Effects of UV-B on motility and photoorientation in the cyanobacterium,Phormidium uncinatum

✍ Scribed by Donat-P. Häder

• Publisher: Springer
• Year: 1984
• Tongue: English
• Weight: 618 KB
• Volume: 140
• Category: Article
• ISSN: 0302-8933
• DOI: 10.1007/bf00409768

✦ Synopsis

UV-B irradiation has a detrimental effect on the survival of populations of the filamentous cyanobacterium, Phormidium uncinatum, at levels slightly higher than those currently measured at the surface of the earth. The organisms are not damaged or killed by UV-B radiation at <300 nm of 200 gWm -2 for up to 20 h; but slightly increased levels of UV-B irradiation (2 h of 200 ~tWm 2 at < 300 nm) drastically impair motility, phototactic orientation and photophobic responses. These photosynthetic organisms require a narrow light intensity range for growth so that any decrease in their ability to actively search for and move into areas of favorable light conditions is bound to affect the survival of a population. The fluorescence yield of both phycobilins and chlorophyll is not altered even after 20 h of UV-B irradiation (200 gWm-2 at 270 nm) indicating that UV-B at that dose does not affect the photosynthetic apparatus. The organisms are killed either by too bright intensities which bleach the photosynthetic pigments or by the lack of energy when they are unable to avoid moving into dark areas.