Seedlings and older plants of 30 ecological races of Themeda australis were
grown under controlled conditions to determine the effect of day length and vernalization
on their flowering and on the incidence of apomixis. The races ranged in origin from
latitude 6°S. in New Guinea to latitude 43°S, in Tasmania.
One race from New Guinea and several from the Northern Territory behaved
as strict short-day plants. The more southerly races, on the other hand, and several from
north Queensland were long-day plants. In some, long days were required for both
initiation and development of the inflorescence, in others apparently only for initiation.
Some races required long days as seedlings, but not as older plants. Races from drier
inland areas tended to be indifferent to day length in their flowering behaviour. At least
four races from the colder areas responded to vernalization.
Both the sexual and the aposporous reproductive pathways are described. Two
races were wholly sexual in their breeding system and two appeared to be almost entirely
aposporous, but most were versatile, displaying both sexual and aposporous reproductive
behaviour. In seven races there was some evidence that day length influenced the
reproductive pathway, short days causing increased apospory in all cases, regardless
of the day length requirements for flowering.
Quantitative genetics of feeding behavior in two ecological races of the pea aphid, Acyrthosiphon pisum
