ABSTRACT
Morpho-anatomical study of Oldenlandia corymbosa L. and Oldenlandia affinis (Roem & Schult.) DC. in the family Rubiaceae was undertaken in order to assess the taxonomic relationship of the two species. Ten samples of each of the two species were randomly collected from their natural regions of provenance, Nkalagu (derived Savanna), Nsukka (derived Savanna), and Otukpo (Southern Guinea Savanna). Both species are herbaceous and are therefore, apomorphous than shrubs and trees, which are plesiomorphous. Comparative morphology and anatomy of the leaves, stems, roots and the flowers (pollen) of the two species were analysed. The results obtained showed great similarities and differences as well as the effect of climate on the species in their study sites. The influence of environment was not significant on O. corymbosa and O. affinis in all the morphological variables: lamina length, lamina diameter, fruit beak length, fruit stalk length, fruit length and fruit diameter in all the study sites. Leaves of both species are bifacial and hypostomatic; anomocytic and paracytic types of stomata were observed in the two species. Variations occurred among the woods of the two species which are diffuse porous with heterogenous rays; biseriate in O. corymbosa with medullary rays of 7 – cell high and uniseriate in O. affinis with medullary rays of 5 – cell high. The mean vessel length and diameter varied significantly (P ≤ 0.05) in O. corymbosa, especially in Nsukka (derived Savanna) and Otukpo (Southern Guinea savanna) in contrast to those in Nkalagu (derived savanna). In O. affinis the wood anatomical parameters varied significantly at P ≤ 0.05 in both the roots and the stems in all the study sites and insignificant in Nsukka and Otukpo in contrast to Nkalagu. This factor was supported by the vulnerability index of O. affinis which was found generally to be more vulnerable than O. corymbosa and this increased towards Otukpo which lies farther north. The variation of these anatomical parameters across species showed the strongest
significant difference. Flowers of both species are complete; racemose and corymbose; petals 4 – merous and white; sepals 4 – merous; bicarpelous ovary but yellowish-white petals in O. affinis; tricolporate pollen type in O. corymbosa but tricolporate and tetracolporate in O. affinis. Therefore, judging from the array of anatomical and morphological variables of the two Oldenlandia species, they should be classified as “moderately” apomorphous.
CHAPTER ONE
Introduction
Oldenlandia is a genus of flowering plants belonging to the family Rubiaceae (Hutchinson, 1959). It consists of approximately 100 species (but estimate of up to 300 species has also been made) and is distributed in all tropical and subtropical regions. The type species for the genus is Oldenlandia corymbosa. Oldenlandia was named by Linnaeus in 1753 in Species Plantarum. The name honours the Danish botanist, Henrik Benard Oldenland (Halford, 1992).
Some botanists have not recognized Oldenlandia, but have placed some or all of its species in a broadly defined Hedyotis (Terrell, 1996). More recently, the circumscription of Hedyotis has been narrowed to a monophyletic group of about 115 species and it no longer includes Oldenlandia. The genus Oldenlandia, as now defined, is several times polyphyletic and will eventually be reduced to a group of species closely related to the type species (Guo et al.,
2013).
Oldenlandia corymbosa is an annual herb with ascending or erect quadrangular stems; leaves are acute at both ends, linear-oblong or narrowly elliptic, 1 – 3.5 cm long, 1.5 – 7 mm wide, sub-sessile or petiole very short. Blade is pale beneath, midrib is prominent; flowers are few and shorter than the leaves; flowers are white or faintly pinkish-purplish, on slender pedicels
4 – 8 mm long; calyx not exceeding ovary; corolla about 2 mm long; stamen inserted just above the base of the tube; capsule is about 2 x 2 mm, exalate, flattened at apex, slightly laterally compressed (Stone, 1996).
Oldenlandia affinis is a slender annual or a perennial herb; stem prostrate to weakly erect,
1 – 4 dm long, few-branches to many-branches, and glabrous. Leaves are narrowly oblong to linear, 15 – 20 (30) mm long, 2 – 5 mm wide, apex acute, base cuneate, petiole ca.1 mm long,
stipules ca. 2.5 mm long, connate margin with several glandular teeth of unequal length. Peduncles ca. 8 -10 (- 15) mm long; calyx 4-toothed, the teeth ca. 1 mm long; corolla lavender to white, thin, broadly tubular, 4-lobed, ca. 2 mm long, the lobes are 1 – 2 mm long. Fruit is very small, somewhat laterally compressed, thinly cartilaginous, ca. 1.5 mm long, ca. 2 – 2.5 mm wide. Seeds are numerous per cell, angular, ca. 0.25 mm long, areolate (Wagner et al., 1999).
In Hawaii, O. corymbosa is naturalized in the vicinity of Hilo, and apparently recently naturalized in Honolulu (Wagner et al., 1999). In New Guinea, it is a weed of the garden and roadsides, and in natural situations; grassland, stream-sides, foreshores (Henty & Pritchard,
1975). It is propagated by seed and is native to tropical Africa, including Madagascar and India
(Stone, 1996).
Oldenlandia has a sweet gland to slightly bitter taste and is slightly cold. It clears heats and toxins, activates blood circulation, removes blood stasis, promotes diuresis, and relieves stranguria (urinary obstruction) (Ou et al., 1990). Extracts of Oldenlandia have been used against various kinds of tumor, especially tumors of the digestive tract, lymphosarcoma, carcinoma of the liver and larynx. It is used also against appendicitis, hepatitis, pneumonia, cholexystitis, urinary infection, furunculosis, cellulites, and snake bite (Ou et al., 1990).
Recent laboratory studies of the action of Oldenlandia suggest that the herb may contribute to inhibiting growth of cancer cells, promoting cancer cell death, and enhancing immune attack against cancer cells. (Gupta et al., 2002). It remains unknown whether these effects actually occur in people who consume the herb. As a preventive health care-agent, Oldenlandia is understood to inhibit mutation of cells by carcinogens. As an immune regulating herb, Oldenlandia remains of interest for use along with modern cancer therapies (Yoshida et al.
1991).
Oldenlandia is found to contain phytochemicals such as oleanolic acid and ursolic acid in significant amount. Both have been shown to have anti-inflammatory and anti-cancer potentials (Chang 1986). Other phytochemicals include: proteins, carbohydrates phenols/tannins, flavonoids, saponins, glycosides, steroids, terpenoids and alkaloids (Edoga et al. 2005). Oldenlandia affinis is well known as a source of cyclic uteroactive peptides (Kalata peptides) and as such, is used as an oxytocic agent during labour in traditional medicine (Gran et al.,
2000).
Several tests on the mutagenic activity and possible cancer chemopreventive properties of Oldenlandia have given positive results; animal tests on immune response stimulation and suppression on the phagocytosis system have also been promising. The antiphlogistic properties attributed to Oldenlandia are interesting. More research is needed to establish the definite medicinal values of these plants (Wong et al., 1992).
1.1 Objectives of the Study
The objectives of the study are:
1. To re-examine the morphology and anatomy of the two closely related species.
2. To utilize the data collected for the delimitation of the species into either new or old taxon.
3. To review claims of diagnostic, pharmacological exploitations and recommend conservation.
This material content is developed to serve as a GUIDE for students to conduct academic research
MORPHO-ANATOMICAL STUDY OF TWO CLOSELY RELATED SPECIES OF OLDENLANDIA (RUBIACEAE) IN NIGERIA
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