High C3 photosynthetic capacity and high intrinsic water use efficiency underlies the high productivity of the bioenergy grass Arundo donax

Webster, Richard J. and Driever, Steven M. and Kromdijk, Johannes and McGrath, Justin and Leakey, Andrew D. B. and Siebke, Katharina and Demetriades-Shah, Tanvir and Bonnage, Steve and Peloe, Tony and Lawson, Tracy and Long, Stephen P. (2016) High C3 photosynthetic capacity and high intrinsic water use efficiency underlies the high productivity of the bioenergy grass Arundo donax. Scientific Reports, 6: 20694. ISSN 2045-2322

Abstract

Arundo donax has attracted interest as a potential bioenergy crop due to a high apparent productivity. It uses C3 photosynthesis yet appears competitive with C4 grass biomass feedstock's and grows in warm conditions where C4 species might be expected to be that productive. Despite this there has been no systematic study of leaf photosynthetic properties. This study determines photosynthetic and photorespiratory parameters for leaves in a natural stand of A. donax growing in southern Portugal. We hypothesise that A. donax has a high photosynthetic potential in high and low light, stomatal limitation to be small and intrinsic water use efficiency unusually low. High photosynthetic rates in A. donax resulted from a high capacity for both maximum Rubisco (V-c,V- max 117 mu mol CO2 m(-2) s(-1)) and ribulose-1:5-bisphosphate limited carboxylation rate (J(max) 213 mu mol CO2 m(-2) s(-1)) under light-saturated conditions. Maximum quantum yield for light-limited CO2 assimilation was also high relative to other C3 species. Photorespiratory losses were similar to other C3 species under the conditions of measurement (25%), while stomatal limitation was high (0.25) resulting in a high intrinsic water use efficiency. Overall the photosynthetic capacity of A. donax is high compared to other C3 species, and comparable to C4 bioenergy grasses.