Duckweed family

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Duckweed family
Different species of dwarf and duckweed, illustration

Different species of dwarf and duckweed, illustration

Systematics
Subdivision : Seed plants (Spermatophytina)
Class : Bedecktsamer (Magnoliopsida)
Monocots
Order : Frog-spoon-like (Alismatales)
Family : Arum family (Araceae)
Subfamily : Duckweed family
Scientific name
Lemnoideae
Bab.

The duckweed family (Lemnoideae) are a subfamily within the arum family (Araceae). They are free-floating aquatic plants in fresh water . The duckweed family includes the five genera Lemna ( duckweed ), Spirodela , Landoltia , Wolffia and Wolffiella . Three of them are also represented with species in Central Europe.

description

The largest ( Spirodela polyrhiza ) and the smallest ( Wolffia globosa )

What they all have in common is that they are only a few millimeters large "leaflets" (more precisely: shoot limbs) that lack a structure in stem and leaf. They float on the surface of water, often colonize them en masse and can completely cover them. These floating carpets are colloquially (mostly in relation to Lemna species) known as duckweed .

They are herbaceous plants . The size of the specimens ranges from the smallest species Wolffia globosa with less than 1 millimeter (about 0.3 millimeters) to the largest species, the multi-rooted pond lens ( Spirodela polyrhiza ) with about 15 millimeters.

Multi-rooted pond lentil ( Spirodela polyrhiza )
Hunchback duckweed ( Lemna gibba )

Duckweed plants are considered to be the fastest growing flowering plants that can also do without land.

Lesser duckweed ( Lemna minor )
Trilateral duckweed ( Lemna trisulca )

Systematics

For a long time this kinship group was considered a separate family Lemnaceae Gray . DNA analyzes suggest that these genera as a subfamily of the family of Lemnoideae Arum include (Araceae). Another synonym for Lemnoideae Bab. is Wolffiaceae Bubani . The subfamily was extensively morphologically revised by the botanist Elias Landolt and his results were later genetically checked in numerous studies, since the duckweed species could potentially be of great importance in aquaculture. Accordingly, the group includes five genera with 37 species

ecology

Duckweed in a pilot plant in the municipality of Oost Gelre , Netherlands. Because of its rapid growth, it is interesting as fodder.

The species of the duckweed family usually float in mass communities on the surface ( Lemna trisulca also submerged) of standing, rather nutrient-rich waters. Air chambers in their branches give them the necessary buoyancy. In the summer half of the year, the entire water surface of small to medium-sized ponds and ponds can be completely covered with a green floating carpet. Either dominant stocks of a single species or societies of several species can be observed. With the root threads hanging down, nutrient salts are absorbed from the free water.

Duckweed society : Spirodela polyrhiza , Lemna minor , Wolffia arrhiza

By covering entire water surfaces, duckweed have a significant impact on the rest of life: only a small amount of sunlight penetrates the water body, which can cause damage. a. Prevents diving leaf plants from growing and making oxygen exchange difficult. At the same time, the water warms up less or only after a delay, so that animal species that are dependent on the outside temperature ( e.g. tadpoles of the cold- blooded frog ) develop and grow only slowly. The large biomass production from branches that die in autumn also contributes to the silting of the water. Excessive growth of duckweed plants indicates a rich to excessive supply of nutrients in the water. This is often partly caused by direct or diffuse inputs from agriculture.

Duckweed reproduces mainly asexually by sprouting , in which the laterally growing shoots either remain connected to the mother plant or become independent. Small, inconspicuous flowers are only rarely monoecious . In autumn, the plants store starch and then sink to the frost-free ground for wintering or to develop winter buds. They also use hydroepizoochory , in which the whole small plant is carried away by animals. This enables them to develop new living spaces. Unlike species native to the tropics, Wolffia globosa remains sterile.

use

Duckweed plants are used as food by fish, higher animals and also by humans worldwide and are among the fastest growing higher plants. In Asia they are used as food, in Europe as animal food. As a self-growing feed, they are used in addition in aquaponics .

They are particularly valued as food because they contain all essential amino acids (dry weight up to 43% protein; also up to 6% fat, of which up to 71% polyunsaturated omega-3 fatty acids , and 17% carbohydrates). They also have the ability to capture significant amounts of nitrogen and minerals from sewage. They contain up to seven times the protein content of soy and up to twice that of a steak . This means that they meet the requirements of the WHO for good pre-school child nutrition.

Fossil species

The discovery of the fossil species Limnobiophyllum scutatum (Dawson) Krassilov was remarkable . This has been found several times in North America, the best specimens from the paleogenic Paskapoo Formation in Alberta, Canada. Here, more than 200 excellently preserved specimens were found in claystone that had deposited in a lake, including not only impressions of leaves, shoots and roots, but also epidermis tissue in cell preservation and flowers, some of which still contained pollen. Limnobiophyllum was a freely floating plant whose extremely short shoot only had three to four rosette-shaped leaves. These were connected to one another by runners ( stolons ). The first finds were classified in the recent genus Spirodela and named Spirodela scutata . The plant forms a morphological bridge between the recent duckweed and the genus Pistia (with the water salad Pistia stratoides as the only species). A close relationship between Pistia and the duckweed was also confirmed on the basis of genetic analyzes, presumably they are sister groups.

