Dp. Hader et al., Photoinhibition by visible and ultraviolet radiation in the red macroalga Porphyra umbilicalis grown in the laboratory, PLANT ECOL, 145(2), 1999, pp. 351-358
Photosynthetic oxygen production and PAM fluorescence measurements were use
d to follow photoinhibition in the red macroalga Porphyra umbilicalis. Expo
sure to simulated solar radiation caused inhibition of the effective photos
ynthetic quantum yield from which the thalli partially recovered in the sha
de in subsequent hours. There were no significant differences between sampl
es exposed to unfiltered radiation and those exposed to radiation from whic
h increasing portions of UV radiation had been removed indicating that the
thalli are well adapted to current levels of solar PAR and UV radiation. Th
is notion was supported by the finding of high concentrations of UV screeni
ng pigments which were even enhanced by exposure to increased UV radiation.
However, when exposed to (only) UV radiation about 50% higher than that en
countered by the organisms in their natural habitat, the photosynthetic yie
ld decreased slowly and did not show any recovery even when the degree of i
nhibition did not exceed 10%.