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Department of Plant Sciences

CAM – working the night shift

A paper on Agave by Nick Owen with Howard Griffiths and Jamie Males from the Physiological Ecology group, and collaborators from Teagasc (Ireland) and Tequila Sauza (Mexico) has been published in Plant Cell and Environment (doi: 10.1111/pce.12610). Eddy covariance methodology was used to measure ecosystem-scale mass (CO2 and H2O) and energy exchange fluxes over a field of the crassulacean acid metabolism (CAM) bioenergy candidate  Agave tequilana. The field was located near Amatitán, Mexico, and data were taken over 252-day period including the transition from wet to dry seasons. This is the first time eddy covariance has been applied to study these plants in the field. Unlike EC studies over forests or conventional crops, measurements over CAM are complicated by the primary uptake of carbon at night, and difficulties of dealing with soil respiration and unmixed canopy boundary layers.

Amazingly, the characteristic four phases of CAM gas exchange were resolved from gas exchange profiles averaged on a monthly basis. Data were scaled to estimate the annual carbon balance at the site and to identify the best environmental predictors of canopy level carbon assimilation. Plants displayed a remarkable capacity to buffer against water deficit, maintaining carbon assimilation over 70 days of drought (soil water potential < plant water potential). These results suggest that the carbon acquisition strategy of ‘drought avoidance’, which is defined as the maintenance of cell water status and the capacity to buffer against contrasting environmental conditions, could offer high yields on low grade lands and resilience to climate change. This is distinct from the strategy of ‘drought tolerance’ employed by arid- and semi-arid C3 and C4 bioenergy crops, which may tolerate low cell water potential or desiccation and exhibit a shorter more rapid growth phase concentrated to periods of high water availability.

  • Owen, N. A., Ní Choncubhair, Ó., Males, J., Laborde, R., Ignacio, J., Rubio‐Cortés, R., Griffiths, H. & Lanigan, G. (2015). Eddy covariance captures four‐phase crassulacean acid metabolism (CAM) gas exchange signature in Agave. Plant, Cell & Environment. DOI: 10.1111/pce.12610