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Photosynthesis under artificial light: the shift in primary and secondary metabolism
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Graphic Essays. Persian Gulf Essays. Statue of Liberty Essays. Haven't found the right essay? Get an expert to write your essay! Get your paper now. Professional writers and researchers. Sources and citation are provided. At very high light intensities, photosynthesis is slowed and then inhibited, but these light intensities do not occur in nature. Carbon dioxide — with water — is one of the reactants in photosynthesis. If the concentration of carbon dioxide is increased, the rate of photosynthesis will therefore increase.
Again, at some point, a different factor may become limiting.
Beyond this concentration, further increases in the concentration of carbon dioxide will not result in a faster rate of photosynthesis, and would appear on a graph as a horizontal line. The chemical reactions that combine carbon dioxide and water to produce glucose are controlled by enzymes. As with any other enzyme-controlled reaction, the rate of photosynthesis is affected by temperature. At low temperatures, the rate of photosynthesis is limited by the number of molecular collisions between enzymes and substrates.
At high temperatures, enzymes are denatured. If the address matches an existing account you will receive an email with instructions to retrieve your username. Google Scholar. Find this author on PubMed. Search for more papers by this author. Providing an adequate quantity and quality of food for the escalating human population under changing climatic conditions is currently a great challenge.
In outdoor cultures, sunlight provides energy through photosynthesis for photosynthetic organisms. They also use light quality to sense and respond to their environment. To increase the production capacity, controlled growing systems using artificial lighting have been taken into consideration. Recent development of light-emitting diode LED technologies presents an enormous potential for improving plant growth and making systems more sustainable. This review uses selected examples to show how LED can mimic natural light to ensure the growth and development of photosynthetic organisms, and how changes in intensity and wavelength can manipulate the plant metabolism with the aim to produce functionalized foods.
The rising population, climate changes, land use competition for food, feed, fuel and fibre production as well as the increasing demand for valuable natural compounds all reinforce the need for artificial growing systems such as greenhouses, soilless systems and vertical gardening, even in spacecrafts and space stations. Most of these growing systems require the application of additional, at least supplementary, light sources to ensure plant growth.
Because these sources are heat dissipaters requiring cooling, artificial systems are frequently at odds with the demand for sustainability in industrial processes. In terms of both economics and sustainability, new lighting technologies such as light-emitting diodes LEDs thus were necessary to be developed [ 1 , 2 ]. Above all technological properties, LEDs should be compatible with the photosynthesis and light-signalling requirements of plants, which are tightly linked with the two main characteristics of light: wavelength and fluence.
Being mostly immobile, photosynthetic organisms must adapt to their biotic and abiotic environments that they sense through different types of receptors, including photoreceptors [ 3 ].
The pigment moiety of photoreceptors allows the receptor to extract from the incoming natural white light the specific information related to the intensity of the environmental light constraints. This information is used to develop the adequate response [ 3 ]. Photosynthesis is a photobiochemical process using light energy to produce ATP and NADPH, ultimately consumed in the assembly of carbon atoms in organic molecules.
Functionally, photons are harvested by protein—chlorophyll Chl —carotenoid complexes that form the light harvesting antenna of photosystems and then transferred to the photosystem reaction centre, where electrons are generated; these processes take place in the chloroplast [ 4 ].
If lighting is too weak, photosynthesis cannot work efficiently and etiolation symptoms appear [ 5 ]. However, excessive light generates oxygen radicals and causes photoinhibition. Both phenomena strongly limit primary productivity [ 6 ]. Photosynthetic processes are often modified in plants grown under artificial lighting, because lamps do not usually mimic the spectrum and energy of sunlight.
Agronomically, new lighting technologies such as LEDs have the potential to cover fluence and wavelength requirements of plants, while allowing specific wavelengths to be enriched, thus supplying the light quantity and quality essential for different phases of growth. The biomass and metabolic products of cultivated plants can therefore be modified. This review gives a brief summary of the types of artificial lighting available for growing photosynthetic organisms.
The capacity of LEDs to mimic the effects of natural light in terms of energy and information, thus ensuring the growth and development of photosynthetic organisms, and the potential for manipulating the plant metabolism to produce functionalized foods through changes in the intensity and wavelength are also reviewed here using selected examples. Artificial lighting should provide plants with energy and information required for development.
For this purpose, fluorescent lamps, particularly those having enhanced blue and red spectra i. However, the spectrum and intensity of fluorescent lights are not stable over a long time see the comparative information in the electronic supplementary material, table S1. High intensity discharge HID lamps, such as metal halide and high-pressure sodium lamps, have relatively high fluence max.
The drawbacks including elevated arc to fire energy requirement, the high operational temperature preventing placement close to the canopy and the spectral distribution high proportion of green—yellow region, significant ultraviolet radiation and altered red : far red ratio , which may shift according to the input power, strongly limit their use and innovation [ 8 ]. LEDs emitting blue, green, yellow, orange, red and far red are available and can be combined to provide either high fluence over full sunlight, if desired , or special light wavelength characteristics, thanks to their narrow-bandwidth light spectrum [ 9 ].
The high efficiency, low operating temperature and small size enable LEDs to be used in pulsed lighting and be placed close to the leaves in interlighting and intracanopy irradiation [ 7 ]. Their long life expectancy and ease of control make them ideal for greenhouses in use all year round [ 7 ]. The LED technology is predicted to replace fluorescent and HID lamps in horticultural systems and to revolutionize controlled growth environments.
From the biological point of view, the main questions about LEDs are related to their ability to mimic and enhance the beneficial effects of natural light while avoiding the adverse influence. Below, selected examples are used to provide a short review on useful properties of LED lights in these aspects. Pioneer experiments on plant growth under red LEDs on lettuce were reported by Bula et al. Martineau et al.
Lettuce grown under red LEDs presented hypocotyls and cotyledons that were elongated, a phenomenon known to be phytochrome-dependent. Under red LEDs illumination, phytochrome stimulation is especially high as far red light is not provided. Although a complete demonstration was not provided, one can hypothesize that the supplemented blue light activated cryptochrome, a blue-light photoreceptor that mediates reduction of hypocotyl length [ 12 ].source site
Influence of Light on Crop Growth | PRO-MIX Greenhouse Growing
The efficiency of red — nm LEDs on plant growth is easy to understand because these wavelengths perfectly fit with the absorption peak of chlorophylls [ 13 ] and phytochrome, while the supplemented blue light introduced the idea that growth under natural light could be mimicked using blue and red LEDs. Some authors attributed this effect to a higher nitrogen content of the blue-light-supplemented plants, whereas others suggested a better stomatal opening, thus providing more CO 2 for photosynthesis.
It is well established that stomata opening is controlled by blue-light photoreceptors [ 15 ]. This is possibly reflected in the increase of shoot dry matter with increasing levels of blue light [ 16 ]. Recently, LEDs have been successfully tested for their ability to allow the growth of agronomically important crops, fruit and flower plants, and even trees [ 14 , 18 ]. The effects of LEDs on plants' growth parameters and metabolism compared with conventional lights: selected examples.
In the absence of light or under deep shade conditions, plants develop etiolation symptoms, such as the absence of Chl, reduced leaf size and hypocotyl elongation [ 5 ]. When the plants are exposed to light, chloroplast differentiation involves the accumulation of proteins, lipids and photosynthetic pigments [ 26 ].
The kinetics of Chl accumulation present a lag phase under white LED light, which is eliminated when plants are grown under blue LED — nm but not in red LED light — nm [ 27 ]. Interestingly, similar Chl amounts were reached, regardless of the LED colour.
Related effect light intensity on photsynthesis
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