Seeds of legumes are generally considered to have physical dormancy and to be orthodox, but most seed biologists are unaware of the various kinds and combinations of dormancy and storage behaviour in seeds of this family. The aim of our study was to document the dormancy and storage behaviour of seeds of 100 native and introduced tropical Fabaceae species in Sri Lanka and classify them into germination/storage behaviour categories. Moisture content (MC) was , 16% for fresh seeds of 94 species and . 29% for those of six. Seeds of these six species had low tolerance for desiccation and for low temperatures. Thus, seeds of six species are non-orthodox and 94 species orthodox. Nine of the 100 species were non-dormant, and 2, 3 and 86 had physiological, physiological epicotyl and physical dormancy, respectively. Six germination/storage behaviour categories were identified among the 100 species. However, as in extratropical regions of the world, orthodox storage behaviour and physical dormancy are characteristic of seeds of the majority of species of Fabaceae in tropical Sri Lanka.

We report epicotyl dormancy of two tropical Ceasalpinioid species; Browneacoccinea, Cynometracauliflora. Heretofore, epicotyl dormancy has been reported in only one Ceasalpinioid species.The kind of dormancy in seeds of C. cauliflorawas described with the new formula Cnd(root)–Cp′1b

We report a new kind of seed dormancy and identify the storage behavior category for an important understory rainforest tree that also is used as an ornamental. While studying seed dormancy of Fabaceae species in Sri Lanka, we observed a considerable delay in emergence of the plumule following radicle emergence in Humboldtia laurifolia. Because epicotyl dormancy has not been reported in Fabaceae, we undertook a detailed morphological study of seed germination in this species. Our aims were to document desiccation tolerance/intolerance and epicotyl dormancy in seeds of H. laurifolia. Drying and low temperature storage were used to evaluate storage behavior of the seeds and imbibition, germination, and seed coat anatomy to categorize seed dormancy in two seed collections. Plumule development before its emergence and effects of light and temperature on plumule emergence were monitored. All seeds that were dried to 15% moisture content or stored at -1°C lost viability. Plumules began to grow 20 ± 5 d from radicle emergence and emerged after 40 ± 3 d. Dark and high illuminance further delayed plumule emergence. Seeds are recalcitrant and have a hitherto unreported kind of epicotyl dormancy, for which we propose the formula .

Tropical rainforests in Sri Lanka are considered as biodiversity hotspots. However, their existence is threatened by multiple climatic and anthropogenic drivers. Our objective was to assess the diversity, endemism and conservation status of these rainforests across a wide altitudinal range. We conducted a complete census of all trees having ≥ 10 cm diameter at breast height in ten one-hectare permanent sampling plots of tropical rainforests from 100 to 2200 m above mean sea level and determined altitudinal trends in tree diversity, floristic composition, endemism and conservation status of tree taxa. While community-scale tree diversity decreased with increasing altitude, substantial altitudinal differentiation of tree taxa was observed. Increasing day-night temperature difference (DTR), decreasing rainfall and increasing cumulative maximum soil water deficit (CSWDmax) with increasing altitude decreased tree diversity and the percentage of endemic species while increasing the percentage of endangered species. These trends show that the ability to colonize the higher altitudes, where lower temperatures and higher soil water deficits act as climate constraints, is a major determinant of tree diversity and endemism in Sri Lankan rainforests across altitude gradients. This hypothesis is supported by the observed increases of the percentages of endangered and vulnerable species from mid- to high altitudes. Most of the dominant species at different altitudes were endemic and are endangered or vulnerable. We conclude that the decrease in diversity and endemism is most likely driven by cold- and drought-sensitivity of these predominantly tropical-adapted tree species so that conservation efforts are most needed at altitudes above 1000 m.