CS08 Biogeochemical Cycles
Date: Tuesday, June 11, 2002
Location: Poster Session - VCC
 
ManleySL, Dept. Biol. Sci., Calif. St. Univ., Long Beach, USA, slmanley@csulb.edu
Wang, N, Y, Dept. Earth System Sci., Univ. of Calif., Irvine, USA, 
 
HALIDE CONTENT AND METHYL HALIDE PRODUCTION OF SELECTED COASTAL MARSH PLANTS AND SEAWEEDS
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Tissue chloride, bromide and iodide concentrations, and methyl halide (MeX) production rates are reported for coastal marsh plants and seaweeds. Certain halophyte and algal species have very high biomass specific MeX production rates for all three, while others produce little or no MeI (e.g. saltwort, Batis, 3 ng MeCl, 0.4ng MeBr, 0-1 pg MeI /gfwt/hr). Although halophyte halide levels remain high throughout the year (e.g. 17-25% dwt Cl, 0.3-5% dwt Br, 5-14 ppm I – Batis), MeX production drops drastically in the winter (e.g. Batis, 5 pg MeCl/gfwt/hr). Daily halide loss as MeX is a minute fraction of tissue halide concentration and is less than the variability in halide content. This suggests that MeX production is not a mechanism to control internal halide levels. As anticipated, cell-free extracts incubated with halide and S-adenosyl-L-methionine (SAM) produced the appropriate MeX. This activity in plants is inhibited by substrates of known methyl transferases such as caffeic acid, the substrate of lignin-specific O-methyl transferase. Methyl halide production may be a result of non-specific methylation of halides by SAM utilizing methyl transferases used in other biosynthetic pathways.