Aquatic plants are [plant ]s that have adapted to living in aquatic environments (saltwater or freshwater). They are also referred to as hydrophytes or macrophytes. A macrophyte is an aquatic plant that grows in or near water and is either emergent, submergent, or floating, and includes helophytes (a plant that grows in marsh, partly submerged in water, so that it regrows from buds below the water surface). In lakes and rivers macrophytes provide cover for fish and substrate for aquatic invertebrates, produce oxygen, and act as food for some fish and wildlifeGenerations ago, people believed that anything green that was not considered an animal was a plant. Today, you know that not all green things are plants and that some plants aren’t green at all. In 1978, a modern classification of plants was proposed by plant ecologist, Robert Whittaker, who gave five divisions: monera (single-celled organism), protoctista (mainly fresh water aquatic plants), fungi (ascomycete, basidiomycete, chytria and penicillium conidiophor), plantae (algae, all seaweed and kelp) and animalia (sponge, jellyfish, insect, etc). The role of aquatic plants is so essential for survival that they belong to two divisions: Plantae and Protoctista.
Physical Characteristics and Adaptation of Aquatic Plants:
Aquatic plants, also termed as hydrophytes or aquatic macrophytes, live within watery environments. In the ecosystem, aquatic plants serve as food and habitat for animals living in the sea and prevent shorelines, ponds and lakes from eroding by providing soil stability.
Characteristics common to aquatic plants:
- Most aquatic plants do not need cuticles or have thin cuticles as cuticles prevent loss of water.
- Aquatic plants keep their stomata always open for they do not need to retain water.
- On each side of their leaves are a number of stomata.
- Aquatic plants have less rigid structure since water pressure supports them.
- Since they need to float, leaves on the surface of plants are flat.
- The presence of air sacs enables them to float.
- Their roots are smaller so water can spread freely and directly into the leaves.
- Their roots are light and feathery since they do not need to prop up the plants.
- Roots are specialized to take in oxygen.
Adaptation of aquatic plants is evident by their structure: deeply dissected and waxy leaves, specialized pollination mechanism and variation in growth pattern. These are the types of plants based on adaptation:
- Totally submerged plants – Are considered true water plants or hydrophytes. Example: Water starwort submerged in a marsh pond.
- Floating plants – Are rooted in floating water (example: water lily) or not rooted in the sediment just on the surface (example: duckweed).
- Swamp plants – Are emergent plants with their lower part submerged. (Example: reed mace)