Taxonomic Distribution of Copper‐zinc Superoxide Dismutase in Green Algae and Its Phylogenetic Importance1

Twenty‐nine species of green algae (from four classes: Charophyceae, Chlorophyceae, Pleurastrophyceae, and Ulvophyceae, but not the Micromonadophyceae), five species of bryophytes, and four species of vascular plants were tested for the presence of iron, manganese, and copper‐zinc superoxide dismutase. Copper‐zinc superoxide dismutase was found in members of the Charophyceae, Bryophyta, and Tracheophyta. Manganese and/or iron superoxide dismutase were found in all classes of green algae and most land plants. The presence of the copper‐zinc form of superoxide dismutase only in the class of green algae hypothesized to be closest to the land plant progenitors strengthens the argument for that phylogenetic relationship. It also suggests that this form of superoxide dismutase was a vital attribute for the survival of the earliest land plants.