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To clarify the genotypic-dependent alternation in D1 protein turnover and PSII repair cycle and its relation to light intensity in senescent leaves of rice, two rice genotypes, namely, the psf mutant and its wild type, were used to determine their temporal differences in terms of the net photosynthetic rate (Pn), chlorophyll fluorescence parameters of PSII, and transcriptional levels of genes that participated in D1 protein turnover during leaf senescence. The results showed that compared to its wild type, the psf mutant had lower Pn, solar energy transmitting efficiency (Fv/Fm), and performance index on absorption basis (PIabs) than its wild type. Moreover, our results showed that the emergence of leaf senescent symptoms for psf mutant mainly depends on light intensity, instead of light quality in the field. The prevention of leaves from sugar starvation and oxidative damage contributes to the regulation of shaded-delayed leaf senescence in the psf mutant. Both non-phosphorylated and phosphorylated D1 proteins in leaves of the psf mutant were found decreasing with leaf senescence, while the non-phosphorylated one had more decrease. The initiation and subsequent progresses of leaf senescence induced by light were closely related to the D1 protein turnover in the leaves of the psf mutant. Partial shading treatment within an intact leaf concomitantly alleviated or even repaired the leaf premature senescent symptoms of the shaded area, which also suppressed D1 protein from being degraded. The key genes (OsPsbA and OsFtsHs) participated in D1 protein de novo synthesis and PSII repair cycle had lower expression during leaf senescence. Among different OsFtsH isoforms, OsFtsH2 exhibited the highest transcriptional levels, and it was also the isoform gene with the largest decline in the light treatment. Meanwhile, OsFtsH5 and OsFtsH7 were only down-regulated in conditions with high light intensity. Therefore, the inhabitation of D1 de novo synthesis and photo-damaged D1 degradation are mainly due to the down-regulation of OsPsbA and OsFtsH2. Other OsFtsH isoforms may play synergistic or complementary roles in D1 protein turnover and PSII repair cycle in light-induced leaf senescence.

Light intensity (I) fluctuates rapidly and is the most important environmental factor affecting photosynthesis. Accurate characterization of light-response curve of leaf-scale photosynthesis (PN-I curve) is fundamental for understanding PN-I relations at the whole-plant and ecosystem scales. A robust PN-I model should be accurate in reproducing PN-I curves over light-limited, light-saturated, and photoinhibitory I levels, and ideally returning key quantitative traits defining the curves, including initial slope of increase (α), dark respiration rate (RD), the maximum net photosynthetic rate (PNmax), and the corresponding saturation intensity (Isat). We need to improve a model reproduction of (1) PN-I responses over low I levels and (2) the widely reported decline of PN at photoinhibitory I levels. Our observation-modelling comparison, shown by the widely used non-rectangular hyperbolic model, led to (1) underestimation of RD, (2) overestimation of PNmax, and (3) failure in reproducing the photoinhibitory response when I surpassed the cultivar-specific Isat. In contrast, our model addressed the above limitations extremely well. The results highlighted the accuracy and robustness of our model, especially in (1) returning key traits defining the curve and (2) reproducing the curve over both low [i.e., 0-50 μmol(photon) m-2 s-1] and photoinhibitory I levels (i.e., beyond Isat).

Phenotypic differentiation of Abies alba was identified among selected provenances originating from the northern edge of this species’ natural geographic range. We posited that although the seed sources of the study populations were not geographically distant, progenies would differ with respect to growth, needle pigment concentration, and values of photochemical parameters in response to contrasting light conditions. Potted seedlings of six provenances were grown for two seasons under low light (LL, 40% of full irradiance) or high light (HL, 100% of full irradiance). The results showed that the provenances differed in diameter at root collar (DRC) and in relative growth rates of height (RGR). Seedlings grown in full light had a greater mean value of DRC than those in LL. LL increased total needle chlorophyll (Chltot) and carotenoid concentrations compared with HL, and Chltot was modified by the provenance of the seedlings. The provenance “Syców”, localized at the northern limit of the species range, showed the lowest value of maximal electron transfer rate (ETRmax) and lower values of growth parameters compared with the other study provenances. Relative growth rate, Chltot, and non-photochemical quenching of fluorescence (NPQ) were correlated with some climatic characteristics of seed stands and formed clusters indicating the local adaptation of the study populations. These results provide evidence of low intraspecific A. alba differentiation in terms of growth dynamics, photochemical capacity, and tolerance to different light regimes. The intraspecific diversity found in our study among the northern lead populations could be, however, important for the natural expansion of this species further north and for the selection of provenances to be used in the programme of the A. alba restoration in the Sudety Mountains, southern Poland, where decline of this species has been observed.

