PARENT SESSION
Poster Session #41: Plant Demography.
Thursday, August 9, 2001. Presentation from 3:30 PM to 5:00 PM. Exhibition Hall

Interpopulation variation in Trachypogon plumosus (Poaceae): phenology, seed morphology and germination.

Baruch, Zdravko¹, ¹

ABSTRACT- T. plumosus is the dominant herbaceous species in non-flooded savannas of northern South America characterized by seasonal rainfall, low soil fertility and frequent fires. Under this general setting, there are large local environmental variations. In 1998, 1999 and 2000 phenology was observed and seeds were collected from 9 populations. Seeds were dehusked, weighed and measured. Germination and viability were determined by standard methods. Soils were analyzed for mineral nutrients and climate data were collected. ANOVAS were done among populations and years and regressions were performed between the measured characters and environmental variables. Reproduction occurs during the rainy season but the time of seed maturity varies 6 months among populations. Highland populations mature later suggesting the effect of low temperature. Caryopsis weight ranged from 0.5 to 1.0 mg and germination percentage from 10 to 70 % among populations. The rank of populations was maintained among years. Caryopsis weight and germination percentage showed significant interpopulational variation and were positively correlated which suggests that (i) there are differences in seed dispersion ability and establishment, and (ii) nutrient reserves favor germination. Caryopsis weight and germination were higher in populations from the drier sites. The awn is hygroscopic and its length also varied significantly among populations. The reproductive characters studied show large interpopulational variability which partially explain the dominance of T. plumosus in a wide range of habitats in Neotropical savannas.

KEY WORDS: seed, germination, savannas, neotropics