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2562. Fitting net photosynthetic light-response curves with Microsoft Excel - a critical look at the models
- Creator:
- Lobo, F. de A., de Barros, M. P., Dalmagro, H. J., Dalmolin, Â. C., Pereira, W. E., de Souza, É. C., Vourlitis, G. L., and Rodríguez Ortíz, C. E.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- fotosyntéza, photosynthesis, curve fitting, iteration, nonlinear regression, PN/I curve, Solver function, 2, and 581
- Language:
- Multiple languages
- Description:
- In this study, we presented the most commonly employed net photosynthetic light-response curves (PN/I curves) fitted by the Solver function of Microsoft Excel. Excel is attractive not only due to its wide availability as a part of the Microsoft Office suite but also due to the increased level of familiarity of undergraduate students with this tool as opposed to other statistical packages. In this study, we explored the use of Excel as a didactic tool which was built upon a previously published paper presenting an Excel Solver tool for calculation of a net photosynthetic/chloroplastic CO2-response curve. Using the Excel spreadsheets accompanying this paper, researchers and students can quickly and easily choose the best fitted PN/I curve, selecting it by the minimal value of the sum of the squares of the errors. We also criticized the misuse of the asymptotic estimate of the maximum gross photosynthetic rate, the light saturation point estimated at a specific percentile of maximum net photosynthetic rate, and the quantum yield at zero photosynthetic photon flux density and we proposed the replacement of these variables by others more directly linked to plant ecophysiology. and F. de A. Lobo ... [et al.].
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
2563. Flavonoid responses in wheat grown at elevated CO2: green versus senescent leaves
- Creator:
- Peñuelas, J., Estiarte, M., and Kimball, B. A.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- carbon based secondary compounds (CBSC), isoorientin, leaf age, litter, phenolics, tricin, and Triticum aestivum
- Language:
- Multiple languages
- Description:
- We compared flavonoids in green, mature, and senescing flag leaves of wheat grown under ambient (AC - 370 μmol mol-1) and elevated (EC - 550 μmol mol-1) concentrations of CO2 in a FACE (Free Air CO2 Enrichment) system. The concentrations of flag leaf flavonoids (e.g., isoorientin and tricin) decreased to one third in mature leaves, and the majoritary isoorientin almost disappeared in senescing leaves. Flavonoid concentrations increased in green well-developed flag leaves under EC (46 % isoorientin and 55 % tricin), whereas the differences disappeared in mature and senescing flag leaves. Predictions of changes in litter phenolic concentrations and their effects on decomposition rates under EC based on changes in green leaves need to be revised. and J. Peñuelas, M. Estiarte, B. A. Kimball.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
2564. Flindt, R. (ed ): Biologie in Zahlen
- Creator:
- Šesták, Z.
