Uptake of carbonyl sulfide (COS) and emission of dimethyl sulfide (DMS) by plants

Higher plants represent a significant sink for atmospheric carbonyl sulfide (COS) and a potential source of dimethyl sulfide (DMS). In the present work, COS uptake was investigated on various plant species (Quercus robur, Juniperus excelsa, Hibiscus spec., Sorghum bicolor) differing in the activities of carbonic anhydrase (CA), the enzyme recognized responsible for COS consumption. COS uptake was observed for all plant species, and the range of COS consumption was 1.5-25 pmol m^-2 s^-1 (deposition velocity 1.2-10.6 mm s^-1). The COS uptake was found to be light-independent, but was strongly under stomatal control. For the C₃ plant species the uptake rates were well correlated with the inherent capacity of CA, a fact that may confer a comfortable tool to model COS uptake by plants, and ultimately may help to decrease the uncertainty in estimates of the global COS sink strength of vegetation. S. bicolor, owing a C₄ metabolism and respective low CA activity, exhibited a relatively high COS uptake rate as compared to the C ₃ plants. Potential reasons for this deviation are discussed. Emission of DMS was species-specific and was only observed in case of Hibiscus spec. under light conditions.