Heliotropium

Like other members of the Heliotropiaceae, plants in the genus Heliotropium have , tetracyclic flowers and actinomorphic corollas. They likewise share in their characteristic terminal styles and highly modified stigmatic heads (basal stigma, infertile apex). Species in the genus are typically herbs or subshrubs exclusively and are characterized by their dry fruits that divide into two or four mericarpids. == Taxonomy ==

Taxonomic revision supported through molecular phylogenetics led to the recognition of Euploca as genus separate from Heliotropium. In contrast, the genus Tournefortia was included in Heliotropium in a 2016 revision. Origins of diversification Three of the four major clades within Heliotropium have their centers of diversity in South America. The origins of the remaining Old World Heliotropium clade can be traced back to a single colonization event from the New World. Heliothamnus diversification is estimated to have taken place in the late Miocene. The age of Heliothamnus suggest that its diversification could have been triggered directly by the uplift of the Andes, something that would have promoted speciation in inner-Andean valleys and the Andean scrub. The majority of endemic Heliothamnus taxa in the region are restricted to these sorts of environments, further supporting this theory as the current leading theory explaining Heliothamnus diversification. Etymology The name "heliotrope" derives from the old idea that the inflorescences of these plants turned their rows of flowers to the Sun. Ἥλιος (helios) is Greek for "Sun", τρέπειν (trepein) means "to turn". The Middle English name "turnsole" has the same meaning. ==Distribution and habitat==

The genus has an almost cosmopolitan distribution. ==Ecology==

Some danaine butterflies, such as male queen butterflies, visit these plants, being attracted to their pyrrolizidine alkaloids. Caterpillars of the grass jewel (Freyeria trochylus), a gossamer-winged butterfly, feed on H. strigosum. == Toxicity ==

The plants are highly toxic to dogs and cats, as well as to humans.'' in India Some species are weeds, and many are hepatotoxic if eaten due to abundant pyrrolizidine alkaloids. There have been cases of canine death due to over-ingestion of this toxic plant. Though it is not palatable and most animals will completely ignore it, there have been cases of horses, swine and cattle being poisoned due to contamination of hay. Heliotrine and heliotridine Seeds of the Heliotropium genus were discovered in the 1940s and 50s to be responsible for liver disease in populations that consumed them in large quantities, either inadvertently (as a contaminant of food crops) or deliberately (associated with the ingestion of herbal infusions for the treatment of certain ailments). The seeds contained high concentrations of pyrrolizidine alkaloids, identified mainly as the of heliotrine (74%), and one or two other compounds similar in character to lasiocarpine. More recently, in 1993 and 2017, there have been reported cases of poisoning in Tajikistan from wheat contaminated with H. lasiocarpum seeds. == Uses ==

Heliotropes are popular garden plants, most notably H. arborescens (garden heliotrope). Garden heliotrope is grown in Southern Europe as an ingredient for perfume. Heliotrope is the main ingredient in perfumes such as Byredo Heliotropia, Molinard Heliotrope, Etro Heliotrope, Fragonard Héliotrope Gingembre and others. The sap of heliotrope flowers, namely of H. europaeum (European heliotrope), was used as a food coloring in Middle Ages and Early Modern French cuisine. == In culture ==

A Classical myth, told in Ovid's Metamorphoses, imagines that the water nymph Clytie, in love with the sun god Helios, was scorned by him. Wasting away, she transformed into the heliotrope, whose flowers supposedly always face the Sun. One of the most famous ragtime piano melodies is "Heliotrope Bouquet", composed in 1907 by Louis Chauvin (the first two strains) and Scott Joplin (the last two strains). The purplish facial rash of dermatomyositis is called "heliotrope rash" because it resembles E. arborescens. ==See also==