Hydrocharitaceae is a

flowering plant Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (). The term angiosperm is derived from the Ancient Greek, Greek words (; 'container, vessel') and (; 'seed'), meaning that the seeds are enclosed with ...

family which includes 14 accepted genera and a total of ca 135 known species (Christenhusz & Byng 2016). The family holds a number of species of

aquatic plants Aquatic plants, also referred to as hydrophytes, are vascular plants and non-vascular plants that have adapted to live in aquatic environments ( saltwater or freshwater). In lakes, rivers and wetlands, aquatic vegetations provide cover for aquat ...

, including tape-grass, the well-known

Canadian waterweed ''Elodea canadensis'' (American waterweed or Canadian waterweed or pondweed) is a perennial aquatic plant, or submergent macrophyte, native to most of North America.Flora of North America''Elodea canadensis''/ref>Plants of British Columbia''Elode ...

, and frogbit. The family includes both freshwater and marine aquatics. They are found throughout the world in a wide variety of habitats, but are primarily tropical.

Description

The species are

annual Annual may refer to: *Annual publication, periodical publications appearing regularly once per year **Yearbook **Literary annual *Annual plant *Annual report *Annual giving *Annual, Morocco, a settlement in northeastern Morocco *Annuals (band), a ...

perennial In horticulture, the term perennial ('' per-'' + '' -ennial'', "through the year") is used to differentiate a plant from shorter-lived annuals and biennials. It has thus been defined as a plant that lives more than 2 years. The term is also ...

, with a creeping monopodial

rhizome In botany and dendrology, a rhizome ( ) is a modified subterranean plant stem that sends out roots and Shoot (botany), shoots from its Node (botany), nodes. Rhizomes are also called creeping rootstalks or just rootstalks. Rhizomes develop from ...

with the

leaves A leaf (: leaves) is a principal appendage of the stem of a vascular plant, usually borne laterally above ground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, stem, ...

arranged in two vertical rows, or an erect main shoot with

root In vascular plants, the roots are the plant organ, organs of a plant that are modified to provide anchorage for the plant and take in water and nutrients into the plant body, which allows plants to grow taller and faster. They are most often bel ...

s at the base and spirally arranged or whorled leaves. The leaves are simple and usually found submerged, though they may be found floating or partially emerse. As with many aquatics they can be quite variable in shape – from

linear In mathematics, the term ''linear'' is used in two distinct senses for two different properties: * linearity of a '' function'' (or '' mapping''); * linearity of a '' polynomial''. An example of a linear function is the function defined by f(x) ...

orbicular Orbicular is an adjective meaning "circular" Orbicular may also refer to: * Orbicular leaf, a plant leaf shape * Orbicularis oculi muscle, a muscle around the eye * Orbicularis oris muscle, a muscle around the mouth * Orbicular batfish, a species ...

, with or without a

petiole Petiole may refer to: *Petiole (botany), the stalk of a leaf, attaching the blade to the stem *Petiole (insect anatomy) In entomology, petiole is the technical term for the narrow waist of some hymenopteran insects, especially ants, bees, and ...

, and with or without a sheathing base. The

flower Flowers, also known as blooms and blossoms, are the reproductive structures of flowering plants ( angiosperms). Typically, they are structured in four circular levels, called whorls, around the end of a stalk. These whorls include: calyx, m ...

s are arranged in a forked, spathe-like

bract In botany, a bract is a modified or specialized leaf, associated with a reproductive structure such as a flower, inflorescence axis or cone scale. Bracts are usually different from foliage leaves in size, color, shape or texture. They also lo ...

or between two opposite bracts. They are usually irregular, though in some case they may be slightly irregular, and either bisexual or unisexual. The

perianth The perianth (perigonium, perigon or perigone in monocots) is the non-reproductive part of the flower. It is a structure that forms an envelope surrounding the sexual organs, consisting of the calyx (sepals) and the corolla (petals) or tepal ...

segments are in 1 or 2 series of 2–3 free segments; the inner series when present are usually showy and petal-like.

