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Duckweed

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Duckweed
Duckweed1.jpg
Scientific Classification
Species
  • L. aequinoctialis
  • L. gibba
  • L. minor
  • L. minuta
  • L. obscura
  • L. perpusilla
  • L. trisulca
  • L. turionifera
  • L. valdiviana
Duckweed2.jpg
Common Duckweed

Duckweed is a type of monocot that comes from the family Lemnaceae, and is one of the smallest flowering plants in the world. It is a family of hydrophytic plants that are free-floating. [1] Duckweed is also known as that green blanket of tiny leaves that tends to cover the surface of stagnant ponds and other bodies of water. Duckweed is a plant that has grabbed the attention of many researchers and environmentalists due to the fact that it is only helping improve the environment. Many studies are being taken place because scientists have found that Duckweed is quite environment friendly and can help in several different processes. Processes such as removing waste from water and creating a new type of energy-saving biofuel.[2]

Anatomy

This is a drawing/sketch of the Duckweed stem and fronds.

Duckweed has a very morphological yet simple structure that consists of a vegetative body and fronds. These plants are no greater than 1 centimeter in length. Their fronds all have various shapes and sizes based on the species of the Duckweed. [3] Duckweed does not have any actual leaves. They have a leaf-like body called the thallus. The length of an average duckweed is around 2-5 millimeters in diameter. It does not have a stem and has small roots. Root length is consistent to the measure of frond-age. [4] The size of the body of the plant varies on different species. The smaller duckweed can grow to be from 1/16 to 1/8 of an inch. Each plant has around two or more leaves connected at the base of the plant, with just a single root hanging low. [5]

For Lemna minor, their shape is more of a circular to oval shape. Lemna trisulca has two different shapes. One kind is more of a elongated shape that is around six to ten millimeters long; while the other size is more of a oval shape that has a shorter stalk. [6] The fronds itself are more healthier under ideal weather conditions, and extreme nutrient availability. The daughter fronds are produced through a pattern of two different pockets on each side of the parent (mature) frond. Although two pockets are only on certain species, others have only one pocket. These pockets are found near to where the roots rise up. The mass of the frond is configured from chlorenchymatous cells. These cells are divided by large spaces that are filled with either air or certain other gases that help provide the fronds buoyancy. The top part of the epidermis is impregnated with cutin. Cutin is a water-repellent material that is wax-like and found in some spaces in plant cells. This forms the cuticle which covers and protects the epidermis. Stomata is also found on the upper side of the epidermis. This is consistent for all four genera.

Reproduction

Duckweed reproduction can be extremely rapid when nutrient levels are at it's best. Reproduction is commonly vegetative and asexual. Vegetative reproduction is a form of asexual reproduction in which plants grow without the manufacture of seeds or spores. [7] Flowers are sometimes produced during reproduction, but can hardly be seen. The flowers are produced when exposed to the sun. [8] Duckweed hardly ever reproduce through seeds. The daughter fronds emerge from one of two reproductive pockets on the sides of a mature frond. One individual frond is able to produce up to ten generations of daughter fronds, starting from a timeline of ten days to several weeks up until dying. [9]

For rapid reproduction, conditions must be ideal in almost all areas. Areas such as: water temperature, pH level, lighting, and nutrients are all ideal. They are one of the kinds of plants that are considered the most vigorous photosynthetic terrestrial plants. In other words, this means that their biomass production is considered to be one of the fastest out of all the plants studied. Their biomass production is extremely rapid matching a reproduction rate in between sixteen hours and two days. [10] Quick reproduction rates also have it's disadvantages. Because Duckweed grows so quickly, this becomes problematic due to problems such as: lack of nutrients, a nourishment imbalance, different poisonous toxins that can harm not only the plant but the body of water (and everything else in it) as well, sudden changes in both pH and temperature, overpopulation of the plant, and a battle between duckweed and other plants competing for light and food. [11]

Each individual frond has it's own life span, and during that life span more daughter fronds are produced. Each individual daughter frond has a smaller mass than the daughter frond produced before it and it's lifespan is also shorter. This size and life span shortage is due to changes in cell numbers. Daughter fronds that are produced later, produce less of their own daughter fronds rather than the earlier daughter fronds who produce more of their own daughter fronds. The fronds produced first, produce more daughter fronds. The fronds that produce later, produce less daughter fronds. [12]

Because reproduction rates are so rapid and Duckweed are able to double their biomass in around 10 days, it provides many uses. This increases harvest rates for bulk plants and feed for different livestock, aquaculture feed, different compost substances, and now in biofuel carbon. [13]

Ecology

A distribution map of Lemna in the U.S.

The duckweed family is distributed world-wide. Most species are found in many of the temperate and sub-tropical regions of the world. They grow in a timely matter during summer months, but also in temperate or even cold regions. They grow at their best performance under warm conditions and sunny weather. [14] They live mostly in calm bodies of freshwater and are often found around the shoreline after the freshwater levels have decreased. [15] Lavish growth, would be found in protected small ponds, or in ditches in swamps where plenty of nutrients can be found. Most Duckweed plants are delicate and acute to freezing weather and to drought. Specific species of Duckweed are able to grow in chill weather (not freezing), although all kinds of Duckweed are extremely sensitive to frost. In freezing conditions, Duckweed are able to survive as seeds or turions that slowly sink to the bottom after being released from their mother fronds. [16] One would be able to find Duckweed almost anywhere except in regions such as waterless deserts or continuing frozen polar areas. Duckweed favors to grow in areas such as the face of calm freshwater ponds. Decaying organic material is also a supreme condition for Duckweed because of all the nutrients and nourishment it provides for the plant. [17]

Surprisingly, Duckweed and other members of the Lemnaceae family have quite a few predators. Such predators include animals like: the clarias catfish, the Ghost-Knight fish (Notopterus), Snakehead, and even more. [18]

Duckweed: A biofuel and waste treatment

An article from the United Press International (UPI) has delivered some new findings for both useful and environment friendly uses for Duckweed. Both US and North Carolina State University researchers say that Duckweed are able to help immaculate animal waste from industrial hog farms and might even be able to help solve our current global energy catastrophe. The researchers from North Carolina State University found that duckweed growing on hog wastewater are able to produce around five to six times more starch than corn (per acre). Professor Jay Cheng and Associate Professor Anne-Marie Stomp said that their results and research found that ethanol production operating from Duckweed could potentially be faster and cheaper than ethanol issued from corn. They called it "killing two birds with one stone." The two birds being biofuel production and wastewater treatment; the one stone being duckweed. The starch that comes from Duckweed can quickly be changed into ethanol, utilizing the same facilities used for corn. Farmers from large-scale hog farms, rid their waste through large "lagoons." It helps manage their animal wastes through biological treatment. The Duckweed from these "lagoons" take the nutrients in the wastewater, and use them for their own growth. This takes hold of all the nutrients and prevents them from being discharged back into the environment. Researchers show that Duckweed is able to purify wastewater and concentrate the nutrients absorbed from the wastewater. [19] This is also a benefit because Duckweed is cheap and easy to plant and grow in order to remove wastewater. They are simple and do not require much to do the job. If farmers worry about algae growing in their clean water ponds, they no longer have to. Duckweed can create a thick layer on the surface of the water, preventing sunlight to penetrate through it which prevents any form of life such as algae from growing. [20]

Gallery

References