Ultraviolet radiation has no effect on respiratory oxygen consumption or enhanced post-illumination respiration in three species of microalgae.
A 30-min exposure to UV-B radiation (1.1 Wm(-2), unweighted) from a xenon arc lamp caused pronounced inhibition (33-78%) of net photosynthetic oxygen production in three species of microalgae, Phaeodactylum tricornutum Bohlin, Dunaliella tertiolecta Butcher and Wolozynskia sp., however, no statistical differences (t-test, alpha=0.05) in dark-respiration rates were found between the control group and the UV-treated group, for any of the species tested. These results indicate: (i) that the respiratory processes responsible for oxygen consumption do not sustain any appreciable impairment registered in the first half-hour after ultraviolet radiation (UVR) exposure; and (ii) any change in respiration that may occur in response to increased repair demands is not detected in this period. Dark-respiration rates were observed to be significantly higher in all species tested (17-29%; t-test, alpha=0.05) following illumination with photosynthetically active radiation, compared to dark-respiration before illumination. This increase, interpreted as enhanced post-illumination respiration (EPIR), was observed in all three species. The magnitude of this increase was not affected by prior exposure to UVR.
Heraud
Philip
P
School of Biological Sciences, Monash University, Wellington Road, Clayton, Melbourne 3800, Australia. phil.heraud@sci.monash.edu.au
Beardall
John
J
D000460:Chlorophyta / Q000378:metabolism* / Q000528:radiation effects*; D003624:Darkness; D010101:Oxygen Consumption / Q000528:radiation effects*; D013045:Species Specificity; D013056:Spectrophotometry, Ultraviolet; D014466:Ultraviolet Rays