Accurately describing the light response curve of electron transport rate (J-I curve) and allocation of electron flow for ribulose biphosphate (RuBP) carboxylation (J C-I curve) and that for oxygenation (J O-I curve) is fundamental for modeling of light relations of electron flow at the whole-plant and ecosystem scales. The non-rectangular hyperbolic model (hereafter, NH model) has been widely used to characterize light response of net photosynthesis rate (A n; A n-I curve) and J-I curve. However, NH model has been reported to overestimate the maximum A n (A nmax) and the maximum J (J max), largely due to its asymptotic function. Meanwhile, few efforts have been delivered for describing J C-I and J O-I curves. The long-standing challenge on describing A n-I and J-I curves have been resolved by a recently developed A n-I and J-I models (hereafter, Ye model), which adopt a nonasymptotic function. To test whether Ye model can resolve the challenge of NH model in reproducing J-I, J C-I and J O-I curves over light-limited, light-saturated, and photoinhibitory I levels, we compared the performances of Ye model and NH model against measurements on two C3 crops (Triticum aestivum L. and Glycine max L.) grown in field. The results showed that NH model significantly overestimated the A nmax and J max for both species, which can be accurately obtained by Ye model. Furthermore, NH model significantly overestimated the maximum electron flow for carboxylation (J C-max) but not the maximum electron flow for oxygenation (J O-max) for both species, disclosing the reason underlying the long-standing problem of NH model-overestimation of J max and A nmax.

Suppression of photorespiration by low O2 concentrations (Method 1) and simultaneous measurements of gas exchange and chlorophyll fluorescence (Method 2) are often used to estimate leaf photorespiration rate (Rp) of C3 plants. However, it is largely unknown whether Method 1 and Method 2 can be used equivalently in estimating Rp. Using a field experiment on two wheat cultivars (T. aestivum JM22 and T. aestivum Z39-118) whose leaf gas exchange and chlorophyll fluorescence at low and normal O2 concentrations (2% versus 21% O2) were simultaneously measured across a wide range of light intensities (I), this study assessed the impacts of the two measures on Rp and its response under changing irradiance conditions. All the above quantities increased with the increasing I until reaching the cultivar-specific maximum values and the corresponding saturation light intensities. However, there were significant differences between Rp estimated by Method 1 and Method 2 at the I range from 150 to 2000 μmol m−2 s−1 for T. aestivum JM22 and from 150 to 1000 μmol m−2 s−1 for T. aestivum Z39-118. These findings demonstrated that the two methods cannot be used equivalently under changing irradiance conditions.

In dioecious woody plants, females often make a greater reproductive effort than male individuals at the cost of lower growth rate. We hypothesized that a greater reproductive effort of female compared with male Taxus baccata individuals would be associated with lower female photochemical capacity and higher activity of antioxidant enzymes. Differences between the genders would change seasonally and would be more remarkable under nutrient deficiency. Electron transport rate (ETRmax), saturation photosynthetic photon flux corresponding to maximum electron transport rate (PPFsat), quantum yield of PSII photochemistry at PPFsat (ΦPPFsat), and chlorophyll a fluorescence and activity of antioxidant enzymes were determined in needles of T. baccata female and male individuals growing in the experiment with or without fertilization. The effects of seasonal changes and fertilization treatment on photochemical parameters, photosynthetic pigments concentration, and antioxidant enzymes were more pronounced than the effects of between-sexes differences in reproductive efforts. Results showed that photosynthetic capacity expressed as ETRmax and ΦPPFsat and photosynthetic pigments concentrations decreased and non-photochemical quenching of fluorescence (NPQ) increased under nutrient deficiency. Fertilized individuals were less sensitive to photoinhibition than non-fertilized ones. T. baccata female and male individuals did not differ in photochemical capacity, but females showed higher maximum quantum yield of PSII photochemistry (Fv/Fm) than males. The activity of guaiacol peroxidase (POX) was also higher in female than in male needles. We concluded that larger T. baccata female reproductive effort compared with males was not at the cost of photochemical capacity, but to some extent it could be due to between-sexes differences in ability to protect the photosynthetic apparatus against photoinhibition with antioxidants.

