Cobalt uptake by Nyssa aquatica, N. sylvatica var. biflora, and Taxodium distichum seedlings

Abstract

Cobalt is a minor contaminant in wetlands that has been linked to accumulation by Nyssa species for many years, though the evidence is largely anecdotal. We examined cobalt uptake characteristics from cobalt-enriched potting soil by Nyssa aquatica (water tupelo), N. sylvatica var. biflora (swamp tupelo), and Taxodium distichum (baldcypress), codominant canopy species of wetland forests of the southeastern United States. Seedlings were grown in 10 1 pots for two growing seasons. Cobalt additions (up to 100 mg/pot) did not affect biomass production of leaves, stems, or roots of the three species. Height was significantly different among treatments within a species, but no treatment was different from the control treatment with no added cobalt. Leaf cobalt concentrations were greater in N. sylvatica var. biflora than N. aquatica during the first year, but similar during the second year. Cobalt concentrations declined from the first to second years for T. distichum leaves. In the 100 mg/pot treatment, leaf cobalt concentrations of both Nyssa species during the second year were 150 times greater than that of T. distichum. Elevated cobalt uptake by Nyssa species is apparently a function of special mechanisms of the genera and not a habitat characteristic.