The authors treat a manuscript missal unknown to this day by experts, which is housed at the Scientific Library in Olomouc (M III 106). After having analysed the manuscript in the line of codicology (Š. Kohout), history of arts (J. Hrbačova), and musicology (S. Červenka), they conclude that this codex was intended for the needs of the Benedictine Convent in Opatovice nad Labem. It was created shortly after the year 1354, its illuminations are the work of a Prague workshop associated with the court of King Charles IV, which participated in the production of a series of exclusive manuscripts, e. g. Liber viaticus of the Bishop Johannes Noviforensis. The Viaticus and the missal of Opatovice are on the same line in terms of decoration. The missal was probably ordered by the then Benedictine Abbot Neplach who maintained frequent official contacts with the Bishop occupying the office of chancellor to Charles IV.
The authors treat a manuscript missal unknown to this day by experts, which is housed at the Scientific Library in Olomouc (M III 106). After having analysed the manuscript in the line of codicology (Š. Kohout), history of arts (J. Hrbačova), and musicology (S. Červenka), they conclude that this codex was intended for the needs of the Benedictine Convent in Opatovice nad Labem. It was created shortly after the year 1354, its illuminations are the work of a Prague workshop associated with the court of King Charles IV, which participated in the production of a series of exclusive manuscripts, e. g. Liber viaticus of the Bishop Johannes Noviforensis. The Viaticus and the missal of Opatovice are on the same line in terms of decoration. The missal was probably ordered by the then Benedictine Abbot Neplach who maintained frequent official contacts with the Bishop occupying the office of chancellor to Charles IV.
Chloroplast PSII photochemical efficiency is upregulated more rapidly than CO2 assimilation during photosynthesis induction, suggesting the existence of other electron sinks than that of CO2 assimilation. We hypothesized that the mitochondrial alternative oxidase (AOX) pathway could be such a sink. Inhibition of the AOX restricted light activation of the malate-oxaloacetate shuttle and caused an excessive reduction of PSI acceptor side and substantial accumulation of QA-, hindering the photosynthetic linear electron transport rate (ETR) and leading to an imbalance between light energy absorption and exploitation during photosynthetic induction. ETR limitation also restricted the formation of thylakoid pH gradient, evidenced by a decreased de-epoxidation of the xanthophyll cycle, thus preventing nonphotochemical quenching. Delayed CO2 assimilation due to thylakoid pH gradient restriction was partially reversed by exogenous ATP application. The AOX pathway acts as a photosynthetic electron sink, protecting the photosynthetic apparatus against photoinhibition and accelerating the induction of CO2 assimilation during photosynthetic induction in Rumex K-1 leaves.
Accurate and nondestructive methods to determine individual leaf areas of plants are a useful tool in physiological and agronomic research. Determining the individual leaf area (LA) of rose (Rosa hybrida L.) involves measurements of leaf parameters such as length (L) and width (W), or some combinations of these parameters. Two-year investigation was carried out during 2007 (on thirteen cultivars) and 2008 (on one cultivar) under greenhouse conditions, respectively, to test whether a model could be developed to estimate LA of rose across cultivars. Regression analysis of LA vs. L and W revealed several models that could be used for estimating the area of individual rose leaves. A linear model having L×W as the independent variable provided the most accurate estimate (highest r2, smallest MSE, and the smallest PRESS) of LA in rose. Validation of the model having L×W of leaves measured in the 2008 experiment coming from other cultivars of rose showed that the correlation between calculated and measured rose LA was very high. Therefore, this model can estimate accurately and in large quantities the LA of rose plants in many experimental comparisons without the use of any expensive instruments. and Y. Rouphael ... [et al.].
