Abstract
Regulated heat dissipation under excessive light comprises a complexity of mechanisms, whereby the supramolecular light-harvesting pigment-protein complex (LHC) shifts state from light harvesting towards heat dissipation, quenching the excess of photo-induced excitation energy in a non-photochemical way. Based on whole-leaf spectroscopy measuring upward and downward spectral radiance fluxes, we studied spectrally contiguous (hyperspectral) transient time series of absorbance A(λ,t) and passively induced chlorophyll fluorescence F(λ,t) dynamics of intact leaves in the visible and near-infrared wavelengths (VIS-NIR, 400-800 nm) after sudden strong natural-like illumination exposure. Besides light avoidance mechanism, we observed on absorbance signatures, calculated from simultaneous reflectance R(λ,t) and transmittance T(λ,t) measurements as A(λ,t) = 1 - R(λ,t) - T(λ,t), major dynamic events with specific onsets and kinetical behaviour. A consistent well-known fast carotenoid absorbance feature (500-570 nm) appears within the first seconds to minutes, seen from both the reflected (backscattered) and transmitted (forward scattered) radiance differences. Simultaneous fast Chl features are observed, either as an increased or decreased scattering behaviour during quick light adjustment consistent with re-organizations of the membrane. The carotenoid absorbance feature shows up simultaneously with a major F decrease and corresponds to the xanthophyll conversion, as quick response to the proton gradient build-up. After xanthophyll conversion (t = 3 min), a kinetically slower but major and smooth absorbance increase was occasionally observed from the transmitted radiance measurements as wide peaks in the green (~ 550 nm) and the near-infrared (~ 750 nm) wavelengths, involving no further F quenching. Surprisingly, in relation to the response to high light, this broad and consistent VIS-NIR feature indicates a slowly induced absorbance increase with a sigmoid kinetical behaviour. In analogy to sub-leaf-level observations, we suggest that this mechanism can be explained by a structure-induced low-energy-shifted energy redistribution involving both Car and Chl. These findings might pave the way towards a further non-invasive spectral investigation of antenna conformations and their relations with energy quenching at the intact leaf level, which is, in combination with F measurements, of a high importance for assessing plant photosynthesis in vivo and in addition from remote observations.
Abstract from the paper’s OpenAlex record; open copy licensed cc-by. Read at the source ↗
The text the model read, with the source record’s inline markup (italics, sub- and superscripts) rendered and its character entities decoded; quote offsets refer to the raw text.
Claims 7
Claim · model-written summary
A fast carotenoid absorbance feature at 500-570 nm appeared within seconds to minutes.
Not reportedTaxon
Verbatim
e0“A consistent well-known fast carotenoid absorbance feature (500-570 nm) appears within the first seconds to minutes”
t0“leaf”
Claim · model-written summary
Fast chlorophyll features showed increased or decreased scattering during light adjustment.
Not reportedTaxon
Verbatim
e0“Simultaneous fast Chl features are observed, either as an increased or decreased scattering behaviour during quick light adjustment”
Claim · model-written summary
The carotenoid absorbance feature coincided with a major fluorescence decrease.
Not reportedTaxon
Verbatim
e0“The carotenoid absorbance feature shows up simultaneously with a major F decrease”
Claim · model-written summary
After xanthophyll conversion, a slower absorbance increase was occasionally observed near 550 and 750 nm.
Not reportedTaxon
Verbatim
e0“After xanthophyll conversion (t = 3 min), a kinetically slower but major and smooth absorbance increase was occasionally observed from the transmitted radiance measurements as wide peaks in the green (~ 550 nm) and the near-infrared (~ 750 nm) wavelengths”
Claim · model-written summary
The later absorbance increase involved no further fluorescence quenching.
Not reportedTaxon
Verbatim
e0“involving no further F quenching”
Claim · model-written summary
The light-induced VIS-NIR absorbance increase had sigmoid kinetics.
Not reportedTaxon
Verbatim
e0“this broad and consistent VIS-NIR feature indicates a slowly induced absorbance increase with a sigmoid kinetical behaviour”
Claim · model-written summary
The authors suggest structure-induced low-energy-shifted redistribution involving Car and Chl explains the response.
Not reportedTaxon
Verbatim
e0“we suggest that this mechanism can be explained by a structure-induced low-energy-shifted energy redistribution involving both Car and Chl.”