CONSERVATION,ENVIRONMENT AND FORESTRY:THE FAMILY EUPHORBIACEAE By Kizito Simon Njaye
INTRODUCTION
According to wikipaedia.org the Euphorbiaceae family also known as the spurge family, are a large family of flowering plants. In common English, they are sometimes called euphorbias, which is also the name of a genus in the family. Most spurges, such as Euphorbia paralias, are herbs, but some, especially in the tropics, are shrubs or trees, such as Hevea brasiliensis.
Some, such as Euphorbia canariensis,are succulent and resemble cacti because of evolution. This family has a cosmopolitan/global distribution, with greatest diversity in the tropics. However, the Euphorbiaceae also have many species in nontropical areas of all continents except Antarctica.
According to Hutchinson(1934) Euphorbiales is the thirty fifth order of the phylum Angiospermae, sub phylum Dicotyledones and division Lignosae. The order consists of a single family,that is, the Euphorbiaceae which has been described in the present text in detail.
Bentham and Hooker(1877) have included the Euphorbiaceae along with other eight families including Urticaceae and Casuarinaceae in their seventh series—the Unisexuales of class Dicotyledones, and division Monochlamydeae.
Engler and Prantl (2014) In the Plant Science 4 U Journal,have included the family Euphorbiaceae along with other nineteen families including Linaceae, Rutaceae and Meliaceae in their twenty third order—the Geraniales of class Dicotyledoneae and sub-class Archichlamydeae using their classification system and method.
According to Eggling,W(1951) ,the Euphorbiaceae family is a large family in Uganda with members showing considerable divergence in characters, but manifest a common origin in essential parts of the flower. Euphorbiaceae family have simple leaves and except Mallotus oppositifolius,the leaves are alternate.
Flowers are unisexual usually occurring on the same plant. Anthers usually 2-celled ,ovary superior or naked,syncarpous composed nearly always of 3 carpels, forming 3 loculi with one or two ovules each.
The fruit occasionally drupe or a berry but typically splits into its constituent carpels elastically ,at the same time each carpel opens ventrally letting the seeds escape.
Seeds often have a conspicuous caruncle.
In Uganda,the examples of Euphorbiaceae family genera and species are:
Alchorn=>A.cordifolia(Luzibaziba-Luganda),A.floribunda ,A.hirtella(Oruzhogwa-Lukiga),A.laxiflora;
Antidesma =>A.laciniatum,A.membranaceum,A.meiocarpum(Kufora-Lugbara);
Bridelia=>B.atroviridis,B.brideliifolia(Mujiji-Lunyankole,Omujimbo-Lukiga,Muanza-Lukonjo),B.ferruginea(Mbaragaza-Lutoro,Azom laiti- Luo),B.micrantha(Katazamiti-Luganda,Odugu kulo- Luo,Mwesende- Lusoga,Olulondamombe-Lugwe),B.scleroneuroides(Larweche-Luo,Orwecho-Langi,Emuduk-Ateso,Nsasira-Lusoga);
Cleisthanthus=>C.polystachyus(Muhindi-Lutoro);
Croton=>C.bukobensis(Omulyanyoni-Lukiga,C.dichogamus,C.macristachys(Musogasoga-Luganda,Omulangara-Lunyankole,Murangara-Lukiga,Muhoti-Lutoro;Ofunze-Lugbara,Mwiyo-Lugwere,Muyemberera-Lusoga),C.megalocarpus(Nkulumire-Luganda,Omutakula-Lukiga,Munyabakakuru-Lutoro,Mutugunda-Lunyakole),C.oxypetalus(Mwatansale-Lukiga);