Stamen The stamen (: stamina or stamens) is a part consisting of the male reproductive organs of a flower. Collectively, the stamens form the androecium., p. 10 Morphology and terminology A stamen typically consists of a stalk called the filament ...

s 1–numerous, in 1 or more series; the inner ones sometimes sterile.

pollen grains Pollen is a powdery substance produced by most types of flowers of seed plants for the purpose of sexual reproduction. It consists of pollen grains (highly reduced microgametophytes), which produce male gametes (sperm cells). Pollen grains h ...

are globular and free but in the marine genera ('' Thalassia'' and ''

Halophila ''Halophila'' is a genus of seagrasses in the family '' Hydrocharitaceae'', the tape-grasses. It was described as a genus in 1806. The number of its contained species, and its own placement in the order Alismatales, has evolved. Description T ...

'') – the pollen grains are carried in chains, like strings of beads. The

ovary The ovary () is a gonad in the female reproductive system that produces ova; when released, an ovum travels through the fallopian tube/ oviduct into the uterus. There is an ovary on the left and the right side of the body. The ovaries are end ...

is inferior with 2–15 united

carpels Gynoecium (; ; : gynoecia) is most commonly used as a collective term for the parts of a flower that produce ovules and ultimately develop into the fruit and seeds. The gynoecium is the innermost whorl of a flower; it consists of (one or more) ...

containing a single

locule A locule (: locules) or loculus (; : loculi) is a small cavity or compartment within an organ or part of an organism (animal, plant, or fungus). In angiosperms (flowering plants), the term ''locule'' usually refers to a chamber within an ovary ...

with numerous ovules on parietal placentas which either protrude nearly to the centre of the ovary or are incompletely developed.

Fruit In botany, a fruit is the seed-bearing structure in flowering plants (angiosperms) that is formed from the ovary after flowering. Fruits are the means by which angiosperms disseminate their seeds. Edible fruits in particular have long propaga ...

s are globular to linear, dry or pulpy, Dehiscence (botany), dehiscent or more usually indehiscent and opening by decay of the Fruit anatomy, pericarp. Seeds are normally numerous with straight embryos and no endosperm. Pollination can be extremely specialised. The most recent phylogenetic treatment of the family recognizes four Family (biology), subfamilies. * Subfamily Anacharioideae (''Appertiella'', ''Blyxa'', ''Egeria (plant), Egeria'', ''Elodea'', ''Lagarosiphon'' and ''Ottelia'') * Subfamily Hydrilloideae (''Enhalus'', ''

'', ''Hydrilla'', ''Maidenia'', ''Najas'', ''Nechamandra'', '' Thalassia'' and ''Vallisneria''). * Subfamily Hydrocharitoideae (''Hydrocharis'', ''Limnobium'') * Subfamily Stratiotoideae (''Stratiotes'') Hydrilla verticillata is it- in Hyderabad W2 IMG 8305

Hydrilla verticillata is it- in Hyderabad W2 IMG 8305

Uses

Some species have become established ornamental plants, and subsequently serious weeds in the wild (especially ''Egeria (plant), Egeria'', ''Elodea'' and ''Hydrilla'').

Genera

14 genera are currently accepted. *''Appertiella'' *''Blyxa'' *''Elodea'' (synonyms ''Apalanthe'' and ''Egeria'' ) *''Enhalus'' *''

'' *''Hydrilla'' *''Hydrocharis'' (synonym ''Limnobium'' ) *''Lagarosiphon'' *''Najas'' Genera of Hydrocharitaceae
''GRIN Taxonomy for Plants'' *''Nechamandra'' *''Ottelia'' *''Stratiotes'' *'' Thalassia'' *''Vallisneria'' (synonym ''Maidenia'' )

References

External links

* * * {{Taxonbar, from=Q156029 Hydrocharitaceae, Aquatic plants Alismatales families Taxa described in 1789 Taxa named by Antoine Laurent de Jussieu