Aquatic plant

Encyclopedia : A : AQ : AQU : Aquatic plant

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Aquatic plants — also called hydrophytic plants or hydrophytes — are plants that have adapted to living in or on aquatic environments. Because living on or under the water surface requires numerous special adaptations, aquatic plants can only grow in water or permanently saturated soil. Aquatic vascular plants can be ferns or angiosperms (from both monocot and dicot families). Seaweeds are not vascular plants but multicellular marine algae, and therefore not typically included in the category, "aquatic plants." As opposed to plants types such as mesophytes and xerophytes, hydrophytes do not have a problem in retaining water due to the abundance of water in its environment. This means the plant has less need to regulate transpiration (indeed, the regulation of transpiration would require more energy than the possible benefits incurred.

Hydrophytes share several survival characteristics:

1. A thin (or no) cuticle. The primary function of cuticles is to prevent waterloss, thus most hydrophytes have no need for cuticles.
2. Stomata that are open most of time: water is abundant. This means that guard cells on the stomata are generally inactive.
3. An increased number of stomata, that can be on either side of leaves.
4. A less rigid structure: water pressure supports them.
5. Large flat leaves on surface plants for flotation.
6. Air sacs for flotation.
7. Smaller roots: water can diffuse directly into leaves.
8. Feathery roots: no need to support the plant.
9. Specialized roots designed to take in oxygen.

For example, some species of buttercup (genus Ranunculus) float slightly submerged in water; only the flowers extend above the water. Their leaves and roots are long and thin and almost hair-like; this helps spread the mass of the plant over a wide area, making it more buoyant. The long roots and thin leaves also provide a greater surface area for uptake of mineral solutes and oxygen.

The wide flat leaves of water lilies (family Nymphaeaceae) help distribute the plants' weight over a large area, thus helping them float near the water surface.

Many fish keepers and aquarium hobbyists keep aquatic plants in their tanks to oxygenate the water for their fish.

Many species of aquatic plant are invasive species in different parts of the world. Aquatic plants make particularly good weeds because they reproduce vegetatively from fragments.

Examples:

• Utricularia (from Latin, utriculus, a little bag or bottle) is a genus of slender aquatic plants, the leaves of which are furnished with floating bladders. They are called bladderworts.
• Water lettuce

Adaptations

• ''Free Floating Plants: In a pond community, they receive more sunlight than the submerged plants. But they also have to compete with one another and try to obtain the most sunlight above.
• Submerged Plants: Submersed leaves receive low levels of sunlight because light energy diminishes rapidly while passing through a water column.''

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All floating Plants

• Has either a air spaces trap in its roots or large air spaces to help it float to obtain sunlight (is already a kind of adaptation)
• Hair on its leaves to trap air in it
• Structural Adaptation

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Duckweed, Water Cabbage

• Chloroplast found on the top surface of the leaves
• Upper Surface has a thick, waxy cuticle to repel water and help to keep the stomata open and clear
• Structural Adaptation

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Water Lily

• Structural Material to Reach higher points and receive more sunlight
• Structural Adaptation

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Floating heart, Water Lily, Yellow pond-lily, water-shield

• Leave’s tend to be broader without major lobbing, Remain flat on the surface, Maximize surface area and Make use of full sunlight, Chloroplast found on the top of leaves
• Structural/ Behavioural Adaptation

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Most Partially-Submerged Plants

• Air spaces within the tissues to keep the plant buoyant so that its leaves can reach the top of the pond, maximizing the amount of sunlight received
• Structural Adaptation

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'''Dissected: Parrots Feather, Hornwort Thread-like: ditch-grass, quillwort'''

• Highly dissected/ divided leaves or thread-like ones, Allows for a bigger surface area (surface to volume – S/V)
• Structural Adaptation

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Hydrilla

• Elongates Rapidly to reach water surface and branches out at water surface, More light can be obtained at the water surface
• Structural/ Behavioural Adaptation

Human nutrition:

• Wild rice (Zizania)
• Water caltrop (Trapa natans)
• Chinese water chestnut (Eleocharis dulcis)
• Indian Lotus (Nelumbo nucifera)
• Water spinach (Ipomoea aquatica)
• Watercress (Rorippa nasturtium-aquaticum)
• Watermimose, Water mimosa ? (Neptunia natans)
• Taro (Colocasia esculenta)
• Rice (Oryza) is originally not an aquatic plant.
• Bullrush, Cattail, (Typha)
• Water-pepper (Polygonum hydropiper)
• Wasabi (Wasabia japonica)

• kjosco? see also Fascioliasis
• totora, (Scirpus californicus)? see also Fascioliasis
• Mint?
• Parsley?
• Khat?
• Alfalfa?

Animal nutrition:

• Water hyacinth (Eichhornia)
• Duckweed: Lemna, Spirodela und Wolffia
• Trichanthera gigantea (Humboldt & Bonpland.) [link] ?

Especially in (South-east) Asia edible, but uncooked Water-plants are suspected of transmitting Fasciolopsiasis.[link]

(Compare also: Fasciola hepatica)

Reference

Cook, C.D.K. (ed). 1974. Water Plants of the World. Dr W Junk Publishers, The Hague. ISBN 9061930243

See also:

• List of freshwater aquarium plant species
• Paddy field
• Swamp
• Seagrass

 

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