Gentianales is an order of flowering plant, included within the asterid clade of eudicots. It comprises more than 20,000 species in about 1,200 genera in 5 families. More than 80% of the species in this order belong to the family Rubiaceae.
Many of these flowering plants are used in traditional medicine. They have been used to treat pain, anxiety, cancers and neurological conditions.
According to molecular clock calculations, the lineage that led to Gentianales split from other plants about 108 million years ago or 81 million years ago.
Taxonomy
In the classification system of Dahlgren the Gentiales were in the superorder Gentianiflorae (also called Gentiananae). The following families are included according to the APG III system:
- Family Apocynaceae (424 genera)
- Family Gelsemiaceae (2 genera)
- Family Gentianaceae (87 genera)
- Family Loganiaceae (13 genera)
- Family Rubiaceae (611 genera)
Phylogeny
The following phylogenetic tree is based on molecular phylogenetic studies of DNA sequences.
Etymology
It takes its name from the family Gentianaceae, which in turn is based on the name of the type genus, Gentiana. The genus name is a tribute to Gentius, an Illyrian king.
Characteristics
This large order has a variety of different plants, ranging from small herbaceous plants and saprophytes to shrubs and large trees. Species are, however, united by their simple and opposite leaves and typically have showy pentamerous flowers (flowers in which components occur in multiples of five) and show nuclear endosperm formation (in which cell division takes place without the cell wall forming between divisions). Vinblastine, which has anti-tumor properties as it disrupts cell division, is used in chemotherapy. It is extracted from the Madagascar periwinkle.