Alternating electric current and alternating electromagnetic fields revolutionized physics and engineering and led to many technologies that shape modern life. Despite these undisputable achievements that have been reached using stimulation by harmonic oscillations over centuries, applications in biology remain rare. Photosynthesis research is uniquely suited to unleash this potential because light can be modulated as a harmonic function, here sinus. Understanding the response of photosynthetic organisms to sinusoidal light is hindered by the complexity of dynamics that such light elicits, and by the mathematical apparatus required for understanding the signals in the frequency domain which, although well-established and simple, is outside typical curricula in biology. Here, we approach these challenges by presenting a mathematical model that was designed specifically to simulate the response of photosynthetic light reactions to light which oscillates with periods that often occur in nature. The independent variables of the model are the plastoquinone pool, the photosystem I donors, lumen pH, ATP, and the chlorophyll fluorescence (ChlF) quencher that is responsible for the qE non-photochemical quenching. Dynamics of ChlF emission, rate of oxygen evolution, and non-photochemical quenching are approximated by dependent model variables. The model is used to explain the essentials of the frequency-domain approaches up to the level of presenting Bode plots of frequency-dependence of ChlF. The model simulations were found satisfactory when compared with the Bode plots of ChlF response of the green alga Chlamydomonas reinhardtii to light that was oscillating with a small amplitude and frequencies between 7.8 mHz and 64 Hz.

• Klíčová slova
• Chlorophyll fluorescence, Fourier analysis, Frequency domain, Harmonic light, Non-photochemical quenching, Oxygen evolution, Plastoquinone pool,
• MeSH
• biologické modely MeSH
• Chlamydomonas reinhardtii fyziologie   účinky záření   MeSH
• chlorofyl metabolismus   MeSH
• fotosyntéza * fyziologie   účinky záření   MeSH
• fotosystém I (proteinový komplex) metabolismus   MeSH
• světlo * MeSH
• teoretické modely MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• chlorofyl MeSH
• fotosystém I (proteinový komplex) MeSH

Our study attempts to address the following questions: among numerous photosynthetic modules, which parameters notably influence the rapid chlorophyll fluorescence (ChlF) rise, the so-called O-J-I-P transient, in conjunction with the P515 signal, as these two records are easily obtained and widely used in photosynthesis research, and how are these parameters ranked in terms of their importance? These questions might be difficult to answer solely through experimental assays. Therefore, we employed an established photosynthesis model. Firstly, we utilized the model to simulate the measured rapid ChlF rise and P515 kinetics simultaneously. Secondly, we employed the sensitivity analysis (SA) tool by randomly altering model parameters to observe their effects on model output variables. Thirdly, we systematically identified significant parameters for both or one of the kinetics across various scenarios. A novel aspect of our study is the application of the Morris method, a global SA tool, to simultaneously assess the significance of model parameters in shaping both or one of the kinetics. The Morris SA technique enables the quantification of how much a specific parameter affects O-J-I-P transient during particular time intervals (e.g., J, I, and P steps). This allowed us to theoretically analyze which step is more significantly influenced by the parameter. In summary, our study contributes to the field by providing a comprehensive analysis of photosynthesis kinetics and emphasizing the importance of parameter selection in modelling this process. These findings can inform future research efforts aimed at improving photosynthesis models and advancing our understanding of photosynthetic processes.

• MeSH
• biologické modely MeSH
• chlorofyl a * metabolismus   MeSH
• chlorofyl metabolismus   MeSH
• fluorescence MeSH
• fotosyntéza * fyziologie   MeSH
• kinetika MeSH
• tylakoidy * metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• chlorofyl a * MeSH
• chlorofyl MeSH

Quantitative measurement of light intensity is a key step in ensuring the reliability and the reproducibility of scientific results in many fields of physics, biology, and chemistry. The protocols presented so far use various photoactive properties of manufactured materials. Here, leaves are introduced as an easily accessible green material to calibrate light intensity. The measurement protocol consists in monitoring the chlorophyll fluorescence of a leaf while it is exposed to a jump of constant light. The inverse of the characteristic time of the initial chlorophyll fluorescence rise is shown to be proportional to the light intensity received by the leaf over a wide range of wavelengths and intensities. Moreover, the proportionality factor is stable across a wide collection of plant species, which makes the measurement protocol accessible to users without prior calibration. This favorable feature is finally harnessed to calibrate a source of white light from exploiting simple leaves collected from a garden.

