Even seaweeds are not protected from sunburn

August 23rd, 2008 - 12:27 pm ICT by IANS  

London, Aug 23 (IANS) Like most humans, many plants also react sensitively to an increased dose of ultraviolet radiation, even though they are dependent on sunlight. With the help of pigments absorbing solar energy and light, plants produce their vitally important building blocks by means of photosynthesis.

However, this has its limits: too much sun means an over-abundance of energy and thus the destruction of the sensitive pigments. The result are black spots, pale leaves and rotten parts.

Since algae cannot apply sun lotion like we do, they develop their own strategies to protect from the sun: “A species of red algae, for instance, produces under increased ultraviolet radiation less red light-harvesting proteins, thus decreasing the absorption of radiation.The typical red of the alga fades and the plant gets white tips,” explained Christian Wiencke, marine biologist at the Alfred Wegener Institute for Polar and Marine Research in the Helmholtz Association.

“The algae additionally produce substances which react similar to melanin in human skins: mycosporin amino acids (MAA).” Melanin absorbs ultraviolet radiation and thus protects the human skin - at the same time, it gives a natural suntan.

The ozone layer usually absorbs the major part of the hard and harmful solar ultraviolet radiation of short wavelength. However, because of stratospheric ozone depletion, these dangerous rays increasingly penetrate to the earth’s surface and, therefore, also into the sea.

Extensive biological experiments are presently being conducted on this complex of problems at the German-French Research Base AWIPEV at Spitsbergen.

“We examine the harmful effects of ultraviolet radiation on algae and their protective mechanisms,” said Wiencke. The ultraviolet radiation particularly harms the algae’s photosynthesis and their hereditary material. These organisms usually react with a decreased rate of growth or a reduction of reproductive success.

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