Effect of UV‐B radiation on the content of UV‐B absorbing compounds and photosynthetic parameters in Parmotrema austrosinense from two contrasting habitats

Abstract

We studied the resistance of Parmotrema austrosinense to UV-B stress. We focused on the effects of a high dose UV-B radiation on the content of chlorophylls, carotenoids and UV-B screening compounds. Photosynthetic parameters were measured by chlorophyll fluorescence (potential and effective quantum yields, photochemical and non-photochemical quenching) and evaluated in control and UV-B-treated lichens. Lichens from two different locations in Cordoba, Argentina, were selected: (i) high altitude and dry plots at (Los Gigantes) and (ii) lowland high salinity plots (Salinas Grandes). UV-B treatment led to a decrease in the content of photosynthetic pigments and UV-B screens (absorbance decrease in 220-350 nm) in the samples from Salinas Grandes, while in Los Gigantes samples, an increase in UV-B screen content was observed. Chlorophyll fluorescence parameters showed a UV-B-induced decline in F /F , Φ and qP indicating limitation of primary photosynthetic processes in photosystem II (PSII) of symbiotic alga, more pronounced in Salinas Grandes samples. Protective mechanism of PSII were activated by the UV-B treatment to a higher extent in samples from Salinas Grandes (NPQ 0.48) than in Los Gigantes samples (NPQ 0.26). We concluded that site-related characteristics, and in particular different UV-B radiation regimen, had a strong effect on resistance of the photosynthetic apparatus of P. austrosinense to UV-B radiation.

Physiological Responses and Metabonomics Analysis of Male and Female Sargassum thunbergii Macroalgae Exposed to Ultraviolet-B Stress

“…Additionally, Y(NPQ) and Y(NO) values reflect to the energy dissipation abilities of PSII systems ( Kramer et al, 2004 ) and upregulated Y(NPQ) generally means that photoautotroph is suffered to stressed conditions and they could activate to their defend mechanisms ( Peter and Rolf, 2005 ; Barták et al, 2018 ). However, when the stressed influences exceed to the tolerance limits, macroalgal Y(NPQ) could not increasing and their energy dissipation abilities will lose efficacy as well as Y(NO) will increase significantly ( Kramer et al, 2004 ).…”