The Difficult to Quantify Cyclic Electron Flux around Photosystem I in Leavesof Flowering Plants
In oxygenic photosynthesis, two photosystems (PS II and PS I) using light, work in series to extract electrons from water to generate reducing power (in the form of NADPH) in linear electron transport, while the energy of the protons after water photo oxidation is conserved in the form of ATP. Additionally, a cyclic electron flux (CEF) around PS I is also coupled to the formation of ATP [1] Together, NADPH and ATP drive the conversion of CO2 into carbohydrates. CEF is central to the regulation of photosynthesis [2] but its quantification, six decades after the discovery, has been difficult because of the absence of net formation of a product or consumption of a reactant [3]