Germination and dormancy states of seeds in the environmental weed Rumex vesicarius (Polygonaceae). I. Seed polymorphism and germination of extracted seeds

In Australia, Rumex vesicarius (Ruby Dock; subgenus Acetosa, section Vesicarii, family Polygonaceae) is an environmental weed, with the potential to have a significant impact on the natural flora and fauna in areas where it grows. Ruby Dock seeds are polymorphic (light and dark of various shades) and of high potential viability. Seeds are enclosed within showy, papery fruiting valves at maturation. Extracted seeds are characterised by non-deep physiological dormancy. Light and dark seeds usually require an after-ripening period of several months, but thereafter germinate at any time of the year in a light–dark rhythm. Light seeds also show excellent germination in constant darkness; they are non-dormant. Dark seeds show conditional dormancy, where germination is inhibited in darkness, but not in a light–dark rhythm. Scarification experiments indicate that the conditional dormancy of dark seeds is related to the pericarp. The pericarp may restrict oxygen consumption by the embryo, contain chemical inhibitors and/or impede radicle protrusion. A range of environmental variables is likely to affect the specific germination requirements of particular seed types. Environmental conditions may induce secondary dormancy, in both light and dark seeds.