Acclimation to UV irradiance in Gracilaria chilensis Bird, McLachlan & Oliveira (Gigartinales, Rhodophyta)

Methanol extracts of tips, cystocarps and thalli segments of Gracilaria chilensis were scanned between 300-700 nm after the samples had been exposed to high and low PAR (80 and 40 umol quanta per m2.second) with and without UV-B light. Whole algae incubated for 3 d at high and low PAR, supplying 4.6 uW UV-B per cm2 during 2 h showed an increase in absorption at 320 nm after the first day of exposure to UV-B light. Tips showed the highest increase in absorption at 320 nm relative to cystocarps and thalli, the mean percentage increase being 38 and 29 per cent at low and high PAR, respectively. The lowest sensitivity was found in thalli and the highest in the tips. There are 32 references.