Nigerian Journal o f Ecology t ( 13-IP) 1999 THE MORPHOLOGY AND ECOLOGY OF THE GENUS SYNSEPALUM (A.Dc) DANIELL (SAPOTACEAE) IN NIGERIA AYODELE, A. E AND CHUKWUKA, K. S. Department of Botany and Microbiology University of Ibadan, Ibadan ABSTRACT The genus Synsepalum is represented by three species in Nigeria. It is confined to me lowland rainforest region o f the country. Synsepalum dulcijicum is called the 'miraculous' berry or the ‘magic plant ’ on account o f the protein based sweetening agent miraculin found in the pulp o f (he fruit. The plant also produces a fairly hardwood which is particularly used as firewood by the indigenous people while the twigs are used as chewsticks. S. stipulatum popularly called the "Blacksmiths' charcoal wood” is known to supply the best charcoal to the Benin blacksmiths. S. glycydorum is not o f much economic importance to the people but it is restricted in its distribution to the Southeastern part o f Nigeria. From the standpoint o f uses and restricted distribution, | there Is need for in-sltu and ex-situ conservation o f these species for sustainable jg utilization. The largest leaves with the longest petioles are found in S. stipulatum, while the smallest leaves with the shortest petioles are in S. dulcificum . The leaves and petioles o f S. glycydorum are intermediate+of the other two species. The leaves generally are elliptic to oblong to oblanceolate in shape with acuminate apices. However, the apex in S. dulcificum may be acute, rounded or rarely re I use. The leaf bases in the genus are usually cuneate. The leaves are glabrous except in S. dulcificum which may be hairy oh the abaxial surface. INTRODUCTION • . V \ The genus Synsepalum (A. Dc) Daniell is represented by three species in Nigeria (Hutchinson and Dalziel, 1963; Keay et al, 1964) of which S. dulcificum (Schum. and Thonn.) Daniell is the best known and cultivated for its high economic value which however remains to be utilized on a commercial basis. It is called the ‘magic plant’ on acoouiit of the miraculous berry (fruits) it produces. The pulp of the reddish yellow fruit contains a protein based sweetening agent called miraculin (Dalziel, 1948; Irvine, 1961) similar to thaumatin found in Thaumatococcus danlc/lli (Bcnn.) Benth and Molcnin in Dioscoreophyllum cumminsii (Slapf.) Diels. Thaumatin is now being formulated into a drink particularly recommended for diabetic patients who are advised to reduce sugar intake in the body. Miraculin is known to have a greater effect in sweetening acidity than countering bitterness 13 UNIV ERSIT Y O F IB ADAN Ayodete, A. E And Chukwuka, K. S.: The Morphology And Ecology O f The Genus Synsepalum (Dalziel, 1948; Irvine, 1961). Thus, for example, it is used to sweeten palm wine (Dalziel, 1948; Irvine, 1961). The fairly hard wood of S. dulcificum is used as iirewood by the indigenous people while the twigs are used as chewsticks (Irvine, 1961). The other two species are usually found in the wild. S. stipulatum (Radik.) Engl, is known as the ‘Blacksmiths’ charcoal because it supplies the best charcoal to the Benin blacksmiths in the present-day Edo State, Nigeria (Keay el a!., 1964; Dalziel, 1948). The stems of small trees of these plants are used for axe-handles and the wood is also cut into planks (Dalziel, 1948). S. glycydorum Wernham is the most uncommon and relatively unknown from an economic standpoint. The Nigerian forest today is under a tremendous pressure resulting from technological advancement, pharmaceutical products and timber utilization and fuel among others. The rate of degradation is so alarming that many of the yet unknown flora or those in danger of extinction will be lost to science in the foreseeable future. Most of the affected plants arc of high economic value which if harnessed could boost the dwindling economy of our country. However, the point here is not in the utilization of these plant parts but on their conservation in-situ and ex-situ for a sustainable utilization. It is frc.i this perspective that the present paper discusses the morphology with