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Changes in thermic limits and acclimation assessment for an alpine plant by chlorophyll fluorescence analysis: Fv/Fmvs. Rfd

Perera-Castro, A.V., Brito, P., González-Rodríguez, A.M.
Photosynthetica 2018 v.56 no.2 pp. 527-536
acclimation, alpine plants, chlorophyll, ecosystems, photochemistry, photosystem II, risk, temperature
A comparison between maximum quantum yield of PSII photochemistry (Fᵥ/Fₘ) and chlorophyll fluorescence decrease ratio (Rfd) for low and high temperature resistance was assessed in a seasonal study of the acclimation in Pterocephalus lasiospermus. Analyzing the regression adjustment of both parameters and the lethal temperatures (LT₅₀), Rfd resulted in being a more sensitive indicator for low and high temperature treatments, since the thermic resistance estimated with Rfd parameter was never higher than those estimated with Fᵥ/Fₘ. Furthermore, the use of Fᵥ/Fₘ led to an overestimation of the acclimation phenomena, with 6ºC of a maximum difference between both parameters. Using Rfd as the indicator parameter, P. lasiospermus acclimated to low temperatures but it kept on being a sensitive species (the lowest LT₅₀ values only achieved–9.9 ± 0.3ºC). bserved (LT₅₀ around 43.5ºC). Thus, according to Rfd evaluation of the thermic threshold, this species could be in risk of damage at low temperatures in this alpine ecosystem.