• Klíčová slova
• actinometry, fluorescence, green materials, irradiance, light intensity, photoactive materials,
• Publikační typ
• časopisecké články MeSH

To keep up with the growth of human population and to circumvent deleterious effects of global climate change, it is essential to enhance crop yield to achieve higher production. Here we review mathematical models of oxygenic photosynthesis that are extensively used, and discuss in depth a subset that accounts for diverse approaches providing solutions to our objective. These include models (1) to study different ways to enhance photosynthesis, such as fine-tuning antenna size, photoprotection and electron transport; (2) to bioengineer carbon metabolism; and (3) to evaluate the interactions between the process of photosynthesis and the seasonal crop dynamics, or those that have included statistical whole-genome prediction methods to quantify the impact of photosynthesis traits on the improvement of crop yield. We conclude by emphasizing that the results obtained in these studies clearly demonstrate that mathematical modelling is a key tool to examine different approaches to improve photosynthesis for better productivity, while effective multiscale crop models, especially those that also include remote sensing data, are indispensable to verify different strategies to obtain maximized crop yields.

• Klíčová slova
• C4 rice, Improving photosynthesis and crop yield, Leaf and crop models, Photorespiration bypasses, Photosynthesis models, Synthetic biology,
• MeSH
• biologické modely MeSH
• fotosyntéza * fyziologie   MeSH
• listy rostlin * fyziologie   metabolismus   růst a vývoj   MeSH
• teoretické modely MeSH
• transport elektronů MeSH
• zemědělské plodiny * růst a vývoj   genetika   fyziologie   MeSH
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH

Plants have evolved multiple regulatory mechanisms to cope with natural light fluctuations. The interplay between these mechanisms leads presumably to the resilience of plants in diverse light patterns. We investigated the energy-dependent nonphotochemical quenching (qE) and cyclic electron transports (CET) in light that oscillated with a 60-s period with three different amplitudes. The photosystem I (PSI) and photosystem II (PSII) function-related quantum yields and redox changes of plastocyanin and ferredoxin were measured in Arabidopsis thaliana wild types and mutants with partial defects in qE or CET. The decrease in quantum yield of qE due to the lack of either PsbS- or violaxanthin de-epoxidase was compensated by an increase in the quantum yield of the constitutive nonphotochemical quenching. The mutant lacking NAD(P)H dehydrogenase (NDH)-like-dependent CET had a transient significant PSI acceptor side limitation during the light rising phase under high amplitude of light oscillations. The mutant lacking PGR5/PGRL1-CET restricted electron flows and failed to induce effective photosynthesis control, regardless of oscillation amplitudes. This suggests that PGR5/PGRL1-CET is important for the regulation of PSI function in various amplitudes of light oscillation, while NDH-like-CET acts' as a safety valve under fluctuating light with high amplitude. The results also bespeak interplays among multiple photosynthetic regulatory mechanisms.

• Klíčová slova
• alternative electron transports, cyclic electron transport, fluctuating light, rapidly reversible nonphotochemical quenching, regulation,
• MeSH
• Arabidopsis * fyziologie   genetika   účinky záření   metabolismus   MeSH
• ferredoxiny metabolismus   MeSH
• fotosyntetická reakční centra (proteinové komplexy) metabolismus   genetika   MeSH
• fotosyntéza * fyziologie   účinky záření   MeSH
• fotosystém I (proteinový komplex) * metabolismus   MeSH
• fotosystém II (proteinový komplex) * metabolismus   MeSH
• membránové proteiny * MeSH
• mutace MeSH
• oxidace-redukce MeSH
• plastocyanin metabolismus   MeSH
• proteiny huseníčku * metabolismus   genetika   MeSH
• světlo * MeSH
• transport elektronů MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• ferredoxiny MeSH
• fotosyntetická reakční centra (proteinové komplexy) MeSH
• fotosystém I (proteinový komplex) * MeSH
• fotosystém II (proteinový komplex) * MeSH
• membránové proteiny * MeSH
• PGR5 protein, Arabidopsis MeSH Prohlížeč
• PGRL1 protein, Arabidopsis MeSH Prohlížeč
• plastocyanin MeSH
• proteiny huseníčku * MeSH

Despite the need for quantitative measurements of light intensity across many scientific disciplines, existing technologies for measuring light dose at the sample of a fluorescence microscope cannot simultaneously retrieve light intensity along with spatial distribution over a wide range of wavelengths and intensities. To address this limitation, we developed two rapid and straightforward protocols that use organic dyes and fluorescent proteins as actinometers. The first protocol relies on molecular systems whose fluorescence intensity decays and/or rises in a monoexponential fashion when constant light is applied. The second protocol relies on a broad-absorbing photochemically inert fluorophore to back-calculate the light intensity from one wavelength to another. As a demonstration of their use, the protocols are applied to quantitatively characterize the spatial distribution of light of various fluorescence imaging systems, and to calibrate illumination of commercially available instruments and light sources.

