Abstract: The morphology (vegetative and floral) of Jatropha L. species (Jatropha curcas L., Jatropha gossypifolia L., Jatropha multifida L. and Jatropha podagrica Hook) in parts of the Niger Delta was investigated. The study aimed at establishing taxonomic affinities and differences between these species based on their leaves, inflorescences, flowers, fruits and seed characteristics. Visual observations, measurements and photographs of relevant organs of wild and ornamental collections of the four species were taken. Results obtained showed that the four species differ distinctively in leaf outline, leaf length, leaf base, margin and texture with the glandular leaf margin of J. gossypifolia and incised lobes of J. multifida being diagnostic and asserting their statuses as taxonomic species. Leaf length varied from 7.01±0.90 cm in J. gossypifolia to 24.75±1.18 cm in J. podagrica. The distinct yellowish-green flower colour of J. curcas distinguishes it from other species which possess different shades of red colour. Variation was observed in fruit shape (ellipsoid and tear-drop shapes) of J. curcas showing that intraspecific morphological or ecological types exist within this species. However, similarities were observed in leaf venation which is actinodromous and basal in all species and in floral arrangement which is cymose. These and other features confirm the relatedness of the species.
INTRODUCTION
The genus Jatropha L. belongs to the family Euphorbiaceae with over 175 species. Common Jatropha species found in the Niger Delta region are Jatropha curcas L., Jatropha gossypifolia L., Jatropha multifida L. and Jatropha podagrica Hook. A number of Jatropha species including J. curcas yield oils and photochemicals of medicinal and domestic importance while others are being used as ornamentals or as hedge plants (Nwokocha et al., 2011; Fairless, 2007; Burkill, 1994). Recently, interest in the use of J. curcas as a major source of biofuel has been advocated in Nigeria (http://allafrica.com/). Some members of the genus have been listed as neglected and underutilized because of limited information available on the biology and systematics of the species (Heller, 1996; Csurhes, 1994).
The utilization of morphological characters (vegetative and floral) for delimitation of closely and distantly related taxa is age long. Recently, Akyalcin et al. (2006), Mbagwu and Edeoga (2006), Agbagwa (2007), Ghosh et al. (2008), Jafari et al. (2009) and Silva et al. (2011) employed these important taxonomic characters (vegetative and floral) in the elucidation of different plant genera. Apart from the foundation work of Hutchinson and Dalziel (1958), the authors are unaware of any recently published work which identified and described species of Jatropha in Nigeria and particularly Niger Delta, where environmental changes are causing gradual elimination of species.
This study reports part of the results of a project on the biology and systematics of Jatropha species in Niger Delta aimed at generating interest on improvement and breeding of J. curcas. Therefore, the purpose of this study is to provide (1) detailed information on the morphology of the four Jatropha species commonly found in the Niger Delta; (2) morphologically compare the four species to deduce their species affinity and update information contained in Hutchinson and Dalziel (1958) with regards to relatedness of these species and (3) provide some basic information to steer further research on the species in the Niger Delta since one of them (J. curcas) is used as biofuel elsewhere.
MATERIALS AND METHODS
Plant materials: Plant materials were collected during field trips to some Local Government Areas in Niger Delta from January 2009 to March 2010. Samples were compared with earlier deposits in the University of Port Harcourt Herbarium and reports in Flora of West Tropical Africa (Hutchinson and Dalziel, 1958). The specimens were lodged at the University of Port Harcourt Herbarium after investigated.
Morphological studies and analysis of data: Observations on morphology were made on matured stands of J. curcas, J. gossypifolia, J. multifida and J. podagrica. Morphological features were described following the Flora of West Tropical Africa (Hutchinson and Dalziel, 1958), Taxonomy of Flowering Plants (Gill, 1988) and Anatomy of Flowering Plants (Metcalfe and Chalk, 1979). For all characters, 10 specimens from 11 localities were measured using a meter rule and venier calliper to determine the length and breadth dimensions of leaves, stems, flowers, fruits and seeds. Results from measurements were fed into Microsoft Excel 2010; the averages and standard deviations were computed using the Statistics package of the Excel 2010. Minute characters were observed using a hand magnifying lens. Photographs of relevant morphological features were taken using a PowerShot A500 Canon digital camera. The floral diagram of the genus based on the floral formula was derived. The research work was carried out at the Biosystematics and Taxonomy Laboratory, Department of Plant Science and Biotechnology, University of Port Harcourt, Nigeria.
