Light emitting diode (LED) : A Revolutionary development in

Plant Tissue Culture and Greenhouse Industry

Rajesh Pati, PhD e-mail: rajeshpati777@gmail.com

Index

• Introduction • How light affects on plants• Effect of different light spectra on plant growth• How LED works• Properties various color of LEDs• Advantage / Limitations• Economics of LED• Effects on in vitro regeneration• Cultivation crops in greenhouse • Effects on greenhouse pest• Effect on pathogenic microbes• Conclusion • References

Introduction• Henry Josef Round of Marconi Labs, begins the journey of LEDs.

• Nick Holonyak, Jr. invented first practical LED in 1962.

• Fluorescent, high pressure sodium, metal halide, and incandescent lampsare commonly using in tissue culture growth rooms as artificial lightsources.

• Fluorescent lamps are most commonly using in tissue culture growthrooms for micropropagation of various crops.

• These lights have a wide range of wavelengths (350-750 nm) and appearsto be unnecessary and are of low quality for promoting plant growth.

• This type of light sources requires high electricity consumption with lowoutput efficiency. Which is ultimately increase the per plant productioncost.

• Thus, there is a urgent need of an efficient light source, which is not onlyimprove the quality of in vitro plants but also minimize per plantproduction costs.

• LED (Light emitting diode) has been proposed as potential alternativelight source for growth and development of in vitro and greenhouse plants.

What is light?• Light is energy, and white light contains all the colors and wavelength of

light. The photosynthesis process allows plant to capture the light energyand turn in to chemical energy in the form of carbohydrate.

Why supplemental light is necessary ?• In general, in the presence of natural light, plant produce more

carbohydrate for use and store. When plants grows inside the house, laband green house, the physical structure shades the plant and induces alight deficit. Supplemental lightning makes up to the difference between,what light plants get and what they need to thrive.

How does light affect plant growth?• Plants require light throughout their whole life-span from germination to

seed production. Three parameters of light is most important:

• Light quantity (intensity): Photosynthesis, photochemical reactionwithin the chloroplasts.

• Light quality (spectral distribution): Red, blue, green, orange redaffects on photomorphogenesis.

• Light duration (photoperiod): Affects flowering.

Effect of different light spectra on plant growth

The flexibility of matching wavelengths of LEDs to plant photoreceptors mayprovide a more optimal production, influencing plant morphology andmetabolism (Kim et al. 2004).

Blue, red, far-red, green and yellow

• Stomata opening, photosynthetic rate, leaf area, increasing number andsize of leaf, Stem, inter-node length & diameter, fresh weight, dry weight,in vitro flowering, Callus induction, proliferation, development andconversion of somatic embryos, development of tap root and lateral roots,Seed germination, PLB induction, proliferation and Shooting

Biochemical parameters

• Increasing chlorophyll, soluble sugar, carotenoid contents, starch and freeamino acid, super oxide, dismutase, catalase, peroxidase activities

How LED works• LED is a unique type of solid-state semiconductor diode that emits light

when a current is applied through the device.• Two elements of processed material, p-type semiconductors and n-type

semiconductors, are placed in direct contact and form the LED chipwhich comprises the p–n junction .

• A current flows only from the Anode post to the Cathode post. Electronsand holes flow into the junction from electrodes with different voltages.When an electron meets a hole, it falls into a lower energy level andreleases energy in the form of a photon. The light produced by a solid-state process is called electroluminescence.

• The energy gap of the semiconductor determines the color (wavelength)of the light and the materials used for an LED have energiescorresponding to near-ultraviolet, visible, or near-infrared light.

+ -

Commercially available LEDs with colors andseniconductor material used

Wavelength range (nm)

Colour Semiconductor material

<400 Ultraviolet Aluminium nitride (AIN)Aluminium gallium nitride (AIGaN)Aluminium gallium indium nitride (AlGaInN)

400–450 Violet Indium gallium nitride (InGaN)450–500 Blue Indium gallium nitride (InGaN)

Silicon carbide (SiC)500–570 Green Gallium phosphide (GaP)

Aluminium gallium indium phosphide (AlGaInP)Aluminium gallium phosphide (AlGaP)

570–590 Yellow Gallium arsenide phosphide (GaAsP)Aluminium gallium indium phosphide (AlGaInP)Gallium phosphide (GaP)

590–610 Orange/amber

Gallium arsenide phosphide (GaAsP)Aluminium gallium indium phosphide (AlGaInP)Gallium phosphide (GaP)