Light-use efficiency (LUE) is an important parameter to assess light energy absorption of leaf. Especially, it is a key factor to affect production and quality of ecosystem. A model of LUE was developed based on a mechanistic model of light-response of photosynthesis. The maximum LUE (LUE光能利用效率(LUE)是评价植物叶片光能利用能力的重要参数,更是影响生态系统生产力大小和质量的主要因素.本文基于植物光合作用对光响应的机理模型推导出植物叶片的光能利用效率模型以及叶片的最大光能利用效率(LUE

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Oxygen effects have long been ambiguous: exacerbating, being indifferent to, or ameliorating the net photoinactivation of Photosystem II (PS II). We scrutinized the time course of PS II photoinactivation (characterized by rate coefficient k i) in the absence of repair, or when recovery (characterized by k r) occurred simultaneously in CO2 ± O2. Oxygen exacerbated photoinactivation per se, but alleviated it by mediating the utilization of electrons. With repair permitted, the gradual net loss of functional PS II during illumination of leaves was better described phenomenologically by introducing τ, the time for an initial k r to decrease by half. At 1500 μmol photons m(-2) s(-1), oxygen decreased the initial k r but increased τ. Similarly, at even higher irradiance in air, there was a further decrease in the initial k r and increase in τ. These observations are consistent with an empirical model that (1) oxygen increased k i via oxidative stress but decreased it by mediating the utilization of electrons; and (2) reactive oxygen species stimulated the degradation of photodamaged D1 protein in PS II (characterized by k d), but inhibited the de novo synthesis of D1 (characterized by k s), and that the balance between these effects determines the net effect of O2 on PS II functionality.

Models describing the relationship between effective quantum efficiency of PS II (ΦPSII) and irradiance (I) are routinely used to determine how irradiance influences effective quantum efficiency and photosynthetic electron transport rate (ETR). However, with no single model one can accurately describe the relationship betweenΦPSIIand I, and explain the interdependence betweenΦPSIIand biophysical properties of photosynthetic pigments, especially in plants growing under low level irradiances. Basing on the mechanistic model of photosynthetic electron transport rate we have developed the model of the relationship betweenΦPSIIandI. The new model reveals thatΦPSIIincreases with photochemistry (kP) and heat dissipation (kD). Furthermore, the values of key parameters calculated using the new model were compared with the values calculated with two other empirical models. The new model was perfectly fitted to the light-response curves ofΦPSII. The key calculated photosynthetic parameters: maximumΦPSII, maximumETRand their corresponding saturation irradiance were close to the measured values. In addition, our model associatesΦPSIIwith intrinsic features of photosynthetic pigments. We concluded thatΦPSIIdecreased with increasingIdue to the decrease in the effective absorption cross-section of photosynthetic pigments molecules.HighlightA model of the relationship between effective quantum efficiency of PS II (ΦPSII) and irradiance (I) has been developed. Using this new model it was found thatΦPSIIdecreased with increasingIdue to the decrease in the effective absorption cross-section of photosynthetic pigments molecules.AbbreviationsETRElectron transport rateETRmaxMaximum electron transport rateFSteady-state fluorescenceFm′Maximum fluorescence in the lightFvVariable fluorescence yield of the dark-adapted leafgiDegeneration of energy level of photosynthetic pigment molecules in the ground stateigkDegeneration of energy level of photosynthetic pigment molecules in the excited statekIIrradianceNPQNon-photochemical quenchingN0Total light-harvesting pigment moleculesPARsatSaturation irradiance corresponding toETRmaxkPRate of photochemical reactionkDRate of non-radiative heat dissipationPS IIPhotosystem IIaeInitial slope of light-response curve of electron transport rateα′Fraction of light absorbed by PS IIβ′Leaf absorptanceξ1Probability of photochemistryξ2Probability of non-radiative heat dissipationξ3Probability of fluorescenceσikEigen-absorption cross-section of photosynthetic pigment from ground stateito excited statekdue to light illuminationEffective optical absorption cross-section of photosynthetic pigment molecule from ground stateito excited statekdue to light illuminationφExciton-use efficiency in PS IIτAverage lifetime of the photosynthetic pigment molecules in the lowest excited stateΣPSIIEffective quantum efficiency of PS II

Tb3+-, Eu3+-activated, and Eu3+/Tb3+-coactivated oxyfluoride borogermanate scintillating glasses with the density of about 6.50 g/cm3 were successfully synthesized by a melt-quenching method. The structure and optical properties including transmittance, photoluminescence (excitation and emission spectra), photoluminescence decay, and X-ray excited luminescence behaviors were studied in detail. Our results reveal that the energy-transfer efficiency from Tb3+ to Eu3+ ions increases with an increase in Eu3+ concentration. The energy-transfer mechanism is also discussed by Dexter's and Reisfeld's semiexperimental methods.

