It is exspected that enhanced solar UV-B radiation on earth will remain however for at least another 50 years. Since increasing short-wavelength solar ultraviolet-B radiation (280-320 nm) is potentially damaging to all living organism UV- B research has focused on human health and on UV-B damage in plant and animals. UV-B radiation may damage DNA and one of the major lesions are thymine dimers, which inactivate DNA, if not repaired. At a sufficiently high PAR-UV-A/UV-B ratio an enzyme, DNA photolyase cleaves the thymine dimers and restores the original DNA strand. In plants, exposed to (enhanced) solar UV-B radiation UV-B absorbing compounds are induced. These UV-B absorbing compounds act as UV-B screens and recuce levels of UV-B in plant tissue and cells, and may thus prevent dimer formation.
There is evidence that in previous times UV-B on earth has been much higher than at present. Along with changes in the composition of the atmosphere and stratosphere, evolution of plant and animal life took place. In the early, primaeval atmosphere, lacking stratospheric ozone and high fluxes of UV- radiation on the earth surface, life was restricted to aquatic ecosystems, where the filtering of UV-B by the water column prevented UV-damage to living organisms.
In the evolution of terrestrial plant life from marine and fresh water plant life, evolution of UV-B absorbing ((poly)phenolic) compounds is assumed, acting among other functions as UV screens. From lower to higher plants there seems to be an increasing degree of complexity of UV-B absorbing (phenolic) compounds. It remains uncertain whether an early, developing stratospheric ozone shield allowed aquatic plants to emerge and evolve to terrestrial habitats, or that the evolution of UV-screens (consisting of UV-B absorbing (phenolic) compounds) in aquatic and land plants made evolution of plant life on earth further possible.
The General objective of UVAQTER is:
To analyse, characterize and compare the functioning of UV-B screens in plants from marine, fresh water and terrestrial ecosystems, following the evolutionary line of algae, charophycean algae, lichens, mosses and higher plants, including amphibious macrophytes.
1. To compare the growth and physiological responses to reduced and enhanced levels (compared to ambient solar UV-B levels). Enhanced levels of solar UV-B include at least levels which simulate a 15% stratospheric ozone depletion secenario.
Do the water and land form of amphibious plant species differ in their adaptation to enhanced UV-B in other words how wide can the range be in adaptation to UV-B within species?
2. To compare the induction of UV-B absorbing compounds in all plants group.
3. To chemically characterize and localize the UV-B absorbing compounds in plant groups from marine, fresh water and terrestrial ecosystems.
4. To determine action spectra for induction of UV-B absorbing compounds and adaptations to UV-B of all plant groups. Action spectra will be constructed not only based on monochromatic radiation, but also on polychromatic radiation.
5. To asses, in a comparative, physiological way the functioning of UV-B absorbing compounds as protective UV-B screens for plants.
6. To asses the physiological and ecological effectiveness/significance of UV-B screens in all plant groups. How do UV-B absorbing compounds alter the distribution of PAR and UV-B radiation within plant tissue (to be measured with fibre optics).
I.e. what part play the UV-B screens in protecting the various plant groups from UV-B damage, such as the formation of thymine dimers. This implies a comparison of the physiological and ecological importance of UV-B screens relative to other UV-B protection mechanism(s) and to repair mechanism(s) of UV-B damage.
7. To integrate and evaluate the physiological and ecological responses of the various plant groups to reduced and enhanced UV-B with particular reference to an evolutionary development of UV-B screens as UV-B adative and protective screens in all plant groups.
Funding SchemeCSC - Cost-sharing contracts