610–760 Red Aluminium gallium arsenide (AlGaAs)Gallium arsenide phosphide (GaAsP)Aluminium gallium indium phosphide (AlGaInP)Gallium phosphide (GaP)

<760 Infrared Gallium arsenide (GaAs)Aluminium gallium arsenide (AlGaAs)

Gupta & Jatothu- 2013, Plant Biotechnol Rep

Comparison between LED and conventional lightning systemsLED light systems Conventional light systems

Advantage: Low electricity requirement High efficiency Low heat generation Low investment in cooling system Reduce cooling cost Long life (50,000 to 100,000 h,)

Limitation High initial investment

Advantage: Low initial investment Low cost compare to LED Easily available

Limitation High electricity requirement Low efficiency More heat generation Increased cooling cost More investment in cooling system Increased production cost Less life (10-15,000h)

The most efficient HPS (High Pressure Sodium) and LED lightning system havealmost equal efficiencies, but the initial capital cost per photon delivered from LEDlightning system is 5-10 times higher than HPS systems.

Economics of LED

Operational cost of LEDs and HPS• Traditional HSP lamps convert only 30% of energy into visible light and rest

of converted in to heat.• LED converts 70% of energy into light.• 150W HSP lamp and 14W LED having similar effects on flowering patterns

of bedding plants, therefore LED is more economic for greenhouse growers(Meng & Runkle, 2014).

Assumptions• Average lighting time in greenhouse: 16 hours/day

• Electricity rate: 9.5 INR/kWh

Calculation• Electricity consumed by 150-Watt HPS: 2.40 kWh/day

• Electricity consumed by 14-Watt LED: 0.22 kWh/day

• Annual electricity consumption: 876 kWh (HPS) and 80.3 kWh (LED)

• Annual electricity cost in INR: 8322.0 for HPS and 763.0 for LED

Nelson & Bugbee, 2014

Photon efficiency and cost per mole of photons, assuming all photons (180o) are captured by plants

Nelson & Bugbee, 2014

Cost per mole photons for four capture assumptions

Fig. Concept of canopy photoncapture efficiency.LED lightning system can provideprecision delivery of photons and thatthey can be a more cost effective option(If widely spaced benches were used) forsupplemental greenhouse lighting(Nelson & Bugbee, 2014).

doi:10.1371/journal.pone.0099010.g002

Bourget et al 2008

Fig. 1: A comparison of the luminous efficiencies(light energy output/electrical energy output) ofselected electric light sources

Fig. 2: A comparison of the lifetimes ofselected electric lamps.

A comparison of the luminous efficiencies and life span of selected electric light sources

Use of LED illumination system in Tissue culture

industry

Effects of LEDs on in vitro plant micropropagationCrop Types of

LEDEffect on plant growth

FRUIT

Banana Blue, Red Red+Blue (80:20)- Increase plantlet growth & fresh weight

Strawberry Blue, Red Red+Blue (70:30)- Increase plantlet growth & fresh weight

Grape Blue, Red Blue- Increase shoots fresh and dry weights, net photosynthetic rate. Red- Increase shoot length, Red+Blue (80:20)- Sugar content and starch accumulation

FOREST TREE

Somatic embryosin Pinus taeda,P. elliottii, P. palustris

Blue, Red Red- Increase somatic embryo germination, conversion, tap root length and more lateral roots.

FIELD CROP

Sugarcane Green Green (530nm)- Increase in vitro side shoot multiplicationCotton Blue, Red Red+Blue - Increase shoots fresh and dry weights, increase

nodal distance, leaf thickness, chlorophyll contents

Modified from Gupta & Jatothu- 2013, Plant Biotechnol Rep

Crop Types of LED

Effect on plant growth

Ornamental

Cymbidium Red, blue Red- Promote leaf growth but decreased chlorophyll content. The effect was reversed by blue light

RehmanniaGlutinosa

Red, blue Blue- Highest dry weight & air exchanges. Red-Elongation of plantlet. Red and Blue mix- Improves net photosynthetic rate

Bulbs of Liliumoriental (Pesaro)

Red, blue Red and Blue mix- Improves regeneration and number of bulblets

Chrysanthemum Blue, red and far-red

Increase in vitro plant fresh & dry weight, leaf area, chlorophyll content and net photosynthetic rate

Zantedeschiajucunda

Blue, Red Blue- enhanced plant height & chlorophyll content

Euphorbia milii & Spathiphyllumconifolium

Blue, red and far-red

Red- Reduced the flowering Far-red- Stimulated flowering

Tripterospermumjaponicum

Blue, Red Red- Promote rooting, while Blue inhibits. Blue+Red mix (70:30) - Improves plant growth

Phalaenopsishybrid seed

Blue, Red Red+Blue (80:20)- Promote growth and development of protocorms, seed germination

Doritaenopsishort.

