Seed dormancy is a key trait used around the world to help understand the ecological dynamics of plant species, however, in some ecosystems such as the Andean forests of Colombia, the identification of dormancy class remains poorly known. To address this, we described the morphology, anatomy and dormancy class of the seeds and fruits of 14 species using microtome sections, light microscopy and scanning electron microscopy. Five native pioneer species showed Morphophysiological Dormancy, three Physical Dormancy + Physiological Dormancy and two Physical Dormancy, whereas two invasive species showed Physiological Dormancy. Only the species of the genus Cecropia had seeds with PY + PD that was promoted by the anatomical structure of the achenes. Of the analysed species, 85% showed dormancy and followed a pattern like other tropical montane ecosystems in the world. The anatomy of achenes and development of seed dormancy play important roles in the capacity of Cecropia species to contribute to the natural regeneration of Andean ecosystems. Additionally, seed dormancy may promote the high invasiveness of Thunbergia alata and Ulex europaeus in the Andean forests of the Central Cordillera of Colombia.

Determining the phylogenetic and biogeographic distribution of physical dormancy remains a major challenge in germination ecology. Here, our goal was to describe a novel water-impermeable seed coat mechanism causing physical dormancy (PY) in the seeds of Chaetostoma armatum (Melastomataceae). Although seed coat permeability tests indicated a significant increase in seed weight after soaking in distilled water, anatomical and dye-tracking analyses showed that both water and dyes penetrated the seed coat but not the embryo, which remained in a dry state. The water and dye penetrated the lumen of the exotestal cells, which have a thin outer periclinal face and thickened secondary walls with U-shaped phenolic compounds. Because of this structure, water and dye do not penetrate the inner periclinal face of the exotestal cells, indicating PY. Puncturing the seeds increased germination more than tenfold compared to that of the control, but GA3 did not increase germination further. A significant fraction of the seeds did not germinate after puncturing, indicating that embryos are also physiologically dormant (PD). This paper constitutes the first report of the water-impermeable seed coat in the Myrtales and the first report of physiophysical (PD+PY) dormancy in a shrub from a tropical montane area.

The fruit of Davidsonia pruriens F. v. Muell. drying and splitting at maturity into two indehiscent mericarps is re-defined as a schizocarpic didrupe. The sclerified mesendocarpic construction of the whole pericarp supports its classification as a drupe. The peculiar fimbriate surface of the mericarp is caused by the destruction of parenchymatous exocarpic and mesocarpic tissues exposing radially elongated mesendocarpic osteosclereids. The seed coat is described as diffusive exotegmic with expanding pachychalaza substituting the two integuments in the chalazal half of the seed. The diffusive exotegmy of the spermoderm supports a close relationship with Cunoniaceae, but refutes any relationships with Saxifragales or with Staphyleaceae or any Hamamelidae. The seed-coat structure indicates advancement and specialization of Davidsonia among Cunoniales; its origin could trace back possibly to Rosales, but never to hamamelidalean stock.