Author:
Bell David T.,Williams Deanne S.
Abstract
Tolerance to high temperatures is an important attribute of seeds of species
that inhabit regions that periodically burn. In some species, seeds not only
survive fire, but require a heat shock in order to germinate. Twenty-one taxa,
representing a range of ecological attributes, were tested for germination
following scarification and boiling-water treatments of up to 90 min duration.
The black-coloured seeds from the serotinous fruits of
Dryandra sessilis (Knight) Domin.,
Hakea lissocarpha R.Br. and four species of
Eucalyptus were vulnerable to temperatures of 100˚C
with increasing duration of exposure associated with reduced germination
percentage. Seeds of Xanthorrhoea preissii Endl., a
species that flowers in response to fire and disperses seed into a post-fire
environment unlikely to experience a second fire, also had few seeds that
could tolerate even 30 s of boiling-water treatment. The reddish coloured,
soil-borne, leguminous species seeds showed enhanced germination after short
durations of 100˚C, but gradually decreasing proportions of seeds
germinated as heat-shock durations were lengthened to 90 min. Within the genus
Eucalyptus, seeds of relatively large mass and thick
seed coats survived longer than seeds of small mass and thin seed coats. In
contrast, within the legumes, seed mass, wall thickness and cellular structure
were not strong indicators of thermal-shock tolerance. Differences in
germination percentage between scarified and short-term heat-shock treatments
indicated that the heat required to break dormancy in Australian legumes may
not always be related to breaking an impervious seed coat. Australian native
legumes appear more tolerant to thermal-shock than species reported from other
regions of the world.
Subject
Plant Science,Ecology, Evolution, Behavior and Systematics
Cited by
55 articles.
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