Association between Carbonyl Sulfide Uptake and (18)Delta during Gas Exchange in C-3 and C-4 Leaves

作者：Stimler Keren; Berry Joseph A; Montzka Steve A; Yakir Dan^*

来源：Plant Physiology, 2011, 157(1): 509-517.

DOI：10.1104/pp.111.176578

Carbonyl sulfide (COS) and (COO)-O-18 exchange by leaves provide potentially powerful tracers of biosphere-atmosphere CO2 exchange, and both are assumed to depend on carbonic anhydrase (CA) activity and conductance along the diffusive pathway in leaves. We investigated these links using C-3 and C-4 plants, hypothesizing that the rates of COS and (COO)-O-18 exchange by leaves respond in parallel to environmental and biological drivers. Using CA-deficient antisense lines of C-4 and C-3 plants, COS uptake was essentially eliminated and discrimination against (COO)-O-18 exchange ((18)Delta) greatly reduced, demonstrating CA's key role in both processes. (18)Delta showed a positive linear correlation with leaf relative uptake (LRU; ratio of COS to CO2 assimilation rates, A(s)/A(c), normalized to their respective ambient concentrations), which reflected the effects of stomatal conductance on both COS and (COO)-O-18 exchange. Unexpectedly, a decoupling between A(s) and (18)Delta was observed in comparing C-4 and C-3 plants, with a large decrease in (18)Delta but no parallel reduction in A(s) in the former. This could be explained by C-4 plants having higher COS concentrations at the CA site (maintaining high A(s) with reduced CA) and a high phosphoenolpyruvate carboxylase/CA activity ratio (reducing O-18 exchange efficiency between CO2 and water, but not A(s)). Similar A(s) but higher A(c) in C-4 versus C-3 plants resulted in lower LRU values in the former (1.16 +/- 0.20 and 1.82 +/- 0.18 for C-4 and C-3, respectively). LRU was, however, relatively constant in both plant types across a wide range of conditions, except low light (<191 mu mol photon m(-2) s(-1)).

• 出版日期2011-9