What is UV light?
Ultraviolet (UV) light is an electromagnetic radiation with a wavelength from 10 nm to 400 nm;
shorter wavelength than that of visible light but longer than X-rays. Ultraviolet radiation can
be broken down into three bands: UV-A (400-320nm), UV-B (320-290nm), and UV-C. Luckily the
ozone layer stops the UV-C rays from reaching earth’s surface, which would have catastrophic
effects.
The potential impacts of an increase in solar UV-B and UV-C radiation reaching the Earth’s surface
due to stratospheric ozone depletion have been investigated by several research groups during
the last 15 years. This has provided for several research papers around UV influence on flora.
What do we need to know for plant growth?
As the sunlight shines down upon a crop, the plants expose their leaf surface and capture solar
rays for conversion to chemical energy via photosynthesis. They’re also using this light energy
for a wide range of developmental signals to optimise the photosynthetic processes and detect
seasonal changes.
These photoresponses include reacting to UV radiation. This involves receptors that detect
specific wavelengths of light which induces developmental or physiological changes. For
scientists to measure the influences of varying light wavelength radiation in plants, they utilise
what is known as an ‘Action Spectrum’.
Action spectra can describe the wavelength specificity of a biological response to sunlight
and uses a graph that plots the magnitude of a light response (photosynthesis) as a function
of wavelength. See graph right However it is extremely difficult for scientists to functionally
distinguish intrinsic responses to individual photoreceptors.
While phytochromes are responsible for absorbing
red and far-red light, they also absorb some blue
light (300-500nm) and UV A (320-400nm) radiation.
These phytochromes mediate many aspects of
vegetative and reproductive development.
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.
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