Patterns of Seed Longevity and Germination in the Tropical Rainforest
This article reviews the factors that affect seed longevity and germination in tropical trees by providing an introduction to literature on the subject.
Conclusions & Takeaways
Seed dormancy varies greatly among tropical trees: Ochroma lagopus (balsa) can remain viable 44 years, while Acacia, Trema, Piper, and Cecropia can remain dormant for only a year. Many seeds have high water content and can germinate quickly (but at the expense of drought tolerance). Cedrela odorata (cedar) and Swietenia macrophylla (mahogany) are wind dispersed seeds with low moisture content, so they often germinate at the beginning of the rainy season. In Mexico, experiments that artificially irrigated forest soil before the onset of the rainy season induced germination of C. odorata and Brosimum alicastrum Another characteristic is delayed germination (unrelated to moisture balance), where seeds delay more than 20 weeks to germinate (but there can be a lot of variability among one species) Seed coat is a strong determinant of dormancy period and germination - nursery seeds placed in manure can speed germination (because of the heat). Heat can remove the seed coat, allow water inside, and induce germination: Ochroma lagopus seeds can remain dormant for several years until heat (from a low intensity fire or from canopy opening) induces germination Heliocarpus donnell-smithii in Mexico requires > 10° C daily temperature fluctuation for germination (ie, a tree-fall gap) Germination can also be regulated by light intensity (multiple examples) Litter is also an important factor for germination but has not been studied extensively
Patterns of Seed Longevity and Germination in the Tropical Rainforest. Annual Review of Ecology and Systematics. 1993;24:69–87. doi:10.1146/annurev.es.24.110193.000441..
- Centro de Ecologia, UNAM., Ciudad Universitaria, Mexico