what are they?
Algae belong to the realm of plants and are thus able, like terrestrial plants, individual substances to manufacture high-energy from sun, water and carbon dioxide. That are capable of photosynthesis, and that's because they have chlorophyll and other pigments. The algae are differentiated from higher plants because they have developed complex structures in their structural organization. Another name often attributed to the algae is "tallofite," because their body plant is a "tall", a structure that is no true tissues or organs specialized, for example, in the absorption of substances from the substrate, a function that in higher plants, is carried out by the roots. This absence in the development of complex cellular organization is likely to include the environment of their choice to live. In fact, the algae live in water or very moist environments, and have no problem in the absorption of
liquid or vice versa, in preserving them. To tell the truth in some algae have evolved different tissues similar to those of terrestrial plants in the transport of nutrients. A final feature that distinguishes the algae, is the absence of flowers, that is sterile structures that protect the reproductive organs.
what they do?
In systems constructed wetland plants have an active role and not merely for the aesthetic treatment.
water treatment is based on the cooperative growth of macrophytes and their associated microorganisms, which play a large part of the process of degradation organic matter. Aquatic plants remove some of the unwanted substances through the assimilation into the tissues and surface and provide a suitable environment for microorganisms that convert the pollutants and reduce the concentration.
In the aquatic natural overgrowth of vegetation formations, especially monospecific, indicates a high trophic status (eutrophic) generated mainly by organic pollution and nutrients (nitrogen compounds and phosphates). This being a state of degradation of the ecosystem is revealed in plants for a win-win situation, which stimulates growth and proliferation of algae and aquatic plants. These act as biological filters, removing pollutants from water and oxygen supply at the same time. Some
helophytes as Phragmites and Typha, mediating the transfer of oxygen from the aerial parts of the rhizosphere through the loss of oxygen from the root, increase the aerobic degradation of organic matter and nitrification. Phragmites australis is particularly important that not only works as an oxygen pump, but is also able to build around his drums microecosistema a very efficient in removing extraneous items (such as pathogenic micro-organisms) (Brix, 1994).
Aquatic plants have the characteristic of a spongy tissue, aerifero parenchyma, particularly developed in stems and roots characterized by large intercellular spaces filled with air.
The roots of aquatic plants are in fact normally submerged in the sediments, ie in an environment poor in oxygen that prevents them from breathing to obtain the necessary energy absorption of the ions. The plant will then carries oxygen to survive the aerial organs (stem and leaves) through the network of canals aerifero parenchyma.
The transfer of oxygen within the plant takes place by passive diffusion according to concentration gradient of gas in the interior and convective flow driven by pressure gradient that is generated for the various physical processes present. Several authors indicate that the pressure gradient causes the differences in temperature and vapor pressure of water through the porous membranes of plant tissues, or the Venturi-induced effect that is generated by the gradient of wind speed around the plant (Armstrnong & Armstrnong, 1990, Brix, 1993). The Venturi-induced effect allows the passage of oxygen into the damaged plants or even death during the winter and at night, because it depends on the temperature outside.
The amount of oxygen transferred to the roots, there are no uniform values \u200b\u200bin the literature, probably due to the different conditions under which the experiments were conducted. The literature has reported a release of oxygen by the roots of Phragmites australis, which ranges from 0.02 g/m2/da values \u200b\u200bbetween 5 and 45 g/m2/d (Reed & Brown, 1992), which vary depending on the density plants, the oxygen demand by the saturated soil and the permeability of the roots.
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