The alismatid monocots are a group of 15 interrelated families of flowering plants, named for their largest order, Alismatales. Like other monocots, they usually have a single embryonic leaf (cotyledon) in their seeds, scattered vascular systems, leaves with parallel veins, flowers with parts in threes or multiples of three, and roots that can develop in more than one place along the stems. The alismatids have adapted to thrive in oceans, temperate zones, deserts, the tropics, and even glacial regions.
Like the earliest monocots, many of the alismatid monocots are aquatic, and some grow completely submerged. Apart from the sweet-flag family of wetlands plants, all the alismatid families are in Alismatales. Some of the plants in this order are invasive aquatic weeds that can disrupt and destabilize ecosystems. Others grow in a variety of habitats, especially plants in the aroid family. This family includes the titan arum, with the world's largest unbranched inflorescence, and also the world's smallest flowering plant, duckweed. __FORCETOC__
From the glossary of botanical terms:
a plant species that completes its life cycle within a single year or growing season
attached close to the base (of a plant or an evolutionary tree diagram)
a vine that leans on, twines around or clings to other plants for vertical support
not woody; usually green and soft in texture
hard and lignified; not herbaceous
The APG IV system is the fourth in a series of plant taxonomies from the Angiosperm Phylogeny Group. In this system, the alismatids are basal within the monocots.
| Type genus and etymology | Total genera; global distribution | Description and uses | Order | Type genus images | ||
|---|---|---|---|---|---|---|
| Acoraceae (sweet-flag family) | Acorus comes from a Latin plant name. | 1 genus, in North America, Europe and Asia | Herbaceous aromatic plants with thin, sword-shaped leaves. The rhizomes are essentially non-vascular. | Acorales | ||
| Alismataceae (water-plantain family) | Alisma comes from a Greek plant name. | 18 genera, worldwide | Herbaceous latex-bearing aquatic plants, usually perennials. They take root in freshwater beds, and some remain submerged. Two species are consumed in Asia, and another was a food source for Native Americans. photosynthesis has been observed in Sagittaria. | Alismatales | ||
| Aponogetonaceae (waterblommetjie family) | Aponogeton is from the Latin for "near (the hot springs at) Aponus". | 1 genus, in Africa, Oceania, and South and Southeast Asia | Herbaceous smooth-stemmed freshwater perennials, usually with long leaf-stalks. Cape pondweed flowers are consumed as a delicacy in South Africa; the tubers are also edible. | Alismatales | ||
| Araceae (aroid family) | Arum comes from a Greek plant name. | 142 genera, worldwide, especially in the tropics | Generally sappy, herbaceous plants growing in soil, in water and on trees, along with a few woody climbers. Many cultures have relied on taro plants (which are toxic when raw) as a staple crop. | Alismatales | ||
| Butomaceae (flowering-rush family) | Butomus is from the Greek for "ox-wounding", named for the sharp leaves. | 1 genus, in temperate Europe and Asia | Smooth-stemmed herbaceous aquatic, swamp or marsh plants, usually with milky latex. They are consumed in parts of Russia, in bread or as a vegetable. | Alismatales | ||
| Cymodoceaceae (turtle-grass family) | Cymodocea was named for Cymodoce, a Greek sea nymph. | 6 genera, in tropical and warm temperate seas | Large perennials, up to 30cm (10inches) long in the genus Cymodocea. They nourish and shelter many crustaceans and fish that are harvested commercially. | Alismatales | ||
| Hydrocharitaceae (frogbit family) | Hydrocharis is from the Greek for "water grace". | 14 genera, worldwide | Annual and perennial aquatic plants. One species is consumed in Asia. Many invasive genera have become entrenched, causing considerable economic damage. | Alismatales | ||
| Juncaginaceae (arrowgrass family) | Juncago (an earlier synonym for the type genus, Triglochin) is from the Latin for "a rush-like plant". | 3 genera, in northern temperate zones, South America, Oceania and parts of Africa | Herbaceous plants with grass-like leaves that grow in soil or water. Two species are edible. | Alismatales | ||
| Maundiaceae (Maund's-arrowgrass family) | Maundia was named for John Maund (1823–1858), a physician and chemist. | 1 genus, in eastern Australia | Aquatic perennials with leaves up to 80cm (30inches) long. The family is likely to become endangered as water tables recede in eastern Australia. | Alismatales | ||
| Posidoniaceae (tapeweed family) | Posidonia was named for Poseidon, a Greek god. | 1 genus, in the Mediterranean and oceans south and west of Australia | Submerged plants with long linear leaves. Genetically identical beds of Posidonia oceanica in the Mediterranean can be kilometers wide and persist for many thousands of years. | Alismatales | ||
| Potamogetonaceae (pondweed family) | Potamogeton comes from Greek and Latin plant names. | 5 genera, worldwide | Aquatic plants, usually perennials. The plants are an important food source for many birds and aquatic animals. | Alismatales | ||
| Ruppiaceae (tasselweed family) | Ruppia was named for Heinrich Bernhard Ruppius (1688–1719). | 1 genus, scattered worldwide, in ponds, marshes and shallow seas | Submerged herbaceous plants, usually annuals with stalkless leaves | Alismatales | ||
| Scheuchzeriaceae (Rannoch-rush family) | Scheuchzeria was named for Johann Gaspar Scheuchzer (1684–1738) and his brother Johann Jacob. | 1 genus, in arctic sphagnum bogs | Perennial aquatic plants. The linear leaves have parallel veins. | Alismatales | ||
| Tofieldiaceae (false-asphodel family) | Tofieldia was named for Thomas Tofield (1730–1779). | 4 genera, mostly in northern boreal and montane zones, with some species in the US, China and Japan | Herbaceous rhizomatous perennials, usually with leaves attached at the plant's base | Alismatales | ||
| Zosteraceae (eelgrass family) | Zostera is from the Greek for "belt". | 2 genera, in temperate and subtropical sea beds | Perennials with simple leaves. The plants have been used as packing material. The dense growths support commercially important fish and shrimp. | Alismatales |