Structural and histochemical analyses of the vegetative organs of Eichhornia crassipes

Abstract

ABSTRACT Water hyacinth (Eichhornia crassipes), a free-floating aquatic macrophyte belonging to the family Pontederiaceae, is invasive in tropical and subtropical areas worldwide. Using brightfield and epifluorescence microscopy, we investigated the anatomical structures and histochemical features allowing this species to float freely, and to successfully invade aquatic environments. The roots of water hyacinth have a lignified endodermis with Casparian bands and no suberin, as well as a lignified cortex and hypodermis. The stem epidermis is covered with a thin cuticle, and lignified sclerenchyma delimit the central cylinder with scattered vascular bundles. Air spaces, which included schizogenous intercellular spaces and lysigenous aerenchyma, were observed in the root cortices, while schizo-lysigenous aerenchyma and protoxylem lacunae were observed in the shoots. Key structural features of the water hyacinth, including barriers (e.g. the endodermis, lignified cortex and hypodermis, and cuticle) and air spaces, may allow this plant to float freely and to invade aquatic environments. Thus, our study identified the anatomical features that allow the water hyacinth to thrive in aquatic environments.