Rethinking the potential productivity of crassulacean acidmetabolism by integrating metabolic dynamics with shoot architecture, using the example of Agave tequilana
New Phytologist
Yu Wang, J. Andrew C. Smith, Xin-Guang Zhu, Steve Long
Abstract
- Terrestrial CAM plants typically occur in hot semiarid regions, yet can show high crop productivity under favorable conditions.
- To achieve a more mechanistic understanding of CAM plant productivity, a biochemical model of diel metabolism was developed and integrated with 3-D shoot morphology to predict the energetics of light interception and photosynthetic carbon assimilation.
- UsingAgave tequilana as an example, this biochemical model faithfully simulated the four diel phases of CO2 and metabolite dynamics during the CAM rhythm. After capturing the 3-Dform over an 8-yr production cycle, a ray-tracing method allowed the prediction of the light microclimate across all photosynthetic surfaces. Integration with the biochemical model thereby enabled the simulation of plant and stand carbon uptake over daily and annual courses.
- The theoretical maximum energy conversion efficiency of Agave spp.is calculated at 0.045–0.049, up to 7% higher than for C3photosynthesis. Actual light interception, and bio-chemical and anatomical limitations, reduced this to 0.0069, or 15.6 Mg ha1yr1dry massannualized over an 8-yr cropping cycle, consistent with observation. This is comparable to the productivity of many C3crops, demonstrating the potential of CAM plants in climates where little else may be grown while indicating strategies that could raise their productivity.
