TY - BOOK
T1 - Seed biology and ex situ storage behaviour of Australian Nymphaea (water lilies): implications for conservation
AU - Dalziell, Emma Louise
PY - 2016
Y1 - 2016
N2 - [Truncated] The iconic, basal angiosperm genus Nymphaea (Nymphaeaceae) occupy many of the
world’s freshwater wetlands, with 18 species occurring in northern Australia. Generally,
our knowledge of wetland plant species is limited, and even more so for species
occurring in the monsoonally driven wet-dry tropics of northern Australia. In order to
guide the management and conservation of Nymphaea in Australia, this thesis seeks to
improve our understanding of these charismatic plants, and presents the first detailed
investigation into the seed biology of the genus.
Investigations into the seed dormancy of Australian Nymphaea revealed that five
species underwent embryo growth prior to radicle emergence, and were thus classified
as having morphophysiological dormancy (MPD). This finding adds to the increasing
body of literature suggesting MPD is basal within the angiosperms. Additionally, all
study species showed a requirement for light, and maximal germination occurred in a
small temperature window between 30-35 °C. A phenomenon previously reported in the
literature that crowding seeds under flooded conditions was observed, and produced
high germination in all species of Nymphaea tested in this study, when incubated under
optimal temperature and light conditions. This response, termed ‘crowding’ was
attributed to the endogenous production and concentration of ethylene by the seeds,
which acts as a germination stimulant.
As all species displayed specific germination requirements, I further investigated how
dormancy may be naturally overcome under natural conditions, and tested treatments
that can be applied to break dormancy ex situ. I found that dormancy loss under
simulated natural conditions occurs in conjunction with increasing (over-night)
temperatures at the onset of the summer wet season, when seeds are permanently
inundated with water. However, when tested under laboratory conditions, temperature
alone did not break dormancy. Cycles of wetting and drying, used to mimic the sporadic
rainfall of northern Australia, acted to completely alleviate dormancy in seeds of one
species (N. lukei), in conjunction with the exogenous application of ethylene. Under
simulated burial conditions, seeds were found to be semi-persistent, and can remain viable in dry soils for > 12 months. However, viability rapidly declined when under
simulated wetting and drying cycles.
AB - [Truncated] The iconic, basal angiosperm genus Nymphaea (Nymphaeaceae) occupy many of the
world’s freshwater wetlands, with 18 species occurring in northern Australia. Generally,
our knowledge of wetland plant species is limited, and even more so for species
occurring in the monsoonally driven wet-dry tropics of northern Australia. In order to
guide the management and conservation of Nymphaea in Australia, this thesis seeks to
improve our understanding of these charismatic plants, and presents the first detailed
investigation into the seed biology of the genus.
Investigations into the seed dormancy of Australian Nymphaea revealed that five
species underwent embryo growth prior to radicle emergence, and were thus classified
as having morphophysiological dormancy (MPD). This finding adds to the increasing
body of literature suggesting MPD is basal within the angiosperms. Additionally, all
study species showed a requirement for light, and maximal germination occurred in a
small temperature window between 30-35 °C. A phenomenon previously reported in the
literature that crowding seeds under flooded conditions was observed, and produced
high germination in all species of Nymphaea tested in this study, when incubated under
optimal temperature and light conditions. This response, termed ‘crowding’ was
attributed to the endogenous production and concentration of ethylene by the seeds,
which acts as a germination stimulant.
As all species displayed specific germination requirements, I further investigated how
dormancy may be naturally overcome under natural conditions, and tested treatments
that can be applied to break dormancy ex situ. I found that dormancy loss under
simulated natural conditions occurs in conjunction with increasing (over-night)
temperatures at the onset of the summer wet season, when seeds are permanently
inundated with water. However, when tested under laboratory conditions, temperature
alone did not break dormancy. Cycles of wetting and drying, used to mimic the sporadic
rainfall of northern Australia, acted to completely alleviate dormancy in seeds of one
species (N. lukei), in conjunction with the exogenous application of ethylene. Under
simulated burial conditions, seeds were found to be semi-persistent, and can remain viable in dry soils for > 12 months. However, viability rapidly declined when under
simulated wetting and drying cycles.
KW - Seed germination
KW - Seed dormancy
KW - Nymphaeaceae
KW - Wet-dry tropics
KW - Basal angiosperms
KW - Seed storage
KW - Freshwater wetlands
M3 - Doctoral Thesis
ER -