Photosynthesis on the edge: photoinhibition, desiccation and freezing tolerance of Antarctic bryophytes
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ORIGINAL ARTICLE
Photosynthesis on the edge: photoinhibition, desiccation and freezing tolerance of Antarctic bryophytes Alicia Victoria Perera‑Castro1 · Jaume Flexas1 · Águeda María González‑Rodríguez2 · Beatriz Fernández‑Marín2 Received: 23 July 2020 / Accepted: 23 September 2020 © Springer Nature B.V. 2020
Abstract In Antarctica, multiple stresses (low temperatures, drought and excessive irradiance) hamper photosynthesis even in summer. We hypothesize that controlled inactivation of PSII reaction centres, a mechanism widely studied by pioneer work of Fred Chow and co-workers, may effectively guarantee functional photosynthesis under these conditions. Thus, we analysed the energy partitioning through photosystems in response to temperature in 15 bryophyte species presenting different worldwide distributions but all growing in Livingston Island, under controlled and field conditions. We additionally tested their tolerance to desiccation and freezing and compared those with their capability for sexual reproduction in Antarctica (as a proxy to overall fitness). Under field conditions, when irradiance rules air temperature by the warming of shoots (up to 20 °C under sunny days), a predominance of sustained photoinhibition beyond dynamic heat dissipation was observed at low temperatures. Antarctic endemic and polar species showed the largest increases of photoinhibition at low temperatures. On the contrary, the variation of thermal dissipation with temperature was not linked to species distribution. Instead, maximum non-photochemical quenching at 20 °C was related (strongly and positively) with desiccation tolerance, which also correlated with fertility in Antarctica, but not with freezing tolerance. Although all the analysed species tolerated − 20 °C when dry, the tolerance to freezing in hydrated state ranged from the exceptional ability of Schistidium rivulare (that survived for 14 months at − 80 °C) to the susceptibility of Bryum pseudotriquetrum (that died after 1 day at − 20 °C unless being desiccated before freezing). Keywords Bryophytes · Energy partitioning · Fertility · Freezing tolerance · Heat dissipation · Non-photochemical quenching
Introduction In Antarctic regions, organisms are exposed to extreme conditions such as low temperatures, drought, strong winds and high irradiances—both visible and ultraviolet—during the Austral summer, and are exposed to sub-zero temperatures Electronic supplementary material The online version of this article (https://doi.org/10.1007/s11120-020-00785-0) contains supplementary material, which is available to authorized users. * Alicia Victoria Perera‑Castro [email protected] 1
Department of Biology, Universitat de Les Illes Balears / INAGEA, Illes Balears, Carretera de Valldemossa Km 7.5, 07122 Palma de Mallorca, Spain
Department of Botany, Ecology and Plant Physiology, Universidad de La Laguna (ULL), 38200 La Laguna, Canarias, Spain
2
and long-standing darkness during the Austral winter. In the South Shetlands Islands of West Antarctica, day
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