Photosynthesis in a sub‐Antarctic shore‐zone lichen

Abstract

Summary• Photosynthetic responses to moisture, light, temperature, salinity and inorganic nitrogen fertilization are reported for a shore-zone lichen Turgidiusculum complicatulum (formerly Mastodia tesselata ), a possible recent introduction to subAntarctic Marion Island.• Optimum moisture contents for net photosynthesis were 225 -346% (ash free, dry mass). Net CO 2 exchange was dominated by a strong temperature dependence of respiration rate. Net photosynthetic rate responded sharply to increasing PPFD and saturated below 300 µ mol m -2 s -1 , but electron transport rate (ETR) increased up to approx. 900 µ mol m -2 s -1 PPFD suggesting that gross photosynthesis responded to light to this level. Nonphotochemical fluorescence quenching increased rapidly with PPFD up to approx. 400 µ mol m -2 s -1 and thereafter more slowly. Even at high PPFD (1050 µ mol m -2 s -1 ) most PSII centres were open.• Salinity did not significantly influence CO 2 assimilation rate; however, NH 4 NO 3 significantly depressed net photosynthesis rate at all salinities except 100% seawater. ETR and dark respiration rate were increased by NH 4 NO 3 .• The response of T. complicatulum to light and temperature enables high rates of CO 2 assimilation under the island's microclimatic regime; if sufficiently hydrated, the lichen would exhibit near maximal photosynthesis rates for approx. 75% of the photoperiod over the year.

Estimation of the annual primary production of the lichen Cetrariella delisei in a glacier foreland in the High Arctic, Ny-�lesund, Svalbard

“…The maximum Pn was maintained at a water content of about 300 % (Fig. 3), which is similar to the optimum water content of other lichens from cold regions (MacFarlane & Kershaw 1980;Smith & Gremmen 2001). On the other hand, R increased gradually with increasing thallus water content.…”

“…It has been predicted that global warming would cause increased rainfall in the Norwegian Arctic (Førland & Hanssen-Bauer 2000). Precipitation timing, duration and intensity would also impact lichen production (Lange 1980;Smith & Gremmen 2001), so future precipitation changes are also important to consider when predicting lichen production. Table 2.…”

Symbiotic lifestyle and phylogenetic relationships of the bionts ofMastodia tessellata(Ascomycota,incertae sedis)

“…Mastodia tessellata and its photobiont have been the focus of several studies in the past few years, with special emphasis placed on the biology of the symbiosis (Kováčik and Pereira, 2001; Lud et al, 2001), the physiology of the alga alone (e.g., Jacob et al, 1991, 1992; Post and Larkum, 1993), and comparison of the responses of Mastodia and Prasiola to several ecophysiological variables (e.g., Huiskes et al, 2001; Smith and Gremmen, 2001a, b; Harańczyk et al, 2003). To shed light on the remaining uncertainties surrounding this leafy green alga–fungus association, the aims of the current study were to (1) infer the phylogenetic position of Mastodiaceae in the fungal tree of life using nuclear ribosomal markers; (2) explore the phylogenetic affinities of P. crispa subsp.…”

Salinity responses of halophytic and non-halophytic bryophytes determined by chlorophyll fluorometry

“…Interestingly, earlier experiments comparing salinity responses of seashore and 'inland' bryophytes (Bates & Brown, 1974, 1975Bates, 1976) were all conducted in the light and it is likely that the membrane permeability increases observed were secondary effects of salt-induced photo-oxidative injury. Smith & Gremmen (2001) found little effect of 19 days' incubation in seawater dilutions on CO 2 assimilation or RETR in a lichen (Turgidiusculum complicatulum) from the shore zone of sub-Antarctic Marion Island. However, they appear not to have carried out the incubations at realistic light levels where reactive oxygen species, ROS might have been generated.…”