Germination of 14 freshwater wetland plants as affected by oxygen and light

• The first experiment to test the interaction between O2 and light on seed germination.
• Low atmospheric O2 (<1%) reduced germination success of all but three test species.
• Reduction in light levels only reduced germination success of S. latifolia.
• O2 and light seem to operate independently in the control of germination.

Oxygen and light are factors that can affect seed germination of wetland plants. We selected seeds from 20 plant species found in temperate eastern North American marsh and wet meadow wetlands, ranging from obligate wetland (OBL), facultative wetland (FAC) and upland (UPL) species. In growth chambers we tested germination success under controlled manipulations of O2 concentration (low [<1%] and atmospheric [∼20%]) and light levels (full light, half light and dark). Our objective was to (1) determine whether oxygen, light and their interaction facilitate germination of wetland seeds; (2) whether timing of germination is affected by oxygen and light; and (3) whether germination is related to wetland functional groups. Six species did not germinate. Of the 14 species that did germinate, a non-native ruderal (Echinochloa crus-galli) had the greatest germination success. However, we found that low O2 reduced germination success of all but three species (Rudbeckia triloba, Sagittaria latifolia and Typha latifolia). Reduction in light levels only reduced germination success of S. latifolia. We conclude that the physiological constraints that control germination operate independently for oxygen and light. It is important to know and anticipate oxygen and light levels when designing a wetland restoration project so that the proper species can be sown that can germinate under the specific conditions. Restoration planners should be aware that anoxic and hypoxic conditions seem to promote the germination of weedy and potentially invasive native and non-native species.