Anatomical, developmental and functional investigation of the stylopodium in Cyperoideae species (Cyperaceae, Poales).

• Using SEM and LM, we examined nutlet samples at various stages, revealing stylopodium's structure. • Germination tests evaluated stylopodium's impact on seed germination under differing water conditions. • Study of five cyperoideae species, including those with both persistent and deciduous stylopodium, showed a consistent ontogenetic origin. • A revealed abscission layer in species with deciduous stylopodium, shed light on this unique trait. • Germination tests showed that persistent stylopodium potentially enhances seed germination, even in water challenges. The stylopodium is a reproductive feature found in the nutlet (fruit) of non-closely related Cyperoideae genera, with little known about its origin and function. We analyzed the stylopodium of Bulbostylis hirtella, Eleocharis sellowiana, Rhynchospora albiceps and R. sparsiflora (with a persistent stylopodium), as well as Fimbristylis dichotoma (with a deciduous stylopodium) to investigate their development and anatomical structure, previous related to water supply. The role of this structure on seed germination was tested in E. sellowiana and F. dichotoma under varying water availability conditions. The results demonstrated that the origin of the stylopodium can be traced to the enlargement of the style base, composed of tracheoids with water-related characteristics. An abscission layer was identified in deciduous stylopodium. Eleocharis sellowiana exhibited significantly higher percentages and rates of seed germination in relation to F. dichotoma , even in challenging water conditions. These findings suggest a potential role of the stylopodium in promoting seed germination, particularly under low water supply. The study emphasizes the significance of considering both historical and current ecological contexts when discussing the function of the stylopodium. Moreover, it underscores the need for further research to fully understand the role of the stylopodium across diverse environments within Cyperoideae genera. [ABSTRACT FROM AUTHOR]