particular reference to the leaf and the distribution of the genus Synsepalum in the Nigerian forest. It highlights the important taxonomic characters of the leaf which are of value in the identification of the three species in the forest. It also forms the first part of a series of papers using leaf morphological (micro and macro)in the identification and delimitation of gradually disappearing forest species groups in Nigeria. MATERIALS AND METHOD All specimens of the three species treated in this study were examined at the Forestry Research Institute Herbarium (Fill), Ibadan and the University of Ibadan Herbarium (IJCI or UIII). Information on all the specimens were recorded and the following quantitative and qualitative leaf morphological characters were scored - leaf length, width, blade length, petiole length, leaf apex , base, shape and margin. RESULTS Leaf Morphology The leaves vary from elliptic to oblong through to oblanceolate with usually acuminate apex though in S. dulcificum the apex may be acute, rounded or rurcly rctuse. The base is usually cuneate while the margin is entire (Table 1, Fig. 1). The largest leaves are found in S. stipulatum with a mean size of 7.84 x 3.14cm. S. glycydorum usually has the size of the leaf intermediate of the others with a mean size of 16.20 x 4.82cm (Table 1). The petiole length also ranges from 0.35cm in S. dulcificum to 2.38 in S. stipulatum with S. glycydorum (1.42cm) intermediate (Table 1). The leaves are usually glabrous on both surfaces except for some form of hairiness on the abaxial surface of S.glycydorum. The leaves of S. dulcificum occur in clusters near the end of the branchlets. The larger leaves at each end are subtended by two 14 UNIV ERSIT Y O F IB ADAN Nigerian Journal o f Ecology I (13-19) 1999 smaller leaves of 4.14 x 1.72cm in size and with very short petioles, 0.20cm long. Distribution The genus is restricted to the lowland rainforest region of Nigeria (Fig. 2) with S. stipulation being the most widespread of the three species. It extends from Ogun and Benin forests to Owerri. Onitsha and Uyo all located in Southeastern Nigeria. Most of the collections of these species are from the forest of Benin in Edo state and its environs. S. glycydorum is said to be only known in Nigeria (Keay et al, 1964) and it is of limited occurrence, usually restricted to the forests of Umudike, Umuahia, Owerri and Calabar towards the eastern part of the countiy. It is thus the most threatened species in the genus in the country. S. dulcificum is the most widespread in Oyo and Ogun forests particularly around Ibadan and Abeokuta in southwestern Nigeria from where many collections have been made. However, few collections are also from Uyo in Akwa-Ibom state. The species are usually found in wet, damp localiliet In the forest. DISCUSSION A number of factors have been listed to assess the vulnerability of species to use by people in the forests (cf. Cunningham 1987, 1991, 1994, 1996; Wild and Mutebi, 1996). S. dulcificum which has the highest potential for economic importance in the genus is a slow growing small tree or shrub, less abundant and of restricted habitat usually prefering areas where the rainfall is not less than 1200mm per annum. These coupled with the fact th at fruits, tw’gs and wood are used by the indigenous people, the plant may thus qualify as one of the forest species under treat and consequently in dire need of protection. If and when the berries are utilized for commercial purposes other than the subsistence purposes, it is doubtful if there would be enough of the trees remaining in the Nigerian forest to cope with such usage. However, the alternatives in using Discoreophyllum cumminsi or Thaumatococcus danielli as sources of molenin and thauinatin respectively may reduce the heavy dependence on miraculin from S. dulcificum. The most vulnerable of the three species treated in this paper is S. glycydorum which is said to be known only in Nigeria and which is restricted to the Southeastern forests. With the current rate of deforestation of the lowland rainforest