Ecological insights into the coexistence of dormancy and desiccation-sensitivity in Arecaceae species

Abstract

Key message Mechanisms controlling germination of > 2600 Arecaceae species adapted to the tropical forests are not clearly understood. This contribution underpins the notion that the coexistence of dormancy and desiccation sensitivity in some Arecaceae species could significantly affect the germination ecology. Although the evolutionary and ecological significance behind this occurrence is unknown, these traits together could limit the germination from inappropriate depths and allow dispersal.• Context Dormancy and desiccation sensitivity, i.e., recalcitrance, are considered as mutually exclusive traits that evolved to maximize seed survival after dispersal; the former by allowing seeds to spread germination risk temporally then synchronize germination with a favorable growing season, and the latter by allowing germination immediately. However, a few species from temperate ecosystems have been known to produce seeds that are both dormant and desiccation-sensitive, but little is known about such a relationship in the tropical forests.• Aims To understand if desiccation sensitivity and dormancy can coexist in Arecaceae species, distributed predominantly in the tropical forests, and compare the seed traits found in Arecaceae species with other desiccation-sensitive species.• Methods Information published in international peer-reviewed journals was reviewed and a database with records on seed dormancy and desiccation sensitivity was created and discussed. • ResultsThis literature survey has identified diaspores of 34 Arecaceae species that have both desiccation-sensitivity and an underdeveloped, small embryo, i.e., morphophysiological dormancy or morphological dormancy. In Arecaceae species, desiccation-sensitivity is neither confined to large-sized diaspores, nor all species adapted to dry ecosystems disperse diaspore during the wet-season; features reported to be prevalent in desiccation-sensitive species of other families. Endocarp is proposed to act as a mechanical barrier preventing water loss and also offer protection against physical damage; however, the extent of protection against water loss from internal structures is contentious. • ConclusionThe possible ecological significance of this unique relationship noted in Arecaceae is currently unknown, and this review puts forward "testable" hypotheses that call for more studies on germination ecology focusing on dispersal and burial.

Did selection for seed traits across the Cretaceous/Paleogene boundary sort plants based on ploidy?

“…With the exception of only a few palms (e.g. coryphoid palms that include Phoenix dactylifera), most palms produce recalcitrant or DS seeds (Baskin and Baskin, 2014;Jaganathan, 2021). Considering that palynological records are typically too poorly resolved taxonomically to record the species-level mass extinction event among plants at the KPB (Nichols and Johnson, 2008), a near mass extinction event recorded in palm pollen diversity in equatorial habitats strongly supports predictions based on the KPB-seed traits hypothesis.…”

Dormancy breaking treatments in Northern Wild Rice (Zizania palustris L.) seed suggest a physiological source of Dormancy

“…However, the actual imbibition of NWR seed has not been directly measured (Dalziell et al 2019), nor has the structure of the NWR pericarp, in order to determine with con dence that it is truly impermeable. Additionally, a review of nearly 900 tree and shrub species found that while about 14% of desiccation sensitive seeds displayed physiological dormancy, only 1.4% of the species had physical dormancy, resulting from an impermeable seed coat (Tweddle et al 2003;Jaganathan 2021). While that study found that most desiccation sensitive seed displayed morphological or morphophysiological dormancy, we believe that the embryo of dormant NWR seed is both differentiated and developed, based upon the pattern of embryo staining when tetrazolium is applied shortly after harvest.…”

Germinação de sementes de Dypsis decaryi submetidas ao estresse salino em duas épocas

“…The higher germination percentage observed during the summer season in this study suggests a correlation with high temperatures and relative humidity levels throughout the days (Table 1). In contrast, during the winter season with lower average temperature and relative humidity, the germination process slows down and shows dispersed germination over time, which can be considered an adaptive trait of the species (Jaganathan, 2021).…”