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Seed Flotation and Postflooding Germination in Tropical terra firme and Seasonally Flooded Forest Species

O. R. Lopez
Functional Ecology
Vol. 15, No. 6 (Dec., 2001), pp. 763-771
Stable URL: http://www.jstor.org/stable/826726
Page Count: 9
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Seed Flotation and Postflooding Germination in Tropical terra firme and Seasonally Flooded Forest Species
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Abstract

1. Seed flotation, postflooding germination and initial height and expansion rates of seedlings of six terra firme (upland forest) and six seasonally flooded forest (SFF) species from Panama were examined as indicators of their potential for dispersal by water. 2. Compared to terra firme species, SFF species had larger seeds with greater volumes and lower seed specific weights, resulting in greater buoyancy. 3. Across all species, seed specific weight was negatively correlated with initial flotation. 4. After 60 days in water, an average of 53% of the seeds of SFF species remained buoyant. In contrast, no seeds of the terra firme species remained buoyant after 15 days. On average more than half the seeds of SFF species germinated after 60 days, while for the terra firme species germination was reduced by 50% after 13 days. 5. Seedling expansion rates of SFF species were twice as fast as those of terra firme species. Three weeks after germination, seedlings of SFF species were twice the height of those of terra firme species, a trait which may minimize immersion of the photosynthetic tissue. 6. The superior flotation and postflooding germination of SFF relative to terra firme species suggests that dispersal by water is an important adaptation in habitats where flooding is common. Lack of hydrochory among terra firme species may be a key selective filter contributing to the poor species diversity found in SFFs even though saplings and adults may be flood-tolerant.

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