A mathematical model of photorespiration and photosynthesis.

Calothrix sp. strain PCC 7601 is a heterocystous, filamentous strain which strongly regulates its content of phycoerythrin and phycocyanin according to the relative supply of green and red light. Quenching analysis has shown that when this strain is grown under green light, energy captured by phycoerythrin is transferred from the phycobilisome to PS I to maintain balanced electron transport. This transfer is reflected in a high qN and serves as a good demonstration that in a cyanobacterium a high qN does not usually reflect excitation dissipation but, rather, reflects the transfer of excitation to PS I at the expense of PS II. Upon transfer to red light or prolonged growth under red light, this excitation transfer stops, the PS II fluorescence yield increases, and qN drops ().

Photosynthesis and photorespiration - modeling the essentials.

Cyanobacterial Respiration - ResearchGate

Cyanobacterial Respiration | SpringerLink

In summary, our analysis suggests that Synechocystis has a large number of AEF pathways involved to preserve optimal photosynthetic processes under environmental perturbation, such as Ci or light availability (photosynthetic robustness). The quantitative analysis of photosynthetic parameters exhibited by iJN678 allowed us to classify these AEF pathways based on (i) photosynthetic yield, (ii) net contribution to the ATP/NADPH ratio, (iii) mechanisms used for ATP/NADPH balancing and/or energy dissipation, (iv) dependency on O2 availability, and (v) LEF target components on which they acted (). This classification represents a valuable tool for better understanding how phototrophs might select among their large array of accessory photosynthetic pathways those that are best suited for efficient response to environmental perturbations.

Respiration in cyanobacteria can occur in the thylakoid membrane ..

The PQ oxidase CydBD and the terminal cytC oxidase CYO were identified as AEF pathways involved in a pseudocyclic electron flow (PCEF) around PSII (). Under LLS, the flow of electrons around PSII resulted in a PSI/PSII ratio of less than 1 but an optimal ATP/NADPH ratio (). The CYO and CydBD pathways could be classified as high and low photosynthetic-yield pathways, respectively, based on the calculated values similar to CEF pathways (). Under CLS, PCEF also enabled optimal growth by acting as an electron sink, indirectly consuming more than 53% of the available photons and preventing internal overreduction (). In agreement with our in silico data, genetic evidence showed that, in the absence of PSI or under high-light conditions, terminal oxidases in Synechocystis used PSII-generated electrons and provided extra ATP levels (, ).

Relationship between photosynthesis and leaf nitrogen concentration in ambient and elevated [CO2] in white birch seedlings.

Advances in Photosynthesis and Respiration | Thomas …

In this review, we discuss pulse-amplitude modulated fluorescence as a rapid, noninvasive monitor of acclimation and photosynthesis in cyanobacteria and cyanolichens. We do not cover the biophysical mechanisms underlying chlorophyll fluorescence emission, which are well reviewed elsewhere (, , , , , , , ). Rather, we summarize some of the potentials and limitations of fluorescence analysis for extracting physiologically and ecologically useful information from cyanobacteria, whose photosynthetic physiology (see Fig. ) and fluorescence patterns (see Fig. ) differ in important respects from those of plants (, , , , , ). In particular, we demonstrate how characteristic changes in nonphotochemical quenching of fluorescence can be used to estimate the light level to which the sample is acclimated. This information can then be used in conjunction with the PS II parameter to estimate electron transport under acclimated conditions.

and Respiration in Cyanobacteria.

The photosynthetic production of oxygen by green plants is an important source of atmospheric oxygen, which most organisms –including plants themselves –require in order to complete their respiratory chains and obtain the energy for life....

Photosynthesis and respiration in article contents cyanobacteria ..

Cyanobacteria are ecologically important photosynthetic prokaryotes that also serve as popular model organisms for studies of photosynthesis and gene regulation. Both molecular and ecological studies of cyanobacteria benefit from real-time information on photosynthesis and acclimation. Monitoring in vivo chlorophyll fluorescence can provide noninvasive measures of photosynthetic physiology in a wide range of cyanobacteria and cyanolichens and requires only small samples. Cyanobacterial fluorescence patterns are distinct from those of plants, because of key structural and functional properties of cyanobacteria. These include significant fluorescence emission from the light-harvesting phycobiliproteins; large and rapid changes in fluorescence yield (state transitions) which depend on metabolic and environmental conditions; and flexible, overlapping respiratory and photosynthetic electron transport chains. The fluorescence parameters FV/FM, FV′/FM′,qp,qN, NPQ, and PS II were originally developed to extract information from the fluorescence signals of higher plants. In this review, we consider how the special properties of cyanobacteria can be accommodated and used to extract biologically useful information from cyanobacterial in vivo chlorophyll fluorescence signals. We describe how the pattern of fluorescence yield versus light intensity can be used to predict the acclimated light level for a cyanobacterial population, giving information valuable for both laboratory and field studies of acclimation processes. The size of the change in fluorescence yield during dark-to-light transitions can provide information on respiration and the iron status of the cyanobacteria. Finally, fluorescence parameters can be used to estimate the electron transport rate at the acclimated growth light intensity.