Seed Dispersal Phenology and Germination Characteristics of a Drought-Prone Vegetation in Southeastern Brazil
2010
Braz, Maria Isabel Guedes | de Mattos, Eduardo Arcoverde
Seed germination is determined by the environmental conditions typical of a habitat and also by the geographical origin of the source species pool. During the Quaternary, Brazilian Atlantic Rain Forest species expanded their distribution into the sandy coastal plains (restingas). Periods of water shortage, however, are frequent in the sandy substrate of the restinga. We investigated whether the germination characteristics of restinga species are more related to their biogeographical origin in the humid forest or to water shortage on sandy substrates. We characterized the seed dispersal phenology of a restinga community and conducted experiments to determine the water requirements for seed germination and the short-term seed dehydration sensitivity of different species. Species shed seeds throughout the year in the restinga. When subjected to Ψ=-0.37 MPa, seed germination percentage decreased and germination time increased in six of ten species when compared with Ψ=0 MPa. Most species showed high seed moisture content (MC>40 %) at seed dispersal. Seeds took 3-17 d to dehydrate when subjected to relative humidity[less-than or equal to]76 percent and only two of eight species had seeds sensitive to short-term dehydration. Thus, rather than a specific set of germination characteristics related to humid or dry habitats, we gathered evidence to show that the germination characteristics of restinga species represent a multiplicity of responses that may be found in both kinds of habitat.
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