Abstract
BACKGROUND AND AIMS: Several ecologically important plant families in Mediterranean biomes have seeds with morphophysiological dormancy (MPD) but have been poorly studied. The aim of this study was to understand the seed ecology of these species by focusing on the prominent, yet intractably dormant Australian genus Hibbertia. It was hypothesized that the slow germination in species of this genus is caused by a requirement for embryo growth inside the seed before germination, and that initiation of embryo growth is reliant upon a complex sequence of environmental cues including seasonal fluctuations in temperature and moisture, and an interplay with light and smoke. Using the results, the classification of the MPD level in species of Hibbertia is considered. METHODS: Four species of Hibbertia in winter rainfall south-western Australia were selected. These species, whilst differing in geographic distributions, are variously sympatric, and all are important understorey components of plant communities. The following aspects related to dormancy break, embryo growth and germination were investigated: temperature and moisture requirements; effects of karrikinolide, gibberellic acid and aerosol smoke; and phenology. KEY RESULTS: Following exposure to wet/dry cycles at low or high temperatures, embryo growth and germination occurred, albeit slowly in all species at low temperatures when moisture was unlimited, corresponding to winter in south-west Australia. Photo regime influenced germination only in H. racemosa. Aerosol smoke triggered substantial germination during the 1st germination season in H. huegelii and H. hypericoides. CONCLUSIONS: Although the study species are con-generic, sympatric and produce seeds of identical morphology, they possessed different dormancy-break and germination requirements. The physiological component of MPD was non-deep in H. racemosa but varied in the other three species where more deeply dormant seeds required >1 summer to overcome dormancy and, thus, germination was spread over time. Embryos grew during winter, but future studies need to resolve the role of cold versus warm stratification by using constant temperature regimes. To include Mediterranean species with MPD, some modifications to the current seed-dormancy classification system may need consideration: (a) wet/dry conditions for warm stratification and (b) a relatively long period for warm stratification. These outcomes have important implications for improving experimental approaches to resolve the effective use of broadcast seed for ecological restoration.
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Claims 8
Claim · model-written summary
Wet and dry cycles permitted slow embryo growth and germination at low temperature with unlimited moisture.
- Treatment
- wet/dry cycles at low or high temperaturese0
- Outcome
- embryo growth and germinatione0
- Qualifier
- slowly in all species at low temperatures when moisture was unlimitede0
HibbertiaOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Following exposure to wet/dry cycles at low or high temperatures, embryo growth and germination occurred, albeit slowly in all species at low temperatures when moisture was unlimited”
t0“Hibbertia”
Claim · model-written summary
Photoregime affected germination only in H. racemosa.
- Taxon
- H. racemosa
Hibbertia racemosae0 - Treatment
- Photo regimee0
- Outcome
- germinatione0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Photo regime influenced germination only in H. racemosa.”
Claim · model-written summary
Aerosol smoke triggered substantial first-season germination in H. huegelii.
- Taxon
- H. huegelii
Hibbertia huegeliie0 - Organ / stage
- 1st germination seasone0
- Treatment
- Aerosol smokee0
- Outcome
- germinatione0
- Direction
- substantiale0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Aerosol smoke triggered substantial germination during the 1st germination season in H. huegelii and H. hypericoides.”
Claim · model-written summary
Aerosol smoke triggered substantial first-season germination in H. hypericoides.
- Taxon
- H. hypericoides
Hibbertia hypericoidese0 - Treatment
- Aerosol smokee0
- Outcome
- germinatione0
- Direction
- substantiale0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Aerosol smoke triggered substantial germination during the 1st germination season in H. huegelii and H. hypericoides.”
Claim · model-written summary
The sympatric congeners had different dormancy break and germination requirements despite identical seed morphology.
- Outcome
- different dormancy-break and germination requirementse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Although the study species are con-generic, sympatric and produce seeds of identical morphology, they possessed different dormancy-break and germination requirements.”
t0“Hibbertia”
Claim · model-written summary
H. racemosa had non-deep physiological dormancy.
- Taxon
- H. racemosaHibbertia racemosae0
- Outcome
- non-deepe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The physiological component of MPD was non-deep in H. racemosa”
Claim · model-written summary
More deeply dormant seeds in three other species required over one summer to break dormancy and germinated over time.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“varied in the other three species where more deeply dormant seeds required >1 summer to overcome dormancy and, thus, germination was spread over time.”
t0“Hibbertia”
Claim · model-written summary
Embryos grew during winter.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Embryos grew during winter”
t0“Hibbertia”