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Division of Agricultural Sciences and Natural Resources • Oklahoma State University
Oklahoma Cooperative Extension Fact Sheets
are also available on our website at:
Oklahoma Cooperative Extension Service
November 2016
Taylor Mills
Graduate Student
Bruce Dunn
Associate Professor, Floriculture
Light is the single most important variable with respect to
plant growth and development and is often the most limiting
factor. Therefore, the use of grow lights in commercial green-
houses is beneficial for plants and growers. The reason for
using grow lights varies and includes increasing light levels
for plant photosynthesis or altering photoperiod. The duration
of light a plant perceives is photoperiod. The different lighting
sources that growers can use include incandescent (INC)
lamps, tungsten-halogen lamps, fluorescent lamps and high
intensity discharge (HID) lamps. Light emitting diodes (LED)
are fourth generation lighting sources and are an emerging
technology in horticulture. Below are advantages and disad-
vantages of LED.
LED Advantages
Energy efficient
Easy installation
More durable
Longer lifetime (less lamp changes)
Low heat emission
LED Disadvantages
Higher initial costs
Heavier weight with some devices (e.g. grow lamps with
heat sinks)
Limited use (e.g. most LED devices are designed and
used in research settings)
Less coverage area
Different ratios of LED colors
High temperatures (of the environment) shorten lifespan
and reduce efficiency
Before choosing a lighting device, several factors such
as costs, efficiency, total energy emissions, life expectancy,
light quality, light quantity, light duration and effect on plant
growth and flowering should be considered. This Fact Sheet
provides information about LED grow lights for use in plant
LED Grow Lights for Plant
Design and Function
The design of LEDs varies and there are three main
structural types, which are lead-wire, surface mounted and
high-power LED. Despite the different designs, each type is
mounted on a printed circuit board; therefore, LEDs function
like computer chips. LEDs are solid-state semiconductors
and when turned on or off, the action is instant. As for life
expectancy (dim to about 70 percent from initial installation),
LEDs can operate up to 50,000 hours. It is not necessary to
replace single diodes or lamps constantly because LEDs do
not burn out. Factors such as design, materials used and
heat release affect life expectancy. Another important feature
of LEDs is that heat does not escape from the surface, but
through a heat sink which allows for close proximity between
plants and LEDs (Figure 1). As for consumption of energy,
LEDs are more efficient and use less energy than any other
traditional greenhouse lights. In addition, operating costs and
carbon emissions are lowered when using LEDs.
Devices and Bulb Types
There are different LED lighting devices (Figures 1, 2
and 3) and bulb types used in horticulture and each provide
a specific need to plants and growers. Bulged reflectors,
Figure 1. Heat sink and standard E26 light bulb base fitting
of Philips® GreenPower LED flowering lamp.
tubular and miniature are the different bulb types. The differ-
ent devices are toplights, inter-lights, tubular LEDs (TLEDs)
and flowering lamps. Toplights, inter-lights and TLEDs are
considered module lighting systems, which are for multi-layer
production systems such as city (vertical) farming, tissue
culture and indoor research facilities, such as grow rooms
and growth chambers. Toplights have high lighting outputs
and low heat emission and are used specifically for high wire
and leafy vegetables. Interlights allow plants to receive light
horizontally and vertically and are used for plants that rise
such as cucumbers and tomatoes. TLEDs are replacement
lamps for traditional fluorescent tubes used in tissue culture
and offer more uniformed lighting and produce less heat. The
latest type on the market are flowering lamps which are high-
powered LEDs and have identical features as incandescent
lamps such as a standard E26 light bulb base fitting (Figure1).
For extending day length (photoperiod alteration) of plants,
flowering lamps are ideal.
Light Emission and Quality
LEDs emit white and colored light. To make white light
(used for general lighting), multiple colors are mixed together.
The mixture can include a combination of blue (B), green (G),
red (R), ultraviolet (UV) and yellow (Y). The colors are con-
verted through a phosphor material coated on LEDs. During
the conversion process, the phosphor material absorbs energy
of short wavelengths (λ) and emits it at longer wavelengths.
Emission of light from LEDs is narrow, reducing light pollution.
