AQUATIC PLANTS: CHARACTERISTICS, CLASSIFICATION AND SPECIES - BIOLOGY - 2025

The aquatic plants, also called macrophytes, hydrophilic or hygrophilous species that are adapted to living in aquatic environments. They are located in bodies of fresh water, salty or brackish water, stagnant waters or swamps, and both with low and high temperatures.

Aquatic plants include various vascular species pteridophytes and angiosperms, including the algae group and some bryophytes. In fact, many of them comprise families of monocots and dicots.

Aquatic plants. Source: pixabay.com

Most of these species have specialized vegetative structures (such as roots, stems, or leaves) to remain floating or submerged under water. In this sense, there are different categories such as floating plants, partially submerged, submerged and marsh plants located on the banks.

The distribution and spread of aquatic plants is determined by various factors such as climatic, water and geological conditions. Thus, the colonization of aquatic ecosystems is determined by the presence of rhizomes, vegetative reproduction mechanisms and means of dispersal.

Among the great variety of existing aquatic plants we can mention the water hyacinth (Eichhornia crassipes) and the lotus flower (Nelumbo nucifera). As well as water lettuce (Pistia stratiotes), water round (Hydrocotyle ranunculoides) and duckweed (Lemna Sp.)

General characteristics

Most aquatic plants possess multiple morphological and physiological adaptations to live in the different habitats present in aquatic environments. In this regard, they present modifications such as specialized stomata, rhizomatous structures, aerenchymal tissue in stems and roots, and thin epidermis with little lignification.

The root system is characterized by a large number of secondary roots or adventitious roots of large volume, extensive and compact. In fact, its main function is the support and anchoring, since the modified stems and leaves are responsible for nutrition and water absorption.

The leaves have morphological modifications and specialized structures to achieve buoyancy on the water surface. The generally oval and succulent floating leaves and the submerged branched and filamentous leaves stand out.

The flowers of these plants are large, showy and brightly colored, or tiny and modified to survive in aquatic environments, with anemophilic or zoophilic pollination. The multiplication is generally carried out by vegetative propagation, often due to the low viability of the seeds.

The types of plants and habitats where these species develop are highly variable. Thus, we can find from completely or partially submerged plants, to free-living or floating plants.

Classification

Floating plants

Aquatic plants that are located on the surface of the water, in which the entire structure of the plant (roots, stem, leaves and flowers) is floating freely. In fact, the roots are not rooted to the bottom of the pond and reproduce freely through a fast-growing rhizome.

Its main function is to cover the surface of the water to prevent the spread of algae and in some cases to clarify or filter the water. The most representative examples are duckweed (Lemna sp.), Water fern (Azolla sp.), Water hyacinth (Eichhornia crassipes) and water cabbage (Pistia stratiotes).

Submerged plants

Aquatic plants that are characterized by remaining completely submerged under the surface of the water. They are located 40 to 90 cm below the surface, guaranteeing a regular supply of oxygen to the flora and fauna of a pond, limiting the development of algae.

The roots fulfill the function of support and anchoring of the plant favoring the absorption of water and nutrients through a modified stem. Some examples are elodea (Egeria najas), water spike (Potamogeton ferrugineum), water fox tail (Myriophyllum aquaticum) and water nettle (Cabomba caroliniana).

Emerged plants

Aquatic plants called marshlands, located on the margins or banks of bodies of water or aquatic gardens. The roots remain submerged in water most of the time, but they are species that can survive without permanent water.

Both the stem and the roots present a tissue called aerenchyma that favors the storage of oxygen necessary for respiration. Representative species include water primrose (Ludwigia grandiflora), edge celery (Apium nodiflorum), sagittarius (Sagittaria montevidensis) and water cress (Rorippa nasturtium-aquaticum).

Rooted and floating plants

Aquatic plants with extensive foliar area that are suspended on the surface of bodies of water or low intensity water courses. The secondary roots supported by a strong rhizome are fixed to the bottom of the substrate.

The most common species of this type of aquatic plant are the European white water lily (Nymphaea alba) and the yellow water lily (Nuphar luteum). As well as the jopozorra (Ceratophyllum demersum) used as an ornamental plant in fish tanks, and the myriophyll (Myriophyllum spicatum).

Oxygenating plants

Aquatic plants used mainly in aquariums whose function is to keep the water container clean and clear. The leaves have the ability to absorb free minerals and carbon dioxide, also limiting the development of undesirable algae.

The entire body of the plant remains completely submerged under the surface, with the exception of the flowers, which emerge on the water. The most representative species is the millefeuille or filigree (Myriophyllum verticillatum), very common in aquariums and fish tanks.

Representative species

Yellow calta (

Known as yellow calta, calta palustre, aquatic marigold or wart, it is a native plant of Europe belonging to the Ranunculaceae family. It is a plant with aquatic habits that grows in humid and swampy ecosystems, or around flooded areas and water reservoirs.

Calta palustris. Source: Isidre blanc

It is a perennial herbaceous species with short 25-30 cm purple stems and glossy dark green dome leaves with a prominent petiole. The yellow and gold flowers are located at the end of the stem in pairs; it is used as a medicinal plant.

