The Gradient of Exciting Radiation within a Sample Affects the Relative Height of Steps in the Fast Chlorophyll a Fluorescence Rise

Sušila, Petr; Lazár, Dušan; Ilı́k, Petr; Tomek, Pavel; Nauš, Jan

doi:10.1023/b:phot.0000040586.39903.db

Cited by 35 publications

(20 citation statements)

References 62 publications

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“…[29,30] The general anatomy of the leaf is designed to transmit light from the surface into the tissue and then scatter it to minimize losses. The elongated palisade cells were suggested to act as 'light pipes' directing light into the tissue.…”

Section: Discussionmentioning

confidence: 99%

Certain Biominerals in Leaves Function as Light Scatterers

et al. 2012

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Cystoliths are amorphous calcium carbonate bodies that form in the leaves of some plant families. Cystoliths are regularly distributed in the epidermis and protrude into the photosynthetic tissue, the mesophyll. The photosynthetic pigments generate a steep light gradient in the leaf. Under most illumination regimes the outer mesophyll is light saturated, thus the photosynthetic apparatus is kinetically unable to use the excess light for photochemistry. Here we use micro‐scale modulated fluorometry to demonstrate that light scattered by the cystoliths is distributed from the photosynthetically inefficient upper tissue to the efficient, but light deprived, lower tissue. The results prove that the presence of light scatterers reduces the steep light gradient, thus enabling the leaf to use the incoming light flux more efficiently. MicroCT and electron microscopy confirm that the spatial distribution of the minerals is compatible with their optical function. During the study we encountered large calcium oxalate druses in the same anatomical location as the cystoliths. These druses proved to have similar light scattering functions as the cystoliths. This study shows that certain minerals in the leaves of different plants distribute the light flux more evenly inside the leaf.

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Section: Discussionmentioning

confidence: 99%

Certain Biominerals in Leaves Function as Light Scatterers

et al. 2012

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“…Since it has been indicated that a transitory conformational change of a pigment-protein complex of PSII core antenna occurs during the IP phase of the Kautsky fluorescence kinetics (Moise and Moya 2004a), fluorescence emission spectra acquired in this part cannot be used. Furthermore, changes in the spectral shape can arise because of the heterogeneity in the fluorescence induction rate constants characteristic of the different leaf layers (Sušila et al 2004). This occurs when a significant gradient of light intensity with leaf depth exists, since less irradiated deeper leaf layers are expected to follow a delayed rising in ChlF.…”

Section: Discussionmentioning

confidence: 99%

A retrieval algorithm to evaluate the Photosystem I and Photosystem II spectral contributions to leaf chlorophyll fluorescence at physiological temperatures

et al. 2011

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A new computational procedure to resolve the contribution of Photosystem I (PSI) and Photosystem II (PSII) to the leaf chlorophyll fluorescence emission spectra at room temperature has been developed. It is based on the Principal Component Analysis (PCA) of the leaf fluorescence emission spectra measured during the OI photochemical phase of fluorescence induction kinetics. During this phase, we can assume that only two spectral components are present, one of which is constant (PSI) and the other variable in intensity (PSII). Application of the PCA method to the measured fluorescence emission spectra of Ficus benjamina L. evidences that the temporal variation in the spectra can be ascribed to a single spectral component (the first principal component extracted by PCA), which can be considered to be a good approximation of the PSII fluorescence emission spectrum. The PSI fluorescence emission spectrum was deduced by difference between measured spectra and the first principal component. A single-band spectrum for the PSI fluorescence emission, peaked at about 735 nm, and a 2-band spectrum with maxima at 685 and 740 nm for the PSII were obtained. A linear combination of only these two spectral shapes produced a good fit for any measured emission spectrum of the leaf under investigation and can be used to obtain the fluorescence emission contributions of photosystems under different conditions. With the use of our approach, the dynamics of energy distribution between the two photosystems, such as state transition, can be monitored in vivo, directly at physiological temperatures. Separation of the PSI and PSII emission components can improve the understanding of the fluorescence signal changes induced by environmental factors or stress conditions on plants.

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“…The amount of photosynthetically useable radiation (I PUR ) at a given depth (x) inside a translucent photosynthetic material should approximately obey Lamberts law (Friend 2001, Sušila et al 2004);…”

Section: Theory: Development Of a Model Of Gross Photosynthesismentioning

confidence: 99%

Modelling photosynthetic photon flux density and maximum potential gross photosynthesis

Ritchie¹

2010

Photosynt.

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Irradiance data software developed by the NREL Solar Radiation Laboratory (Simple Model of Atmospheric Radiative Transfer of Sunshine, SMARTS) has been used for modelling photosynthesis. Spectra and total irradiance were expressed in terms of quanta [mol m -2 s -1 , photosynthetic photon flux density, PPFD (400-700 nm)]. Using the SMARTS software it is possible to (1) calculate the solar spectrum for a planar surface for any given solar elevation angle, allowing for the attenuating effects of the atmosphere on extraterrestrial irradiance at each wavelength in the 400-700 nm range and for the thickness of atmosphere the light must pass through during the course of a day, (2) calculate PPFD vs. solar time for any latitude and date and (3) estimate total daily irradiance for any latitude and date and hence calculate the total photon irradiance for a whole year or for a growing season. Models of photosynthetic activity vs. PPFD are discussed. Gross photosynthesis (P g ) vs. photosynthetic photon flux density (PPFD) (P g vs. I) characteristics of single leaves compared to that of a canopy of leaves are different. It is shown that that the optimum irradiance for a leaf (I opt ) is the half-saturation irradiance for a battery of leaves in series. A C 3 plant, with leaves having an optimum photosynthetic rate at 700 μmol m -2 s -1 PPFD, was used as a realistic worked example. The model gives good estimates of gross photosynthesis (P g ) for a given date and latitude. Seasonal and annual estimates of P g can be made. Taking cloudiness into account, the model predicts maximum P g rates of about 10 g(C) m -2 d -1 , which is close to the maximum reported P g experimental measurements.

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The Gradient of Exciting Radiation within a Sample Affects the Relative Height of Steps in the Fast Chlorophyll a Fluorescence Rise

Cited by 35 publications

References 62 publications

Certain Biominerals in Leaves Function as Light Scatterers

Certain Biominerals in Leaves Function as Light Scatterers

A retrieval algorithm to evaluate the Photosystem I and Photosystem II spectral contributions to leaf chlorophyll fluorescence at physiological temperatures

Modelling photosynthetic photon flux density and maximum potential gross photosynthesis

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