• MeSH
• fluorescence MeSH
• fluorescenční barviva * chemie   MeSH
• fluorescenční mikroskopie metody   MeSH
• fluorescenční spektrometrie MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• fluorescenční barviva * MeSH

In natural environments, plants are exposed to rapidly changing light. Maintaining photosynthetic efficiency while avoiding photodamage requires equally rapid regulation of photoprotective mechanisms. We asked what the operation frequency range of regulation is in which plants can efficiently respond to varying light. Chlorophyll fluorescence, P700, plastocyanin, and ferredoxin responses of wild-types Arabidopsis thaliana were measured in oscillating light of various frequencies. We also investigated the npq1 mutant lacking violaxanthin de-epoxidase, the npq4 mutant lacking PsbS protein, and the mutants crr2-2, and pgrl1ab impaired in different pathways of the cyclic electron transport. The fastest was the PsbS-regulation responding to oscillation periods longer than 10 s. Processes involving violaxanthin de-epoxidase dampened changes in chlorophyll fluorescence in oscillation periods of 2 min or longer. Knocking out the PGR5/PGRL1 pathway strongly reduced variations of all monitored parameters, probably due to congestion in the electron transport. Incapacitating the NDH-like pathway only slightly changed the photosynthetic dynamics. Our observations are consistent with the hypothesis that nonphotochemical quenching in slow light oscillations involves violaxanthin de-epoxidase to produce, presumably, a largely stationary level of zeaxanthin. We interpret the observed dynamics of photosystem I components as being formed in slow light oscillations partially by thylakoid remodeling that modulates the redox rates.

• Klíčová slova
• cyclic electron transport, frequency analysis, nonphotochemical quenching, photosynthetic oscillation, regulation,
• MeSH
• Arabidopsis * metabolismus   MeSH
• chlorofyl metabolismus   MeSH
• fotosyntetická reakční centra (proteinové komplexy) * genetika   MeSH
• fotosyntéza fyziologie   MeSH
• fotosystém II (proteinový komplex) metabolismus   MeSH
• membránové proteiny metabolismus   MeSH
• mutace genetika   MeSH
• proteiny huseníčku * genetika   metabolismus   MeSH
• světlo MeSH
• světlosběrné proteinové komplexy metabolismus   MeSH
• transport elektronů MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Research Support, U.S. Gov't, Non-P.H.S. MeSH
• Názvy látek
• chlorofyl MeSH
• fotosyntetická reakční centra (proteinové komplexy) * MeSH
• fotosystém II (proteinový komplex) MeSH
• membránové proteiny MeSH
• PGR5 protein, Arabidopsis MeSH Prohlížeč
• PGRL1 protein, Arabidopsis MeSH Prohlížeč
• proteiny huseníčku * MeSH
• světlosběrné proteinové komplexy MeSH

The light-induced transthylakoid membrane potential (ΔΨ) can not only drive the ATP synthesis through the ATP-synthase in chloroplasts but serve as an essential modifier in the acclimation of photosynthesis to fluctuating light conditions. It has been manifested that during photosynthesis, the light-induced ΔΨ is responsive to multiple factors among which the ion channels/transporters (e.g., V-K+, VCCN1, and KEA3) are key to adjust the ion distribution on the two sides of the thylakoid membrane and hence shape the kinetics of ΔΨ. However, an in-depth mechanistic understanding of ion fluxes on adjusting the transthylakoid electric potentials is still unclear. This lack of a mechanistic understanding is due to the experimental difficulty of closely observing ion fluxes in vivo and also hacking the evolution of parameters in a highly intertwined photosynthetic network. In this work, a computer model was applied to investigate the roles of ion fluxes on adjusting transthylakoid electric potentials upon a temporal cycle of a period of high illumination followed by a dark-adapted phase. The computing data revealed that, firstly, upon illumination, the dissipation of the steady-ΔΨ by ∼10 mV is contributed from the V-K+-driven K+ flux whilst ∼8 mV of the steady-ΔΨ is dissipated by the VCCN1-pumped Cl- flux, but there were no appreciable KEA3-evoked variations on ΔΨ; secondly, on transition from high light to darkness, V-K+ and KEA3 are serving as major contributors whereas VCCN1 taking a counterbalancing part in shaping a standard trace of ECS (electrochromic shift), which commonly shows a sharp fall to a minimum before returning to the baseline in darkness. Besides, the functional consequences on components of ΔΨ adjusted by every particular ion channel/transporter were also explored. By employing the model, we bring evidence that particular thylakoid-harbored proteins, namely V-K+, VCCN1, and KEA3, function by distinct mechanisms in the dynamic adjustment of electric potential, which might be mainly importnat under fluctuating light conditions.

