The light reactions of photosynthesis: Monitoring pathways, energy and photoprotection in greenhouse and crop studies

Photosynthesis by plants, algae and cyanobacteria uses energy from light to capture atmospheric CO 2 and synthesise carbohydrates. The biochemistry of the light-dependent reactions of photosynthesis involves high-energy, reactive intermediates which must be carefully controlled and the photosynthetic machinery repaired, as these routinely cause damage to the proteins of the photosynthetic apparatus. The focus of this review is the energetic and molecular mechanisms by which oxygenic photosynthesis is regulated, and how the safe operation of complex assemblies of membrane proteins is managed under fluctuating light conditions. The advent of low-cost, portable fluorimeters suitable for greenhouse and field use has accelerated plant phenotyping studies: the information that can be provided by them is presented here using examples from crops in controlled environments. Data here, from crops grown under contrasting light wavelengths, are used to illustrate the biochemical and biophysical parameters that can be used to interpret plant photosynthetic processes and their regulation.