Polypropylene Fragments Block Pollen–Pistil Interactions and Reduce Seed Production in a Monkeyflower Species

Abstract

Microplastics, which are indicative of global change, pervade all ecosystems, and their mass surpasses the total animal biomass of Earth. Pollination, the transfer of pollen among plants, is a key process that allows for plant reproduction and plant population prevalence. Plant reproduction could be altered by microplastics at several stages: plastic-polluted animals can act as pollinators, and airborne plastic fragments can be deposited on the stigmatic surfaces of pistils, interfering with pollen−pistil interactions, clogging pollen tube development and reducing seed production. To test this hypothesis, we examined the impact of polypropylene fragments (<63 μm) deposited on stigmatic surfaces on seed production by studying the Andean-yellow monkeyflower Erythranthe lutea (Phrymaceae). We combined hand-pollination treatments and ultrastructural observations and reported the adverse effect of polypropylene fragments on seed production when this material was deposited on stigmas, but the mass and germination levels of the obtained seeds did not differ. Optical and scanning electron microscopy observations of the pollen tube ultrastructure revealed that pollen tube development was disrupted by the addition of polypropylene fragments. The results point to the potential deleterious effects of microplastics on a crucial ecosystem process, pollination, which might have consequences for most angiosperms and crop production.