Lotus Flower (

Aquatic plant also known as sacred lotus, Indian lotus or Nile rose is a species belonging to the Nelumbonaceae family. It is a plant traditionally used in water gardens, due to the color and showiness of its flowers that range from intense pink to white.

Nelumbo nucifera. Source: Shin- 改

The simple and peltate leaves of 25 - 100 cm are floating due to the presence of hydrophobic waxes that cover their surface. The reproductive system forms a large conical receptacle with 12-30 carpels and their tubular stigmas, while around it numerous stamens are located with pollen-loaded anthers.

Water hyacinth (

In water hyacinth, also known as aguapey, camalote, bora flower, lechuguín, reyna, tarop or tarulla, it is a species of the Pontederiaceae family. Native to the Amazon basins in South America, it is a floating plant used in aquatic gardens and for medicinal purposes.

Eichhornia crassipes. Source: Katia from Porto Alegre, Brazil

It is characterized by a short stem or rhizome, rosette leaves, swollen petioles, and inflorescence with numerous bluish flowers and a yellow spot on the perianth. Wildly it grows in tropical and subtropical ecosystems in freshwater bodies such as lagoons, lakes, and reservoirs.

Water lettuce (

Pistia stratiotes, better known as lettuce or water cabbage, is a floating plant in the Araceae family. It is a perennial and floating aquatic plant, used in aquatic gardens and small ponds due to its high reproductive capacity.

Pistia stratiotes. Source: Kurt Stüber

It requires high levels of solar radiation and adapts to various ecosystems, which is why it is considered an invasive species in various environments. As an ornamental it is undemanding, since it only requires water and develops quickly in partially or totally sunny places.

Duckweed (

Aquatic plant with small oblong leaves and fast growing belonging to the Araceae family, considered an invasive species of bodies of water. Cosmopolitan species that has a vegetative body in a thaloid form. In it, the stem is not differentiated from the leaves, and its root is thin and whitish.

Lemna minor. Source: Kurt Stüber

It is used in aquatic gardens that receive little solar radiation under their surface, being useful as food for the decorative fish present in the pond. It only requires full sun exposure and fresh water to be able to reproduce abundantly, becoming a pest of aquatic ecosystems.

Water lily (

The water lily or yellow lily is a rhizomatous aquatic plant adapted to high levels of humidity that belongs to the Iridaceae family. It is commonly cultivated in ponds, water gardens of a certain depth, and even in streams or banks of moderately flowing water courses.

Iris pseudacorus. Source: I, Photo2222

It is a species of easy propagation due to the fact that it multiplies by rhizomes or seeds that are dispersed by water and wind. It is characterized by its flower with three yellow petals with garnet or purple touches provided with hermaphrodite reproductive apparatus.

Millefeuille or filigree (

An aquatic herb of the Haloragaceae family, known as plumber, greater filigree, water yarrow or water spike yarrow. It is an aquatic oxygenating plant that acts as a filter for minerals and carbon dioxide, preventing the growth of invasive algae.

Myriophyllum verticillatum. Source: Kristian Peters - Fabelfroh 15:25, 23 October 2006 (UTC)

Ideal aquatic species for the decoration of aquariums where it is required to keep the water clear and free of impurities. It is characterized by its long racemose stems with numerous whorls. It requires little care, just full direct sun exposure and keeping its rapid growth under control.

Water lily (

Perennial aquatic plant known as blue water lily, Egyptian lotus or Egyptian blue lotus, it is a species belonging to the Nymphaeaceae family. Its natural habitat is located on the banks of the Nile River and East Africa, in addition to having been introduced in India and Southeast Asia.

Nymphaea caerulea. Source: Rl

The Water Lily has rounded green leaves, and its flowers of various shades (white, yellow, blue or purple) emerge from a short peduncle. It is usually planted directly at the bottom of ponds or in submerged pots, maintaining a continuous supply of organic matter.

Papyrus (

Papyrus is a marsh plant native to the Mediterranean Sea basin belonging to the Cyperaceae family. It is a rhizomatous species whose characteristic stem with a triangular section usually reaches five meters in height.

Cyperus papyrus. Source: Akire gatuna

The duster-shaped leaves emerge from the end of each stem, long, thin and green. It is a very appreciated species to locate at the ends of aquatic gardens; however, it is highly adaptable in various environments.

References

1. Arreghini Silvana (2018) Aquatic plants (macrophytes). Scientific and Technological Center (CCT) Mendoza. Recovered at: mendoza-conicet.gob.ar
2. Cirujano S., Meco M. Ana & Cezón Katia (2018) Aquatic Flora: Micrófitos. Superior Council of Scientific Investigations. Royal Botanical Garden. Recovered at: miteco.gob.es
3. Hydrophytes and Hygrophytes (2002) Morphology of Vascular Plants. Topic 3: Adaptations of the corm. Morphology and Vascular Plants. Recovered at: biologia.edu.ar
4. Lot, A., Novelo Retana, A., Olvera García, M. and Ramírez García, P. (1999) Catalog of Aquatic Angiosperms of Mexico. Emerging, submerged and floating strictite hydrophytes. Institute of Biology, National Autonomous University of Mexico.
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