Another great feature regarding color emission from LEDs is
that the composition can be created or adjusted (color tun-
ing) for specific plant responses. Depending on type, LEDs
can emit wavelengths between 250 nm (UV) and 1,000 nm
(infrared) or more, which is referred to as light quality and is
related to photosynthetically active radiation (PAR). Wave-
lengths in the range of 400 and 700 nm are considered to be
optimum for plants. However, 440 (B), 660 (R) and 730 (FR)
nm are greatly optimized by most plants. Blue light increases
chlorophyll production, resulting in healthier foliage. Red and
far-red light promotes growth and flowering, which is useful
for long-day plants under short-day conditions.
Light Measurements
Lumens, lux (lx) and foot-candles (fc) are units mea-
sured in plant light studies. However, studies using LED
have replaced these units with photosynthetic photon flux
(PPF), photosynthetic photon flux density (PPFD), and daily
light integral (DLI). The most common units for measuring
PAR are PPF and PPFD. The PPF is a measurement of total
light amount produced each second by a lighting source and
is expressed in micromoles per square meter per second
(µmol·m2·s-1). Depending on the device, PPF of LEDs can
range between 13 and 2000 µmol·m2·s-1. Another measure-
ment, expressed in µmol·m2·s-1, is the PPFD that measures
the amount of light reaching a given surface. A PPFD between
400 and 800 µmol·m2·s-1 is recommended for improved plant
growth. Measurement of total light amount being delivered to
Figure 3. Philips® GreenPower LED flowering lamp.
Figure 2. LED Grow Master’s LGM550 light bar.
Table 1. Comparisons among lighting sources.
LED HID Incandescent Fluorescent
Lifespan 50,000 hours 24,000 hours 750 to 100 hours 10,000 hours
Watts 12 to 215 35 to 2,000 40 to 500 46 to 225
Ranking of Price Per Unit Highest High Lowest Medium
Energy Consumption Lowest Highest Medium Medium
Cost to Operate Lowest High High High
Efficiency Very high Medium Low Medium
Spectrum Narrow and broad Broad Narrow Broad
Table 2. Plant responses to LED spectra.
Lighting conditions Plant Effects Reference
Red (660 nm) Lettuce seedlings Elongated hypocotyls and Hoenecke et al., 1992
Red (660 nm) Strawberry Increased photosynthetic Yanagi et al., 1996
(Fragaria xananassa L.) rates in leaves
Red (660 nm) + blue Rice Increased photosynthetic Matsuda et al., 2004
(470 nm) rates in leaves
Supplemented blue with Wheat seedlings Restored chlorophyll Tripathy and Brown, 1995
30 µmol·m-2·s-1 PPF or synthesis
red with 100 µmol·m-2·s-1
Infrared (880 nm and 935 nm) Etiolated oat seedlings Increased and decreased Johnson et al., 1996
concentration of mesocotyl
and coleoptile tissue respectively;
straightened seedlings; activated
Red + white + far-red Dianthus (Dianthus chinensis Delayed flowering Kohyama et al., 2014
(700 to 800 nm) for night ‘Floral Lace Purple’ and
interruption ‘Super Parfait Strawberry’)
Petunia (Petunia xhybrida Promoted early flowering
‘Easy Wave Burgundy Star’)
Dianthus, both cultivars Promoted longer internodes (height)
Red + white (600 to 700 nm) Ageratum (Ageratum Inhibited height
for night interruption houstonianum ‘Hawaii Blue’)
and calibrachoa (Calibrachoa
x hybrida ‘Callie White’)
Red:blue (100:0; 450 nm or Petunia (Petunia x hybrida Stem length shortened; Lopez and Currey, 2013
627 nm) with 70 µmol·m-2·s-1 ‘Suncatcher Midnight Blue’) increased dry mass of leaves,
PPF cuttings roots, and root:shoot ratio
Sole source lighting of blue Impatiens (Impatiens walleriana Inhibited height
(446 nm) with ‘SuperElfin XP Red’), petunia
160 µmol·m-2·s-1 PPF (Petunia x hybrida ‘Wave
Pink’), salvia (Salvia splendens
‘Vista Red’), and tomato
(Solanum lycopersicum
‘Early Girl’) seedlings
Sole source lighting of red Impatiens, petunia, salvia Increased leaf area and Wollaeger and Runkle, 2014
(634 nm and 664 nm) with and tomato seedlings fresh shoot weight
160 µmol·m-2·s-1 PPF
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been designated to handle inquiries regarding non-discrimination policies: Director of Equal Opportunity. Any person (student, faculty, or staff) who believes that discriminatory practices have
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Issued in furtherance of Cooperative Extension work, acts of May 8 and June 30, 1914, in cooperation with the U.S. Depar tment of Agriculture, Director of Oklahoma Cooperative Extension
Service, Oklahoma State University, Stillwater, Oklahoma. This publication is printed and issued by Oklahoma State University as authorized by the Vice President for Agricultural Programs and
has been prepared and distributed at a cost of 20 cents per copy. 1116 GH.
