Confocal measurement of microplastics uptake by plants

Microplastics (MPs, plastics 100 nm–5 mm in diameter) are estimated to accumulate in agricultural soils in quantities that exceed the total MP burden in ocean waters. Despite a wealth of information relating to the accumulation of MPs in aquatic species, there is little information on the uptake of MPs by terrestrial plants. Information about location of MPs in plant tissues is critical to understand the modes of their interaction with plants. Polystyrene (PS) is one of the most commonly used plastic polymers worldwide and it is often found in MPs sampled in the environment. The performance of traditional detection methods (i.e., transmission electron microscopy, TEM and scanning electron microscopy, SEM) for nanoparticles is limited due to the extensive sample preparation and the limited field of view. Here we report an approach for the imaging of different sizes of PS plastic beads (ranging from submicrometer to micrometer-sized) within plant tissues by using confocal laser scanning microscope (CLSM). Fluorescent dye Nile blue or 4-chloro-7-nitro-1,2,3-benzoxadiazole were encapsulated into the PS microbeads through swelling method and they were used to detect the localization of PS beads in the root and the green tissue respectively. • This is a simple and rapid approach for imaging of MPs in plant. • The fluorescent dyes can produce bright and stable emission signals that are distinguishable from the autofluorescence background of plant tissues. • The dyes leakage in the aqueous phase can be assumed to be negligible.