Differentiation of seed germination traits in relation to the natural habitats of three <Emphasis Type="Italic">Ulmus</Emphasis> species in Japan |
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| Authors: | Haruto Nomiya |
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| Institution: | (1) Kyushu Research Center, Forestry and Forest Products Research Institute, Kumamoto 860-0862, Japan |
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| Abstract: | Germination traits of three Japanese Ulmus species, including two summer-fruiting species, U. davidiana var. japonica (UD) and U. laciniata (UL), and an autumn-fruiting species, U. parvifolia (UP), were investigated. Germination tests that controlled light (16 h dark–8 h light/24 h dark) and temperature (alternating
20–30°C/constant 23°C) conditions were conducted just after seed dissemination. Under the preferred (light and alternating
temperature) conditions, UD germinated quickly and percentage germination was high (99%), whereas UL and UP germinated moderately
to slowly (65.2 and 23.8%, respectively) and the remaining seeds were primarily dormant. When the seeds were exposed to unsuitable
conditions for germination, secondary dormancy was induced in all three Ulmus species. Because primary and secondary dormancy of these species was not strict, the existing dormancy could be released
by moist conditions and low temperature during the winter. Thus, all three Japanese Ulmus can germinate either just after seed dissemination or in the following spring. Nevertheless, the predominant germination
of summer-fruiting UD just after seed dissemination seems to be advantageous for finding safe sites that might become available
after a large-scale fluvial disturbance. Similarly, the delayed germination of autumn-fruiting UP until the following spring
seems to be advantageous for preventing germination at the end of the growing season. Summer-fruiting UL had a more negative
response to favorable light conditions just after seed dissemination, which seems to be advantageous for establishment in
canopy gaps. These germination traits seem to be adaptive responses to the dominant disturbance regimes of their natural habitats. |
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