Occurrence of dimethylsulfoxide in leaves, stems, and roots of Spartina alterniflora

Abstract

Spartina alterniflora is unique among salt marsh macrophytes in its synthesis of dimethylsulfoniopropionate (DMSP). One potential degradation product of DMSP is dimethylsulfoxide (DMSO). The concentrations of DMSP and DMSO were determined for S. alterniflora plants collected from Mobile Bay, Alabama. Although the distribution of DMSO within healthy S. alterniflora tissues mirrored somewhat that of DMSP, with the highest concentrations found in leaf tissue followed by stem and root tissue, the DMSO/DMSP ratio in root tissue was more than twice that in leaf or stem tissue. This is likely the result of a higher rate of DMS(P) oxidation in roots. It has been proposed that DMSP functions as an antioxidant in certain marine phytoplankton, and a similar function may be operational in S. alterniflora. Enhanced oxidative stress in the S. alterniflora root zone may help explain the high DMSO/DMSP ratio. In support of this idea was the finding that the DMSO/DMSP ratio was higher in tissues presumably experiencing increased oxidative stress such as yellowing S. alterniflora leaves and senescing segments of individual leaves compared to healthy tissue. The occurrence of DMSO in tissues of S. alterniflora is consistent with DMS(P) functioning as an antioxidant in this plant. Higher DMSO/DMSP ratios in stressed leaves further supports that role. However, specific roles for DMSP, DMS, or DMSO in oxidative stress protection in S. alterniflora remain to be demonstrated.