- Format:
- Type:
- model:internalpart and TEXT
- Language:
- Multiple languages
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
2565. Fluorescence emission, energy transfer and structure of pliycobílisomes from NostocflagelUforme Born. et Flah. during dissociation
- Creator:
- Lu, Rong-zhao and Liu, Bin
- Format:
- Type:
- model:internalpart and TEXT
- Language:
- Multiple languages
- Description:
- Changes in fluorescence emission spectra (293 and 77 K) of phycobilisomes from Nostoc flagelUforme during dissociation in phosphate buffer of various molarity were studied. There were three bands in 77 K fluorescence emission spectra of partly dissociated phycobilisomes: F648, F666 and F686, characteristic of C-phycocyanin (C-PC), allophycocyanin (APC) and allophycocyanin-B (APC-B), respectively. In severely dissociated phycobilisomes, the F666 band was veiy weak, which indicated that linkage between C-PC and APC was severely dissociated, most of the energy trapped by C-PC could not be transferred to APC, but some of it could be transferred directly to APC-B. The phycobiliproteins in these phycobilisomes constitute an energy transfer chain: PEC^C;PC-»APC-»AP^-B. A new model of phycobilisome structure is suggested, in which some C-PC contact directly with APC and others contact with APC-B.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
2566. Fluorescence excitation spectra of drought resistant and sensitive genotypes of triticale and maize
- Creator:
- Grzesiak, M. T., Rzepka, A., Hura, T., Grzesiak, S., Hura, K., Filek, W., and Skoczowski, A.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- Triticale and Zea
- Language:
- Multiple languages
- Description:
- An influence of soil drought (7 or 14 d) and 7 d recovery on changes of leaf fluorescence excitation spectra at wavelengths of 450, 520, 690, and 740 nm (F450, F520, F690, F740) for drought resistant and sensitive genotypes of triticale and maize was compared. In non-stressed plants the differences between maize and triticale were observed for F450 and F520, but not for F690 and F740. Drought caused the increase in F450, F520, and F690 and this increase was more distinct for drought sensitive genotypes. After re-hydration, chlorophyll fluorescence mostly recovered to values of control plants. Drought caused significant increase in F690/F740 but not in F450/F690 and F450/F520. For triticale, highest increase in F690/F740 was observed in the 4th and 7th leaves of resistant genotype and contrarily in maize for the sensitive one. After recovery, the F450/F520, F450/F690, and F690/F740 ratios mostly returned to values of control plants. and M. T. Grzesiak ... [et al.].
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
2567. Fluorescence hole-burning and site-selective studies of LHCII
- Creator:
- Gibasiewicz, K., Rutkowski, M., and van Grondelle, R.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- chlorophyll, fluorescence, light-harvesting complex II, line-narrowing, and zero-phonon line
- Language:
- Multiple languages
- Description:
- We report the observation of two types of changes in fluorescence spectra of LHCII at 4.2 K following intense illumination of the sample with a spectrally narrow laser beam at wavelengths between 678 and 686 nm. Nonspecific changes (burning-wavelength independent) are characterized by two relatively broad bands: a positive one at - 678.7 nm and a negative one at - 680.8 nm. These changes reveal a -1.3-nm blue shift of the distribution of final emitters in LHCII, from 680.3 nm to - 679.0 nm independent of the excitation wavelength. Specific fluorescence changes (burning-wavelength dependent) are characterized by a sharp hole exactly at the burning wavelength, and positive changes directly to the shorter-and longer-wavelength side of the narrow hole. The negative changes are interpreted as zero-phonon holes, while the positive features are assigned to non-photochemical products. In the low-burning intensity experiment, in addition to the zero-phonon holes, we observed also the holes to the longer wavelength of the zero-phonon hole, which were assigned to a sum of phonon and pseudo-phonon side bands. The shapes of these extra holes are identical to the shapes of the holes revealed in the fluorescence line narrowing experiment. On the basis of the low-burning intensity experiment we estimated the upper limit of the electron-phonon coupling strength for LHCII, characterized by a Huang-Rhys factor of 1.5. and K. Gibasiewicz, M. Rutkowski, R. van Grondelle.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
2568. Fluorescence imaging of light acclimation of brazilian atlantic forest tree species
- Creator:
- Dos Anjos, L., Oliva, M. A., and Kuki, K. N.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- botanika, botany, chlorophyll fluorescence, light stress, photochemical efficiency, thermal dissipation, xanthophyll cycle, 2, and 58
- Language:
- Multiple languages
- Description:
- In the pursuit of knowledge on the biological behavior of Brazilian Atlantic Forest tree species, this study evaluated the susceptibility of the light-demanding species, Schinus terebinthifolia Raddi., Pseudobombax grandiflorum (Cav.) A. Robyns and Joannesia princeps Vell., and of the shade-tolerant species, Hymenaea courbaril L. var. stilbocarpa and Lecythis pisonis Camb, to photoinhibition and acclimation capacity. These species were first cultivated under two irradiance conditions, I20 (20% direct sunlight radiation) and I100 (all-sky or direct sunlight) and then transferred from I20 to I100. The effects of the sudden increase in light radiation intensity on photosynthetic activity were then evaluated through chlorophyll (Chl) fluorescence imaging, HPLC xanthophylls analysis, and cell membrane lipid peroxidation measurements. Light-demanding species were found to present a higher photochemical efficiency and higher acclimation capacity under high light irradiance than shade-tolerant species. The higher photoinhibition tolerance observed in light-demanding species was associated to their higher capacity for photochemical dissipation and dissipation of excess excitation energy via the xanthophyll cycle, leading to a lower ROS generation. The obtained results suggested that a knowledge of acclimation capacity, by means of Chl fluorescence imaging yields, is a useful indicator of species successional grouping., L. Dos Anjos, M. A. Oliva, and K. N. Kuki., and Obsahuje bibliografii
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
2569. Fluorescence induction of photosynthetic bacteria
- Creator:
- Sipka, G., Kis, M., Smart, J. L., and Maróti, P.
