Nuphar
Nuphar is a genus of aquatic plants in the family Nymphaeaceae, with a temperate to subarctic Northern Hemisphere distribution. Common names include water-lily (Eurasian species; shared with many other genera in the same family), pond-lily, alligator-bonnet or bonnet lily, and spatterdock (North American species).[1]
The etymology of the word is: medieval Latin nuphar, from medieval Latin nenuphar, thence from Arabic nīnūfar, thence from Persian nīlūfar, thence from Sanskrit nīlōtpala = blue lotus flower.[2] For botanical gender, the name is treated as feminine.[3][4]
The genus is closely related to Nymphaea. Nuphar differs in that its petals are much smaller than its 4-6 bright yellow-coloured sepals, whereas in Nymphaea, the petals are much larger than the sepals. The genera also differ in the maturation of their fruit; while maturing, Nuphar fruit remain above water level on their scapes, whereas fruit of Nymphaea sink below water level immediately after their flowers close, and there they mature. In both genera the leaves float and have a radial notch from the circumference to the point of attachment of the petiole. Depending on the species, the leaves of most species range from cordate to practically circular with the petiole attached in the middle, giving a peltate appearance. Some however, have modified versions of that leaf morphology; for example the leaves of Nuphar sagittifolia have leaves of an elongated sagittate form.
The number of species in the genus is still under review.[3][5] Until the mid-20th century, some botanists treated the genus as just a single variable species (for which the European name N. lutea has priority),[6][7] while some other authorities accepted about a dozen more species on the basis of traditional taxonomic standards.[4] Recent molecular work has shown that there are substantial differences between the Eurasian species (sect. Nuphar) and American species (sect. Astylus), except for North American N. microphylla which clusters with the Eurasian species.[4][8] Molecular taxonomy has shown conclusively that recognition of so few species is out of the question, and forced an increased number of recognised species; some sources list about seventy.[3] The Kew Gardens plant list includes over twenty accepted species, subspecies and varieties; it also has a similar number as yet unresolved, together with over twenty synonyms.[5]
Nuphar species occur in ponds, lakes, and slow-moving rivers, growing in water up to 5 metres deep; different species are variously adapted either to nutrient-rich waters (e.g. Nuphar lutea) or nutrient-poor waters (e.g. Nuphar pumila).[11]
Wetland soils are hypoxic, and this genus is known to be capable of temporary growth even in the absence of oxygen.[12] Also there can be mass flow of oxygen-containing air, entering by means of the young leaves, passing through the rhizome, and exiting through the older leaves.[13] Both of these physiological adaptations to flooding are considered typical of many wetland and aquatic plants.[14]
