ACCUMULATION OF THE COMPATIBLE SOLUTE 3-DIMETHYLSULFONIOPROPIONATE INSUGARCANE AND ITS RELATIVES, BUT NOT OTHER GRAMINEOUS CROPS

The tertiary sulfonium compound 3-dimethylsulfoniopropionate (DMSP) is found at high levels in many marine algae, but among higher plants it has been reported to accumulate only in Spartina (Gramineae) and one other genus. Cultivated and wild species from 23 genera of Gramineae w ere tested for DMSP accumulation in leaves of non-stressed plants, usi ng an indirect gas chromatographic assay. Sugarcanes and closely relat ed species accumulated up to 6 mu mol g(-1) fresh wt; other species co ntained no more than 0.3 mu mol g(-1) fresh wt. In sugarcanes, mature leaves had higher levels of DMSP than expanding leaves, immature inter nodes and mature internodes. The identity of DMSP was confirmed by a n ovel gas chromatography-mass spectrometry method, by fast atom bombard ment mass spectrometry and by H-1 nuclear magnetic resonance. Mass spe ctral evidence indicated that DMSP levels in leaves were at least ten- fold higher than glycine betaine levels, suggesting that DMSP may have replaced glycine betaine as a compatible osmolyte in sugarcane. Consi stent with this possibility, DMSP was as effective as glycine betaine in relieving osmotic inhibition of bacterial growth, and was accumulat ed to concentrations above 1 M by osmotically stressed bacterial cells . Because DMSP is the biological precursor of dimethylsulfide, sugarca ne fields may be sources of dimethylsulfide emissions.