Blue, Red Blue+Red- Increased plant growth, carbohydrates, chlorophyll, and carotenoids contents

Effects of LEDs on in vitro plant micropropagation

Modified from Gupta & Jatothu- 2013, Plant Biotechnol Rep

Effects of LEDs on in vitro plant micropropagationCrop Types of

LEDEffect on plant growth

Ornamental

Chrysanthemum Blue, red and far-red

Blue-Enhanced plantlet extension, root formation, photosynthetic pigments

Gossypiumhirsutum L.

Blue, Red Blue+Red (50:50) – Increase fresh weight and stem length of plantlets. Blue- Increase chlorophyll content, stomata development and leaf area, Red- Promote root growth

PLBs ofDendrobiumofficinale

Blue, Red Blue+Red (2:1): Promote the shooting of PLBs

Shoot tips ofOncidium

Blue, Red, Green, Yellow

Red- LEDs enhanced induction, proliferation, & carbohydrate contents of PLBs, Blue- Promoted the enzyme activities

Anthurium andreanum

Blue, Red Red- Promote callus development. Blue- Shoot regeneration

Bletilla ochraceaSchltr

Blue, Red, Green, Yellow

Green and orange- Seed germination Orange and red- Induced rhizoid formation

Modified from Gupta & Jatothu- 2013, Plant Biotechnol Rep

www.growingmagazine.com

Use of LED illumination system in growth room

www.optexlighting.com

Use of LED illumination system in cultivation of crops

in Greenhouse

Cultivation of crops under Green houseCrop Types of

LEDEffects on plant growth

FruitStrawberry Blue, Red Blue- Increase yield, Red- Increase mallic and oxalic acid,

Red+Blue- Fruit hardness, self-life, anthocyanin acidity and glucose content

Field cropSugarcane Green Green- Increase growth, side offshoots, glucose contentCotton Blue, Red Red+Blue- Increase shoots fresh and dry weights, nodal

distance, leaf thickness, chlorophyll contents Wheat Red Red- High morphogenesis, photosynthesis and seed yieldPepper Ultra bright

white & RedUltra bright white & Red- Improve growth and photo-morphogenesis

VegetablesTomato Red, Far-Red Red, Far-Red- Increase seedling germination, yield, chlorophyll,

systemic disease resistance against root knot nematode.

Cucumber Blue, Red Blue+Red- Improves growth, seed quality, physiological and biochemical characteristics

Lettuce Blue, Red Blue+Red- Improves growth, nutritional quality, chlorophyll, gaseous exchange in leaves, stomatal condensation, photosynthesis rate

Chinese cabbage Blue Blue- Increase growth, yield and respiration rate

Strawberry cultivation under LED

hydroponicshabitat.com

ajw.asahi.com

www.led-ohmax.com www.compoundsemiconductor.net

Vegetable cultivation under LED

hortamericas.blogspot.com www.henkwildschut.com

Vegetable cultivation under LED

www.decorfox.comwww.bigpictureagriculture.com

www.floralab.fr

Flower cultivation under LED

www.edengrowrooms.comhortamericas.blogspot.com

Effects of different light spectra on Greenhouse Pests

Effect of LED on Integrated Pest Management (IPM)

• The direct effects of artificial lighting on IPM must be studied in the contextof plant-mediated effects of artificial light on arthropods, as both types ofmanipulations are possible, particularly with LEDs (Johansen et al, 2011,Ann Appl Biol).

• If LED systems can be configured to help reduce insect damage and insectrelated vectored disease in greenhouse, this system will gain additionalusefulness by becoming an important component of the growers IPMprogramme and could help to reduce the annual per hectare costs ofgreenhouse pest control (Morrow, R.C. , www.reeis.usda.gov/web)

• Developments in artificial lighting technologies and greenhouse claddingmaterials increase the possibilities of manipulating pests and beneficialspecies.

• Low level of UV-Radiation reduces the invasion of whiteflies and thripsinto the greenhouse facility.