Fast Ce3+-activated borogermanate scintillating glasses with the density of 5.58–5.67 g/cm3 were synthesized by melt quenching method in air atmosphere for the first time. The optical transmittance and X-ray absorption near edge spectroscopy results confirm that Ce4+ ions can be effectively reduced to Ce3+ ions by adding 0.31 mol% Si3N4 as a strong reducing agent during glass synthesis. The luminescence behavior under both ultraviolet and X-ray excitations indicate that the proposed Ce3+-activated borogermanate scintillating glasses have a broad emission band centered at 430 nm and a decay time of less than 25 ns. This will be of great interest in high-energy physics and nuclear physics engineering.

A mechanistic model of light-response of photosynthetic electron flow and its application YE Zi-Piao, HU Wen-Hai, XIAO Yi-An, FAN Da-Yong, YIN Jian-Hua, DUAN Shi-Hua, YAN Xiao-Hong, HE Li, and ZHANG Si-Si School of Life Sciences, Jinggangshan University, Ji’an, Jiangxi 343009, China; Maths & Physics College, Jinggangshan University, Ji’an, Jiangxi 343009, China; State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China; Rice Research Institute of Jiangxi Academy of Agricultural Sciences, Nanchang 330200, China; College of Forest Resources and Environment, Nanjing Forestry University, Nanjing 210037, China; and Agricultural College, Jiangxi Agricultural University, Nanchang 330045, China

Models describing the light response of photosynthetic electron transport rate (ETR) are routinely used to determine how light absorption influences energy, reducing power and yields of primary productivity; however, no single model is currently able to provide insight into the fundamental processes that implicitly govern the variability of light absorption. Here we present development and application of a new mechanistic model of ETR for photosystem II based on the light harvesting (absorption and transfer to the core 'reaction centres') characteristics of photosynthetic pigment molecules. Within this model a series of equations are used to describe novel biophysical and biochemical characteristics of photosynthetic pigment molecules and in turn light harvesting; specifically, the eigen-absorption cross-section and the minimum average lifetime of photosynthetic pigment molecules in the excited state, which describe the ability of light absorption of photosynthetic pigment molecules and retention time of excitons in the excited state but are difficult to be measured directly. We applied this model to a series of previously collected fluorescence data and demonstrated that our model described well the light response curves of ETR, regardless of whether dynamic down-regulation of PSII occurs, for a range of photosynthetic organisms (Abies alba, Picea abies, Pinus mugo and Emiliania huxleyi). Inherent estimated parameters (e. g. maximum ETR and the saturation irradiance) by our model are in very close agreement with the measured data. Overall, our mechanistic model potentially provides novel insights into the regulation of ETR by light harvesting properties as well as dynamical down-regulation of PSII. © 2012 Springer-Verlag Berlin Heidelberg.

A mathematical formulation of the relationship between optical absorption coefficient of photosynthetic pigment molecules and light intensity was developed. It showed that physical parameters of photosynthetic pigment molecule (i.e., light absorption cross-section of photosynthetic pigment molecule, its average lifetime in the excited state, total photosynthetic pigment molecules, the statistical weight, or degeneracy of energy level of photosynthetic pigment molecules in the ground state and in the excited state) influenced on both the light absorption coefficient and effective light absorption cross-section of photosynthetic pigment molecules. Moreover, it also showed that both the light absorption coefficient and effective light absorption cross-section of photosynthetic pigment molecules were not constant, they decreased nonlinearly with light intensity increasing. The occupation numbers of photosynthetic pigment molecules in the excited states increased nonlinearly with light intensity increasing.

A study of energy transfer was performed in gadolinium–terbium-doped silicate glasses at room temperature. Enhanced Tb3+ luminescence and a decrease in the Gd3+ emission were observed as a result of energy transfer from Gd3+ ions to Tb3+ ions. The energy transfer efficiencies, transfer probabilities as well as average donor–acceptor distances were also calculated. It is concluded that the energy transfer mechanism between Gd3+ and Tb3+ ion is mainly electric dipole–dipole in nature.

