Artificial Lighting In Agriculture
It has been known for a long time that plants cannot grow without light; nevertheless, it has only been in the last one hundred years, thanks to advancements in science and technology, that the precise effect that light has on plants has been fully discovered.
The use of artificial lighting in agriculture is aimed at providing a source of light that is analogous to the light that is provided by the sun. Because of advancements in technology, LED lights have emerged as the best option for horticulture lighting, particularly those that can have their spectra specifically tailored to the needs of the plant. In compared to more conventional lighting options, such as high-pressure sodium (HPS) and fluorescents, lights that employ LEDs provide significant benefits in terms of their impact on the environment and their production efficiency.
A report on the use of artificial lighting in agriculture was authored by Valoya and co-authored by researchers from the University of Almeria and Buresinnova. The report was published in January 2018. The research presents tests that make use of various spectra and kinds of light in order to determine the impact that each form of light can have on plants depending on the circumstances under which they are grown. The following is a snippet from the study that you can read.
1. Light and the communication between plants
Electromagnetic waves are responsible for the transmission of energy through the atmosphere. Examples of electromagnetic waves include microwaves, radio or television waves, X-rays, ultraviolet rays, or visible light. Electromagnetic waves can be distinguished from one another by their varying frequencies and wavelengths. The electromagnetic spectrum is comprised of a wide range of frequencies and wavelengths, some of which are better recognised than others (for example, microwaves, radio waves, visible light, and so on).
Electromagnetic radiation possesses a dual nature; while it moves through space as waves, it also exchanges energy in the form of particles (photons). In 1905, Albert Einstein was the first person to argue that light possesses characteristics of both particles and waves simultaneously. Photons are the names of the particles that are contained within a beam of light. Photons whose wavelengths correspond to longer distances (lower frequencies) carry less energy than photons whose wavelengths correspond to shorter distances.
The human eye is able to detect light with wavelengths between 400 and 700 nanometers (nm), which roughly corresponds to the portion of the electromagnetic spectrum that is utilised by plants during the process of photosynthesis. Therefore, light with a wavelength between 400 and 700 nm is referred to as photosynthetically active radiation (or simply PAR). The spectrum of wavelengths that can be seen in sunlight is continuous, extending well beyond the visual range. The human eye is responsible for converting various wavelengths into colours, which are then processed in the human brain. The colour blue is produced by light with a wavelength that is closer to 400 nm, whereas the colour red is produced by light with a wavelength that is closer to 600 nm. The yellow-green wavelength range is the one that the human eye responds to most sensitively.
2. Pigments, photoreceptors, and the chemical process of photosynthesis in plants
In almost the same range as the human eye, the light spectrum is absorbed by plants; however, in contrast to people, plants are better able to take in red and blue light.
Chlorophyll is one of the primary chemicals that enables plants to absorb light and use the energy it provides to turn water and carbon dioxide into oxygen and other complex organic molecules. This process is known as photosynthesis. Chlorophyll is a plant pigment that can be found in intracellular chloroplasts. Chlorophyll molecules are green in colour, and they are in fact the cause of the green coloration found in stems and leaves. There are two primary forms of chlorophyll that may be found in higher plants. These are chlorophyll a and chlorophyll b, and their light absorption curves differ from one another in a very tiny way. Due to this relatively minor distinction, they are able to capture different wavelengths, thereby capturing a greater portion of the sunlight spectrum. As a result of chlorophylls' ability to absorb primarily red and blue light while reflecting green wavelengths, plants seem green to our eyes.
However, chlorophyll is not the only pigment found in plants; so-called accessory pigments (such as carotenoids and xanthophylls, among others) and phenolic substances (such as flavonoids, anthocyanins, flavones and flavonoids) absorb wavelengths other than just red and blue. Yellow, red, and violet are the colours that make up the accessory pigments. In addition to luring birds and insects, the use of these hues helps protect tissues from the damaging effects of external stressors such intense light irradiation.
Photoreceptors are another type of particle that is capable of absorbing light. The three primary classes of photoreceptors are referred to as phytochromes, phototropins, and cryptochromes. In addition, the UVR8 photoreceptor is a specialised photoreceptor that only responds to ultraviolet light. Each type of photoreceptor is sensitive to a specific wavelength range of light and is in charge of a particular physiological reaction in plants. These responses are as follows:
Phototropins have an effect on both the physical position of the chloroplasts and the opening of the stomata. They are able to soak up blue light.
The internal clock of plants is controlled by cryptochromes, which monitor their environment for signals related to light. In addition to this, they are associated with morphological responses, such as the suppression of stem elongation, the enlargement of cotyledons, the development of anthocyanins, and photoperiodic blooming. The wavelengths of UVA (ultraviolet), blue, and green light are taken in by cryptochromes.
Flowering is triggered by phytochromes, which are also responsible for the formation of seeds. Stem elongation, leaf expansion, and the "shade avoidance syndrome" are all controlled by phytochromes in plants. The ratio of red and far-red light that is present in the environment has an effect on the photostationary state of the phytochrome molecule, which in turn mediates the reactions that are regulated by phytochromes.
Flowering, the development of seeds, and other functions such as germination, timing of flowering, and plant shape are all activities that are light dependent. Photosynthesis, the process that supplies the energy for the formation of biomass, is just one of these processes. These behaviours are intricately connected to the quality of the light that the plant receives from its surroundings, which is how the plant interprets signals from its surroundings. These responses are mediated by wavelengths that are both inside and outside of the PAR region, including UV and far-red irradiation.
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