Photosynthesis Research

, Volume 90, Issue 1, pp 29–43

Rapid light-response curves of chlorophyll fluorescence in microalgae: relationship to steady-state light curves and non-photochemical quenching in benthic diatom-dominated assemblages

  • João Serôdio
  • Sónia Vieira
  • Sónia Cruz
  • Helena Coelho
Regular Paper

DOI: 10.1007/s11120-006-9105-5

Cite this article as:
Serôdio, J., Vieira, S., Cruz, S. et al. Photosynth Res (2006) 90: 29. doi:10.1007/s11120-006-9105-5

Abstract

Rapid light-response curves (RLC) of variable chlorophyll fluorescence were measured on estuarine benthic microalgae with the purpose of characterising its response to changes in ambient light, and of investigating the relationship to steady-state light-response curves (LC). The response of RLCs to changes in ambient light (E, defined as the irradiance level to which a sample is acclimated to prior to the start of the RLC) was characterised by constructing light-response curves for the RLC parameters αRLC, the initial slope, ETRm,RLC, the maximum relative electron transport rate, and Ek,RLC, the light-saturation parameter. Measurements were carried out on diatom-dominated suspensions of benthic microalgae and RLC and LC parameters were compared for a wide range of ambient light conditions, time of day, season and sample taxonomic composition. The photoresponse of RLC parameters was typically bi-phasic, consisting of an initial increase of all parameters under low ambient light (E < 21–181 μmol m−2 s−1), and of a phase during which αRLC decreased significantly with E, and the increase of ETRm,RLC and Ek,RLC was attenuated. The relationship between RLC and LC parameters was dependent on ambient irradiance, with significant correlations being found between αRLC and α, and between ETRm,RLC and ETRm, for samples acclimated to low and to high ambient irradiances, respectively. The decline of αRLC under high light (ΔαRLC) was strongly correlated (P < 0.001 in all cases) with the level of non-photochemical quenching (NPQ) measured before each RLC. These results indicate the possibility of using RLCs to characterise the steady-state photoacclimation status of a sample, by estimating the LC parameter Ek, and to trace short-term changes in NPQ levels without dark incubation.

Keywords

Diatoms Microphytobenthos Chlorophyll fluorescence PSII electron transport Non-photochemical quenching Photoacclimation Rapid light curves 

Abbreviations

α, β

Initial slope and photoinhibition parameter of the ETR versus E curve (μmol−1 m2 s)

ΔαRLC

High light-induced decrease of the initial slope of a RLC (=αm,RLCαRLC)

αm,RLC

Maximum value of a αRLC versus E curve

a*

Optical absorption cross-section of PSII

DD, DT

Diadinoxanthin and diatoxanthin

ΔF

Variable fluorescence (=FmFs) (dimensionless)

ΔF/Fm

Effective quantum yield of PSII (dimensionless)

E

Ambient spectrally averaged photon irradiance of PAR (400–700 nm): the irradiance level to which the sample acclimated to when ETR and NPQ are determined, and immediately before the start of a RLC (μmol m−2 s−1)

Ek

Light-saturation parameter of the ETR versus E curve (μmol m−2 s−1)

ENPQmin

Irradiance under which NPQ reaches a minimum value in a NPQ versus E curve

ETR

Relative electron transport rate (=E × ΔF/Fm) measured (dimensionless)

ETRm

Maximum relative electron transport rate of the ETR versus E curve (dimensionless)

Fo, Fm

Minimum and maximum fluorescence emitted by a dark-adapted sample (arbitrary units)

Fs, Fm

Steady-state and maximum fluorescence emitted by a light-adapted sample (arbitrary units)

Fm, m

Maximum Fm value measured during a LC

Fv/Fm

Maximum quantum yield of PSII of a dark-adapted sample (dimensionless)

LC

Steady-state ETR versus E curve

NPQ

Non-photochemical quenching of fluorescence [=(Fm, mFm)/Fm] (dimensionless)

PSII

Photosystem II

qE

Energy quenching, rapidly reversible component of NPQ

qI

Photoinhibitory quenching, slowly reversible component of NPQ

RCII

Reaction center of PSII

RLC

Rapid ETR versus E curve subscript denoting a parameter of a RLC.

Copyright information

© Springer Science+Business Media B.V. 2006

Authors and Affiliations

  • João Serôdio
    • 1
  • Sónia Vieira
    • 1
  • Sónia Cruz
    • 1
  • Helena Coelho
    • 1
  1. 1.Departamento de Biologia & CESAMUniversidade de Aveiro, Campus de SantiagoAveiroPortugal

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