Spectroscopic properties of various concentrations Dy3+-doped silicate glasses were characterized by excitation and emission spectra. The optimal doping concentration of Dy3+ ions was found to be 3.0 wt%, and the nature of resonance energy transfer was confirmed to be electric dipole–dipole interaction according to Huang’s rule. Simulation of white-light for these glasses was also performed by varying the excitation wavelength. The results show that the white-light luminescence color could be tuned to various wavelength excitations, and the present silicate glass is more suitable for generation of white-light for blue LED chips.

The calculated maximum net photosynthetic rate (P N) at saturation irradiance (I m) of 1 314.13 µmol m−2 s−1 was 25.49 µmol(CO2) m−2 s−1, and intrinsic quantum yield at zero irradiance was 0.103. The results fitted by nonrectangular hyperbolic model, rectangular hyperbolic method, binomial regression method, and the new model were compared. The maximum P N values calculated by nonrectangular hyperbolic model and rectangular hyperbolic model were higher than the measured values, and the I m calculated by nonrectangular hyperbolic model and rectangular hyperbolic model were less than measured values. Results fitted by new model showed that the response curve of P N to I was nonlinear at low I for Oryza sativa, P N increased nonlinearly with I below saturation value. Above this value, P N decreased nonlinearly with I.

A new mechanistic model of the photosynthesis-light response is developed based on photosynthetic electron transport via photosystem II (PSII) to specifically describe light-harvesting characteristics and associated biophysical parameters of photosynthetic pigment molecules. This model parameterizes 'core' characteristics not only of the light response but also of difficult to measure physical parameters of photosynthetic pigment molecules in plants. Application of the model to two C3 and two C4 species grown under the same conditions demonstrated that the model reproduced extremely well (r(2)0.992) the light response trends of both electron transport and CO2 uptake. In all cases, the effective absorption cross-section of photosynthetic pigment molecules decreased with increasing light intensity, demonstrating novel operation of a key mechanism for plants to avoid high light damage. In parameterizing these previously difficult to measure characteristics of light harvesting in higher plants, the model provides a new means to understand the mechanistic processes underpinning variability of CO2 uptake, for example, photosynthetic down-regulation or reversible photoinhibition induced by high light and photoprotection. However, an important next step is validating this parameterization, possibly through application to less structurally complex organisms such as single-celled algae.

Simultaneous measurements of leaf gas exchange and chlorophyll fluorescence for Koelreuteria paniculata Laxm. at 380 ± 5. 6 and 600 ± 8. 5 μmol mol -1 were conducted, and the photosynthetic electron flow via photosystem II (PSII) to photosynthesis, photorespiration, and other electron-consuming processes were calculated. The results showed that the photosynthetic electron flow associated with carboxylation (J c), oxygenation (J o), and other electron-consuming processes (J r) were 72. 7, 45. 7, and 29. 4 μmol(e -) m -2 s -1 at 380 μmol mol -1, respectively; and 86. 1, 35. 3, and 48. 2 μmol(e -) m -2 s -1 at 600 μmol mol -1, respectively. Our results revealed that other aspects associated with electronconsuming processes, except for photosynthesis and respiration, were neither negligible nor constant under photorespiratory conditions. Using maximum net photosynthetic rate (P max), day respiration (R), photorespiration rate (R l), and maximum electron flow via PSII (J max), the use efficiency of electrons via PSII at saturation irradiance to fix CO 2 was calculated. The calculated results showed that the use efficiency of electrons via PSII to fix CO 2 at 600 μmo l mol -1 was almost as effective as that at 380 μmol mol -1, even though more electrons passed through PSII at 600 μmol mol -1 than at 380 μmol mol -1. © 2012 Springer Science+Business Media B.V.

Transparent and colorless CeO2-activated borogermanate glasses with about 5.60 g/cm3 were successfully synthesized by a melt-quenching method in air atmosphere. Both the optical transmittance and X-ray absorption near edge spectroscopy (XANES) spectra confirm that Ce4+ can be effectively reduced to its trivalent state, i.e. Ce3+ ions, by minor quantity of Si3N4 addition as a strong reducing agent. The luminescence characteristics excited by both ultraviolet and X-ray light were studied and the optimal content of Si3N4 was determined. The developed dense Ce3+-activated borogermanate glasses is featured with a broad emission band centered at 430 nm and a decay time of about 30 ns, which will be a promising candidate to scintillating crystals and ceramics.