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从叶片光谱吸收变化观察到的体内光保护机制表明 VIS-NIR 缓慢诱导的构象色素床变化。

In vivo photoprotection mechanisms observed from leaf spectral absorbance changes showing VIS-NIR slow-induced conformational pigment bed changes.

机构信息

Laboratory of Earth Observation, Image Processing Laboratory, University of Valencia, C/Catedrático José Beltrán, 2, 46980, Paterna, Valencia, Spain.

Optics of Photosynthesis Laboratory, Institute for Atmospheric and Earth System Research/Forest Sciences, Faculty of Agriculture and Forestry, University of Helsinki, 00014, Helsinki, Finland.

出版信息

Photosynth Res. 2019 Dec;142(3):283-305. doi: 10.1007/s11120-019-00664-3. Epub 2019 Sep 20.

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.

摘要

受调控的过剩光下的热耗散包含了一系列机制,通过这些机制,超分子光捕获色素蛋白复合物(LHC)从光捕获状态转变为热耗散状态,以非光化学方式猝灭过量的光诱导激发能。基于测量向上和向下光谱辐射通量的整片叶子光谱学,我们研究了完整叶子在可见光和近红外波长(VIS-NIR,400-800nm)中吸收光谱 A(λ,t)和被动诱导叶绿素荧光 F(λ,t)动态的连续光谱(高光谱)瞬态时间序列,这些时间序列是在突然受到强烈的自然光照暴露后获得的。除了光避免机制外,我们还观察到吸收特征上的主要动态事件,这些事件具有特定的起始和动力学行为,这些特征是从同时测量的反射率 R(λ,t)和透射率 T(λ,t)计算得出的 A(λ,t)=1-R(λ,t)-T(λ,t)。在最初的几秒钟到几分钟内,可以从反射(反向散射)和透射(前向散射)辐射差中看到,在可见的快速类胡萝卜素吸收特征(500-570nm)中出现了一致的、众所周知的特征。同时观察到快速的 Chl 特征,要么表现为在快速调整光时散射行为增加或减少,这与膜的重新组织一致。类胡萝卜素吸收特征与主要的 F 降低同时出现,并且与质子梯度建立时的快速叶黄素转化相对应。叶黄素转化后(t=3 分钟),偶尔可以从透射辐射测量中观察到动力学较慢但较大且平滑的吸收增加,表现为在绿色(约 550nm)和近红外(约 750nm)波长处的宽峰,不涉及进一步的 F 猝灭。令人惊讶的是,与高光响应相关,这种宽而一致的 VIS-NIR 特征表明,一种缓慢诱导的吸收增加具有指数动力学行为。与亚叶级别的观察结果类似,我们认为这种机制可以通过涉及类胡萝卜素和叶绿素的结构诱导的低能量转移能量再分配来解释。这些发现可能为进一步的非侵入性光谱研究天线构象及其与完整叶片水平能量猝灭的关系铺平道路,这对于评估植物活体光合作用以及从远程观测中评估光合作用非常重要,同时结合 F 测量。

https://cdn.ncbi.nlm.nih.gov/pmc/blobs/35ed/6874624/bf840213802e/11120_2019_664_Fig1_HTML.jpg

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