plants every day is DLI and is expressed as moles of photons
per square meter per day (mol·m2·d). The ideal DLI depends
on the crop or species itself, as requirements of plants vary
greatly as well as a grower’s geographic location. A general
DLI of 5 to 10, 10 to 20, 20 to 30, and 30 to 50 are ideal for
low, medium, high and very high light plants, respectively.
In research, quantum sensors and spectroradiometers
are devices used to measure these light parameters and are
costly (pricing ~$1,000 or more). A cheaper alternative are
light meters with a price range between $40 and $200.
Coverage Area and LED Placement
Light intensity (high light or low light) needs of a plant and
total area of grow space determine how many LED watts (W)
are needed. It is important to know because some LEDs do
not operate at full capacity. It is recommended that for high
light plants in a 1 square foot grow space to use 25 W and 16
W for low light plants. If a grower increases the square feet of
a grow space, watts needed will increase as well. Placement
of an LED refers to its distance from the plant canopy as well
as the spacing between individual light units. Placement of an
LED is based on the following:
Plant type (e.g. high light or low light)
Device type (e.g. toplights, inter-lights, TLEDs and flower-
ing lamps)
Coverage area
Environmental conditions (e.g. natural lighting)
Manufacturer recommendation
A rule of thumb to consider when placing LEDs is that the light
from one device should overlap with the light from another,
creating an even spread of light over the growth space to
ensure proper plant growth.
Plant Growth and Flowering
LEDs are the ideal lighting type because growers can
select them based on spectral output. Plants of all types and
stages respond to a specific wavelength which enhances their
development, quality and productivity. LEDs emitting R or FR
are best for flowering ornamentals. Emission of B is ideal
for vegetative growth. Vegetable and ornamental seedlings
(plugs) as well as propagated plants (e.g. seeds, cuttings, and
bulbs) respond well to R, B or R+B. An overview of different
plant responses to light spectra is given in Table 2.
LED Manufacturers
There are several companies worldwide that manufac-
ture LED products specifically for horticulture. The top selling
companies are Philips (Amsterdam, Netherlands), Illumitex
(Austin, TX, USA), Osram (Munich, Germany), and Cree Inc.
(Durham, NC, USA) and LumiGrow (Emeryville, CA, USA).
Additional reading
The information given herein is for educational purposes only. Reference to commercial products or trade names is made with
the understanding that no discrimination is intended and no endorsement by the Cooperative Extension Service is implied.
... Thus installation of cooling systems becomes critical in such situations. This contributes to the unnecessary expenditure of time and resources 3,[8][9][10][11] . ...
... Far-red light of the wavelength 730 nm was reported to be successful for flowering and overall growth in plants. Plants absorb blue light to increase the chlorophyll content, enhancing the overall development of the plants 9 . Therefore, the absence of the blue wavelength contributes towards the cultures under far-red LED being terminated. ...
