Germination Ecology of Catchfly (Silene conoidea) Seeds of Different Colors

ABSTRACT Catchfly (Silene conoidea), an annual herb, is usually recognized as an emerging weed species in Eurasia and North America. The presence of somatic seed polymorphism might aid in the adaptation of this weed in different climatic conditions. We conducted laboratory and greenhouse experiments to study the seed polymorphism and influence of various environmental factors like temperature, salt stress, osmotic stress and burial depth on the germination and emergence characteristics of catchfly. Optimum germination of seeds of all colors was recorded at a temperature of 15 oC. Germination of catchfly seeds of all colors followed decreasing trend as NaCl concentration increased from 50 mM to 200 mM. Seed germination was maximum (87-96%) at 0 MPa but gradually decreased to 40% as osmotic stress increases up to -0.4 MPa and completely inhibited at 0.6 MPa of all seed colors. A slight increase (from 60 to 95%) in the germination of seeds of black and dark brown colors was observed when seeding depth increased from 0 to 2 cm but decreased when seeding depth increased from 2 to 4 cm in seeds of all colors. There was no emergence of catchfly at seeding depth of 6 cm or greater. Our results concluded that catchfly seeds have the potential to germinate and emerge in various environmental conditions, but germination/emergence percentage of seeds of all colors will be different in different environmental conditions. Soil amendments including deep ploughing may aid for the successful management of this weed in cultivated areas.

Seed polymorphism, dormancy and germination of Salsola affinis (Chenopodiaceae), a dominant desert annual inhabiting the Junggar Basin of Xinjiang, China

Salsola affinis C.A. Meyer, a dominant annual that primarily occurs in deserts of the Junggar Basin, China, produces three types of utricles that differ in shape, size, colour and size of wings on the fruits. Type A fruits have lignified perianths with long wings and green utricles, and they can easily be dispersed long distances from the mother plant by wind. Type B fruits have lignified perianths with short wings, or no wings, and green utricles, and they are tightly attached to the mother plant. Type C fruits have tepals without wings and yellow utricles, and are also attached tightly to the mother plant. Freshly harvested Type A and Type B seeds (utricles) can germinate at 5–30°C in light or in darkness. Rate and final percentage of germination of Type B seeds are higher than those of Type A seeds. Type C seeds have non-deep physiological dormancy; they germinate slowly and to a low percentage. Four weeks of cold stratification, scarification of covering layers (pericarp and seed coat) and treatment with KNO3 can increase the percentage and rate of seed germination. Utricle polymorphism may allow Salsola affinis to respond to spatial and temporal variations in environmental conditions, thus increasing the chances for survival of this annual species in its harsh desert habitats.

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.