author(s) : Howaida I. Abd-Alla and Abdel-Fattah M. Rizk

Duckweeds (Lemnaceae), monocotyledonous aquatic plants, are represented by 37 species. The 37 species are categorized into five well-defined genera: Spirodela (2 species), Landoltia (1), Lemna (13), Wolffiella (10) and Wolffia (11). These aquatic angiosperms are cosmopolitan in distribution except for some endemic species (Sree et al., 2016).
Duckweed (Landoltia punctata) is the smallest and simplest flowering aquatic plant in the world, and its growth highly adaptable across a broad range of climates (Tao et al., 2017).
Duckweeds grow very fast and proliferate quickly by budding, allowing them to colonize freshwater habitats rapidly and produce 13 to 38 metric tons / hectare/year dry weight of plant mass. Since duckweeds can absorb pollutants (e.g., N, P and heavy metals) from wastewater, they have been commonly used in the treatment of domestic and animal wastewater streams for many years (Wang et al., 2014a).
Meanwhile, because of the relatively high starch and low lignin content in this plant, it has been proved to be an ideal bioresource for bioethanol production (Cheng and Stomp, 2009; Xu et al., 2012).
Duckweeds can be utilized to produce ethanol, butanol and biogas (Cui and Cheng, 2015). Duckweeds, especially species belonging to Wolffia (Araceae), have been traditionally eaten in some parts of the world as a component of the nutritious human diet.
Duckweeds are eaten as salad, mixed in soups or curries or in omelettes (Appenroth et al., 2017). In many parts of the world, duckweeds are consumed by domestic and wild fowl, fish, herbivorous animals, and humans (Rusoff et al., 1980).