• Klíčová slova
• Diffusion potential, Donnan potential, Ion flux, Mathematical model, Membrane potential, Thylakoid membrane,
• MeSH
• adenosintrifosfát metabolismus   MeSH
• chloroplasty metabolismus   MeSH
• fotosyntéza * MeSH
• světlo * MeSH
• tylakoidy metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• adenosintrifosfát MeSH

Plants growing in nature often experience fluctuating irradiance. However, in the laboratory, the dynamics of photosynthesis are usually explored by instantaneously exposing dark-adapted plants to constant light and examining the dark-to-light transition, which is a poor approximation of natural phenomena. With the aim creating a better approximation, we exposed leaves of pea (Pisum sativum) to oscillating light and measured changes in the functioning of PSI and PSII, and of the proton motive force at the thylakoid membrane. We found that the dynamics depended on the oscillation period, revealing information about the underlying regulatory networks. As demonstrated for a selected oscillation period of 60 s, the regulation tries to keep the reaction centers of PSI and PSII open. We present an evaluation of the data obtained, and discuss the involvement of particular processes in the regulation of photosynthesis. The forced oscillations provided an information-rich fingerprint of complex regulatory networks. We expect future progress in understanding these networks from experiments involving chemical interventions and plant mutants, and by using mathematical modeling and systems identification and control tools.

• Klíčová slova
• Pisum sativum, Fluctuating light, forced oscillations, pea, photosynthesis, photosystem I and II, proton motive force, regulation,
• MeSH
• fotosyntéza fyziologie   MeSH
• fotosystém I (proteinový komplex) metabolismus   MeSH
• fotosystém II (proteinový komplex) * metabolismus   MeSH
• hrách setý * metabolismus   MeSH
• listy rostlin metabolismus   MeSH
• rostliny metabolismus   MeSH
• světlo MeSH
• transport elektronů fyziologie   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• fotosystém I (proteinový komplex) MeSH
• fotosystém II (proteinový komplex) * MeSH

The transthylakoid membrane potential (ΔΨm) is essential because it can drive the ATP synthesis through the CF0-CF1 type of ATP-synthase in chloroplasts as an energetic equivalent similar to ΔpH. In addition, a high fraction of proton motive force (PMF) stored as the ΔΨm component is physiologically important in the acclimation of photosynthesis to environmental stresses. It has been shown that ΔΨm is the sum of the Donnan potential difference (ΔΨdn) and the diffusion potential difference (ΔΨd). Specifically, ΔΨdn, ΔΨd, and ΔΨm are strongly associated with the ionic activities near the membrane surface, particularly, the extent of ion binding to the charged/neutral sites adjacent to the membrane surface. However, an in-depth analysis of the effect of altered cationic binding to the membrane surface on adjusting the transthylakoid electric potentials (ΔΨdn, ΔΨd, and ΔΨm) is still missing. This lack of a mechanistic understanding is due to the experimental difficulty of closely observing cations binding to the membrane surface in vivo. In this work, a computer model was proposed to investigate the transthylakoid electric phenomena in the chloroplast focusing on the interaction between cations and the negative charges close to the membrane surface. By employing the model, we simulated the membrane potential and consequently, the measured ECS traces, proxing the ΔΨm, were well described by the computing results on continuous illumination followed by a dark-adapted period. Moreover, the computing data clarified the components of transthylakoid membrane potential, unraveled the functional consequences of altered cationic attachment to the membrane surface on adjusting the transthylakoid electric potential, and further revealed the key role played by Donnan potential in regulating the energization of the thylakoid membrane. The current model for calculating electric potentials can function as a preliminary network for the further development into a more detailed theoretical model by which multiple important variables involved in photosynthesis can be explored.

• Klíčová slova
• Donnan potential, diffusion potential, ions, mathematical model, membrane potential, thylakoid membrane,
• Publikační typ
• časopisecké články MeSH