Simultaneous in vivo recording of prompt and delayed fluorescence and 820-nm reflection changes during drying and after rehydration of the resurrection plant Haberlea rhodopensis

Abstract

A new instrument (M-PEA), which measures simultaneously kinetics of prompt fluorescence (PF), delayed fluorescence (DF) and modulated light reflection at 820nm (MR), was used to screen dark-adapted leaves of the resurrection plant Haberlea rhodopensis during their progressive drying, down to 1% relative water content (RWC), and after their re-watering. This is the first investigation using M-PEA, which employs alternations of actinic light (627-nm peak, 5000 micromol photons m(-2) s(-1)) and dark intervals, where PF-MR and DF kinetics are respectively recorded, with the added advantages: (a) all kinetics are recorded with high time resolution (starting from 0.01 ms), (b) the dark intervals' duration can be as short as 0.1 ms, (c) actinic illumination can be interrupted at different times during the PF transient (recorded up to 300 s), with the earliest interruption at 0.3 ms. Analysis of the simultaneous measurements at different water-content-states of H. rhodopensis leaves allowed the comparison and correlation of complementary information on the structure/function of the photosynthetic machinery, which is not destroyed but only inactivated (reversibly) at different degrees; the comparison and correlation helped also to test current interpretations of each signal and advance their understanding. Our results suggest that the desiccation tolerance of the photosynthetic machinery in H. rhodopensis is mainly based on mechanism(s) that lead to inactivation of photosystem II reaction centres (transformation to heat sinks), triggered already by a small RWC decrease.

Photosynthetic characterization of Jerusalem artichoke during leaf expansion

“…Monitoring modulated reflection change near 820 nm is a very convenient way to follow the redox state of PSI. The operating mechanism of this instrument has been elucidated by Strasser et al (2010) in detail. In this study, leaves were dark adapted for 30 min before they were measured.…”

Efeito da Fertilização Amoniacal na Aclimatação de Ingá Sob Alta e Moderada Irradiância

“…Em seguida, as folhas foram expostas a um pulso de luz saturante de intensidade de 3.000 µmol m -2 s -1 durante 1 s (Gonçalves et al, 2007). Com base nas análises do teste JIP foram obtidos os parâmetros de rendimento quântico máximo do PSII (F v /F m ) e o índice de desempenho (PI total ), que compreende a eficiência na utilização de um fóton absorvido pelo PSII para a redução dos aceptores finais de elétrons do PSI (Strasser et al, 2010).…”

“…recuperação dessas plantas, que alcançaram o patamar das plantas sob irradiância moderada. Os valores de PI total , cujo parâmetro possibilita uma interpretação mais ampla da fase fotoquímica da fotossíntese (Strasser et al, 2010), demonstraram, por sua vez, que a retomada no desempenho fotoquímico em plantas expostas à alta irradiância foi mais proeminente sob fertilização amoniacal (I + NH 4 + e NH 4 + ) a partir do 21º dia de experimentação (Figura 2).…”

Effects of temperature and irradiance on photosystem activity during Alhagi sparsifolia leaf senescence

“…It was documented that inactivation of water-splitting complex resulted in further reduction of PSII photochemical activity (Gruszecki et al 1991, Joshi et al 1993, Königer et al 2000, Lu et al 2002, Chen et al 2010. The values of ΨE o (Strasser et al 2010) reflects the efficiency of electron acceptors of the chain which comprises the secondary quinone acceptor, plastoquinone (PQ), cytochrome (cyt) and plastocyanin (PC). The electron transport in PSI acceptor side was calculated as δ/(1 -δ), where δ means probability with which an electron from the intersystem electron carriers is transferred to electron acceptors at the PSI acceptor side.…”

“…Irradiance was 3 600 μmol m -2 s -1 to generate fast fluorescence curves expanding from O (taken as F o ) to P (F m ) for all the treatments. An analysis of the fast OJIP fluorescence rise has been developed, called as JIP-test (Strasser et al 2010). A WeatherHawk-500 (Campbell Scientific, Salt Lake City, USA) was set that automatically collected weather data every 15 min.…”