Nymphaeaceae () is a family of flowering plants, commonly called water lilies. They live as rhizomatous aquatic herbs in temperate and tropical climates around the world. The family contains five genera with about 70 known species. Water lilies are rooted in soil in bodies of water, with leaves and flowers floating on or rising from the surface. Leaves are oval and heart-shaped in Barclaya. Leaves are round, with a radial notch in Nymphaea and Nuphar, but fully circular in Victoria and Euryale. Water lilies are a well-studied family of plants because their large flowers with multiple unspecialized parts were initially considered to represent the floral pattern of the earliest flowering plants. Later genetic studies confirmed their evolutionary position as basal angiosperms. Analyses of floral morphology and molecular characteristics and comparisons with a sister taxon, the family Cabombaceae, indicate, however, that the flowers of extant water lilies with the most floral parts are more derived than the genera with fewer floral parts. Genera with more floral parts, Nuphar, Nymphaea, Victoria, have a beetle pollination syndrome, while genera with fewer parts are pollinated by flies or bees, or are self- or wind-pollinated. Thus, the large number of relatively unspecialized floral organs in the Nymphaeaceae is not an ancestral condition for the clade.
Description
Vegetative characteristics The Nymphaeaceae are annual or perennial, aquatic, rhizomatous herbs. The family is further characterized by scattered vascular bundles in the stems, and frequent presence of latex, usually with distinct, stellate-branched sclereids projecting into the air canals. Hairs are simple, usually producing mucilage (slime). Leaves are alternate and spiral, opposite or occasionally whorled, simple, peltate or nearly so, entire to toothed or dissected, short to long petiolate, with blade submerged, floating or emergent, with palmate to pinnate venation. Stipules are either present or absent.
Generative characteristics Flowers are solitary, bisexual, radial, with a long pedicel and usually floating or raised above the surface of the water, with girdling vascular bundles in receptacle. Some species are protogynous and primarily cross-pollinated, but because male and female stages overlap during the second day of flowering, and because it is self-compatible, self-fertilization is possible. Female and male parts of the flower are usually active at different times, to facilitate cross-pollination, although this is just one of several reproductive strategies used by these plants. There are 4–12 sepals, which are distinct to connate, imbricate, and often petallike. Petals lacking or 8 to numerous, inconspicuous to showy, often intergrading with stamens. Stamens are 3 to numerous, the innermost sometimes represented by staminodes. Filaments are distinct, free or adnate to petaloid staminodes, slender and well differentiated from anthers to laminar and poorly differentiated from anthers; pollen grains usually monosulcate or lacking apertures. Carpels are 3 to numerous, distinct or connate. The fruit is an aggregate of nuts, a berry, or an irregularly dehiscent fleshy spongy capsule. Seeds are often arillate, more or less lacking endosperm.
Taxonomy
Nymphaeaceae has been investigated systematically for decades because botanists considered their floral morphology to represent one of the earliest groups of angiosperms. Modern genetic analyses by the Angiosperm Phylogeny Group researchers has confirmed its basal position among flowering plants. In addition, the Nymphaeaceae are more genetically diverse and geographically dispersed than other basal angiosperms. Nymphaeaceae is placed in the order Nymphaeales, which is the second diverging group of angiosperms after Amborella in the most widely accepted flowering plant classification system, APG IV system.
Nymphaeaceae is a small family of three to six genera: Barclaya, Euryale, Nuphar, Nymphaea, Ondinea, and Victoria. The genus Barclaya is sometimes given rank as its own family, Barclayaceae, on the basis of an extended perianth tube (combined sepals and petals) arising from the top of the ovary and by stamens that are joined in the base. However, molecular phylogenetic work includes it in Nymphaeaceae. The genus Ondinea has recently been shown to be a morphologically aberrant species of Nymphaea, and is now included in this genus. The genera Euryale, of far east Asia, and Victoria, from South America, are closely related despite their geographic distance, but their relationship toward Nymphaea need further studies. The sacred lotus was once thought to be a water lily, but is now recognized to be a highly modified eudicot in its own family Nelumbonaceae of the order Proteales.
Fossils
Several fossil species are known, including Cretaceous representatives of Nymphaea, as well as fossil genera such as Jaguariba from the Cretaceous of Brazil, Allenbya from the Ypresian of British Columbia, Notonuphar from the Eocene of Antarctica, Nuphaea from the Eocene of Germany, Susiea from the Late Paleocene Almont Flora of North Dakota, USA, and Barclayopsis from the Maastrichtian of Eisleben, Germany.
Invasiveness The beautiful nature of water lilies has led to their widespread use as ornamental plants. The Mexican waterlily, native to the Gulf Coast of North America, is planted throughout the continent. It has escaped from cultivation and become invasive in some areas, such as California's San Joaquin Valley. It can infest slow-moving bodies of water and is difficult to eradicate. Populations can be controlled by cutting top growth. Herbicides can also be used to control populations using glyphosate and fluridone.
Culture
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