Effects of ambient versus reduced UV‐B radiation on high arctic Salix arctica assessed by measurements and calculations of chlorophyll a fluorescence parameters from fluorescence transients

Abstract

Document VersionPublisher's PDF, also known as Version of record Link back to DTU Orbit Citation (APA): Albert, K. R. (2005). Effects of ambient versus reduced UV-B radiation on high arctic Salix arctica assessed by measurements and calculations of chlorophyll-a fluorescence parameters from fluorescence transients. Physiologia Plantarum, 124,[208][209][210][211][212][213][214][215][216][217][218][219][220][221][222][223][224][225][226] Effects of ambient versus reduced UV-B radiation on high arctic Salix arctica assessed by measurements and calculations of chlorophyll a fluorescence parameters from fluorescence transients A UV-B exclusion-experiment was conducted in the high Arctic Zackenberg, NE Greenland, in which Salix arctica leaves during most of the growing season were fixed perpendicular to the solar zenith angle, thereby receiving maximal solar radiation. Covered with Teflon and Mylar foil, the leaves received approximately 90 and 40% of the ambient UV-B irradiance, respectively. The effects were examined through recordings of chlorophyll a fluorescence transients, determination of biomass and analysis of total carbon and nitrogen content and amount of soluble flavonoids in the leaves. The processing of light was analysed by means of the chlorophyll a fluorescence transient, using the so-called JIP test, as evolved by Reto J. Strasser and his coworkers. Reduction of the UV-B irradiance caused a rise in many of the fluorescence parameters during July, but not in August (late season). Thus increases in the efficiency that an absorbed photon will be trapped by the PSII reaction centre with the resultant reduction of Q A to Q A -(ET 0 /ABS 5 F V /F M ) and the efficiency that an electron residing on Q A -will enter the intersystem electron transport chain (ET 0 /TR 0 ) were observed in reduced UV-B. Moreover, estimated per cross-section of leaf sample, the number of active PSII reaction centres (RC/ CS M ) and electron transport rate (ET M /CS M ) and all performance indexes (PI ABS , PI CSo and PI CSm ) were increased in reduced UV-B. The total soluble flavonoid content was highest in ambient UV-B. The treatment effects on fluorescence parameters that were directly measured (e.g. F 0 and F M ) and those that were derived (e.g. quantum efficiencies, parameters per PSII reaction centres and per cross-section of leaf sample) are discussed in relation to one another, in relation to daily and seasonal variation, and from the perspective of evaluating the relative importance of UV-B of donor and acceptor side capacity in Photosystem II. In conclusion, the experimental set-up and non-invasive measurements proved to be a sensitive method to screen for effects of UV-B stress.Abbreviations -D1, core subunit of PSII; JIP test, analysis of parameters derived from the fluorescence transient (see Table 1); Mn cluster, four ion cluster which is a part of OEC going through five redox states during water splitting; OEC, oxygen evolving complex extracting electrons from water; PSI, Photosystem I; PSII, Photosystem II; Q A , ...

Solar Ultraviolet-B Radiation Increases Phenolic Content and Ferric Reducing Antioxidant Power in Avena sativa

“…Plant responses to UV-B tend to be subtle and species-specific, especially when studies are conducted outside under realistic spectral regimes. Responses to elevated and ambient UV-B include increases in DNA-damage and antioxidant response [2], alterations in plant morphology and architecture [3,4], slight reductions in chlorophyll fluorescence parameters associated with photosystem II [PSII; 5,6] and lower biomass accumulation [7][8][9][10][11]. The most common response of field-grown plants to elevated and ambient levels of UV-B appears to be an increase in concentrations of UV-absorbing phenolics [1,12,13] that may ameliorate potentially damaging UV-B before it reaches sensitive chromophores [14][15][16].…”

Photoprotection, photosynthesis and growth of tropical tree seedlings under near-ambient and strongly reduced solar ultraviolet-B radiation

“…The effect of UV-B on plants is studied experimentally by either using filters to attenuate the UV-B exposure or by using supplementary lights to increase the UV-B exposure (e.g., Albert et al, 2005;Ballare et al, 2001;Bassman et al, 2001;Day and Neale, 2002;Flint et al, 2003;Qaderi and Reid, 2005;Rousseaux et al, 2004;Searles et al, 1995;Tevini, 2004). These reports reveal a great variety of UV-B effects on photosynthesis, morphology, and growth.…”

Effect of Exclusion of Solar UV radiation on Plants

“…Bredahl et al (2004, p.363) reported higher maximal photochemical efficiency (measured as the chlorophyll fluorescence parameter Fv/Fm) under UV-B reduction. Quantum efficiencies, specific and phenomenological fluxes were all enhanced by UV exclusion indicating a negative impact of ambient UV on all of these parameters in the plant species (Albert, Mikkelsen, & Ro-Poulsen, 2005, Albert, Mikkelsen, & Ro-Poulsen, 2008, Albert et al, 2010, p.1542Kataria et al, 2013, p.140). The increases in the efficiency that an absorbed photon will be trapped by the PSII reaction centre with the resultant reduction of QA to QA -(ET0/ABS = FV/FM) and the efficiency that an electron residing on QA-will enter the intersystem electron transport chain (ET0/TR0) were observed in reduced UV-B.…”

“…The UV-exclusion experiments showed that a reduction of the ambient UV-B level resulted in decreased content of UV-B absorbing compounds and lower stress level indicated by increased maximal quantum yield (FV/FM) and Performance Indexes (PI) (Bredahl, Ro-Poulsen, Mikkelsen, 2004;Albert et al, 2005Albert et al, , 2008Albert et al, , 2010Kataria et al, 2013, p.140). Bredahl et al (2004, p.363) reported higher maximal photochemical efficiency (measured as the chlorophyll fluorescence parameter Fv/Fm) under UV-B reduction.…”