Abstract
Dimethylsulfoniopropionate (DMSP) and dimethyl sulphide (DMS) are compounds found mainly in marine phytoplankton and in some halophytic plants. DMS is a globally important biogenic volatile in regulating of global sulfur cycle and planetary albedo, whereas DMSP is involved in the maintenance of plant-environment homeostasis. Plants emit minute amounts of DMS compared to marine phytoplankton and there is a need for hypersensitive analytic techniques to enable its quantification in plants. Solid Phase Micro Extraction from Head Space (HS-SPME) is a simple, rapid, solvent-free and cost-effective extraction mode, which can be easily hyphenated with GC-MS for the analysis of volatile organic compounds. Using tomato (Solanum lycopersicum) plants subjected to water stress as a model system, we standardized a sensitive and accurate protocol for detecting and quantifying DMSP pool sizes, and potential DMS emissions, in cryoextracted leaves. The method relies on the determination of DMS free and from DMSP pools before and after the alkaline hydrolysis via Headspace-Solid Phase Micro Extraction-Gas Chromatography-Mass Spectrometry (HS-SPME-GC-MS). We found a significant (2.5 time) increase of DMSP content in water-stressed leaves reflecting clear stress to the photosynthetic apparatus. We hypothesize that increased DMSP, and in turn DMS, in water-stressed leaves are produced by carbon sources other than direct photosynthesis, and function to protect plants either osmotically or as antioxidants. Finally, our results suggest that SPME is a powerful and suitable technique for the detection and quantification of biogenic gasses in trace amounts.
Highlights
Biogenic dimethyl sulphide (DMS), a compound mainly emitted by marine environment, is a significant natural source of tropospheric sulfur (Stefels et al, 2007; Vallina and Simò, 2007; Oduro et al, 2012)
Dimethyl sulphide is derived from the enzymatic cleavage of DMSP, an organic sulfur compound synthetized in the chloroplast from methionine imported from cytosol (Trossat et al, 1996; Gage et al, 1997; Oduro et al, 2012)
Stomatal conductance decreased from 0.20 ± 0.20 to 0.09 ± 0.01 mmol s−1 (∼50% of the initial value) (Figure 5A), whereas A dropped from 11 ± 0.86 to the value of 4.9 ± 0.64 μmol m−2s−1 when the Fraction of Transpirable Soil Water (FTSW) of water-stressed S. lycopersicum pots reached 30% compared to FTSW100 (Figure 5B)
Summary
Biogenic DMS (dimethyl sulfide), a compound mainly emitted by marine environment, is a significant natural source of tropospheric sulfur (Stefels et al, 2007; Vallina and Simò, 2007; Oduro et al, 2012). DMS is important biogeochemically because its emission facilitates cycling of sulfur from the oceans to the continents (Stefels et al, 2007). In global terms, and in comparison to marine organisms, higher plants are not as significant sources of DMS and atmospheric sulfur. Dimethyl sulphide is derived from the enzymatic cleavage of DMSP, an organic sulfur compound synthetized in the chloroplast from methionine imported from cytosol (Trossat et al, 1996; Gage et al, 1997; Oduro et al, 2012). Because methionine synthesis requires nitrogen and sulfur, it was shown that nitrogen availability affected the concentration of DMSP (Otte and Morris, 1994; Gage et al, 1997; Mulholland and Otte, 2002)
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