Seed characteristics of plant species from riverine wetlands in Venezuela.
Seed characteristics of 76 plant species from wetlands along four black-water and two white-water rivers in the Southeastern Venezuelan Llanos were examined. Weight, length, width, colour, appendages, shape, and dispersal type of seeds were determined. Life form, leaf type and fruit type of plants also were described. Thirty-eight percent were perennial heloculms, 28% helosuffrutescents, 13% heloterophytes and 5% annual heloculms. Dominant leaf types were nanophylls and microphylls. Ninety-six percent of species showed dehiscent and indehiscent dry fruits (achene, capsule, nutlet, follicle). Sixty-five percent of species had seed dry weights between 32 and 315 µg. Lengths and widths of the seeds ranged from 0.2 to 6.2 mm and 0.1 to 4.1 mm, respectively. Seventy-six percent of species had seeds which were reddish brown, yellowish brown and amber in colour, with 17% black and 7% white. Seventy-seven percent of species had seeds represented by pterochory, pogonochory, sclerochory, desmochory, and pleochory dispersal types, with 11% sarchochory, and 12% barochory. The seed size showed significant differences among families, life forms, geometric shapes and dispersal types. In general, species from wet and open environments (marshes) along black- and white-water rivers showed low variation in seed colour and size, and were dispersed mainly by abiotic agents.