Discoclaoxylon=>D.hexandrum;
Drypetes=>D.ugandensis(Naligwalim-Luganda),D.gerradii(Mushabarara-Lunyankole,Kakoba-Lukiga),D.leonesis(Mushabarara-Lunyankole),D.principum(Omukokora-Lukiga);
Elaeophorbia=>E.drupifera(Nkururu-Lutoro);
Euphorbia=>E.breviarticulata,E.candelabrum(Enkukuru-Lunyankole,Mukukulu-Lukenye,Kikukulu-Lukonjo/Lusoga,Weri-Lugbara,Kilidzoki-Madi,Epopong-Ateso/Langi,Lidwa-Lugishu);E.dawei,E.grantii(Ebuka-Langi),E.neglecta(Synonym E.obovalifolia),E.teke(Omukoni-Lusese),E.tirucali(Nkoni-Luganda/Lutoro/Lukiga,Oruyenzhe-Lunyankole,Orukoni-Lunyoro,Lukone-Lukenye/Lusoga,Oligo-Langi,Kilajok-Acholi,Luhoni-Lugwere/Lunyole),E.venenifica;
Fluegga=>F.virosa(Lukandia-Luganda/Lukenye/Lusoga,Omuturika-Lunyankole,Mbwera-Lutoro,Kyikyi-Lugbara,Lakago-Acholi,Lire-Madi,Elakat-Lango,Elachasi-Ateso,Siwira-Lugishu,Luhandwa-Lunyuli,Mukandwa-Lugwere,Omujanjasi-Lugwe);
Gelonium=>G.procerum;
Heywoodia=>H.lucens;
Hynenocardia=>H.acadia(Nabaluka-Luganda,Eteregu/Ebilaboni-Ateso,Mutatatankubebe-Lunyoro,Ika/Ikaraka/Karago-Lugbara,Leka-Madi,Okang/Okango-Luo,Enandwe-Lugwe,Cheburoko-Sebei);
Macaranga=>M.kilimandscharica(Muhoti-Lutoro,Omurara/Omusasa-Lukiga,Muhunga-Lukonjo,Luwesu-Lugishu,Kaptebema-Sebei,M.lancifolia(Omuburashasha-Lukiga),M.monandra(Omufurafura-Lukiga),M.pynaertii,M.schweinfurthii(Mweganza-Luganda,Mukokoma-Lunyankole,Gumudoadoa-Lugishu);
Maesobotrya=>M.purseglovei(Ekizogo-Lukiga);
Mallotus=>M.oppositifolius;
Micodesmis=>M.puberula;
Neoboutonia=>N.africana(Afukafuku-Acholi),N.macrocalyx(Onwanya/Echanya-Lukiga,Kiona-Lukonjo,Chebakwa-Sebei,Mudoadoa-Lugishu,N.melleri(Kafunkula-Luganda,Mukoko-Lutoro,Kiona-Lukonjo),N.mannii;
Phyllanthus=>P.discoideus(Muremanpango-Lunyankole,Omukale/Omuhahara-Lukiga,Odzeki-Madi,Mutaigumbwa-Lugwere/Lukenye,Kataibale-Luganda,P.floribundus(Temelezi-Madi,Awajawaja-Acholi,Ekodokodo-Langi,P.guineesis,P.polythanthus,P.reticulatus;
Pseudagrostistachys=>P.ugandensis;
Ricinodendron=>R.heudelotii(Musodo-Lunyoro);
Synademum=>S.cymosum;
Tetrorchidium=>T.didymostemon;
Thecacoris=>T.lucida;
Uapaca=>U.guineesis(Mukusu-Luganda,U.sansibarica
DESCRIPTION
The Euphorbiaceae family is characterized by hypogynous; actinomorphic; unisexual; petals usually absent, if present sometimes quite sympetalous (Jatropha)-, syncarpous with 1-2 ovules pendulous from the inner angle; stamens various; seeds often with a conspicuous caruncle; endosperms mostly copious; stipules mostly present.There are about 283 genera and 7,300 species in this family.
The leaves are alternate, seldom opposite, with stipules. They are mainly simple, but where compound, are always palmate, never pinnate. Stipules may be reduced to hairs, glands, or spines or in succulent species are sometimes absent.
The plants can be monoecious or dioecious. The radially symmetrical flowers are unisexual, with the male and female flowers usually on the same plant. As can be expected from such a large family, a wide variety exists in the structure of the flowers. The stamens(the male organs) number from one to 10 (or even more). The female flowers are hypogynous(of a plant or flower) having the stamens and other floral parts situated below the carpels (or gynoecium). that is, with superior ovaries.
