The light responses in plants can also be distinguished by the amount of light required to
induce them. However this can also be difficult to measure as the plant canopy itself can have a
dramatic effect on both the quantity and quality of incidental light reaching individual plants.
Plants growing beneath the canopy use phytochromes to sense the light ratio and regulate such
processes as shade-avoidance, competitive interactions and seed germination.
Cryptochromes, phototropins and Zeitlupe ZTL are the 3 primary photoreceptors that mediate
the effects of UV-A and blue light energy. As in the case of plant hormone signalling, light
signalling typically involves interactions between multiple photoreceptors and their signalling
intermediates. Photoreceptors are also sensitive to light quantity, quality and duration.
UV-B light is primarily mediated by the UV-R8 Monomer, a 7-bladed
B-Propeller protein (see image right). In addition to its cytotoxic
(toxic to cells) effects, UV-B radiation can also elicit a wide range of
photomorphogenic responses. Our current challenge is to clarify
how UV-B exposed plants can balance the damage and adaptation
responses in a photobiologically dynamic environment.
It has been proven that UV light influences many
photomorphogenic responses including gene regulation, flavonoid
biosynthesis, leaf & epidermal cell expansion, stomatal density and
increased photosynthetic efficiency.
We understand that UV radiation can damage membranes, DNA and proteins. However many
plants can sense the presence of the radiation and protect themselves. Numerous agricultural
crops can synthesize simple phenolic compounds and flavonoids that act as ‘sunscreens’ and
remove damaging oxidants and free radicals that are induced by the high-energy UV photons.
In certain crop species, these phenolic compounds can be extremely desirable and it can be
beneficial to the farmer to ‘enhance’ this aspect of production.
So how do we utilise this UV energy without causing damage to our crops?
Modern lamp manufacturers (such as HI-PAR Horticultural Lighting, Hortivision and DLI) are
specialising in horticultural lighting technology that includes precisely calculated amounts of
UV-A and UV-B output (Check out our range of premium lamps!). Advances in CMH (Ceramic
Metal Halide) and MH (Metal Halide) bulbs have allowed for optimised amounts of UV light to
encourage essential oil production.
These bulbs are currently used by essential oil and herb farmers who are seeking to increase the
flavours and resin production from their crop. Although this is a very recent field of botanical
science there are reports of dramatic increases in essential oils from including higher UV bulbs in
flowering crops.
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