Evaluation in contrasting climates of dormancy characteristics of seed of Digitaria milanjiana.
Seed of 4 ecotypes of Digitaria milanjiana with different dormancy characteristics related to climatic origin were exposed at the soil surface during 1981 at 3 sites in N. Australia with contrasting climates. All sites received summer rainfall, although at Katherine no rain fell during May to Sept. At Katherine temp. were high throughout the year; Narayan was characterised by cool winters and springs and Landsdown showed intermediate temp. No accession showed adaptive germination characteristics at Narayen; the high rainfall equatorial ecotype germinated in winter when survival would have been limited while the low rainfall equatorial and low rainfall tropical ecotypes failed to break dormancy by the following wet season. At Lansdown only the low rainfall tropical ecotypes retained dormancy during the dry season and were germinable by the start of the wet season, while at Katherine all accessions were germinable by the start of the wet season. All accessions showed opt. germination at 25°C.