• Red and blue light induces resistance in plants to pathogenic fungi, but onthe other hand, it increase the inability of locating host plant and reducedvisibility of pray (Vänninen et al 2012, ISHS Acta Hort.).

Behavioral and biological responses to different light spectra in greenhouse pests and beneficial insects and mites

WavelengthSpectrum

Dominant wavelengths

(nm)

Response Species

UV-C 250–254 Slight avoidanceAvoidance, Reduced egg production,Reduced survival

Tetranychus urticaeT. urticae

UV-B 280–320 AvoidanceReduced egg productionReduced egg survivalReduced survival (adults, larvae)

T. urticae, Caliothrips phaseoliT. urticaeT. urticae, Neoseiulus womersleyiT. urticae

UV-A 320–360 Avoidance T. urticaeUV <400 Avoidance

Reduced egg production, Reduced egg survival, Delayed development (egg, protonymphs), Attraction

T. urticaeT. urticaeT. urticaeFrankliniella occidentalis, Aphis faba,Trialeurodes vaporariorum, Aphidiuscolemani, Diglyphus isae, Eretmocerus mundus

Modified from Johansen et al, Ann Appl Biol 159 (2011) 1–27UV: ultraviolet

WavelengthSpectrum

Dominant wavelengths

(nm)

Response Species

UV-blue White

310–520 AttractionAttractionNo response

Bemisia tabaciF. occidentalisB. tabaci, Liriomyza sativae,T. vaporariorum

Violet 400–440 AttractionRepellent (negative phototaxis), Increased take-off rate Increased walking activity, No response

F. occidentalisT. vaporariorum

Violet-blue 400–500 RepellentPrevent diapause

T. vaporariorum, L. sativaeOrius insidiosus

Blue 440–490 AttractionRepellentNo response

F. occidentalis,Frankliniellaschulzei, B. tabaci, T. vaporariorum, L. sativae, B. tabaci, T. vaporariorum

Behavioral and biological responses to different light spectra in greenhouse pests and beneficial insects and mites

UV: ultraviolet Modified from Johansen et al, Ann Appl Biol 159 (2011) 1–27

WavelengthSpectrum

Dominant wavelengths

(nm)

Response Species

Green-yellow 480–610 AttractionLanding

A. fabae, B. tabaci, T. vaporariorum, F. occidentalis, L. sativae, Spodoptera litura (larvae),B. tabaci, T. vaporariorum

Green 500–550 AttractionLanding

Landing and stayingWalking towards targetProbingNo response

T. urticae (when lack of food), A. fabae, B. tabaci, T. vaporariorum, L. sativae, Aphidius ervi, Eretmoceruseremicus (nonmigratory females)A. fabae, Myzus persicae, B. tabaci,T. vaporariorumT. vaporariorumM. persicaeMacrosiphum euphorbiae, M. persicae, T. urticae (when fresh food is available), B. tabaci, T. vaporariorum, E. eremicus (males)

Spring green 510 Attraction B. tabaci

Behavioral and biological responses to different light spectra in greenhouse pests and beneficial insects and mites

Modified from Johansen et al, Ann Appl Biol 159 (2011) 1–27

WavelengthSpectrum

Dominant wavelengths

(nm)

Response Species

Lime green 520–530 Attraction Aphis gossypii, B. tabaci,T. vaporariorum, Bradysia coprophila

Citrus green — Attraction F. occidentalisLime yellow — Attraction F. occidentalisYellow 560–590 Attraction

LandingWalking towards targetProbing

A. fabae, B. tabaci (nonmigratory), T.vaporariorum, F. occidentalis,F. schulzei, L. sativae, Aphidius erviB. tabaci, A. fabae, M. euphorbia,M. persicaeM. euphorbiae, M. persicae

Orange 590–635 ProbingNo response

M. euphorbiae, M. persicaeT. vaporariorum

Red 575–700635–700

AttractionProbingWalking towards targetNo response

F. schulzei, B. tabaciM. euphorbiae, M. persicaeM. euphorbiaeT. vaporariorum, B. tabaci

Infrared >700 No response A. fabae

Behavioral and biological responses to different light spectra in greenhouse pests and beneficial insects and mites

Modified from Johansen et al, Ann Appl Biol 159 (2011) 1–27

Effect of different light spectra to control growth of

microbial pathogens

Effect of different light spectra to control growth of microbial pathogensType of light Microcidal effect

Red Red is promising light device for photodynamic therapy (PDT) that caneffectively inhibit bacteria (Altermia aureus), yeast and microcrustaceansgrowth (Peloi et al, 2008)

Blue LED Inhibition of grey mold disease of Tomato (Kim et al, 2013, Plant PhysiolMicrobiol)

Blue (405nm) Complete inactivation of Staphylococcus aureus. (Maclen et al, 2009, Appl.Environ Microbiol).

