The rate of net CO2 uptake is proportional to dim light and saturates when the light exceeds the plant's assimilation capacity. This simple relationship between constant light and photosynthesis becomes intriguingly complex when the light oscillates. The rates of photosynthesis may differ between the descending and ascending phases of light oscillation. This hysteresis changes with the frequency and amplitude of the light and reports on the dynamics of the photosynthetic reactions and their regulation. Here, we investigated the chlorophyll fluorescence response of Arabidopsis thaliana to light oscillating with three different amplitudes: 100-200, 100-400, and 100-800 μmol photons m-2 s-1, each with periods ranging from 1 s to 8 min. The light amplitudes and periods were chosen to represent light patterns often appearing in nature. Three genotypes were compared: wild-type Col-0 and npq1 and npq4 mutants that are incapacitated in the rapidly reversible energy-dependent non-photochemical quenching (qE). The experiments identified two major dynamic patterns. One was found in oscillation periods shorter than 30 s, characterized by constitutive hysteresis and non-linearity. The other was mainly formed by regulatory hysteresis, occurring when the oscillation periods were longer than 30 s. The mathematical model simulating the chlorophyll fluorescence dynamics qualitatively reproduced the constitutive and regulatory dynamic patterns observed in the experiments. The model simulations illustrated the dynamics of plastoquinone pool reduction and variables affecting non-photochemical quenching that form the constitutive and regulatory hysteresis types. The model simulations provided mechanistic insights into molecular processes forming the plant response to oscillating light.

• Klíčová slova
• chlorophyll fluorescence, frequency domain, harmonics, mathematical model, photosynthesis,
• MeSH
• Arabidopsis * účinky záření   fyziologie   metabolismus   genetika   MeSH
• chlorofyl metabolismus   MeSH
• fluorescence MeSH
• fotosyntéza účinky záření   fyziologie   MeSH
• proteiny huseníčku metabolismus   genetika   MeSH
• světlo * MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• chlorofyl MeSH
• proteiny huseníčku 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

The present paper aims to open discussion on the information content, physical mechanism(s), and measuring protocols to determine the partitioning of the absorbed light energy in oxygenic photosynthetic organisms. Revisiting these questions is incited by recent findings discovering that PSII, in addition to its open and closed state, assumes a light-adapted charge-separated state and that chlorophyll a fluorescence induction (ChlF), besides the photochemical activity of PSII, reflects the structural dynamics of its reaction center complex. Thus, the photochemical quantum yield of PSII cannot be determined from the conventional ChlF-based protocol. Consequently, the codependent quantity - the quantum yield of the so-called nonregulatory constitutive nonphotochemical quenching (npq) - loses its physical meaning. Processes beyond photochemistry and regulatory npq should be identified and characterized by multifaceted studies, including ChlF. Such investigations may shed light on the putative roles of dissipation and other energy-consuming events in the stress physiology of photosynthetic machinery.

• Klíčová slova
• Fv/Fm, chlorophyll a fluorescence, constitutive nonregulatory dissipation, nonphotochemical quenching, quantum yield, structural dynamics,
• Publikační typ
• časopisecké články MeSH

Natural SiO2 nanoparticles (SiO2-NPs) are widely distributed in the environment, and at the same time, synthetic SiO2-NP may be applied in agriculture. Evaluations of physiological responses to SiO2-NPs treatment of plants are controversial. They are often performed at adaxial leaf sides whereas NPs permeate leaf tissues through stomata located at the abaxial leaf side in the majority of bifacial plants. We measured coefficients of the functional dorsoventral asymmetry of NPs-stressed Chelidonium majus leaves, S, by values of the CO2 assimilation rate (SP N), dark respiration (SR), maximal and operating quantum yields of photosystem II (SFv/Fm, SFv'/Fm'; using PAM-fluorometry), and oxygen coefficients of photosynthesis (SΨO2; using photoacoustics). The results indicated that SP N and SΨO2 were significantly influenced by SiO2-NPs treatment, since P N and ΨO2 were declining more markedly when the light was directed to the abaxial side of leaves compared to the adaxial side. Overall, SiO2-NPs-induced stress increased 'anoxygenity' of photosynthesis.

• Klíčová slova
• CO2 assimilation kinetics, cyclic electron transport around PSII, energy storage, photobaric signal, photothermal signal, transpiration kinetics,
• Publikační typ
• časopisecké články MeSH