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Aquatic plant facts for kids

Kids Encyclopedia Facts
FloatingRedBlueLilies
Water lillies, with flowers above the water
Nymphaea 02 ies
Section of the stem of a water lilly

Aquatic plants are plants that have adapted to live in the water. This can be either freshwater, such as in rivers and lakes, saltwater as in the sea, or brackish water, as in the estuary of a river.

They are also referred to as hydrophytes or macrophytes to distinguish them from algae and other microphytes. A macrophyte is a plant that grows in or near water and is either emergent, submergent, or floating. In lakes and rivers macrophytes provide cover for fish , substrate for aquatic invertebrates, produce oxygen, and act as food for some fish and wildlife.

Some aquatic plants are partly submerged, others are totally submerged. Common adaptations include leaves that float on the water, and special tissue that allows to transport air and other gases inside the plant.

Classification of Macrophytes

Marchantiales cf Conocephalum 20071111
Many liverworts grow either submerged or on land.
CeratophyllumSubmersum
'Ceratophyllum submersum, a free-floating plant that grows completely submerged
Eriocaulon aquaticum
Eriocaulon aquaticum, an isoetid example, grows submerged in water.
Waterlettuce
Pistia stratiotes, an example of a pleuston, a plant that floats freely on the water surface
Lysichton americanus in Lochnabo Burn, Scotland
Lysichiton americanus grows rooted in the bottom with leaves and flowers above the waterline.
Waterlily (238959085)
Water lilies grow rooted in the bottom with leaves that float on the water surface.

Based on growth form, macrophytes can be characterised as:

  • Emergent
  • Submerged
    • Rooted: rooted to the substrate
    • Unrooted: free-floating in the water column
    • Attached: attached to substrate but not by roots
  • Floating-leaved
  • Free-floating

Emergent

An emergent plant is one which grows in water but pierces the surface so that it is partially in air. Collectively, such plants are emergent vegetation.

This habit may have developed because the leaves can photosynthesis more efficiently in air and competition from submerged plants but often, the main aerial feature is the flower and the related reproductive process. The emergent habit permits pollination by wind or by flying insects.

There are many species of emergent plants, among them, the reed (Phragmites), Cyperus papyrus, Typha species, flowering rush and wild rice species. Some species, such as purple loosestrife, may grow in water as emergent plants but they are capable of flourishing in fens or simply in damp ground.

Submerged

Submerged macrophytes completely grow under water with roots attached to the substrate or without any root system. Helophytes are plants that grows in a marsh, partly submerged in water, so that it regrows from buds below the water surface. Fringing stands of tall vegetation by water basins and rivers may include helophytes.

Floating-leaved

Floating-leaved macrophytes have root systems attached to the substrate or bottom of the body of water and with leaves that float on the water surface. Common floating leaved macrophytes are water lilies (family Nymphaeaceae), pondweeds (family Potamogetonaceae).

Free-floating

Free-floating macrophytes are aquatic plants that are found suspended on water surface with their root not attached to substrate, sediment, or bottom of the water body. They are easily blown by air and provide breeding ground for mosquitoes. Example include Pistia spp commonly called water lettuce, water cabbage or Nile cabbage.

Morphological classification

The many possible classifications of aquatic plants are based upon morphology. One example has six groups as follows:

  • Amphiphytes: plants that are adapted to live either submerged or on land
  • Elodeids: stem plants that complete their entire lifecycle submerged, or with only their flowers above the waterline
  • Isoetids: rosette plants that complete their entire lifecycle submerged
  • Helophytes: plants rooted in the bottom, but with leaves above the waterline
  • Nymphaeids: plants rooted in the bottom, but with leaves floating on the water surface
  • Pleuston: vascular plants that float freely in the water

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