Mechanism for the hydrogen sulfide‐induced growth limitation in wetland macrophytes

Abstract

Hydrogen sulfide, a phytotoxin that often accumulates in anoxic marine and freshwater marsh soils, suppressed the activity of alcohol dehydrogenase (ADH), the enzyme that catalyzes the terminal step in alcoholic fermentation, in the roots of two wetland macrophytes. This inhibition of root ADH activity with increasing sulfide concentration was associated with decreases in root total adenine nucleotide pool (ATP + ADP + AMP), the adenylate energy charge ratio (AEC), nitrogen uptake (percent recovery of 15 NH 4 + ‐N) and growth (leaf elongation). These responses were species‐specific with a greater negative impact in the freshwater marsh species that naturally inhabits low‐sulfide environments. These findings lend support to the hypotheses that ADH activity, as a measure of fermentative metabolism, is important in maintaining the root energy status of wetland plants under hypoxic‐anoxic conditions, that there is a significant negative effect of H 2 S on the anoxic production of energy in these roots, and that an important negative effect of H 2 S on plant growth is an inhibition of the energy‐dependent process of N uptake.