Scoop-shaped pores change how pollen is released from poricidal flowers

Abstract Approximately 10% of angiosperms have poricidal flowers where pollen can only be released via a narrow aperture upon mechanical perturbations. Although the morphology of pore-like apertures likely determines how pollen is released and placed on pollinators, the functional significance of pore diversity remains unknown. Here, we establish critical baseline knowledge on pore morphological diversity across 523 species from six poricidal families, finding that pores either carry scoop-shaped modifications or do not. Using artificial pollen release experiments, we demonstrate functional differences, with scoop-bearing species having narrower, faster-moving pollen streams than non-scoop-bearing species. In a selected scoop-bearing species, we further demonstrate that the functionality of scoop-shaped pores is sensitive to variation in mechanical perturbations, with low-frequency vibrations expelling larger quantities of pollen with a more dispersed pollen cloud than high-frequency vibrations. In conclusion, differences in pore morphology may critically determine the accuracy of pollen placement on pollinators, making pore morphology a hitherto overlooked trait in flowers relying on aerosolization of pollen grains.