Relationships between carbonyl sulfide (COS) and CO₂ during leaf gas exchange

Abstract

Summary• Carbonyl sulfide (COS) exchange in C 3 leaves is linked to that of CO 2 , providing a basis for the use of COS as a powerful tracer of gross CO 2 fluxes between plants and the atmosphere, a critical element in understanding the response of the land biosphere to global change.• Here, we carried out controlled leaf-scale gas-exchange measurements of COS and CO 2 in representative C 3 plants under a range of light intensities, relative humidities and temperatures, CO 2 and COS concentrations, and following abscisic acid treatments.• No 'respiration-like' emission of COS or detectable compensation point, and no cross-inhibition effects between COS and CO 2 were observed. The mean ratio of COS to CO 2 assimilation flux rates, A s ⁄ A c , was c. 1.4 pmol lmol )1 and the leaf relative uptake (assimilation normalized to ambient concentrations, (A s ⁄ A c ) (C a c ⁄ C a s )) was 1.6-1.7 across species and conditions, with significant deviations under certain conditions. Stomatal conductance was enhanced by increasing COS, which was possibly mediated by hydrogen sulfide (H 2 S) produced from COS hydrolysis, and a correlation was observed between A s and leaf discrimination against C 18 OO.• The results provide systematic and quantitative information necessary for the use of COS in photosynthesis and carbon-cycle research on the physiological to global scales.

Bryophyte gas‐exchange dynamics along varying hydration status reveal a significant carbonyl sulphide (COS) sink in the dark and COS source in the light

“…Previously, Kuhn & Kesselmeier (2000) had suggested the existence of a nonzero Γ S in lichens. Nonzero Γ S values have also been observed in some higher plants (Kesselmeier & Merk, 1993) but their influence on the overall COS uptake rate seemed small (Seibt et al ., 2010; Stimler et al ., 2010). These observations, together with other studies conducted on plants senescing, under fungal attack or under heat and drought stress (Bloem et al ., 2012; Maseyk et al ., 2014; Commane et al ., 2015), suggest that plant COS emissions may be more ubiquitous than previously assumed.…”

“…The estimated leaflet relative uptake rates (LRU of 0.2 for the moss, S. purum , and 0.9 for the liverwort, M. polymorpha , in the light and at optimal hydration status) found in our study were lower than current LRU estimates for vascular plants, which range between 1.4 and 2 (Seibt et al ., 2010; Stimler et al ., 2010). If we were to estimate the contribution of cryptogamic covers to the global COS budget from their current estimates of CO 2 uptake (3.9 Pg C yr −1 according to Elbert et al ., 2012) following the same LRU approach as proposed for vascular plants (Sandoval‐Soto et al ., 2005; Campbell et al ., 2008), with atmospheric mixing ratios of 400 μmol CO 2  mol −1 and 540 pmol COS mol −1 , we would arrive at an estimate between 0.005 and 0.024 Tg COS yr −1 (for LRU of 0.2 and 0.9, respectively).…”

Soil fluxes of carbonyl sulfide (COS), carbon monoxide, and carbon dioxide in a boreal forest in southern Finland

“…The hydrolysis occurs in parallel to CO 2 hydration, the main physiological function of carbonic anhydrase (Badger and Price, 1994;Henry, 1996). Because of the irreversible COS hydrolysis in leaves, COS is taken up concurrently with CO 2 through stomata and is not emitted back from leaves (Sandoval-Soto et al, 2005;Stimler et al, 2010). This allows COS to serve as a tracer with which to quantify terrestrial photosynthesis independently from respiration (Montzka et al, 2007;Campbell et al, 2008;Seibt et al, 2010;Wohlfahrt et al, 2012;Asaf et al, 2013;Berry et al, 2013;Billesbach et al, 2014;Maseyk et al, 2014).…”

“…Sun et al: Soil COS, CO, and CO 2 fluxes at Hyytiälä COS participates in land carbon cycle processes due to its chemical similarities to CO 2 (Kettle et al, 2002;Montzka et al, 2007;Berry et al, 2013). In leaf chloroplasts and soil microbes, COS as a substrate of carbonic anhydrase is hydrolyzed irreversibly to CO 2 and H 2 S (Protoschill-Krebs and Kesselmeier, 1992;Protoschill-Krebs et al, 1996;Stimler et al, 2010Stimler et al, , 2011Kesselmeier et al, 1999;Saito et al, 2002;Kato et al, 2008;Ogawa et al, 2013). The hydrolysis occurs in parallel to CO 2 hydration, the main physiological function of carbonic anhydrase (Badger and Price, 1994;Henry, 1996).…”

Seasonal fluxes of carbonyl sulfide in a midlatitude forest

“…Leaf-scale studies have confirmed the OCS link to photosynthesis (14,15). Initial OCS ecosystem flux estimations were made using flask sampling followed by analysis via gas chromatography-mass spectrometry (GC-MS) (13,16), but these studies did not have sufficient resolution to examine daily or hourly controls on the OCS flux.…”