Nymphaeaceae

Botanical characteristics

The plants belonging to this family are herbaceous fully adapted to aquatic life, typically rooting with secondary root systems that attach to the muddy bottom through fleshy rhizomes, often tuberous. The hypogeal stem is fleshy, flexible, and rich in aeriferous tissues, which ensure buoyancy and the transfer of oxygen to the roots. The epigeal part of the stem is practically absent.

The leaves are broad, generally floating, with a flat blade and a more or less leathery texture. They are peltate, meaning the petiole is inserted towards the center of the blade, in a narrow and deep notch. The shape of the leaves varies from round to cordate or sagittate, with a continuous margin, sometimes toothed. The upper surface is green, waxy, and equipped with stomata for gas exchange, while the lower surface can assume purplish colors due to the presence of anthocyanins, which convert sunlight into heat, favoring metabolic processes. Leaf dimorphism is often observed, with submerged leaves lighter and more fragile, with a thin blade and not peltate. In some extra-European species, leaves with spiny veins or raised edges are noted.

The flowers are large, hermaphroditic, and floating, usually solitary, placed in the leaf axil or in an extra-axillary position, supported by long cylindrical peduncles whose length varies according to the water depth. Their opening occurs mainly during the day, although some tropical species have nocturnal blooming. The particular arrangement of the floral organs is expressed in a spirocyclic perianth, with sepals (4-7) and numerous petals arranged in a spiral, gradually decreasing in size towards the center, fading into filamentous structures comparable to stamens. The androecium is formed by a large number of stamens with linear anthers with longitudinal dehiscence, while the gynoecium includes an ovary from semi-inferior to superior, multi-carpellary (3 or more carpels), with laminar placentation and anatropous ovules. The styles are numerous and arranged in a crown.

The fruits are globose berries with irregular dehiscence, often capable of maturing underwater or just at the water surface. The axial tissue that protects the carpels detaches at maturity releasing numerous ellipsoid seeds, smooth or pubescent, with endosperm, facilitating their dispersal.

Distribution and diversity

Probably originating from Asia, the family has a cosmopolitan distribution, with species present in temperate and tropical climates worldwide, from the northern hemisphere to southern Africa, Australia, and New Guinea. They are hardy species well adapted to various aquatic environments, including marshy areas subject to temporary water level drops.

Main genera and representative species

The main genus is Nymphaea, which gives the family its name. Other well-known genera include Euryale and Victoria, the latter famous for large leaves with raised edges. In Italy, several species of water lilies are present, mainly belonging to the genus Nymphaea, with white, pink, or blue flowers, typical of ponds, lakes, and still waters.

Etymology

The name of the family derives from the most important genus, Nymphaea. The origin of the name seems to trace back to the Arabic word “nenufar,” which in turn derives from the Persian “blue lotus.” The term was introduced into botanical nomenclature in 1534 by Otto Brunfels, while the currently accepted scientific name “Nymphaeaceae” was proposed by the English botanist Richard Anthony Salisbury in 1805.

Curiosities and uses

Water lilies play an important ecological role in aquatic ecosystems, providing habitat and food resources to numerous insects, particularly flies, which are the main pollinators of this family. Some species have fragrant and showy flowers that contribute to the biodiversity of wet environments. Their ornamental appearance makes them highly appreciated in aquatic gardens and decorative fountains.

Sources

• Wikipedia
• Internal botanical database