The Effects of Aluminum Concentration on Growth Responses in Six Spartina alterniflora Genotypes
Elevated soluble aluminum concentrations can adversely affect plant growth. During a drought, wetland soils may experience higher than normal soluble aluminum due to the oxidation of metal sulfides and resulting decreases in pH, which mobilizes metallic cations. Louisiana coastal salt marshes were subject to a record-setting drought in the winter and spring of 2000 which was coincident with the die-off of large expanses of salt marsh, termed " brown marsh ". Spartina alterniflora was the primary plant species affected. However, because some individuals within large areas of die-off survived the brown marsh event, they may have been the more resistant genotypes. To determine if genotypic resistance to aluminum existed, six genotypes of the common salt-marsh cord-grass Spartina alterniflora, five surviving genotypes, and a commercial variety (Vermillion), were dosed with aluminum chloride (AlCl3) at concentrations ranging from 0.2 mM to 10.8 mM. No death was observed in any of the genotypes at aluminum concentrations as high as 10.8 mM, although growth rates decreased to near zero. The results of this study indicate that, as a species, the resistance of Spartina alterniflora to aluminum may surpass the threshold of any plant species studied to date. All genotypes in the experiment were found to tolerate extremely high concentrations of aluminum, although declines in stem elongation rate and cumulative stem height were evident in all Al treatments. I estimated the differential aluminum tolerance by using the first significant decrease in growth rate when the genotype x concentration effect was significant. The first significant decrease approach had the best resolution for determining genotype variability when used with the stem elongation data. Although insufficient evidence exists to determine if aluminum toxicity caused the brown marsh event in Louisiana, based on the results of this thesis, the aluminum concentrations would have had to reach extremely high levels to have been the sole cause of the brown marsh dieback.
Advisor:Lawrence Rouse; Irving Mendelssohn; Robert Gambrell
School:Louisiana State University in Shreveport
School Location:USA - Louisiana
Source Type:Master's Thesis
Keywords:oceanography coastal sciences
Date of Publication:12/20/2004