Germination, Emergence, Vegetative Growth and Flowering of Two Silvergrasses, Vulpia bromoides (L.) S.F. Gray and V. myuros (L.) C.C. Gmel

Abstract

Effect of temperature and light on seed germination percentage and rate, depth of burial and seasonality on seedling emergence, and temperature and photoperiod on both vegetative growth and flowering were examined for two species of silvergrass in Australia. Maximum germination percentage was high for both taxa and occurred over a broad range of temperatures. In darkness, both optimum temperature for germination and germination rate were higher for V. myuros than for V. bromoides. In light, optimum temperature was similar for both species, although V. myuros maintained its higher rate. In addition, light doubled the range of temperatures over which the two species were able to germinate. Emergence of both taxa was retarded if seeds were buried below surficial depths but was consistently higher for V. myuros than for V. bromoides at all depths. Upon fulfilling an after-ripening requirement of 2-3 months, fresh seed could germinate and emerge in the field at any season but most seed germinated with the first substantial summer or early autumn rain. Vegetative growth of both species was stimulated initially by high temperatures and long photoperiods but, subsequently, growth was much greater at low temperatures and short photoperiods. This changing response with age to temperature and photoperiod corresponds to expected changes in field environments as plants age naturally V. rnyuros usually maintained higher rates of growth than V. bromoides. Low temperatures and short photoperiods also were required for flowering, particularly for V. myuros. Flowering was the only measured characteristic for which V. bromoldes had greater environmental tolerance than V. myuros. These characteristics of silvergrass relate to their incidence in direct drilled crops in the higher rainfall zones of southern Australia, compared to their relative absence in conventionally sown crops.