Full-text available
The use of artificial light sources such as light-emitting diodes (LEDs) has become a prerequisite in tissue culture studies to obtain morphogenetic enhancements on in vitro plants. This technology is essential for developmental enhancements in the growing plant cultures due to its light quality and intensity greatly influencing the in vitro growing explants at a cellular level. The current study investigates the effects of different light-emitting diode (LED) spectra on the growth of apical buds of Ficus carica var. Black Jack. Ficus carica, commonly known as figs is rich in vitamins, minerals, and phytochemicals capable of treating microbial infections and gastric, inflammatory, and cardiac disorders. Apical buds of Ficus carica var. Black Jack, presented morphogenetic changes when grown under six different LED spectra. The highest multiple shoots (1.80 per growing explant) and healthy growing cultures were observed under the blue + red LED spectrum. Wound-induced callus formation was observed on apical buds grown under green LED spectrum and discolouration of the growing shoots were observed on the cultures grown under far-red LED spectrum. Multiple shoots obtained from the blue + red LED treatment were rooted using 8 µM indole-3-acetic acid (IAA), and the rooted plantlets were successfully acclimatised. Compared with the other monochromatic LEDs, blue + red proved to be significantly better for producing excellent plant morphogeny. It is apparent that blue and red LED is the most suitable spectra for the healthy development of plants. The findings have confirmed that the combination of blue + red LED can potentially be used for enhancing growth yields of medicinally and commercially important plants.
... Morphogenetic processes among plants such as stem and root elongation, leaf expansion, biochemical pathways, and metabolisms are greatly affected by the availability of quantity and quality of light. Morphological effects on the in vitro growing plants can occur based on the availability of the photosynthetically active radiation (PAR) [32,33]. LED spectra are used for micropropagation of plants to enhance the cellular level properties of the plants. ...
Full-text available
Background Clonal propagation is one of the attributes of plant tissue culture. Therefore, analysis of genetic stability among the in vitro cultured plants is a crucial step. It helps to signify the clonal propagation of the micropropagated plants. Regenerated Ficus carica var. Black Jack plantlets were established using woody plant medium supplemented with 20 μM 6-Benzylaminopurine and 8 μM Indole-3-acetic acid under different light treatments such as normal fluorescent white light (60 μmol m−2 s−1), and four different LED spectra, white (400–700 nm), blue (440 nm), red (660 nm) and blue + red (440 nm + 660 nm). Genetic stability analysis was performed on the in vitro and ex vitro plants of Ficus carica var. Black Jack.Methods and resultsTen primers of each, ISSR and DAMD molecular markers, were used to assess the genetic stability of the eight samples of Ficus carica var. Black Jack. ISSR markers showed 97.87% of monomorphism whereas DAMD markers showed 100% monomorphism. Polymorphism of 2.13% was observed for the UBC840 ISSR–DNA primer which was negated under the genetic similarity index analysis for the eight samples. The findings of this study revealed that ISSR and DAMD markers are efficient in determining the polymorphism and monomorphism percentage among the in vitro and ex vitro samples of Ficus carica var. Black Jack.Conclusion Monomorphism of 100% obtained using DAMD markers and more than 95% of monomorphism obtained using ISSR markers indicate that the regenerated plants are significantly genetically stable. These molecular markers can be used to test the genetic stability of in vitro regenerated plants. It is recommended that genetic stability analysis should be performed for long-term maintenance of such micropropagated plants.
Full-text available
In vitro propagation has been significant in producing a large number of genetically stable regenerated plants. Regenerated Ficus carica var. Black Jack plantlets were established using woody plant medium (WPM) supplemented with 20 µM 6-Benzylaminopurine (BAP) and 8 µM Indole-3-acetic acid (IAA) under different light treatments such as normal fluorescent white light (60 µmol.m − 2 .s − 1 ), and four different LED spectra, white (400– 700nm), blue (440nm), red (660nm) and blue + red (440nm + 660nm). Genetic stability analysis was performed on the in vitro and ex vitro plants of Ficus carica var. Black Jack. Ten (10) primers of each ISSR and DAMD molecular marker were used to assess the genetic stability of the eight (8) samples of Ficus carica var. Black Jack, acquired over two years. The findings of this study revealed that inter simple sequence repeats (ISSR) and directed amplification of minisatellite DNA (DAMD) markers (DNA primers) are efficient in determining the polymorphism and monomorphism percentage among the in vitro and ex vitro samples of Ficus carica var. Black Jack. ISSR markers showed 97.87% of monomorphism whereas DAMD markers showed 100% monomorphism. Polymorphism of 2.13% was observed for the UBC840 ISSR – DNA primer which was negated under the genetic similarity index analysis for the eight samples. It is recommended that genetic stability analysis should be performed for long-term maintenance of micropropagated plants.
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