Abstract
The terrestrial flora of Antarctica’s frozen continent is restricted to sparse ice-free areas and dominated by lichens and bryophytes. These plants frequently battle sub-zero temperatures, extreme winds and reduced water availability; all influencing their ability to survive and grow. Antarctic mosses, however, can have canopy temperatures well above air temperature. At midday, canopy temperatures can exceed 15°C, depending on moss turf water content. In this study, the optimum temperature of photosynthesis was determined for six Antarctic moss species: Bryum pseudotriquetrum, Ceratodon purpureus, Chorisodontium aciphyllum, Polytrichastrum alpinum, Sanionia uncinata, and Schistidium antarctici collected from King George Island (maritime Antarctica) and/or the Windmill Islands, East Antarctica. Both chlorophyll fluorescence and gas exchange showed maximum values of electron transport rate occurred at canopy temperatures higher than 20°C. The optimum temperature for both net assimilation of CO2 and photoprotective heat dissipation of three East Antarctic species was 20–30°C and at temperatures below 10°C, mesophyll conductance did not significantly differ from 0. Maximum mitochondrial respiration rates occurred at temperatures higher than 35°C and were lower by around 80% at 5°C. Despite the extreme cold conditions that Antarctic mosses face over winter, the photosynthetic apparatus appears optimised to warm temperatures. Our estimation of the total carbon balance suggests that survival in this cold environment may rely on a capacity to maximize photosynthesis for brief periods during summer and minimize respiratory carbon losses in cold conditions.
Highlights
Antarctica is considered the coldest continent on Earth, since the surface air temperature can reach annual means of -23°C (-45°C in interior regions higher than 1500 m a. s. l.) (Fortuin and Oerlemans, 1990)
The objectives of this study were (1) to model the daily carbon balance of Antarctic mosses during summer based on canopy surface temperature and its effect on photosynthesis, (2) to test the interspecific differences and the possible buffering effect of water content on moss canopy temperature, and (3) to determine the temperature responses of net CO2 assimilation, electron transport rate, gm and photoprotection mechanisms assessed by NPQ
B. pseudotriquetrum, S. antarctici, Chorisodontium aciphyllum, Polytrichastrum alpinum and Sanionia uncinata were located at Fildes Peninsula and Ardley Island near Escudero Station
Summary
Antarctica is considered the coldest continent on Earth, since the surface air temperature can reach annual means of -23°C (-45°C in interior regions higher than 1500 m a. s. l.) (Fortuin and Oerlemans, 1990). In the South Shetlands Islands of Maritime Antarctica the daytime mean air temperatures vary between -5°C and 13°C in the summer and only reach -30°C in winter (Convey and Smith, 2005; Pearce, 2008). In these southern latitudes, terrestrial vegetation – mainly lichens and bryophytes – is restricted to ice-free areas (Peat et al, 2007; Ochyra et al, 2008). Soil surface temperatures have been recorded to be much warmer than the ~2 m air temperatures reported by meteorological stations, with maximum differences of 10.7°C (Schenker and Block, 1986), 25°C (Smith, 1996) or even 27°C (Matsuda, 1968) in summer. Antarctic mosses will normally be in a dormant state protected by a thick, insulating layer of snow
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