in Nigeria, it ieems unlikely if the species will not be extinct in the nearest future if efforts are not made to conserve il. The maintenance of essential ecological resources arid life support systems, preservation of genetic diversity and sustenance of any useful species or ecosystems are the three objectives emphasized by the World Conservation Strategy (IUCN, UN'F.P and WWF, 1980) which are imperative for suslainabje existence. In Nigeria, these are goals which must transcend organised in-door fora. The sincere pursuance of these objectives is desired from government functionaries and conservationists The task before us can only be accomplished in the face of a collective orientation. This implies that both the government and the citizens must ^ pool resources together in order to conserve and preserve these forest resources which are our collective natural heritage. 15 UNIV ERSIT Y O F IB ADAN Ayodele, A. E And Chukwuka. K. S.: The Morphology And Ecology O f The Genus Synsepalum Fig-1 Map showing the distribution of the genus Synsepalum in Nigeria 16 UNIV ERSIT Y O F IB ADAN 2 c m Nigerian Journal o f Ecology I (13-19) 1999 Fig- 2 Leaf shapes in the genus 5hynsepalum .,*» Nigeria a -c , 5. • dulcificum: d and e; 5 • aivcydorum; fr-h 5 stipulatum ■ UNIV ERSIT Y O F IB ADAN Ayodele, A. E And Chukwuka, K. S..' The Xlorphology And Ecology O f The Genus Synsepalum REFERENCES Cunningham, A. B. (1987). Commercial craftwork: Balancing out human needs and resources. South African Journal of Botany 53 (4): 259-266 Cunningham,A. B. (1991). Development of a conservation policy, on commercially exploited medicinal plants. A case study from Southern Africa. In: I ley wood, V, Synge, II. and Akerele, O. (eds). Conservation of medicinal plants, pp 337-354. Cambridge University Press, Cambridge. Cunningham, A. B. (1994). Integrating local plant resources and habitat management. Biodiversity and Cfinsspalkn 3 : 104-115 Cunningham, A. B. (1996). Peonle nark and plant use. Recommendations for Multiple-use zones and development alternatives around Bwindi Inpenetrable National Park, Uganda.People and Plants Working Paper 4. UNESCO, Paris. Dalziei, J. M. (1948); The useful plants of West Africa. Crown Agents for the Colonies, London. Hutchinson. J. and Dalziei, J. M. (1963). Flora of West Trcpical Africa. Vol. II. Crown Agentsfor Overseas Governments and Administration, London. Irvine, F. R. (1961). Woody Plants__of Ghana.Oxford University Press, London. IUCN/UNEP/WWF (1980). World Conservation Strategy: Living resources conservation for sustainable development. Inter-national Union for Conservation of Nature and Natural Resources, United Nations Environmental Programme and World Wildlife Fund, Gland, Switzerland. Keay, R.W.J., Onochic, C.F.A. and Standfield, D.P. (1964). Nigerian Trees. Vol. II. Department of Forest Research, Ibadan, Nigeria. Wild, R.G. and Mutcbi, 7. (1996). Conservation through community__USfi , pf__nlwl resources. Establishing collaborative management at Bwindi Impenetrable and Mgahinga Goirilla National Parks, Uganda. People and Plants Working Paper 5. UNESCO, Paris. is UNIV ERSIT Y O F IB ADAN Nigerian Journal o f Ecology l (13-19) 1999 Table 1. Leaf morphological features of the genus Synsepalum in Nigeria Leaf shape Leaf Apex Leaf Base Leaf Margin Leaf Blade Length Petiole Length Length Width S. dulcificum Elliptic/ , Acute/Rounded/ Oblanceolate Acuminate Rarely refuse Cuneate Entire 7.84*0.54 4.80-11.00 3.14* 027 1*50-4.60 7.49* 0.51 4.50-10.30 0.35* 0.05 • 0.10-0.70 4.14* 0.32 2.10-5.60 l.72± 0.17 0.60-2.70 3.94 tO.31 1.90-5.20 020*0.02 •• 0.10-0.40 S. glycydorum Elliptic/ Acuminate Oblanceolate Cuneate Entire 16.20*1.05 13.90-19.50 4.82±0.35 3.70-5.80 14.78*0.90. 13.00-18.00 1.42*0.38 0.60-2.80 S. stipulatum Elliptic Acuminate Oblanceolate Cuneate Entire 18.19±0.93 9.80-29.20 4.84*0.27 2^0-6.90 15.81*0.82 820-25.30 2.38*0.17 1.10-4.00 All measurements in centimeter (mean * standard error) / range. * • Mean values for mature terminal leaflets. £* Mean value for subtended leaflets UNIV ERSIT Y O F IB ADAN