Temperature response of mesophyll conductance in three C sub(4) species calculated with two methods: super(18)O discrimination and in vitro V sub(pmax)

• Published in: The New phytologist Vol. 214; no. 1; pp. 66 - 80
• Main Authors: Ubierna, Nerea, Gandin, Anthony, Boyd, Ryan A, Cousins, Asaph B
• Format: Journal Article
• Language: English
• Published: 01.04.2017
• Subjects: Miscanthus; Setaria viridis; Zea mays
• ISSN: 0028-646X; 1469-8137
• DOI: 10.1111/nph.14359

* Mesophyll conductance (g sub(m)) is an important factor limiting rates of C sub(3) photosynthesis. However, its role in C sub(4) photosynthesis is poorly understood because it has been historically difficult to estimate. * We use two methods to derive the temperature responses of g sub(m) in C sub(4) species. The first ( Delta super(18)O) combines measurements of gas exchange with models and measurements of super(18)O discrimination. The second method (in vitro V sub(pmax)) derives g sub(m) by retrofitting models of C sub(4) photosynthesis and super(13)C discrimination with gas exchange, kinetic constants and in vitro V sub(pmax) measurements. * The two methods produced similar g sub(m) for Setaria viridis and Zea mays. Additionally, we present the first temperature response (10-40 degree C) of C sub(4) g sub(m) in S. viridis, Z. mays and Miscanthus giganteu s. Values for g sub(m) at 25 degree C ranged from 2.90 to 7.85 mu mol m super(-2) s super(-1) Pa super(-1). * Our study demonstrated that: the two described methods are suitable to calculate g sub(m) in C sub(4) species; g sub(m) values in C sub(4) are similar to high-end values reported for C sub(3) species; and g sub(m) increases with temperature analogous to reports for C sub(3) species and the response is species specific. These results improve our mechanistic understanding of C sub(4) photosynthesis.