Gram-positive bacteria is more susceptible than Gram-negative to blue light(Daniela et al 2013, Photomedicince Laser Surgery)Bactericidal effect on Escherichia , Salmonella, Shigella, Listeria andMycobacterium sp. In liquid suspension and on exposed surface (Murdoch etal, 2012, The scientific World J.).

Inhibitory effect on intracellular bacteria Chlamydiatra chomatis (Vasson etal., 2012, BMC Microbiol)

Blue (470nm) Effectively inhibits bacteria (Leuconostoc mesenteroides, Bacillus atrophaeus,Pseudomonas aeruginosa), Filamentous fungi (Penicillum digitatum andFusarium graminearum), (Lucca et al., 2012, Letters in Applied Microbiol)

Conclusion• What specific spectra and photosynthetic flux densities are required by

different plant species and varieties in different ontogenesis stage, whatwavelength combinations should be selected seeking for maximalproductivity, optimal nutritional quality are still to be workout/part ofinvestigation. (Olle & Virsile, 2013)

• LED lightning system can provide precision delivery of photons and thatthey can be a more cost effective option (If widely spaced benches were used)for supplemental greenhouse lighting.

• The high capital cost of LED lighting systems is an important aspectdelaying the establishment of LED technology in laboratory and greenhouselighting.

• The high capital cost means that the 5 years cost of LED lightning system ismore than double that of HPS lightning system.

• Economic analysis has clearly shown that LEDs can reduce the electricitycost and investment (high capital cost) will be returned as profit in long-term operations.

• Manufacturers are working to improve all types of lighting technologies andthe cost per photon will likely continue to decrease as new technologies,reduced prices, and improved reliability become available.

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plant growth and morphogenesis. Plant Biotechnol Rep, 7:211–220• Johansen et al, (2011). In the light of new greenhouse technologies: 2. Direct effects of artificial lighting on

arthropods and integrated pest management in greenhouse crops. Ann Appl Biol, 159: 1–27• Morrow R.C. (2008). LED Lighting in Horticulture. Hort. Science, 43(7): 1947-1950.• Nelson JA and Bugbee B (2014) Economic Analysis of Greenhouse Lighting: Light Emitting Diodes vs. High

Intensity Discharge Fixtures. PLoS ONE 9(6): e99010• Olle M. and Virsile A. (2013). The effect of light emitting diode lightning on greenhouse plant growth and quality.

Agri. Food Science. 22: 223-234.• Sing D et al (). LEDs for Energy Efficient Greenhouse Lighting.• Peloi et al (2008). Photodynamic effect of light-emitting diode light on cell growth inhibition induced by methylene

blue. J Biosci. 33(2):231-7.• Maclean (2009). Inactivation of Bacterial Pathogens following Exposure to Light from a 405-Nanometer Light-

Emitting Diode Array. Appl Environ Microbiol. 75(7): 1932–1937.• Phoenix (2003). The phototoxicity of phenothiazinium derivatives against Escherichia coli and Staphylococcus

aureus. FEMS Immunol Med Microbiol, 39(1):17-22.• De Lucca et al (2012). Blue light (470 nm) effectively inhibits bacterial and fungal growth. Letters in Applied

Microbiology 55: 460-466.• Lynne et al (2012). Bactericidal Effects of 405 nm Light Exposure Demonstrated by Inactivation of Escherichia,

Salmonella, Shigella, Listeria, and Mycobacterium Species in Liquid Suspensions and on Exposed Surfaces.Scientific World Journal, doi: 10.1100/2012/137805

• Violet et al. (2013). Wavelength and Bacterial Density Influence the Bactericidal Effect of Blue Light onMethicillin-Resistant Staphylococcus aureus (MRSA). Photomedicine and Laser Surgery, 31(11):547-553.doi:10.1089/pho.2012.3461

• Wasson et al (2012). Inhibitory effects of 405 nm irradiation on Chlamydia trachomatis growth andcharacterization of the ensuing inflammatory response in HeLa cells. BMC Microbiol. 15(12):176.

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