Damasonium Minus
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''Damasonium minus'' is a species of flowering plant in the water-plantain family known by the common names starfruit and star-fruit (not to be confused with the cultivated
starfruit Carambola, also known as star fruit, is the fruit of '' Averrhoa carambola'', a species of tree native to tropical Southeast Asia. The mildly poisonous fruit is commonly consumed in parts of Brazil, Southeast Asia, South Asia, the South Pacif ...
). It is native to
Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...
, where it occurs everywhere except the
Northern Territory The Northern Territory (commonly abbreviated as NT; formally the Northern Territory of Australia) is an states and territories of Australia, Australian territory in the central and central northern regions of Australia. The Northern Territory ...
.''Damasonium minus''.
Threatened Flora of Tasmania.
It is perhaps best known as an agricultural weed. It is a major weed of Australian rice crops. This species is an emergent
aquatic plant Aquatic plants are plants that have adapted to living in aquatic environments (saltwater or freshwater). They are also referred to as hydrophytes or macrophytes to distinguish them from algae and other microphytes. A macrophyte is a plant that ...
. It is an annual or short-lived perennial herb growing up to a meter tall. The floating or emergent leaves have blades up to 10 centimeters long by 4 wide and lance-shaped to heart-shaped. They are borne on petioles up to 30 centimeters long. The branching
inflorescence An inflorescence is a group or cluster of flowers arranged on a stem that is composed of a main branch or a complicated arrangement of branches. Morphologically, it is the modified part of the shoot of seed plants where flowers are formed o ...
has whorls of flowers. Each flower has tiny green
sepal A sepal () is a part of the flower of angiosperms (flowering plants). Usually green, sepals typically function as protection for the flower in bud, and often as support for the petals when in bloom., p. 106 The term ''sepalum'' was coined b ...
s and white or pink petals a few millimeters long. The star-shaped
aggregate fruit A raspberry fruit (shown with a raspberry beetle larva) is an aggregate fruit, an aggregate of drupe">raspberry_beetle.html" ;"title="raspberry fruit (shown with a raspberry beetle">raspberry fruit (shown with a raspberry beetle larva) is an aggre ...
is made up of follicles containing seeds.''Damasonium minus''.
New South Wales Flora Online. National Herbarium, Royal Botanic Garden, Sydney.
This plant grows in habitat with slow-moving and still water, such as
swamp A swamp is a forested wetland.Keddy, P.A. 2010. Wetland Ecology: Principles and Conservation (2nd edition). Cambridge University Press, Cambridge, UK. 497 p. Swamps are considered to be transition zones because both land and water play a role in ...
s. In agriculture, this plant has been called "the most important broadleaf weed in the Australian rice crop." Most rice is grown in Victoria and
New South Wales ) , nickname = , image_map = New South Wales in Australia.svg , map_caption = Location of New South Wales in AustraliaCoordinates: , subdivision_type = Country , subdivision_name = Australia , established_title = Before federation , es ...
. This weed has been controlled with the
herbicide Herbicides (, ), also commonly known as weedkillers, are substances used to control undesired plants, also known as weeds.EPA. February 201Pesticides Industry. Sales and Usage 2006 and 2007: Market Estimates. Summary in press releasMain page fo ...
bensulfuron-methyl, but it has become less effective as herbicide-resistant strains have evolved. A
pathogenic In biology, a pathogen ( el, πάθος, "suffering", "passion" and , "producer of") in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a germ ...
fungus A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from th ...
, ''
Rhynchosporium alismatis ''Rhynchosporium'' is a genus of fungi that causes leaf scald disease on several graminaceous hosts. It includes five currently accepted species: '' R. secalis'' from rye and triticale, '' R. orthosporum'' from '' Dactylis glomerata'', ...
'', was discovered on the plant, and it has become an option for biological control as a
mycoherbicide A mycoherbicide is a herbicide based on a fungus. As a biological agent, these "mycoherbicides... work by producing toxic compounds that dissolve the cell walls of targeted plants". Unlike traditional herbicides, mycoherbicides can reproduce themse ...
. The fungus causes chlorosis and
necrosis Necrosis () is a form of cell injury which results in the premature death of cells in living tissue by autolysis. Necrosis is caused by factors external to the cell or tissue, such as infection, or trauma which result in the unregulated dige ...
of the leaves on the mature plant and stunting of immature individuals. If immature weeds in a paddy are stunted, the rice plants may have a competitive advantage. The fungus can kill seedlings, and if it infects the inflorescence of the weed it can reduce seed weight and viability.Cother, E. J., et al. "Development of the mycoherbistat fungus ''Rhynchosporium alismatis'' for control of Alismataceae weeds in rice." In: Hill, J. E. and B. Hardy, Eds. ''Proceedings of the Second Temperate Rice Conference''. June 13–17, 1999. Sacramento, California. pg. 509. The fungus can also help control another rice weed, ''
Alisma lanceolatum ''Alisma lanceolatum'' is a species of aquatic plant in the water plantain family known by the common names lanceleaf water plantain and narrow-leaved water plantain. It is widespread across Europe, North Africa and temperate Asia. It is natural ...
''.


References

{{Taxonbar, from=Q15296272 Alismataceae Agricultural pests Freshwater plants