Respiratory energy demands and scope for demand expansion and destruction

Abstract

Nonphotosynthetic plant metabolic processes are powered by respiratory energy, a limited resource that metabolic engineers—like plants themselves—must manage prudently.

Why cutting respiratory CO2 loss from crops is possible, practicable, and prudential

“…(a) Modelling for a generic grain crop to show the potential increase in biomass carbon accumulation, relative to the unmodified crop, given by a 6.5% reduction in maintenance respiration achieved by extending the lifespan of 15 abundant enzymes. 67 (b) The comparable global scales of anthropogenic CO 2 release to the atmosphere from fossil carbon sources and respiratory CO 2 release from crops, that is, the quantity of CO 2 they are estimated to output. Crop CO 2 release was estimated using a value of 60 Gt carbon y −1 for terrestrial plant respiration 78 and assuming 14% is from crops, based on the contribution of crops to terrestrial primary productivity.…”

“…Improved longevity traits for several enzymes could be stacked to give similar or larger increases. Modelling such stacking in a mid‐latitude grain crop (increasing tenfold the CCRs of 15 abundant low‐CCR enzymes to cut maintenance respiration by 6.5%, and otherwise making conservative assumptions) predicted a 2.4% biomass yield increase (Figure 4a) and a 2.9% grain yield increase 67 . Such extra carbon income could be channelled to contribute to three global imperatives: sustaining yields, retaining carbon in the soil and drawing down atmospheric CO 2 , as discussed below and in a recent review 67 centred on respiratory energy budgets.…”

“… Cutting crop respiration in relation to sustaining crop yields and sequestering atmospheric CO 2 . (a) Modelling for a generic grain crop to show the potential increase in biomass carbon accumulation, relative to the unmodified crop, given by a 6.5% reduction in maintenance respiration achieved by extending the lifespan of 15 abundant enzymes 67 . (b) The comparable global scales of anthropogenic CO 2 release to the atmosphere from fossil carbon sources and respiratory CO 2 release from crops, that is, the quantity of CO 2 they are estimated to output.…”

“…Because crop maintenance respiration releases about the same amount of carbon as harvested products contain (Figure 1b), 11,67 it follows that for each 1% reduction in photosynthate (sugar) used for maintenance respiration, yield could rise by roughly half to three‐quarters that amount if all the sugar saved is partitioned to harvested parts, after accounting for growth respiration and translocation cost. Annual yield advances in major crops have now fallen to ~1%, whereas about twice this is needed to meet the projected 2050 demands from rising population, diet changes and biofuel production 68,69 .…”

Focus on respiration

“…Bridging between the crop level and biochemical processes, Bathe et al (2023 ) revisit the principles of plant respiratory energy budgeting and estimating the costs of metabolic processes. They then apply these principles to assess how synthetic biology interventions that add new metabolic demands or cut existing ones could affect crop yield and carbon sequestration.…”