EFFECTS OF SOLAR-RADIATION AND SOLAR-RADIATION DEPRIVED OF UV-B AND TOTAL UV ON PHOTOSYNTHETIC OXYGEN PRODUCTION AND PULSE AMPLITUDE-MODULATED FLUORESCENCE IN THE BROWN ALGA PADINA-PAVONIA
Dp. Hader et al., EFFECTS OF SOLAR-RADIATION AND SOLAR-RADIATION DEPRIVED OF UV-B AND TOTAL UV ON PHOTOSYNTHETIC OXYGEN PRODUCTION AND PULSE AMPLITUDE-MODULATED FLUORESCENCE IN THE BROWN ALGA PADINA-PAVONIA, FEMS microbiology, ecology, 19(1), 1996, pp. 53-61
The effects of solar radiation on photosynthetic oxygen production and
pulse amplitude modulated (PAM) fluorescence were measured in the mar
ine brown macroalga Padina paronia harvested from different depths fro
m the Greek coast near Korinth. In fluence rate-response curves the li
ght compensation point for photosynthetic oxygen production increased
and the saturation level decreased with increasing exposure rime to so
lar radiation. Cutting off the UV-B wavelength range (280-315 nm) from
solar radiation reduced the inhibition of photosynthesis, and the org
anisms were less affected when all of the UV radiation was filtered ou
t, Algae collected from 7 m depth were much more prone to photoinhibit
ion than those harvested from rock pools exposed to unfiltered solar r
adiation. During continuous exposure to solar radiation, rock pool alg
ae showed photoinhibition after longer periods of time than specimens
from 7 m or from dark adapted habitats. When subjected to unfiltered s
olar radiation the ratio of the variable fluorescence to the maximal f
luorescence F-v/F-m (F-v = F-m - F-o) rapidly declined with increasing
exposure time. However, again algae from 7 m depth were more pr one t
o photoinhibition than rock pool algae. The differences between the tw
o ecological strains were less obvious when UV-B or total UV was remov
ed from solar radiation. Only in the latter case a complete recovery w
as observed after 2 h while, when exposed to unfiltered sunlight, only
the rock pool algae recovered completely within that time.