Spirodela is a genus of aquatic plant

Aquatic plant

Aquatic plants are plants that have adapted to living in aquatic environments. They are also referred to as hydrophytes or aquatic macrophytes. These plants require special adaptations for living submerged in water, or at the water's surface. Aquatic plants can only grow in water or in soil that is...

. It is one of several genera containing plants commonly called duckweed. Spirodela species are members of the Araceae

Araceae

Araceae are a family of monocotyledonous flowering plants in which flowers are borne on a type of inflorescence called a spadix. The spadix is usually accompanied by, and sometimes partially enclosed in, a spathe or leaf-like bract. Also known as the Arum family, members are often colloquially...

 under the APG II system

APG II system

The APG II system of plant classification is the second, now obsolete, version of a modern, mostly molecular-based, system of plant taxonomy that was published in April 2003 by the Angiosperm Phylogeny Group. It was a revision of the first APG system, published in 1998, and was superseded in 2009...

. They were formerly members of the Lemnaceae.

Spirodela species are free-floating thalli

Thallus (tissue)

Thallus, from Latinized Greek θαλλός , meaning a green shoot or twig, is the undifferentiated vegetative tissue of some organisms in diverse groups such as algae, fungus, some liverworts, lichens, and the Myxogastria. Many of these organisms were previously known as the thallophytes, a polyphyletic...

, 2-5 plants may remain connected to each other. Plants are green, but may have a red or brown underside. Multiple root

Root

In vascular plants, the root is the organ of a plant that typically lies below the surface of the soil. This is not always the case, however, since a root can also be aerial or aerating . Furthermore, a stem normally occurring below ground is not exceptional either...

s (7 to 12) emerge from each thallus. Spirodela is larger (10 mm) than Lemna

Lemna

Lemna is a genus of free-floating aquatic plants from the duckweed family. These rapidly-growing plants have found uses as a model system for studies in community ecology, basic plant biology, in ecotoxicology, in production of biopharmaceuticals, and as a source of animal feeds for agriculture...

(2–5 mm, one root per thallus).

Certain species of Spirodela overwinter as turions, a dormant form that lacks air pockets and so sinks to the bottom of the pond. In spring turions rise to the surface and germinate to start a new population.

Spirodela often forms floating mats with related species, e.g. Lemna

Lemna

Lemna is a genus of free-floating aquatic plants from the duckweed family. These rapidly-growing plants have found uses as a model system for studies in community ecology, basic plant biology, in ecotoxicology, in production of biopharmaceuticals, and as a source of animal feeds for agriculture...

and Wolffia

Wolffia

Wolffia is a genus of 9 to 11 species which include the smallest flowering plants on Earth. Commonly called watermeal or duckweed, these aquatic plants resemble specks of cornmeal floating on the water. Wolffia species are free-floating thalli, green or yellow-green, and without roots. The flower...

.

There are three species. Spirodela punctata is sometimes treated as Landoltia punctata.

External links

• Armstrong, W. (2005) Wayne Armstrong's treatment of the Lemnaceae.
• Cross, J.W. (2006). The Charms of Duckweed.
• The Duckweed Genome Project