Chlorophyll fluorescence in the resurrection plant Selaginella lepidophylla (Hook. & Grev.) Spring during high-light and desiccation stress, and evidence for zeaxanthin-associated photoprotection

Abstract

Abstract. The function of photosystem (PS)II during desiccation and exposure to high photon flux density (PFD) was investigated via analysis of chlorophyll fluorescence in the desert resurrection plant Selaginella lepidophylla (Hook. and Grev.) Spring. Exposure of hydrated, physiologically competent stems to 2000 gmol. m-2. s-1 PFD caused significant reductions in both intrinsic fluorescence yield (Fo) and photochemical efficiency of PSII (Fv/FM) but recovery to pre-exposure values was rapid under low PFD. Desiccation under low PFD also affected fluorescence characteristics. Both Fv/FM and photochemical fluorescence quenching remained high until about 40% relative water content and both then decreased rapidly as plants approached 0% relative water content. In contrast, the maximum fluorescence yield (FM) decreased and non-photochemical fluorescence quenching increased early during desiccation. In plants dried at high PFD, the decrease in Fv/FM was accentuated and Fo was reduced, however, fluorescence characteristics returned to near pre-exposure values after 24-h of rehydration and recovery at low PFD. Pretreatment of stems with dithiothreitol, an inhibitor of zeaxanthin synthesis, accelerated the decline in Fv/FM and significantly increased Fo relative to controls at 925 pmol. m-2. s-1 PFD, and the differences persisted over a 3-h low-PFD recovery period. Pretreatment with dithio- QA, the primary electron acceptor of PSII, and prevented the synthesis of zeaxanthin relative to controls when stems were exposed to PFDs in excess of 250 lamol. m-2.s-1. These results indicate that a zeaxanthin-associated mechanism of photoprotection exists in this desert pteridophyte that may help to prevent photoinhibitory damage in the fully hydrated state and which may play an additional role in protecting PSII as thylakoid membranes undergo water loss.

Changes in net photosynthesis, chlorophyll fluorescence and xanthophyll cycle interconversions during freeze-thaw cycles in the Mediterranean moss Leucodon sciuroides

“…Additionally, desiccation leads to the impairment of PSIImediated electron transport and Q A reduction (Deltoro et al 1998). Similar changes have been described during desiccation in other poikilohydric plants, such as lichens (Lange et al 1989;Calatayud et al 1997), algae (Chen and Hsu 1995) or the resurrection plant Selaginella lepidophyla (Eickmeier et al 1993).…”

Strong quenching of chlorophyll fluorescence in the desiccated state in three poikilohydric and homoiochlorophyllous moss species indicates photo-oxidative protection on highly light-exposed rocks of a tropical inselberg

“…Conversely, in desiccated mosses and lichens F 0 is reduced to almost zero and increases again during rewetting. The thalli appear well photo-protected in the desiccated state (Calatayud et al, 1997;Eickmeier et al, 1993;Heber et al, 2000Heber et al, , 2001Lange et al, 1989).…”

Photoprotection Conferred by Changes in Photosynthetic Protein Levels and Organization during Dehydration of a Homoiochlorophyllous Resurrection Plant

“…NPQ has been shown to be active in desiccation-tolerant bryophytes and pteridiophytes (Eickmeier et al, 1993;Oliver, 1996), in homoiochlorophyllous angiosperms (Alamillo and Bartels, 2001;Georgieva et al, 2009;Huang et al, 2012), and during the initial stages of drying in poikilochlorophyllous angiosperms (Beckett et al, 2012). Photoinhibition, when damage to PSII (mainly to its D1 subunit) exceeds the repair capacity, typically under conditions of light stress, is also observed in homoiochlorophyllous resurrection plants (e.g.…”