RESULTS AND DISCUSSION
Morphological descriptions of Jatropha species in West Africa based on herbarium specimens deposited at Kew are reported by Hutchinson and Dalziel (1958). The vegetative and floral morphological descriptions in this present study were based on fresh specimens collected from different localities as shown in Table 1. Details of vegetative and floral characteristics of the different species are presented in Table 2 while Table 3 contains information on leaf architecture of the species. All the species studied are monoecious, perennial and sub-woody shrubs.
Taxonomy relies greatly on morphology to discriminate groups and leaf morphology is central to plant taxonomy and systematics (Viscosi and Cardini, 2011). A major diagnostic character of Jatropha is the leaf which is distinctly different for all four species (Fig. 1). The diagnostic features with respect to leaf morphology include the leaf phyllotaxy and organization, shape, surface, texture, margin, types and shape of lobes, presence and nature of stipules, petioles, venation and architecture of the leaf (Table 2).
| Table 1: | Sources, Collection localities, collector and sample numbers of Jatropha species |
| Table 2: | Macromorphological characters of the four Jatropha species |
| Table 3: | Summary of leaf architecture of the Jatropha species studied |
For instance, the leaf shape of J. curcas and J. gossypifolia are broadly ovate with deeply to shallowly cordate leaf base and acute or acuminate tip; J. multifida has altenuate tip (or tailed apex) while Jatropha podagrica is orbicularly ovate with peltate leaf base and acuminate tip. Likewise the leaf margin of the species varied from entire to undulating in J. curcas, to serrated or serrulate and minutely toothed with glandular tips in J. gossypifolia, incised with alternately arranged leaf projections or pointed segments in J. multifida and sinulate for J. podagrica. While leaf lobes ranged from 3 to 5 palmate lobes in J. gossypifolia and J. podagrica, 3 to 7 palmate lobes were observed in J. curcas while J. multifida was pinnately lobed into 9 or 11 segments (Fig. 1). Extensive use of leaf morphological characters in delimitation of related species abounds in literature. Recently, Ratha and Paramathma (2009) attempted separation of twelve Jatropha species in India based on leaf morphological features. Similarly, Agbagwa (2007) and Mbagwu and Edeoga (2006) utilized related leaf characters in delimitation of members of the genera Abrus and Vigna, respectively. Thus, leaf morphology is critical in identification of common Jatropha species in Niger Delta.
The usefulness of flowers and inflorescences in taxonomic discrimination of species cannot be overemphasized. Ratha and Paramathma (2009) demonstrated this fact in Indian Jatropha species where different distinct shades of colours of flowers and inflorescences were reported for the different species. The identified Jatropha species in this present study are unisexual with inflorescences made up of solitary to clustered cymose flowers. However, their forms varied with J. curcas possessing biparous or dichasial cyme type while J. multifida and J. podagrica had the multiparous or polychasial cyme as shown in Fig. 2 and 3 and Table 2. Variation was observed in J. gossypifolia whose peduncle is pubescent with fine, whitish hairs ending with a flowered leaf opposed, uniparous or scorpioid cyme. All species possessed rosaceous-shaped flowers which are regular, pentamerous, polypetalous and unisexual. Hermaphroditic flowers were observed in J. curcas (Fig. 3a).