The genera in tribe Euphorbieae, subtribe Euphorbiinae (Euphorbia and close relatives) show a highly specialized form of pseudanthium ("false flower" made up of several true flowers) called a cyathium. This is usually a small, cup-like involucre consisting of fused-together bracts and peripheral nectary glands, surrounding a ring of male flowers, each a single stamen. In the middle of the cyathium stands a female flower, a single pistil with branched stigmas. This whole arrangement resembles a single flower.
The fruit is usually a schizocarp, but sometimes a drupe. A typical schizocarp is the regma, a capsular fruit with three or more cells, each of which splits open explosively at maturity, scattering the small seeds.
The family contains a large variety of phototoxins (toxic substances produced by plants), including deterpene esters, alkaloids, and cyanogenic glycosides (e.g. root tubers of cassava). The seeds of the castor oilplant Ricinus communis contain the highly toxic carbohydrate binding protein ricin.
A milky latex is a characteristic of the subfamilies Euphorbioideae and Crotonioideae, and the latex of the rubber tree Hevea brasiliensisis the primary source of natural rubber. The latex is poisonous in the Euphorbioideae, but innocuous(not harmful or poisonous) in the Crotonoideae.
White mangrove, also known as blind-your-eye mangrove latex (Excoecaria agallocha), causes blistering on contact and temporary blindness if it contacts the eyes, hence its name. Other common names are milky mangrove, buta buta (Malay), and gewa (Bangaledesh). The latex of spurge was used as a laxative.
Recent molecular studies have shown that the enigmatic family Rafflesiaceae, which was only recently recognized to belong to order Malpighiales, is derived from within the Euphorbiaceae.
Euphorbiaceae are monoecious and open polluted and so self incompatibility is rare - although it has been reported in the past apparently this was in error. It is confirmed to be absent or incomplete in herbaceous Chmaessyce by Ehrenfeld 1976, Hevea by Bouharmont (1962), and Manihot by Jennings 1963 and George & Shifriss 1967(all in wikipaedia.org).
Stem:
Herbaceous or woody, erect, very rarely climbing as in a tropical genus Tragia. The species of Xylophylla possess flat phylloclades. The stem is branched. It may be cylindrical, angular or flat. Usually solid but sometimes hollow as in Ricinus communis. Many stems possess spines. In many Euphorbia sp., the stems become fleshy, green and cactus like in appearance.
Leaves:
The form and position of leaves are variable. The arrangement is usually alternate but sometimes they are opposite, e.g., Euphorbia hirta. In Pedilanthus the leaves are arranged alternately in the lower region of the plant whereas opposite in the floral region.
Usually the leaves are simple but in some they are deeply incised, e.g., Ricinus, Manihot, etc. In many Euphorbias the leaves are scaly and caducous. In many cases the leaves are reduced to spines. In few cases the leaves are replaced by cladodes. Usually the leaves are stipulate. In Jatropha sp., the stipules become branched and hair-like. In many Euphorbia sp., they are represented by glands or spines.
Inflorescence:
The inflorescence varies greatly. It may be racemose or cymose or sometimes complex. In Euphorbia, the inflorescence is peculiar but very characteristic and known as cyathium. This is the modification of a cyme. In cyathium inflorescence a large number of male flowers each represented by a stalked stamen are found arranged around a central stalked female flower. The female flower consists of gynoecium only.
The complete inflorescence looks like a single flower. The bracts are being arranged like a perianth. The bracts are so united that they form a cup-like structure. In Acalypha the inflorescence is catkin type. In Croton and Ricinus the flowers are arranged in terminal racemes. In Jatropha the inflorescence is of cymose type and the flowers are arranged in terminal cymes. In Manihot the flowers are being arranged in racemes.
Flowers:
The flowers are always unisexual. They are much reduced and may be monoecious or dioecious. In Euphorbia sp., each male flower is represented by a single stalked stamen. The flowers are incomplete, regular, actinomorphic and hypogynous.
