The current annual food production cannot sustain population growth and is limited by rates of photosynthetic efficiency. Some strategies to improve photosynthetic efficiency include modification of the photorespiratory pathway which could substantially alter metabolic energy demands, specifically the ATP and reductant demands. Such altered energy demands might pose a problem in terms of photosynthetic efficiency because to operate efficiently and without photodamage the energy demand from metabolism must be matched with that supplied in a process referred to as energy balancing. There is a lot of focus on how processes which supply ATP and reductant mediate energy balancing, however, there is much less focus on how changes in metabolic demand drives these responses. In terms of metabolism, photorespiration consumes substantial amounts of energy making the pathway an important component in leaf energetics. The energetic costs of photorespiration are often discussed; however, less emphasis is placed on how the energy demands from photorespiration might be involved in achieving energy balance. Overall, this dissertation explored the role of the energy demands of photorespiration in achieving energy balance. First, I contextualized the energy demands of photorespiration within the greater metabolic network by quantifying the contribution of individual pathways to energy demand. Next, I examined the impact of increased and decreased energy demands from photorespiration on the light reactions and found a novel role for the energy demands of photorespiration in energy balancing. More specifically, the ATP consumption from photorespiration assisted in maintaining photosynthetic efficiency. I leveraged the associated phenotype to create a screening platform which identified candidate genes involved in responding to dynamic shifts energy demand. I also examined whether the decreased photosynthetic efficiency associated with altered energetic demands might restore over time and the regulation surrounding this. Finally, this dissertation concludes with future directions which would begin to address some of the outstanding questions raised throughout.
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