Photosynthesis: basics, history and modelling

Abstract

Background With limited agricultural land and increasing human population, it is essential to enhance overall photosynthesis, and thus, productivity. Oxygenic photosynthesis begins with light absorption, followed by excitation energy transfer to the reaction centers, primary photochemistry, electron and proton transport, ATP synthesis, and then CO2 fixation (Calvin-Benson cycle, as well as Hatch-Slack cycle). We mention here some of the discoveries related to this process, such as the existence of two light reactions and two photosystems connected by an electron transport ‘chain’ (the Z-scheme), chemiosmotic hypothesis for ATP synthesis, water oxidation clock for oxygen evolution, steps for carbon fixation, and finally the diverse mechanisms of regulatory processes, such as “state transitions” and “non-photochemical quenching” of the excited state of chlorophyll a. Scope In this review, we emphasize that mathematical modeling is a highly valuable tool in understanding and making predictions on photosynthesis. Different mathematical models have been used to examine current theories on diverse photosynthetic processes; these have been validated through simulation(s) of available experimental data, such as chlorophyll a fluorescence induction, measured with fluorometers using continuous (or modulated) exciting light, and absorbance changes at 820 nm (ΔA820 ) related to redox changes in P700, the reaction center of Photosystem I. Conclusions We show in this review the important role of modeling in deciphering and untangling complex photosynthesis processes taking place simultaneously, as well as in predicting possible ways to obtain higher biomass and productivity in plants, algae and cyanobacteria.

Can Ceylon Leadwort (Plumbago zeylanica L.) Acclimate to Lead Toxicity?—Studies of Photosynthetic Apparatus Efficiency

“…Plants can preserve their photosystems not only by redirecting electrons to cycling flow but also via several other alternative electron transport pathways, like 'water-water cycle' (O 2 reduction at the acceptor side of PSI followed by ascorbate peroxidase reaction) [73] and chlororespiration (terminal plastoquinone oxidase (PTOX)-mediated reduction of O 2 when PQ-pool is over-reduced) [65,74]. The activation of these pathways is often observed in plants under stress conditions and connected with redox state unbalance influencing both ferrodoxin and PQ pool [75]. The impairment of redox state can result from the excessive energy absorbed and failure in its exploitation on the PSI acceptor side and/or in the dark reactions of photosynthesis.…”

Efeito Do Ambiente Luminoso Em Forrageiras De Clima Tropical Em Sistemas Silvipastoris

“…Portanto, a dinâmica de crescimento das plantas em um sistema de produção será em relação à intensidade das alterações da quantidade e qualidade da luz. A radiação solar que chega ao nível do solo é utilizada pelas plantas via fotossíntese para converter o carbono atmosférico em componentes essenciais para o seu crescimento, desenvolvimento e demais processos metabólicos como respiração e reprodução (STIRBET et al, 2019).…”

“…A eficiência de conversão da energia luminosa em energia química determina a produção final de matéria seca de uma planta (BELLASIO; GRIFFITHS, 2014). A energia luminosa utilizada nessa conversão por meio da fotossíntese está restrita ao comprimento de onda do espectro da RFA, com picos de absorção em 680 e 700 nm (STIRBET et al, 2019).…”

“…Elétrons contidos nos fotossistemas das moléculas dos pigmentos fotossintetizantes (i.e., clorofila a, principalmente) passam por uma sequência de reações até a produção de ATP. As moléculas de clorofila e os demais pigmentos fotossintetizantes utilizam a RFA dos comprimentos de ondas, desse modo a quantidade da radiação incidente determina a máxima eficiência fotossintética da planta (STIRBET et al, 2019).…”

Special issue in honour of Prof. Reto J. Strasser - A comparative chlorophyll a fluorescence study on isolated cells and intact leaves of Bouteloua gracilis (blue grama grass)

“…Here, we have assumed that differences in the initial Chl fluorescence (FO) (measured with direct light) from the blue grama grass cells are mainly due to differences in Chl concentration between the samples (see e.g., Strasser et al 2004). This is a reasonable assumption since the PQ pool is expected to be all in the oxidized state (see discussion in Stirbet et al 2019;cf. Feild et al 1998 for information on chlororespiration that could, in principle, affect it).…”