Perianth:
Occasionally, both calyx and corolla are present, e.g., Croton. In majority of cases either calyx or corolla or both are absent. In Ricinus communis the calyx is present and the corolla absent. In Euphorbia hirta both the whorls of calyx and corolla are absent. In Jatropha sp., both calyx and corolla are present.
In Acalypha indica the perianth is represented by four minute sepaloid petals. In Phyllanthus only sepaloid perianth is present. In Euphorbia the perianth is absent or represented by tiny scaly structures.
The perianth consists of 4 to 5 petals. The calyx and corolla consists of 4 or 5 sepals or petals. The aestivation is valvate or imbricate.
Androecium:
The number of stamens varies from one to many. Usually as many stamens are present as many perianth leaves. In Euphorbia a single stalked stamen represents a single male flower. In Ricinus sp., usually five stamens are present, each stamen is profusely branched. In Jatropha they are arranged in two whorls each of five stamens.
In many the stamens are indefinite, e.g., Croton. The filaments may be free or united. The anthers are dithecous. They dehisce either by apical pores or by transverse or longitudinal slits.
Gynoecium:
Three carpels (tricarpellary), syncarpous; the ovary is trilocular, superior. Each locule contains one or two pendulous, anatropous ovules. The placenation is axile.
Fruit:
The fruits are schizocarpic. The fruits break violently and dehisce into one seeded cocci.
Such type of fruit is termed regma which is characteristic of Ricinus sp. The sp., of Trewia and Bridelia bear drupe fruit. Phyllanthus emblica also bears drupe.
Seeds:
The seed is endospermic. In Ricinus caruncle develops from the micropyle. The cotyledons either lie flat or are folded within the endosperm.
TAXONOMY
According to eFloraParner (2014) The family Euphorbiaceae is the fifth-largest flowering plant family and has about 7,500 species organised into 300 genera,37 tribes, and three subfamilies; Acalyphoideae,Crotonoideae and Euphorbioideae.Amongst the oldest fossils of the group include the permineralised fruit Euphorbiotheca deccanensis from the Intertrappean Beds of India, dating to the late Maastrichtian at the end of the Cretaceous, around 66 million years ago.
DISTRIBUTION
The plants of the Euphorbiaceae family are found throughout the world. However, they are not found in arctic regions. In our country the family is represented by several genera such as, Euphorbia, Ricinus, Phyllanthus, Croton, Pedilanthus, etc. In the desert regions of Africa and elsewhere the family is represented by cactus-like plants of different species of Euphorbia.
Heath like Euphorbias are quite common in Australia. In Britain only two genera, i.e., Euphorbia and Mercurialis are found, which are represented by sixteen and two species respectively.
Tap and branched. The roots of Manihot utilissima(Cassava plant) and M .palmata are tuberous and rich in starch.
HABITAT
The plants exhibit great variation in their habit. The plants may be herbs, shrubs or trees.
Euphorbia hirta, E. thymifolia, E. helioscopica, E. peplus; E. heterophylla, E. cristata, E. elegans; Phyllanthus niruri, Croton sp., Acalypha indica, etc., are annual or prennial herbs. Euphorbia pulcherrima, E. splendens, are beautiful shrubs. Pedilanthus sp., and
Jatropha sp., are shrubby plants.
Euphorbia royleana, E. tirucalli are cactus like shrubs. Ricinus communis (Arand) is a tall annual and becomes small tree-like in habit. The tree habit of the family is represented by Phyllanthus emblica (Amla), Bischofia javanica, Putranjiva roxburghii, etc.
Havea brasiliensist (rubber tree) is a large tree 60 to 100 feet in height and 8-12 feet in girth. Species of the genus Tragia are tropical climbers. Majority of the members of the family possess large laticiferous vessels which contain latex.
IMPORTANCE AND USES OF THE EUPHORBIACEAE FAMILY
Economic benefits
Some species of Euphorbiaceae have economic significance, such as cassava (Manihot esculenta), castor oil plant (Ricinus communis), Barbados nut (Jatropha curcas), and the Para rubber tree (Hevea brasiliensis), Rubber: Several species of Hevea, Man/hot gives common rubber in their latex, Oils: Some plants give wood oil, artist oil and other drying oils. These oils are used in paints. These oils are extracted from the seeds of several species. Dyes:Chrozophora gives dye.
