Bonnetiaceae

Bonnetia sessilis (left) and Bonnetia paniculata (right), illustration.

The Bonnetiaceae are a plant family of shrubs and trees in tropical South America, Southeast Asia and Malaysia. They belong to the order Malpighienartigen and include the three genera Bonnetia, Archytaea and Ploiarium together with about 33 species. The wood is used locally for its high durability as a building material, but has no economic significance.

Features

The Bonnetiaceae are evergreen shrubs or usually little branched trees. Your heartwood is reddish dark brown and heavy. The nodes are trilakunär with three leaf-trace strands, or unilakunär with a leaf-trace strand. The highest representatives of the family is reached up to 25 meters Ploiarium alterniflorum, a tree, the heights of growth. The plants are hairless. Only in the leaf axils, there are small clusters of multicellular trichomes, the Kollateren be called and can secrete mucilage.

Bonnetiaceae are rich in xanthones and anthraquinones, which are also found in the closely related Clusiaceae and St. John's wort plants ( Hypericaceae ).

The spirally arranged leaves are close together and are short-stalked. The petioles contain a cylindrical medullary layer that penetrates the stem in whole or in part. The leaves are variable in shape of blade and its thickness depending on the type. The leaf margin is finely serrated. Striking is the sophisticated Parallelnervatur, which is unique to the dicotyledons, and monocotyledonous some similar. This feature limits the family against the Teestrauchgewächse ( Theaceae ).

The stomata are paracytisch. In some species there are special vascular bundles with a Leitbündelscheide of two concentric layers: an inner layer having a plurality of layers of fibers, and an outer layer, the endodermis of thin-walled cells with Casparian strips. There are mucous cells At the top of the mesophyll.

Very variable are the types with respect to thickness of the cuticle, the relative proportion or the thickness of palisade and spongy, and the presence of stone cells ( sclereids ) or crystals in the mesophyll.

Flowers

The hermaphrodite flowers are in zymösen inflorescences. Each flower stalk arises from the axil of a single carrier sheet, often arise, however, from the flower stalk up to two more bracts, which may be very close at the calyx. The perianth is clearly differentiated into two petal circles. The five sepals ( sepals ) are free or fused only at the base. They are fleshy ( about 10 to 20 cells thick), scaly and often different. During the sepals at Bonnetia and Archyteae remain at maturity, they fall in Ploiarium for fruit ripening. In Bonntia the sepals are often reddish. For example kathleenae and B. rubicunda found on the sepals Kollateren.

The crown is rotated. The five petals ( petals ) are strongly thickened ( thicker than the sepals ), fleshy ( about 8 to 15 cells thick ) and scale-like. They are purple, white heather, red, or yellow. For example bolivarensis or B. steyermarkii they are slimy.

The stamens are numerous, at Bonnetia are in a single stamen circle from a two to four stamens wide range. Often several are fused at the base into a tube. The series forms a complete circle at the base of the flower. In Archytaea and Ploiarium the stamens are in five groups. In Archytaea the lower two-thirds are fused. The anthers are fused at the base to the filaments. They consist of the usual two counters and four pollen sacs. They often shorter than the upper, the lower pollen sacs. The pollen grains are 28-60 micrometers long with a round seed opening.

The genera Archytaea and Ploiarium form between the stamen groups on the basis of disc-shaped flowers nectaries.

The ovary consists of three (rarely four) carpels at Bonnetia and five carpels in the other two genera. The stylus is round, with B. fasciculata but flattened. The point-shaped scar is papillose. The numerous ovules are anatrop. The Mikropylenkanal is formed by the outer integument ( exostomale micropyle ).

The fruits are capsules septizide, a sub-form of the gap capsules with many seeds. The seeds are unusually small, with an exceptionally thick woody seed coat.

Distribution and threat

The family is widespread in northern South America and the Caribbean, as well as in Southeast Asia, specifically in West Malaysia, Cambodia, the Moluccas and New Guinea. Here you will find the species of the genus Bonettia only in South America and with a kind on Cuba, whereas Archytea and Ploiarium also be found in Asia. The center of diversity Bonnetia, that is the area where most of the species are native, is located in the Guayana Highlands, where there are 27 species, all of which are up to B. paniculata endemic.

Archytea prefers open habitats on poor soil. Ploiarium grows in the lowlands near the sea on swampy ground, or on nutrient-poor sandy soil in Borneo. Bonnetia grows over especially the mesas in Guyana, where they thrive on moist, scree slopes of sandstone and quartz sands.

Since many species of the family are endemic, they are particularly vulnerable. So lists the IUCN on their Red List of Threatened Species 13 species in the genus Bonnetia. The species no longer found in 1978 as ptariensis will even out as critically endangered (critical endangered ), the species of the genera Archytea and Ploiarium are less at risk.

System

The Bonnetiaceae are closely related to the Clusiaceae and the paraphyletic however Teestrauchgewächsen ( Theaceae ). However, a phylogenetic study in 2004 also showed evidence of a close relationship with the Kielmeyeroideae and Ternstroemiaceae, but these are uncertain.

Kinship with St. John's wort plants ( Hypericaceae ) and the Podostemaceae as shown in the following cladogram, however, seems certain.

Clusiaceae

Bonnetiaceae

Hypericaceae

Podostemaceae

As with almost all tropical plant families the internal classification of Bonnetiaceae is controversial. Dickison and Weitzman 1996 preconceived six genera in the family together. A year later, Weitzman and Stevens painted the genera Acopanea Steyerm, Neblinaria Maguire and Maguire Neogleasonia but out again and it remained now three genera with a total of around 33 species. :

• Archytaea Martius with two types. Archytaea augustifolia Maguire
• Archytaea triflora Martius

• Bonnetia ahogadoi ( Steyerm. ) ALWeitzman & PFStevens
• Bonnetia anceps Mart. & Zucc.
• Bonnetia bolivarensis Steyerm.
• Bonnetia celiae Maguire
• Bonnetia chimantensis Steyerm.
• Bonnetia colombiana ( Maguire ) Steyerm.
• Bonnetia cordifolia Maguire
• Bonnetia fasciculata P.F.Stevens & A.L.Weitzman
• Bonnetia holostyla Huber.
• Bonnetia huberiana Steyerm.
• Bonnetia jauaensis Maguire
• Bonnetia kathleenae Lasser
• Bonnetia lanceifolia Kobuski
• Bonnetia maguireorum Steyerm.
• Bonnetia martiana ( Maguire ) Steyerm.
• Bonnetia multinervia ( Maguire ) Steyerm.
• Bonnetia neblinae ( Maguire ) Steyerm.
• Bonnetia paniculata Spruce & Benth.
• Bonnetia ptariensis Steyerm.

• Bonnetia roraimae Oliver
• Bonnetia roseiflora ( Maguire ) Steyerm.
• Bonnetia rubicunda ( Sastre ) ALWeitzman & PFStevens
• Bonnetia sessilis Bentham
• Bonnetia steyermarkii Kobuski
• Bonnetia tepuiensis Kobuski & Steyerm.
• Bonnetia toronoensis Steyerm.
• Bonnetia wurdackii Maguire

• Ploiarium alternifolium ( Vahl ) Melchoir
• Ploiarium sessile ( Scheff. ) Hallier f
• In P. pulcherrimum Melchior it is not likely to be an independent Art