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Published In: Species Plantarum 1: 176. 1753. (1 May 1753) (Sp. Pl.) Name publication detailView in BotanicusView in Biodiversity Heritage Library
 

 

Project Name Data (Last Modified On 5/4/2020)
Acceptance : Accepted
Note : Tribe Morindeae
Project Data     (Last Modified On 5/15/2020)
Notes:

Morinda includes perhaps 30 species of trees and shrubs, with several species in the Neotropics, Africa, Asia, and the Pacific region. This genus is characterized by its leaves generally elliptic and with pubescent domatia, triangular and usually interpetiolar stipules, distinctive subglobose, capitate inflorescences and fruits with the flowers and individual fruits fused together, generally showy bright white flowers, and succulent or juicy drupaceous fruits. The leaves are sometimes markedly anisophyllous, so the developed leaf appears to be alternate; these anisophyllous leaves are sometimes borne on a reduced internode, so the leaves appear to be ternate. This anisophyllous arrangement is often produced at a terminal node with an inflorescence (Johansson, 1994), so the terminal or pseudoaxillary inflorescence appears to be borne in a leaf-opposed position. The development of calycophylls (or perhaps petaloid bracts) is occasional in some individual species; the presence of these has been at one point considered a species-level difference, but cultivation has found this is a feature of individual plants or lines. The multiple fruits (sometimes referred to as syncarps, or a drupecetum) are unusual in Rubiaceae, but not unique to this tribe or this genus. In many species, the inflorescence is relaively small but enlarges markedly as the fruits develop. The syncarpic fruits of many Morinda species are relatively large, and perhaps dispersed by mammals (in addition to humans). One species, Morinda citrifolia, has an unusually broad range: this species characteristically grows on ocean beaches and disperses at least in part by water, and is found it in the Caribbean, around tropical Africa, and through the Indian and Pacific Oceans. Morinda citrifolia is also widely cultivated, locally for food and commercially as a nutriceutical (Razafimandimbison et al, 2010), and Morinda panamensis is locally cultivated in the Neotropics for its edible fruits. Neither of these species has a commercial market for their edible fruits, because these are insipid to somewhat fetid-tasting and are an acquired taste. 

The circumscription of Morinda has been problematic for some time, and narrowed markedly in recent years (Razafimandimbison et al., 2008). In the Neotropics, Appunia has been separated based on its flowers that are not fused together, although sometimes these appear to be fused at first glance. Appunia has more species than Morinda in the Neotropics, and is found widely in the region while Morinda in its current, narrowed circumscription is found basically in the Caribbean basin. In the Paleotropics Gynochthodes has been separated based on molecular systematic analysis (Razafimandimbison et al, 2009), and it has fused flowers but differs from Morinda in its generally scrambling or lianescent habit and dioecious flowers. Gynochthodes has not been comprehensively surveyed, but many more species than Morinda; Morinda has not been surveyed as a whole, either. The excellent study by Johansson (1994) reviews the combined group Morinda-Gynochthodes, with a range of reproductive biology.

The fused flowers and fruits of Morinda are distinctive, but in sterile condition this genus is sometimes overlooked.In the Neotropics, Morinda is similar vegetatively to some species of Isertia, but those have branched inflorescences with separate fruits. Fused (or apparently fused) flowers are fruits are also found in several other Rubiaceae that have been confused with Morinda. In the Neotropics, Schradera appears to be similar in its syncarpic headss although apparently its closely packed hypanthia and fruits are not fully fused; also, plants of Schradera are lianescent or clambering with adventitious roots while Neotropical Morindas are erect, free-standing shrubs and trees. In the Paleotropics, Nauclea and Breonia are similar  in inflorescence structure, but can be separated by their generally rather large stpules that are held erect and flatly pressed together at the stem apex, and then caducous. Morinda has also been confused with Gynochthodes and Appunia; their differences are outlined above. 

The genus description and discussion here apply to Morinda world-wide, but the species treatments are focussed on the Neotropical plants. See Lorence et al. (2012, and online in the Flora Mesoamericana project) for a useful treatment for some of the Neotropical species. 

Author: C.M. Taylor. The content of this web page was last revised on 4 May 2020.
Taylor web page: http://www.mobot.org/MOBOT/Research/curators/taylor.shtml

Distribution:

Pantropical, in seasonal to humid, generally lowland vegetation in the Caribbean region of the Americas, widely Africa, on the coasts in Madagascar and Indian Ocean region, rather widely in southeast Asia, and across the Pacific; most species in Asia and the Pacific, one widespread species found across most of the range of the genus, and this and another species sometimes cultivated in humid tropical regions.

References:

 

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Shrubs and trees, unarmed, terrestrial, with raphides in the tissues, sometimes with anisophylly and reduced nodes so leaves appear subopposite. Leaves opposite or rarely ternate, petiolate, entire or rarely sinuate to lyrate, with higher-order venation not lineolate, often with pubescent domatia in axils of secondary and sometimes tertiary veins; stipules interpetiolar or sometimes fused around the stem, triangular, generally erect and valvate in bud, persistent or caducous. Inflorescences terminal, pseudoaxillary, or apparently leaf-opposed, fasciculate to cymose, with 1 (or perhaps 2 to several) subglobose head(s), these each several-flowered with flowers fused together, pedunculate to subsessile, bracts developed or reduced. Flowers sessile, bisexual, distylous or sometimes homostylous, protandrous, fragrant, perhaps noctural or diurnal; hypanthia fused within an inflorescence, angled; calyx limb reduced to shortly lobed, without or occasionally with calycophylls; corolla salverform to funnelform, white to yellow, internally glabrous except pubescent in upper part, lobes (3)4--7, triangular, valvate in bud, sometimes with appendages; stamens (3)4--7, inserted above middle of corolla tube, anthers ellipsoid to oblong, dorsifixed in distal part, opening by linear slits, sometimes with prolonged apical appendage, included or exserted; ovary 2-locular or incompletely 4-locular with false septa, with ovules 1 in each locule, inserted on septum near its base; stigmas 2, included or exserted. Fruits multiple, comprising the entire infructescence, drupaceous, subglobose, fleshy, at maturity dirty white, with calyx limb persistent; pyrenes 2-4 per flower, 1-locular, oblong to obovoid or reniform, bony or cartilaginous, adaxially plane to sulcate, apparently dehiscent by preformed slits; seeds 1 per pyrene, ellipsoid.

 

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