Source of food
Cassava (Manihot esculenta) is grown in many countries in the world and is one the Euphorbia species that is used as food and its starch is used for both domestic and industrial uses by man.
Ornamental uses
Many are grown as ornamental plants, such as poinsettia (Euphorbia pulcherrima) or garden croton (Codiaeum variegatum). Leafy spurge (Euphorbia esula) and Chinese tallow(Triadica sebifera) are invasive weeds in North America,E.turicali in Africa is used as a live fence,as a boundary marker for land demarcation and building kraals in livestock keeping areas .
The most dangerous Euphorbiaceae member is the castor oil plant (Ricinus communis ) because of their ricin content in the seeds. Ornamental plants: The plants of this family have attractive colours. So they am commonly used as ornamental plants. Examples: Euphorbiu splenclens. Euphorbia pulcherrima,castor bean.
Medicinal uses
Although some species of the Euphorbiaceae have been used in traditional medicine,as of 2019, there is no rigorous clinical evidence that euphorbia extracts are effective for treating any disease.The fruit of Phyllanthus emblica has many medicinal uses.Majority of plants in the world including those of the family Euphorbiaceae are the source of numerous medicines both clinical and traditional ones.Researcher every day are discovering new and manufacturing new medicines and vaccines from plant extracts world wide.
Phytotoxins
Poisons: The milky juice of many plants like Mercuriolis has deadly poisons. Some are very dangeous for stomach. Some can cause blindness of eyes, Therefore, these poisons are used for murder and suicides. These are also used to kill some insects.
Numerous Euphorbiaceae species are listed on the poisonous plant database of the US Food and Drug Administration mainly because of the toxic sap.
Ecological uses
Some Euphorbia plants can co-exist ecologically with other organisms such as insects and other plants within the habitats where they exist.
Others are habitat type indicators for example Euphorbia tirucalli,E.floribunda are indicators of Arid/Semi-arid habitats.
Vulnerability and Extinction
Some species are facing the risk of becoming extinct. These include the Euphorbia species E. appariciana, E. attastoma, E. crossadenia, and E. gymnoclada.This is due to a number of factors such as anthropogenic factors that is man and his activities,farming,bush burning,tree felling,clearance of land for construction and non-anthropogenic natural factors such as the effects of climatic change and global warming.
Conclusion
Man and nature are inseparable.This implies that for man to continue sustainably surviving on Mother Earth there is need to ensure the proper and sustainable conservation,management and utilization of the remaining plant and animal resources on earth while conserving for the future generations and posterity.All plant resources on earth including those of the family Euphorbiaceae are significantly important in their entirety and there is also a need to protect and conserve them.The effects of global warming and climate change are real,this calls for man’s interventions to ensure that these vital species of plants and animals do not become extinct and disappear from Mother Earth.
Quote “We all have a responsibility to protect endangered species, both for their sake and for the sake of our own future generations.” – Loretta Lynch, the former United States Attorney General.
REFERENCES
· Hutchinson, John (1934). The families of flowering plants, arranged according to a new system based on their probable phylogeny. 2 vols (1st ed.). Macmillan. Volume 1: Dicotyledonae 1926, Volume 2: Monocotyledonae 1934.
· Wikipaedia.org https://en.wikipedia.org/wiki/Euphorbiaceae
· Eflora Parner,
· Bentham, George (February 1877). "On the Distribution of the Monocotyledonous Orders into Primary Groups, more especially in reference to the Australian Flora, with notes on some points of Terminology". Journal of the Linnean Society of London, Botany. 15 (88): 490–520. doi:10.1111/j.1095-8339.1877.tb00261.x.
· Plant Science 4 U,https://www.plantscience4u.com/2014/06/engler-and-prantl-system-of.html.
· William Eggling(1956) The Indigenous Trees of the Uganda Protectorate,Publ British Colonial Publishers.
KIZITO SIMON NJAYE
AFRICAN RESEARCH CONSULT-UGANDA CHAPTER,
RESEARCH ASSOCIATE
Telephone: +256 782672632 / +256 758844318
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