Hydrophytes are defined as aquatic plants whose water needs are maximum and which have adapted to living submerged or floating in the water. These plants include both angiosperms and ferns. Algae, organisms devoid of real tissues of conduction, do not come by convention considered in this category.
Due to the particular environment that these plants have colonized, they show some special adaptations:
– a very thin or absent cuticle;
– stomata with guard cells mostly inactive, which remain open;
– the lack of large areas of supporting tissues as the hydrostatic thrust of the water supports them;
– roots specialized in oxygen capture;
– absorbent roots small and inactive;
– aerial fabrics with floating function.
Hydrophytes reproduce quite easily, even from small portions of them; many of their species are considered invasive in many parts of the world.
In this grouping, according to Raunkjaer’s classification for biological form, aquatic plants with perennial buds completely submerged or swimming in the water are thus included.
Hydrophytes are distinguished in:
– Nat hydrophytes natants: are floating aquatic plants, not anchored to the bottom and without true roots (Ceratophyllum, Utricularia);
– Radic Hydrophytic radishes: aquatic plants rooted at the bottom, and thus submerged perennial organs (Nymphaea, Potamogeton), belong to this subgroup.