| Fig. 1(a-d): | Habit of (a) J. curcas, (b) J. gossypifolia, (c) J. multifida and (d) J. podagrica |
| Fig. 2(a-d): | Inflorescence of (a) J. curcas, (b) J. gossypifolia, (c) J. multifida and (d) J. podagrica |
| Fig. 3(a-d): | Androecium (m), gynoecium (f) and hermaphroidite (h) of (a) J. curcas, (b) J. gossypifolia, (c) J. multifida and (d) J. podagrica |
Variations were observed in the flower colour. The flowers of J. curcas were yellowish-green in colour, purplish-red for J. gossypifolia, bright red and reddish orange in J. multifida and J. podagrica, respectively. The floral formula for the species studied (Fig. 4) can be represented as follows:
Male flower: ⊗, ♂, ♀, K5, C5, A1,
G0
Female flower: ⊗, ♀, K5, C5, A0,
G3
Hermaphrodite flowers (J. curcas): ⊗, ♀, ♂, K5,
C5, A1, G3
The fruits and seeds of the Jatropha species showed variations of taxonomic relevance (Fig. 5 and 6, Table 2). J. gossypifolia and J. podagrica fruits are 3-seeded globose capsule, sparingly pubescent to glabrous, usually green in colour, turning brown and dehiscing into 2-valved cocci when mature; comparatively, J. multifida are 3-seeded ellipsoid capsule, glabrous, green to yellow in colour turning dark brown when mature and dehisces. J. curcas was observed to have both ellipsoid and tear-drop-shaped fruits (Fig. 5a, b) implying that there may be morph-or ecotypes in this species. This fact is of significant important since only the ellipsoid shaped fruit has been reported (Fairless, 2007; www.desert-tropicals.com; http://www.latimes.com/; Ratha and Paramathma, 2009). Based on overall morphological data, a taxonomic key to the species of the genus studied is hereby presented as follows:
| • | Pistil elliptic syncarpous, 3-celled, triovulate, 3 spreading bifurcate style that is fused atthe base with 2-lobed stigma per style……….2 |
| • | Pistil globose syncarpous, 6-ribbed and 3-celled, triovulate of about 0.2 cm long, 3 spreading style of about 0.2 cm long that is fused at the base with 2-lobed stigma per style……………3 |
| • | Seed ellipsoid and triangular-convex in shape, black in colour some mottled with grey to cream thin lines and cream with brown hue aril………. J. curcas |
| • | Seed spherical to oval in shape, pale brown in colour and whitish brown aril…………. J. multifida |
| • | Flowers is dark red in colour, seed length 0.7-0.8 cm long, pale grey to brown in colour and dark brown aril, stem stout and cylindrical…………J. gossypifolia |
| • | Flowers reddish-orange in colour, seed length 0.9-1.1 cm, pale brown with grey hue in colour and dark brown aril, stem stout; stem cylindrical and swollen at the base………J. podagrica |
| Fig. 4: | Floral diagram of Jatropha (a) Male plant, (b) Female plant and (c) Hermaphrodite |
| Fig. 5(a-d): | Fruits of (a) J. curcas and its variation in shape (i and ii) (b) J. gossypifolia (c) J. multifida and (d) J. podagrica |
| Fig. 6(a-d): | Seed of Jatropha species studied. (a) The ellipsoid shape of J. curcas and its variation in shape (i and ii) (b) J. gossypifolia (c) J. multifida and (d) J. podagrica |
One major factor hampering the breeding and development of sustainable conservation of Jatropha in Nigeria is that the information available on germplasm of Jatropha is scattered and not readily accessible. This has resulted, frequently, in uncoordinated research efforts as well as inefficient approaches to the conservation of these genetic resources. This study however, has unequivocally identified four Jatropha species in the Niger Delta. It is hoped that the information compiled will contribute to: (1) ease of identification of the species by researchers based on the taxonomic key (2) identifying constraints in and possible solutions to the use of the crops (3) identifying possible untapped genetic diversity for breeding and crop improvement programmes and (4) detecting existing gaps in available conservation and use approaches. It also intends to contribute to improvement of the potential value of these crops through increased use of the available genetic diversity and forms a valuable reference source for all researchers involved in conservation, improvement and promotion of J. curcas as a biofuel plant in Nigeria.
CONCLUSION
Taxonomy relies greatly on morphology to discriminate groups. This study has identified and confirmed for the first time the occurrence of four species of Jatropha (J. curcas, J. gossypifolia, J. multifida and J. podagrica) in the Niger Delta based on gross morphology. The morphological description of the species provided herein clearly separates the identified species into distinct species and provides easy identification guide to researchers from different background wishing to collect and perform studies on Jatropha species. More especially, the descriptions shall be of incalculable help to horticulturists seeking to breed and domesticate species like J. multifida and J. podagrica for their beautiful and showy flowers. The information also solves the problems of identification which may arise during sample collection in the field/wild between the members of the genus and other morphologically similar genera. This study therefore affirms and authenticates the species as individual species occurring in the Niger Delta.