Hymenoxys odorata
Encyclopedia
Hymenoxys odorata is a species of flowering plant in the daisy family
known by the common names bitter rubberweed and western bitterweed. It is native to the southwestern United States from California
to Texas
and northern Mexico, where it grows in dry regions. This is an annual herb producing a branching stem to a maximum height near 60 centimeters. The stems are covered in a foliage of short leaves which are divided into narrow, pointed lobes. The plentiful flower heads
contain bright yellow disc florets and about eight short yellow ray florets.
This plant is poisonous to livestock; it is mostly a problem of the sheep industry. The toxic compounds are sesquiterpene
lactone
s called hymenovin and hymenoxon. When ingested by sheep the plant produces inflammation
of the stomach
, renal
necrosis
, and toxic hepatitis
, as well as inhibition of clotting factors
. An ill sheep may be bloated, anorexic
, weak, drooling, and vomiting. Acute and chronic, cumulative poisoning is often fatal. Sheep tend to avoid the plant because they find it distasteful but they will eat it in the absence of other forage.
Asteraceae
The Asteraceae or Compositae , is an exceedingly large and widespread family of vascular plants. The group has more than 22,750 currently accepted species, spread across 1620 genera and 12 subfamilies...
known by the common names bitter rubberweed and western bitterweed. It is native to the southwestern United States from California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
to Texas
Texas
Texas is the second largest U.S. state by both area and population, and the largest state by area in the contiguous United States.The name, based on the Caddo word "Tejas" meaning "friends" or "allies", was applied by the Spanish to the Caddo themselves and to the region of their settlement in...
and northern Mexico, where it grows in dry regions. This is an annual herb producing a branching stem to a maximum height near 60 centimeters. The stems are covered in a foliage of short leaves which are divided into narrow, pointed lobes. The plentiful flower heads
Head (botany)
The capitulum is considered the most derived form of inflorescence. Flower heads found outside Asteraceae show lesser degrees of specialization....
contain bright yellow disc florets and about eight short yellow ray florets.
This plant is poisonous to livestock; it is mostly a problem of the sheep industry. The toxic compounds are sesquiterpene
Sesquiterpene
Sesquiterpenes are a class of terpenes that consist of three isoprene units and have the molecular formula C15H24. Like monoterpenes, sesquiterpenes may be acyclic or contain rings, including many unique combinations...
lactone
Lactone
In chemistry, a lactone is a cyclic ester which can be seen as the condensation product of an alcohol group -OH and a carboxylic acid group -COOH in the same molecule...
s called hymenovin and hymenoxon. When ingested by sheep the plant produces inflammation
Inflammation
Inflammation is part of the complex biological response of vascular tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. Inflammation is a protective attempt by the organism to remove the injurious stimuli and to initiate the healing process...
of the stomach
Stomach
The stomach is a muscular, hollow, dilated part of the alimentary canal which functions as an important organ of the digestive tract in some animals, including vertebrates, echinoderms, insects , and molluscs. It is involved in the second phase of digestion, following mastication .The stomach is...
, renal
Kidney
The kidneys, organs with several functions, serve essential regulatory roles in most animals, including vertebrates and some invertebrates. They are essential in the urinary system and also serve homeostatic functions such as the regulation of electrolytes, maintenance of acid–base balance, and...
necrosis
Necrosis
Necrosis is the premature death of cells in living tissue. Necrosis is caused by factors external to the cell or tissue, such as infection, toxins, or trauma. This is in contrast to apoptosis, which is a naturally occurring cause of cellular death...
, and toxic hepatitis
Hepatitis
Hepatitis is a medical condition defined by the inflammation of the liver and characterized by the presence of inflammatory cells in the tissue of the organ. The name is from the Greek hepar , the root being hepat- , meaning liver, and suffix -itis, meaning "inflammation"...
, as well as inhibition of clotting factors
Coagulation
Coagulation is a complex process by which blood forms clots. It is an important part of hemostasis, the cessation of blood loss from a damaged vessel, wherein a damaged blood vessel wall is covered by a platelet and fibrin-containing clot to stop bleeding and begin repair of the damaged vessel...
. An ill sheep may be bloated, anorexic
Anorexia (symptom)
Anorexia is the decreased sensation of appetite...
, weak, drooling, and vomiting. Acute and chronic, cumulative poisoning is often fatal. Sheep tend to avoid the plant because they find it distasteful but they will eat it in the absence of other forage.