- Format:
- print, bez média, and svazek
- Type:
- model:article and TEXT
- Subject:
- přenos elektronů, electron transfer, bacterial photosynthesis, fluorescence transients, intact cells, 2, and 581
- Language:
- Multiple languages
- Description:
- The kinetics of bacteriochlorophyll fluorescence in intact cells of the purple nonsulfur bacterium Rhodobacter sphaeroides were measured under continuous and pulsed actinic laser diode (808 nm wavelength and maximum 2 W light power) illumination on the micro- and millisecond timescale. The fluorescence induction curve was interpreted in terms of a combination of photochemical and triplet fluorescence quenchers and was demonstrated to be a reflection of redox changes and electron carrier dynamics. By adjustment of the conditions of single and multiple turnovers of the reaction center, we obtained 11 ms-1 and 120 μs-1 for the rate constants of cytochrome c23+ detachment and cyclic electron flow, respectively. The effects of cytochrome c2 deletion and chemical treatments of the bacteria and the advantages of the fluorescence induction study on the operation of the electron transport chain in vivo were discussed., G. Sipka, M. Kis, J. L. Smart, P. Maróti., and Obsahuje bibliografické odkazy
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
2570. Fluorescence lifetime imaging (FLI) in real-time - a new technique in photosynthesis research
- Creator:
- Holub, O., Seufferheld, M. J., Gohlke, C., Govindjee, and Clegg, R. M.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- Arabidopsis, Chlamydomonas, FLIM, frequency domain, homodyne, microscopy, modulation, phase, photosystems 1 and 2, stress, time domain, and Zea
- Language:
- Multiple languages
- Description:
- We describe an instrument that allows the rapid measurement of fluorescence lifetime-resolved images of leaves as well as sub-cellular structures of intact plants or single cells of algae. Lifetime and intensity fluorescence images can be acquired and displayed in real time (up to 55 lifetime-resolved images per s). Our imaging technique therefore allows rapid measurements that are necessary to determine the fluorescence lifetimes at the maximum (P level) fluorescence following initial illumination during the chlorophyll (Chl) a fluorescence transient (induction) in photosynthetic organisms. We demonstrate the application of this new instrument and methodology to measurements of: (1) Arabidopsis thaliana leaves showing the effect of dehydration on the fluorescence lifetime images; (2) Zea mays leaves showing differences in the fluorescence lifetimes due to differences in the bundle sheath cells (having a higher amount of low yield photosystem 1) and the mesophyll cells (having a higher amount of high yield photosystem 2); and (3) single cells of wild type Chlamydomonas reinhardtii and its non-photochemical quenching mutant NPQ2 (where the conversion of zeaxanthin to violaxanthin is blocked), with NPQ2 showing lowered lifetime of Chl a fluorescence. In addition to the lifetime differences referred to in (1) and (2), structural dependent heterogeneities in the fluorescence lifetimes were generally observed when imaging mesophyll cells in leaves. and O. Holub ... [et al.].
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public