Light emitting diode (LED) : A Revolutionary development in Plant Tissue Culture and Greenhouse Industry
Rajesh Pati, PhD e-mail:
[email protected]
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 lamps are commonly using in tissue culture growth rooms as artificial light sources.
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Fluorescent lamps are most commonly using in tissue culture growth rooms for micropropagation of various crops.
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These lights have a wide range of wavelengths (350-750 nm) and appears to be unnecessary and are of low quality for promoting plant growth.
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This type of light sources requires high electricity consumption with low output efficiency. Which is ultimately increase the per plant production cost.
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Thus, there is a urgent need of an efficient light source, which is not only improve the quality of in vitro plants but also minimize per plant production costs.
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LED (Light emitting diode) has been proposed as potential alternative light 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 energy and 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, lab and green house, the physical structure shades the plant and induces a light 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, within the chloroplasts.
photochemical reaction
• Light quality (spectral distribution): Red, blue, green, orange red affects 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 may provide a more optimal production, influencing plant morphology and metabolism (Kim et al. 2004). Blue, red, far-red, green and yellow •
Stomata opening, photosynthetic rate, leaf area, increasing number and size of leaf, Stem, inter-node length & diameter, fresh weight, dry weight, in vitro flowering, Callus induction, proliferation, development and conversion 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 free amino 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.
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Two elements of processed material, p-type semiconductors and n-type semiconductors, are placed in direct contact and form the LED chip which comprises the p–n junction .
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A current flows only from the Anode post to the Cathode post. Electrons and holes flow into the junction from electrodes with different voltages. When an electron meets a hole, it falls into a lower energy level and releases energy in the form of a photon. The light produced by a solidstate process is called electroluminescence.
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The energy gap of the semiconductor determines the color (wavelength) of the light and the materials used for an LED have energies corresponding to near-ultraviolet, visible, or near-infrared light.
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Commercially available LEDs seniconductor material used
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colors
Wavelength range (nm)
Colour
