Lemnoideae

Lemnoideae is a subfamily of flowering plants in the family Araceae, commonly known as duckweeds. Members are among the smallest and fastest-growing aquatic plants, existing as free-floating mats on still or slow-moving freshwater and wetlands. The group is cosmopolitan, occurring in temperate and tropical regions.

Taxonomically, Lemnoideae is placed within Araceae; in older classifications it was treated as a separate family, Lemnaceae. Modern systems typically regard it as a subfamily containing five extant genera: Lemna, Spirodela, Landoltia, Wolffia, and Wolffiella. The duckweeds show a range of frond sizes and forms, from the tiny, rootless Wolffia to larger, multi-frond Lemna.

Morphology and reproduction are characterized by a simple, flat, leaf-like thallus (frond). Roots, when present, are short and primarily aid anchorage or incidental nutrient uptake; several genera are effectively rootless. Reproduction is predominantly asexual by budding, enabling rapid clonal growth. Sexual reproduction with tiny flowers occurs but is rare in natural populations.

Ecology and applications: duckweeds contribute as important primary producers in freshwater ecosystems and respond quickly to nutrient enrichment. They are used in wastewater treatment and nutrient removal, as well as in phytoremediation and pond management. They provide forage for waterfowl and, in some cases, for domestic animals. Research into Lemnoideae also covers potential applications in biofuel production and carbon sequestration, though dense duckweed mats can reduce dissolved oxygen and sometimes clog waterways.

Notes: taxonomic and phylogenetic work continues to refine the circumscription of the subfamily and its genera within Araceae.