A mathematical model for photoinhibition of leaf photosynthesis was developed by formalising the assumptions that (1) the rate of photoinhibition is proportional to irradiance; and (2) the rate of recovery, derived from the formulae for a pseudo first-order process, is proportional to the extent of inhibition. The photoinhibition model to calculate initial photo yield is integrated into a photosynthesis-stomatal conductance (gs) model that combines net photosynthetic rate (PN), transpiration rate (E), and gs, and also the leaf energy balance. The model was run to simulate the diurnal courses of PN, E, gs, photochemical efficiency, i.e., ratio of intercellular CO2 concentration and CO2 concentration over leaf surface (Ci/Cs), and leaf temperature (T1) under different irradiances, air temperature, and humidity separately with fixed time courses of others. When midday depression occurred under high temperature, gs decreased the most and E the least. The duration of midday depression of gs was the longest and that in E the shortest. E increased with increasing vapour pressure deficit (VPD) initially, but when VPD exceeded a certain value, it decreased with increasing VPD; this was caused by a rapid decrease in gs. When air temperature exceeded a certain value, an increase in solar irradiance raised T1 and the degree of midday depression. High solar radiation caused large decrease in initial photon efficiency (α). PN, E, and gs showed reasonable decreases under conditions causing photoinhibition compared with non-photoinhibition condition under high irradiance. The T1 under photoinhibition was higher than that under non-photoinhibition conditions, which was evident under high solar irradiance around noon. The decrease in Ci/Cs at midday implies that stomatal closure is a factor causing midday depression of photosynthesis. and Qiang Yu, J. Goudriaan, Tian-Duo Wang.
Winter wheat plants were grown in open top chambers either at 365 µmol mol-1 (AC) or at 700 µmol mol-1 (EC) air CO2 concentrations. The photosynthetic response of flag leaves at the beginning of flowering and on four vertical leaf levels at the beginning of grain filling were measured. Net photosynthetic rates (PN) were higher at both developmental phases in plants grown at EC coupled with larger leaf area and photosynthetic pigment contents. The widely accepted Farquhar net photosynthesis model was parameterised and tested using several observed data. After parameterisation the test results corresponded satisfactorily with observed values under several environmental conditions. and N. Harnos, Z. Tuba, K. Szente.
The paper presents a simple box model simulating the temporal variation of atmospheric 13CO2 concentration, atmospheric CO2 mixing ratio and 13C content of plant material. The model is driven by observed meteorological and measured biosphere-atmosphere CO2 exchange data. The model was calibrated and validated using measurements from a Hungarian atmospheric monitoring station. The simulated atmospheric stable carbon isotope ratio data agreed well with the measured ratios considering both the magnitude and the seasonal dynamics. Observed deviations between the measured and simulated δ13Cair values were systematically negative in winters, while deviations were random in sign and smaller by an order of magnitude during periods when the vegetation was photosynthetically active. This difference, supported by a significant correlation between the deviation and modeled fossil fuel contributions to CO2 concentration, suggests the increased contribution of 13C-depleted fossil fuel CO2 from heating and the lower boundary layer heights during winter. and D. Hidy ... [et al.].
Theoretical modelling is often overlooked in photosynthesis research even if it can significantly help with understanding of explored system. A new model of light-induced photosynthetic reactions occurring in and around thylakoid membrane is introduced here and used for theoretical modelling of not only the light-induced chlorophyll (Chl) a fluorescence rise (FLR; the O-J-I-P transient), reflecting function of photosystem II (PSII), but also of the 820 nmtransmittance signal (I820), reflecting function of photosystem I (PSI) and plastocyanin (PC), paralleling the FLR. Correctness of the model was verified by successful simulations of the FLR and I820 signal as measured with the control (no treatment) sample but also as measured with 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone- (inhibits electron transport in cytochrome b 6/f) and methylviologen- (accepts electrons from iron-sulphur cluster of PSI) treated samples and with the control sample upon different intensities of excitation light. From the simulations performed for the control sample, contribution of the oxidised donor of PSI, P700, and oxidised PC to the I820 signal minimum (reflects maximal accumulations of the two components) was estimated to be 75% and 25%, respectively. Further in silico experiments showed that PC must be reduced in the dark, cyclic electron transport around PSI must be considered in the model and activation of ferredoxin-NADP+-oxidoreductase (FNR) also affects the FLR. Correct simulations of the FLR and I820 signal demonstrate robustness of the model, confirm that the electron transport reactions occurring beyond PSII affect the shape of the FLR, and show usefulness and perspective of theoretical approach in studying of the light-induced photosynthetic reactions.