Comparative <Emphasis Type="Italic">in vitro</Emphasis> germination ecology of <Emphasis Type="Italic">Calopogon tuberosus</Emphasis> var. <Emphasis Type="Italic">tuberosus</Emphasis> (Orchidaceae) across its geographic range |
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Authors: | Philip J Kauth Michael E Kane Wagner A Vendrame |
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Institution: | (1) Plant Restoration, Conservation and Propagation Biotechnology Program, Environmental Horticulture Department, University of Florida, PO Box 110675, Gainesville, FL 32611, USA;(2) Tropical Research and Education Center, University of Florida, 18905 SW 280th, St Homestead, FL 33031, USA |
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Abstract: | Seed responses to temperature are often essential to the study of germination ecology, but the ecological role of temperature
in orchid seed germination remains uncertain. The response of orchid seeds to cold stratification have been studied, but the
exact physiological role remains unclear. No studies exist that compare the effects of either cold stratification or temperature
on germination among distant populations of the same species. In two separate experiments, the role of temperature (25, 22/11,
27/15, 29/19, 33/24°C) and chilling at 10°C on in vitro seed germination were investigated using distant populations of Calopogon tuberosus var. tuberosus. Cooler temperatures promoted germination of Michigan seeds; warmer temperatures promoted germination of South Carolina and
north central Florida seeds. South Florida seed germination was highest under both warm and cool temperatures. More advanced
seedling development generally occurred at higher temperatures with the exception of south Florida seedlings, in which the
warmest temperature suppressed development. Fluctuating diurnal temperatures were more beneficial for germination compared
to constant temperatures. Cold stratification had a positive effect on germination among all populations, but South Carolina
seeds required the longest chilling treatments to obtain maximum germination. Results from the cold stratification experiment
indicate that a physiological dormancy is present, but the degree of dormancy varies across the species range. The variable
responses among populations may indicate ecotypic differentiation. |
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