LED Light Sources for Plant Research
If you are searching for LED Zeppelin/Robert Plant go back now!
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LED Light Sources for Plant Research If you are searching for LED Zeppelin/Robert Plant go back now!
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Kevin M. Folta, Assistant Professor, Plant Molecular and Cellular Biology Program, Horticultural Sciences Department, University of Florida, Gainesville FL 32611. kfolta@ifas.ufl.edu Home Page
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Thank you for your interest and patience. I have been actively designing new architectures and controls and have been experimenting with many LED products. I have decided on a combination of LEDs and controllers that work perfectly and provide outstanding spectral coverage, power and controllability at an affordable price. I have identified appropriate heat sinks, power supplies and circuits to run outstanding set ups for plant research applications. I hope to make the protocols for their construction available soon.
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Why LEDs?
 Studies of photomorphogenesis (light-mediated development) in plants have benefited from the use of monochromatic light to isolate the effects of specific photoreceptors and the responses they mediate. For instance, blue light strongly inhibits hypocotyl (stem) elongation. This information has been used to screen mutant populations to identify individual plant lines that contain lesions in the light sensing apparatus. Growth of mutagenized seedlings under continuous blue light produced a series of plants with long hypocotyls (Koornneef et al., 1980). These were later shown to be defects in cryptochrome 1, a blue light sensor that directs stem growth inhibition (Ahmad and Cashmore, 1993). Recent advances in semiconductor technology have produced light-emitting diodes (LED's) that produce high fluence-rate light at specific wavelengths. These are optimal for use in studies of photomorphogenesis in plants because:
For these and other reasons LED technology is superior to colored filters used in conjunction with standard bulbs. We have used the following LED sources in photomorphogenic research and are ambitiously characterizing the ways in which such regimes can be used to support, or perhaps control, plant growth and development. The problem is, the commercially available stuff is just too expensive for the average consumer or well-financed laboratory! Below I present some of our most useful infrastructure and its capacity. In the near future I hope to provide plans on how to devise such resources for research, production, home and hobby use.
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This setup is four
individual chambers each supporting three 25 W channels in red, blue and
green. This particular arrangement allows us to illuminate four
cake-pan sized flats (30 x 30 cm) with over 120 µmol m-2 s-1
light. The fluence rate (intensity) of the red, green and blue LEDs
are all individually adjustable with a pulse wave modulator, and mirrored
sides and front ensure adequate light scattering, increase fluence rate and
eliminate the incidence of "hotspots".
This setup is controlled by the panel above. LEDs are attached to an aluminum plate attached to a large aluminum heat sink and fan. The experiment shows seedlings being subjected to the same red and blue treatment with increasing amounts of green. The far right chamber has strictly red blue, the first has a small amount of green and the third has the most green, appearing white to the eye. |
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This arrangement is one that is not likely too useful for most applications, but works great in a laboratory that studies the effect of light on early plant architecture. Each chamber runs 9 watts of LED, each color individually controllable with a pulse wave modulator. Seedlings are grown on a nutrient agar medium on vertical square Petri plates in each experimental condition. The laboratory has 12 individual chambers like this dedicated to seedling research. Each set of LEDs are attached to an aluminum plate with thermal epoxy- a heat sink and fan is located on the other side. The cost of one set of LEDs, the electronics, mirrors, heatsink, fan and box is about $50, and takes about a day to assemble. | |
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This system is very similar to that above, only it allows for seedlings to be grown under precise light quantities and qualities on horizontal plates. Such a system allows study of long-term effects on plant physiology and even studies of light-specific gene expression. | |
Individual light qualities can be individually adjusted to assess the effect of combinations of various wavebands in controlling physiological processes of interest. |
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We have also retrofit old refrigerators with an LED infrastructure, but as the size increases there are significant challenges in the management of hot spots. Still, these resources are adequate for pilot studies and for generating a lot of plant biomass in a short time. |
Some other resources:
American Bright LED -- A good one if you have no experience with electronics, as the 3W LED elements come attached to a small board with an appropriate current limiting resistor for use with 12V. Individual arrays cost about $7-$10 and are extremely bright. They can be driven with a computer power supply or comparable source, just make sure there is enough current rating to drive these high-current devices. Website: www.americanbrightled.com If you order form them, please tell them Kevin Folta sent you.
Lumileds -- a Phillips subsidiary, Lumileds makes a nice product that claims the most lumens per dollar. I still prefer the American Bright product because it is hard for me to acquire high wattage, low resistance resistors, so theirs represent a plug-n-play alternative to the lumiled product. Website: http://www.lumileds.com
Quantum Devices Q-Beam -- The old standby for photomorphogenesis research. Quantum Devices has supplied the phytochrome research with an outstanding tool: the red/far-red light source. The Q-Beam has output in both red and far-red that are both controllable in a very linear manner. A timer controls light pulses to 0.1 s. Red to far-red ratios can be established. These are also available in blue. Advantages: Precise fluence-rate control, internally cooled, historical precedent. Disadvantages: Bulky source and separate controller/power supply. Price: $3300 (you pay for precision). Website: www.quantumdev.com
Norlux Hex Arrays -- Norlux produces a single chip-based array that contains red, blue and green LED's. They are sold as "demo" units with an RGB hex chip and an R hex-chip, or as single hex-chips. Advantages: Precise control of RGB. Quite linear control and excellent fluence rate. Small profile and excellent light propagation free of "hotspots". Disadvantages: Red LED's emit at 630 nm. Far-red, UV etc may be available on request for an extra charge. Excellent product support and rapid shipping. Price: "demo" units are around $250, single RGB chips are around $100. Website:Their website is www.norluxcorp.com. We used almost exclusively Norlux hex chips for a long time, but they were very reluctant to work with us on price. We were hoping to exclusively develop a relationship with them to generate new fixtures and tools for plant biology. No interest on their end.
LEDtronics Floodlamps -- LEDtronics makes a variety of LED lamps for residential and commercial use. Typical applications include traffic lights, spot lights and automobile lamps. We have successfully used the blue and green 130-LED array. Advantages: Plugs into standard Edison base, high fluence rate output, 100,000 h lifespan, durable design. Disadvantages: Light-scattering plastic should be used to minimize "hotspots" LED's emit at 630 nm, no 730 nm available. Customer service seemed bothered by my inquiries. Price: $200-400 depending on wavelength. Website: www.ledtronics.com
"One of the major problems with which both teachers and researchers is
confronted is that of gadgetry."
R.M. Klein (1963) American Biology Teacher 25:
96-100.