Photosynthetic processes in two algal species from Antarcticlakes in response to stress factors
2013
Klebsormidium sp. and Zygnema sp. are typical algal species
forming microbiological mats in Antarctic lakes, streams and
seepages of the James Ross Island (Antarctica). For
physiological study focused on their photosynthesis, two
strains collected at the island (Klebsormidium sp. SNOKHOUSOVA
et ELSTER 2008/8, and Zygnema sp. SNOKHOUSOVA et ELSTER 2009/8)
were obtained from Culture Collection of Autotrophic Organisms,
Institute of Botany, Třeboň. Cultivation was carried out in
liquid 3N BBM solution under constant temperature and a 12/12 h
light/dark period in a FS130 phytoscope (PSI). In this study,
we present the results of experiments focused on interspecific
differences in photosynthesis as dependent on light,
temperature, repetitive photoinhibition and osmotic stress.
Light-response curves of photosynthesis: Simultaneous
measurements of oxygen evolution rate (OER) and effective
quantum yield of PSII (PSII yield) by an inbuilt Theta 90 (ldv)
oxygen electrode and a FL-400 (PSI), fluorometer, respectively,
were done at fixed above-zero temperatures. In both species,
OER and yield PSII were well related throughout a range of
light (0-500 micromols m-2 s-1 of photosynthetically active
radiation (PAR). Photoinhibitory treatment: Using a FMT 400
photobioreactor (PSI), repetitive photoinhibition and dark
recovery was studies in Klebsormidium sp. by simultaneous
measurements of OER and PSII yield. The data revealed large
resistance of the two species against photoinhibition, however,
the courses of respiratory OER and potential PSII yield
measured at dark changed with increasing number of
photoinhibitory treatment. Osmotic stress: The effects of salt
(NaCl) treatment on excitation energy transfer from light
harvesting complexes to photosystem II (PSII) in two Antarctic
algae: Klebsormidium sp. and Zygnema sp. were investigated
using chlorophyll fluorescence transients (OJIPs). Short-term
salt stress led to significant changes in the shape of OJIPs
indicating altered functioning of PSII. With time of exposition
to NaCl treatment, the fluorescence yield at the phases J, I
and P declined considerably in both species.
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