MACROPHYTES: CHARACTERISTICS, HABITAT, CLASSIFICATION AND IMPORTANCE - SCIENCE - 2025

The macrophytes and aquatic plants are plant species adapted to living in aquatic environments. They are made up of a heterogeneous functional set of plants of economic importance in aquatic ecosystems.

In fact, species as dissimilar as vascular plants -angiosperms and pteridophytes-, filamentous algae, bryophytes, some monocots and dicotyledons make up this group.

Eichhornia crassipes (water hyacinth). Source: pixabay.com

In this regard, the aquatic macrophytes or hydrophytes have their vegetative structures (roots, stems and leaves) floating or submerged under water. This category includes fully submerged, partially submerged, and floating plants.

Factors such as climate, geological and hydric conditions and topography are fundamental to determine the distribution of macrophytes. The colonization of various aquatic ecosystems is subject to the abundance of rhizomes, clonal development and dispersal mechanisms.

Of the great variety of aquatic macrophytes, the water lettuce (Pistia stratiotes), the water hyacinth (Eichhornia crassipes) and the salvinia (Salvinia Spp.) Stand out. Likewise, the redondita de agua (Hydrocotyle ranunculoides), and certain species of duckweed (Spirodella Spp. And Lemna Spp.).

characteristics

- Macrophytes are macroscopic plants of aquatic life, made up of macroalgae, angiosperms and pteridophytes (ferns and mosses).

- These plants have adapted to aquatic habitats, in this regard they have developed thin epidermis, little lignified and specialized stomata.

Pistia strartiotes (water lettuce). Source: pixabay.com

- Herbaceous and rhizomatous stems have a fragile appearance due to the extensive aerenchyma that surrounds them.

- The root system is not very extensive and compact, characterized by a large volume of adventitious roots.

- The roots generally have an anchoring function since the absorption of water and nutrients is carried out by the modified stem and leaves.

- Most of the leaves have different morphologies, green-creamy tones and functionally adapted to survive in aquatic environments.

- Two types of leaves are located, the floating, generally oval and succulent, and the submerged, filamentous and fractionated.

- The flowers are generally showy and brightly colored, or tiny and modified, with anemophilic or zoophilic pollination.

- Propagation is normally carried out by vegetative multiplication, sexual reproduction per seed being limited due to the low viability of the seeds.

- Living habitats are completely variable, from completely or partially submerged plants, to free-living or floating ones.

Habitat

Aquatic plants or macrophytes frequently inhabit sources of salt or fresh water, in addition they prefer static and low-circulation aquifers. The main bodies of water where they develop are lagoons, dams, swamps, river banks, drains, and even mangrove ecosystems.

Classification

The classification of macrophytes is made based on the form of development and the relationship with the environment where they live.

Rooted and floating macrophytes

They are aquatic plants with a large foliar area suspended on the surface of stagnant water or gentle water currents. The strong rhizomes with a large number of secondary roots are fixed to the bottom of the substrate.

The most representative species are Ceratophyllum demersum (jopozorra), used as an ornamental plant in fish tanks, and Myriophyllum spicatum (myriophyll). Likewise, the Nymphaea alba (European white water lily) and Nuphar luteum (yellow water lily), used in water gardens.

Nymphaea alba (white water lily). Source: pixabay.com

Submerged macrophytes

The main characteristic of this type of aquatic plant is that it remains completely submerged under water. They are large-volume plants, located in the photic region of the body of water, where they take advantage of resources from the aquatic and terrestrial environment.

The root system fulfills only the anchoring function, the absorption of water and nutrients is carried out through the modified stem. Some examples are Cabomba caroliniana, Egeria naias, Myriophyllum aquaticum, Potamogeton ferrugineum, and P. pedersenii.

Cabomba caroliniana. Source: Leslie J. Mehrhoff, University of Connecticut, Bugwood.org, via Wikimedia Commons

Marsh macrophytes or emerging hydrophytes

Aquatic plants that are located in the humid zones around the bodies of water or the edge of the rivers. They are characterized by the presence of specialized tissues -aerrenchyma- that allows them to keep oxygen stored for their vital functions.

Species such as Ludwigia grandiflora and L. peploides have floating stems from which the leaf structures are born. Apium nodiflorum (border celery), Sagittaria montevidensis (sagittarius) and Rorippa nasturtium-aquaticum (watercress or water cress) are other representative species.

Sagittaria montevidensis (sagittarius). Source: I, KENPEI

Free-living or floating macrophytes

Aquatic plants that live on the surface of the water, most of its structure - stems, leaves and flowers - are floating. In this case the roots are not subject to the bottom of the body of water, they have a fast growing rhizome.

Some examples are Lemna sp. (duckweed) characterized by a robust corm and Azolla sp. (water fern) with floating leaves. As well as Eichhornia crassipes (water hyacinth) and Pistia stratiotes (water cabbage) with rosette shape and leaves modified to float.

Azolla sp. (water fern). Source: Kurt Stüber, via Wikimedia Commons

Importance

Macrophytes are plant structures adapted to live in special conditions on the surface of water or flooded areas. From a practical point of view they are usually used as a source of carbon -humus- in soils poor in organic matter.

In this regard, they are raw material for the preparation of concentrated feed for cattle, goats, sheep, fish, and even for human consumption. Some species have medicinal and cosmetic properties, likewise it is used for the manufacture of cellulose and the obtaining of bio-gas.

They are considered excellent bioindicators of water quality, since they are highly sensitive to chemical, physical and hydrological changes in water. In this regard, the presence of macrophytes in an ecosystem is determined by pH, eutrophication, temperature and water circulation.

However, the presence of some species of aquatic plants can constitute a serious ecological problem. The increase in the population of the Lemna minor species constitutes an invasive pest in sedimentation ponds or fish and crustacean culture.

The accumulation of macrophytes favors the absence of oxygen in water bodies due to the accumulation of organic matter. In fact, they prevent light from entering the photic region by reducing the release of oxygen from the photosynthetic algae.

Lemna minor (duckweed). Source:

Some species act as an environment for the spread of pests and diseases, and accumulation and decomposition generates bad odors. In hydraulic works they tend to cause obstructions in channels, reservoirs, dams and water courses, weakening said infrastructures

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. Gallego M. Bianyth D. (2015). Characterization of the Macrophytes of the meander of Say wetland as an input for the conservation tools (Graduate Thesis). University Santo Tomas. Faculty of Environmental Engineering. P 79
4. García Murillo Pablo, Fernández Zamudio Rocío and Surgeon Bracamonte Santos (2009) Inhabitants of water: Macrophytes. Andalusian Water Agency. Ministry of Environment. Junta de Andalucía. 145 p.
5. Hydrophytes and Hygrophytes (2002) Morphology of Vascular Plants. Topic 3: Adaptations of the corm. Morphology and Vascular Plants. Recovered at: biologia.edu.ar
6. Ramos Montaño, C., Cárdenas-Avella, NM, & Herrera Martínez, Y. (2013). Characterization of the community of aquatic macrophytes in lagoons of the Páramo de La Russia (Boyacá-Colombia). Developing Science, 4 (2), 73-82.