The genus is proven with another species ( Limnobiophyllum expansum ) up to the Miocene .

literature

further reading

  • Wenqin Wang, Y. Wu, Y. Yan, M. Ermakova, Randall A. Kerstetter, J. Messing: DNA barcoding of the Lemnaceae, a family of aquatic monocots. In: BMC Plant Biology , Volume 10, 2010, p. 205. doi: 10.1186 / 1471-2229-10-205

Web links

Commons : Duckweed  - Collection of images, videos and audio files

Individual evidence

  1. ↑ Christel Kasselmann: aquarium plants. 1999, p. 438.
  2. ↑ a b c Wenqin Wang, Randall A. Kerstetter, Todd P. Michael: Evolution of Genome Size in Duckweeds (Lemnaceae). In: Journal of Botany , Volume 2011, 9 pages, doi: 10.1155 / 2011/570319 .
  3. ↑ mdr.de: Super-Food from the pond | MDR.DE. Retrieved February 7, 2019 .
  4. ↑ Lidia I. Cabrera, Gerardo A. Salazar, Mark W. Chase, Simon J. Mayo, Josef Bogner, Patricia Dávila: Phylogenetic relationships of aroids and duckweeds (Araceae) inferred from coding and noncoding plastid DNA. In: American Journal of Botany , Volume 95, 2008, pp. 1153-1165. Full text PDF ( Memento from May 11, 2013 in the Internet Archive ) doi: 10.3732 / ajb.0800073
  5. ↑ The subfamily Lemnoideae of the Araceae on the AP website .
  6. ↑ a b c d Klaus J. Appenroth, Nikolai Borisjuk, Eric Lam (2013): Telling Duckweed Apart: Genotyping Technologies for the Lemnaceae. Chinese Journal of Applied & Environmental Biology 19 (1): 1-10. doi: 10.3724 / SP.J.1145.2013.00001
  7. ↑ K. Sowjanya Sree, Manuela Bog, Klaus-Juergen Appenroth (2016): Taxonomy of duckweeds (Lemnaceae), potential new crop plants. Emirates Journal of Food and Agriculture 28 (5): 291-302. doi: 10.9755 / ejfa.2016-01-038
  8. ↑ Manuela Bog, Ulrich Lautenschlager, Maria F. Landrock, Elias Landolt, Joerg Fuchs, K. Sowjanya Sree, Christoph Oberprieler Klaus-J. Appenroth (2015): Genetic characterization and barcoding of taxa in the genera Landoltia and Spirodela (Lemnaceae) by three plastidic markers and amplified fragment length polymorphism (AFLP). Hydrobiologia 749: 169-182. doi: 10.1007 / s10750-014-2163-3
  9. ^ DH Les, DJ Crawford: Landoltia (Lemnaceae), A New Genus of Duckweeds. In: Novon , Volume 9, 1999, pp. 530-533.
  10. ↑ a b c Heng Li, Elias Landolt: Lemnaceae. - Same text online as the printed work , In: Wu Zheng-yi, Peter H. Raven, Deyuan Hong (Ed.): Flora of China . Volume 23: Acoraceae through Cyperaceae . Science Press / Missouri Botanical Garden Press, Beijing / St. Louis 2010, ISBN 978-1-930723-99-3 , pp. 80 (English). .
  11. ↑ Christel Kasselmann (1999), p. 440.
  12. ↑ Ulf Schmitz, Steffen Köhler, Hasko Nesemann (2016): New evidence of the Columbian dwarf duckweed Wolffia columbiana in Europe - How many alleged occurrences of Wolffia arrhiza are actually neophytes? Publications of the Bochum Botanical Association 8 (1) 1–10.
  13. ↑ Tobias Böckermann: Biggest owl, smallest plant: record holder of nature in Emsland. Retrieved February 7, 2019 .
  14. ↑ So far completely underestimated: Thanks to this plant, nobody will have to go hungry any more. March 17, 2017, accessed February 7, 2019 .
  15. ↑ Sarah Maria Brech: Duckweed: Why duckweed is on the way to becoming a new superfood . March 13, 2017 ( welt.de [accessed February 7, 2019]).
  16. ↑ Klaus-J. Appenroth, K. Sowjanya Sree, Manuela Bog, Josef Ecker, Claudine Seeliger, Volker Böhm, Stefan Lorkowski, Katrin Sommer, Walter Vetter, Karla Tolzin-Banasch, Rita Kirmse, Matthias Leiterer, Christine Dawczynski, Gerhard Liebisch, Gerhard Jahreis: Nutritional Value of the Duckweed Species of the Genus Wolffia (Lemnaceae) as Human Food . In: Frontiers in Chemistry 6, October 29, 2018, doi : 10.3389 / fchem.2018.00483 .
  17. ↑ Ruth A. Stockey, Georgia L. Hoffman, Gar W. Rothwell (1997): The fossil monocot Limnobiophyllum scutatum: Resolving the Phylogeny of Lemnaceae. American Journal of Botany 84 (3): 355-368. (open access) doi: 10.2307 / 2446009