Aquatic plant
[5][6][7] Aquatic plants only thrive in water or in soil that is frequently saturated, and are therefore a common component of swamps and marshlands.
[12] Fully submerged aquatic plants have little need for stiff or woody tissue as they are able to maintain their position in the water using buoyancy typically from gas filled lacunaa or turgid Aerenchyma cells.
Many fully submerged plants have finely dissected leaves, probably to reduce drag in rivers and to provide a much increased surface area for interchange of minerals and gasses.
In floating aquatic angiosperms, the leaves have evolved to only have stomata on the top surface to make use of atmospheric carbon dioxide.
[15] For carbon fixation, some aquatic angiosperms are able to uptake CO2 from bicarbonate in the water, a trait that does not exist in terrestrial plants.
[32] This is considered a form of phenotypic plasticity as the plant, once submerged, experiences changes in morphology better suited to their new aquatic environment.
[35][36] Terrestrial plants no longer had unlimited access to water and had to evolve to search for nutrients in their new surroundings as well as develop cells with new sensory functions, such as statocytes.
[16] In aquatic plants diffuse boundary layers (DBLs) around submerged leaves and photosynthetic stems vary based on the leaves' thickness, shape and density and are the main factor responsible for the greatly reduced rate of gaseous transport across the leaf/water boundary and therefore greatly inhibit transport of carbon dioxide.
[37] Although most aquatic angiosperms can reproduce by flowering and setting seeds, many have also evolved to have extensive asexual reproduction by means of rhizomes, turions, and fragments in general.
Many small animals use aquatic plants such as duckweeds and lily pads for spawning or as protective shelters against predators both from above and below the water surface.
[38] They compete with phytoplanktons for excess nutrients such as nitrogen and phosphorus, thus reducing the prevalence of eutrophication and harmful algal blooms, and have a significant effect on riparian soil chemistry[39] as their leaves, stems and roots slow down the water flow, capture sediments and trap pollutants.
Excess sediment will settle into the stream bed due to the reduced flow rates, and some aquatic plants also have symbiotic microbes capable of nitrogen fixation and breaking down the pollutants trapped and/or absorbed by the roots.
[46] Macrophytes promote the sedimentation of suspended solids by reducing the current velocities,[47] impede erosion by stabilising soil surfaces.
The additional site-specific macrophytes' value provides wildlife habitat and makes treatment systems of wastewater aesthetically satisfactory.
Conversely, overly high nutrient levels may create an overabundance of macrophytes, which may in turn interfere with lake processing.
[3] Macrophyte levels are easy to sample, do not require laboratory analysis, and are easily used for calculating simple abundance metrics.
[3] Phytochemical and pharmacological researches suggest that freshwater macrophytes, such as Centella asiatica, Nelumbo nucifera, Nasturtium officinale, Ipomoea aquatica and Ludwigia adscendens, are promising sources of anticancer and antioxidative natural products.
Hot water extract prepared from the leaf of Ludwigia adscendens exhibits alpha-glucosidase inhibitory activity more potent than that of acarbose.
