharmacal. 26: 413-419 Pate, D.W., 1994. Chemical Ecology of Cannaibs. Journal of the International Hemp Ssoc 2:29, 32-37 Lydon, John, Alan H. Teramura, and C. Benjamin Coffman. 1987. UV-B Radiation Effects on Photosynthesis, Growth, and Cannabinoid Production of Two Cannabis sativa Chemotypes. Photochemistry and Photobiology, 46:2 pp. 201-206
Results to date on Cannabis with SETi UV
SETi has produced 4-foot UVB supplemental fixture with ~1 W/m2 (or 1 umol/m2 s)
• 8 hour exposure to UVB during final 3 weeks prior to harvest • Increased trichome activity—ie # of trichomes increase
Summ ary
0.06 0.05 0.04 0.03 0.02 0.01 0.00
270.0
280.0
290.0
3 00.0
310.0
320.0
EXTRA SLIDES
Secondary Plant Metabolites Secondary plant metabolites mediate many aspects of the interaction of plants with their environment by: • Acting as feeding deterrents against herbivores • Pollinator attractants • Protective compounds against pathogens or various abiotic stresses • Antioxidants • Signaling molecules
In contrast to previous studies in which UVB was exclusively a stress factor, recent studies have highlighted the regulatory properties of low, ecologically-relevant UVB levels that trigger distinct changes in the plant’s secondary metabolites resulting in an accumulation of mainly phenolic compounds, carotenoids, and glucosinolates.
UVB Perception and Signaling Plants specifically detect and respond to UVB radiation, and can be measured as: • Characteristic changes in gene expression • Physiology and/or morphology • Altered accumulation of plant secondary metabolites.
In general, UVB effects on secondary plant metabolites is DOSE DEPENDENT: • Morphological structure of the plant organ • Developmental stage of the plant tissue • Kinetics of the UVB accumulation response
RULE OF THUMB:
1. UVB sensibility of the plant increases with extended surface area and with progressed physiological development. 2. Levels of some metabolites, including antioxidants are rapidly up-regulated following UVB exposure
Botany 101—Basic Principles
Light-Dependent Reactions
Light-Independent Reactions
Ultimate goal for any artificial light would be to replicate the complete solar spectrum at appropriate power densities
Artificial Solar Sources
Similar to other applications that utilize HID Lamps, LEDs have started to replace the legacy technology due to the following: Less Heat New Spectra not available under HIDs Tunable Lights—control of spectrum throughout growth cycle Lower cost of ownership