Hydrophytes are well adapted to aquatic environments.
Some morphological character of hydrophytes :
- Roots may be absent (Wolffia, Utricularia) or poorly developed (Hydrilla).
- Roots, if present, are mostly concerned with Anchorage (Ranunculus).
- Root caps are replaced by toot-pockets (Eichhornia, Pistia)
- In some cases floating roots may develop in addition to normal roots (Jussiaea).
- The submerged parts are generally surrounded by mucilage for protection.
- The stems are weak, slender with long internodes. (Hydrilla).
- The submerged leaves are either ribbon-like (Vallisneria) or finely dissected (Ceratophyllum).Floating leaves are generally large, broad and thick (Victoria).
- Floating leaves are generally large, broad and thick (Victoria).
- Heterophylly is common in partially submerged plants (Ranunculus).
- In some hydrophytes, the petioles of leaves are spongy due to the presence of air cavities (Eichhornia, Trapa).
- They multiply by means of tubers (Sagittaria), Stolons (Vallisneria) offsets (Eichhornia) of species buds (Utricularia).
- The plants are dull pale green in color, It is an adaptation to absorb the maximum of light falling on them.
Important examples of hydrophytes
It is a minute gregarious aquatic plant which is found floating freely on the surface of the water in ponds and lakes. The plant body seems like a thallus. There is no distinction between stem and leaves. Leaves are represented by 2-5 green, flat segments called fronds. A few unbranched roots bear roots pockets.
The root system is highly reduced. Toot hairs are absent. The upper surface of fronds is covered over by waxy coating. Stomata on fronds are present on upper surface only. Anatomically, the fronds possess aerenchyma. Mechanical tissues are absent.
2.Pistia (Water Cabbage)
It is small, free-floating, aquatic herb (Hydrophytes) which is found in ponds. The growth is by means of offsets. The sessile leaves arise in clusters in rosette form at the nodes. A bunch of adventitious roots is present on the lower side at each node.
The stem is horizontally growing offset. The plant afloat on the water surface with the help of spongy stem, and horizontally spreading outer leaves, The roots bear root pockets. The cuticle and stomata are present on leaves. Leaves are spathulate or obcordate in outline. The leaves possess palisade parenchyma. Vegetative reproduction by means of fragmentation of offsets is common.
3.Eichhornia (Water hyacinth)
It is a floating aquatic herb (Hydrophytes) found in ponds and lakes. When the water level is low the plant may become rooted in the mud. It grows by means of offsets, which bear nodes. The leaves and roots are borne at the nodes in clusters. Leave are the kidney-shaped or rhomboidal outline, aerial and with swollen petioles. The roots are pinkish or brownish in color.
The stem, offset, is spongy and with the help of inflated petioles of large leaves make the plant buoyant. The roots act as balancers. The leaves possess water-proof cuticular covering and have shining or glossy surface. They bear stomata and palisade parenchyma.
4. Potamogeton crispus
The plant is a submerged hydrophyte growing in ponds, lakes, tanks, and watercourses, The plant has an elongated, slender and delicate spongy stem bearing thin, ribbon-like, pale green leaves. The mechanical tissue is absent in stem. The leaves are sessile and translucent. The margins of leaves are waxy. The leaves do not provide any resistance to water currents.
The covering of mucilage on the whole plant protects it from rotting effect of water. the leaves lack cuticle, stomata and palisade parenchyma. Spongy parenchyma is present. The stem possesses a central cavity, lack mechanical tissue and contains abundant aerenchyma in cortical regions. Another species, P.pectinatus bear long thread like leaves. It has anchor and highly branched stem.
It is a submerged flowering aquatic herb (Hydrophytes) that is found suspended in the waters of ponds and water courses. Roots are generally absent, but sometimes the plant may get attached when the leafy shoots function rhizoids. The stem and branches are long, narrow and delicate bearing spongy tissue.
The leaves are borne in whorls of 6-10 at each node. They are branched dichotomously to form several thread-like segments. Branches are produced singly at the nodes. The leaves are crowded toward the apex of the stems or branches. The flowers are also submerged.There is a mucilage covering on whole of the plant. The plant stands erect. The color of the plant is pale or dull greens.
The plant is submerged, a flowering aquatic herb(Hydrophytes) found growing in freshwater ponds, tanks, and water courses. The plant is anchored to the substratum by means of adventitious roots. The stem is delicate, spongy and flexible bearing 3-8 leaves. mostly arranged in whorls. Basal nodes may have opposite leaves.
The leaves are lacking stomata, cuticle and palisade parenchyma. The leaves are thin, flexible and sessile. The internal structure shows the absence of mechanical tissue, a central cavity, and aerenchymatous cortex. There is a protecting covering of mucilage all over the plant surface. The color of the plants is dull pale-green.
The Vallisneria is submerged hydrophyte, flowering plant that grows abundantly in freshwater ponds, tanks, and water courses. The plant is attached to the substratum by means of adventitious roots. The stem is reduced to rootstock which bears large, radical leaves. The leaves are large and ribbon-shaped, multicostate and entire.
The leaves lack cuticle, stomata and palisade parenchyma, but possess spongy parenchyma enclosing wide air cavities. The plant grows by means by stolons. The plants are dioecious.