Stemonaceae

Stemonaceae Temporal range: Upper Cretaceous – recent 84–0 Ma PreЄ Є O S D C P T J K Pg N
Croomia heterosepala
Scientific classification
Kingdom:	Plantae
(unranked):	Angiosperms
(unranked):	Monocots
Order:	Pandanales
Family:	Stemonaceae Caruel[1]
Genera
Croomia Stemona Stichoneuron Pentastemona

The Stemonaceae are a family of monocotyledonous flowering plants placed in the order Pandanales. The family consists of four genera with between 25 and 35 species distributed in areas with seasonal climate across Southeast Asia and tropical Australia. One native species is found in the United States.

Description and ecology

The Stemonaceae contain various herbeceous plants, many of which are crawling or climbing species preferring moist or dry tropical habitats.^[2] They form underground organs as spindle-shaped rhizomes used for reservation of nutrients. The stems are sometimes erect or trailing with green or yellow-green color or in some cases with reddish appearance. Leaves are dark green and also alternate in the majority of the members. Flowers are born in short cymes produced from the lower parts of the plant. Seeds are ellipsoidal or globular.

Flower morphology

As in other members of the Pandanales, the flower morphology in the Stemonaceae is distinctively developed and rather atypical for other monocots.^[3] In the majority of the species, flowers are tetramerous (composed of four identical parts) or sometimes dimerous.^[4] Stamens are distinguishable and four in number. In most of the members, tepals are four. They are smooth or sometimes papilate which is probably because they function as odour-producing components (osmophores). However, in Pentastemona, the flowers are pentamerous and the number of stamens is five. Microsporogenesis is successive. Reproductive structures are colored in shades of purple, maroon, green, or yellow. They imitate carrion and sometimes release such smell - flies visiting the flowers function as pollinators.

Phylogeny and evolution

The Stemonaceae family is sister to other two families in the Pandanales that together form a clade - these are Cyclanthaceae and Pandanaceae. Pentastemona diverged first from the family, so is a sister clade to the rest of it. Actually, the genus demonstrates characteristics rather more different from other members of the Stemonaceae.^[5] In earlier classifications, it was placed in its own family. However, Stemona is sister to the other two genera that together form a clade. The family appears in Late Cretaceous - around 84 Mya, although the stem group diverged earlier in the same period - 108 Mya.^[6]

Uses

The family contains plants with various therapeutical and other uses in places such as China, Laos, Japan, Thailand, and others.^[7] Some members are used for making an insecticide. In Laos, people use them against fleas and lice by making an infusion which they drink to make their blood poisonous. Plants from the family are used for the preparation of a fish poison. Others play a role in folk medicine and are valued for their antibacterial, antitussive, antifungal, and other properties against lung or skin diseases.

References

• Stemonaceae in L. Watson and M. J. Dallwitz (1992 onwards), The families of flowering plants
• Pentastemonaceae in L. Watson and M. J. Dallwitz (1992 onwards), The families of flowering plants
• Flora of China: Stemonaceae
• Flora of North America: Stemonaceae
• NCBI Taxonomy Browser: Stemonaceae
• CSDL, Texas: Stemonaceae