Germination of Eucalyptus sieberi, L. Johnson seeds. I. Response to substrate and atmospheric moisture.

Consistent germination of Eucalyptus sieberi L. Johnson seeds required a low vapor pressure deficit (< 5 x 10(-6) MPa) and a high matric water potential (> -5 x 10(-3) MPa). Eucalyptus sieberi seeds, under moist but less favorable conditions, were unable to germinate but underwent changes that enabled them to germinate more rapidly when suitable conditions occurred. Such pregerminative development was interrupted but not reversed by a dry period as long as eight months. This may explain how seeds of this species germinate successfully on the surface of exposed seedbeds subject to intermittent drying.