ABSTRACT
Morpho- anatomical features of leaf, rachis, stem (bark), root, fruit, flower and pollen of Albizia adianthifolia (Schum.)W.F. Wight and Albizia chevalieri Harms. were studied with the goal to assess the taxonomic (pleisomorphic and apomorphic) characters in the two species, as well as to explore the agricultural and functional wood traits of ecological significance of the two species in relation to environmental conditions and locations. Five samples of each species from four ecological zones were randomly selected from their stands at locations in University of Nigeria, Nsukka (Derived savannah), Alabusa in Benue State (Guinea savannah), Kainji in Niger State (Sudan savannah) and Sapele in Delta State (Tropical rainforest). The results obtained from this investigation indicated similarities in structure, which highlighted interspecies phylogenetic relationships and reasons for them to be in the same family, while the differences in structure showed reasons for them to exist as two distinct species. The leaves of both species are hypostomatic. The stomata were anomocytic in A. adianthifolia, and cyclocytic in A. chevalieri. However, the width of stomata and aperture of both species decreased with ecological shift from wetter areas into drier areas. The stomata length showed strong positive correlations with stomata width and aperture width at p≤ 0.01, while it showed weak positive correlations with aperture length at p≤0.05. On the other hand, aperture length showed strong positive correlations with the width of stomata and aperture at p≤0.01. Ellipsoidal-multicellular trichomes occurred on the abaxial surface of the leaves in A. adianthifolia and on the adaxial surface of leaves in A. chevalieri. Glandular structures were present on the abaxial surface of the leaves in A. adianthifolia, while in A. chevalieri prismatic crystals occurred on the adaxial surface of the leaves. The epidermal cells were wavy with striations in A. adianthifolia and polygonal in A. chevalieri. Umbel inflorescences in A. adianthifolia are more “apomorphic” than panicle inflorescences in A. chevalieri. The wood of A. adianthifolia was diffuse-porous and A. chevalieri ring-porous. The vessel frequency in A. chevalieri per field of view was 16.4 as against 4.7 in A. adianthifolia. Rays are homocellular in A. adianthifolia and heterocellular in A. chevalieri; paratracheal parenchyma lozenge-aliform in A. adianthifolia and aliform confluent in A. chevalieri; fibres septate in A. adianthifolia and non-septate in A. chevalieri; fibre tracheids and libriform fibres occur in A. adianthifolia. The presence of crystalliferous deposits in the fibre strands of A. chevalieri is hereby reported for the first time. The fibres in A. chevalieri are longer, have thicker walls, wider lumen area and higher coefficient of flexibility than those in A. adianthifolia. The vessel diameter in radial direction not only showed the strongest and most significant correlations to other wood anatomical variables, but also to ecological parameters and tree morphology at p ≤ 0.01. On the other hand, the climate of the different ecological zones had weak impact on ray width, vessel length, vessel wall diameter, fibre lumen diameter and fibre diameter at p ≤ 0.05. The pollen of both species was shown to be inaperturate polyad, while sculpturing pattern was psilate in A. adianthifolia and scrabate in A. chevalieri. Also, the values for exine thickness in both species was highest in samples from Sudan and Rain forest zones, higher in the Guinea savannah and high but lowest in the Derived savannah. All quantitative parameters of pollen showed positive correlations at p ≤ 0.01. The vulnerability and mesomorphy indices of A. adianthifolia in the study area were significantly higher than those of A. chevalieri. Data obtained from the vulnerability indices in this study suggest that A. chevalieri is probably better acclimated to varying soil moisture and drought conditions than A. adianthifolia. Also, the wood of A. chevalieri may find more use in pulp production and wood construction than A. adianthifolia.
CHAPTER ONE
1.0 INTRODUCTION
Albizia adianthifolia (Schum.)W.F.Wight and Albizia chevalieri Harms. belong to the genus Albizia Durazz. and to the family Fabaceae – subfamily Mimosoideae. The name of the genus Albizia was first published by Durazzini in a rare periodical, “Magazino Toscana” in 1772. The description was based on a plant grown from seeds from Asia, which were brought by Fillippo Degali Albizi, a Florentine nobleman in 1749 from Constaninopole to Florence (Nielsen, 1979).
The genus Albizia is a pantropical genus and includes at least 470 genera. Lewis and Rico- Arce (2005) reported a figure between 120 -140 species. In Africa, there are 36 endemic species and in the Neotropics 22 species having small to large (up to 30 m) trees of sympodial growth and have been shown to possess monopodial trunk, a short bole and spreading crown (Rico-Arce et al. 2008). They are fast growing trees or shrubs without prickles or spines. Generally, the trees are characterized by alternate, petiolate and bipinnate leaves with entire margins. Leaflets are opposite with elliptic, rhombic, obovate or oblong shape and are up to 3-60mm long, stipules are present (1-6mm long) and may be poorly differentiated, ephemeral or sometimes lacking. Inflorescences are axillary and solitary or fascicled and pedunculate (Hutchinson and Dalziel,
1958).
The flowers are bisexual or occasionally male. The calyx has 5 teeth or lobes and the corolla is gamopetalous with usually 5 lobes. Stamens are numerous (19-50) and prominent, with filaments united in a staminal tube. The pod is oblong, straight and flat. Seeds are usually flat (ILDIS, 2005).
Albizia is known to be a pioneer of forest re-establishment due to the large quantity of seeds, ability to establish readily in the open and to thrive in diverse climates and altitudes. They are easy to propagate and handle in plantation production (Anon, 1979). Also, Albizia species are highly valued as understory shade trees for crop plantations, soil erosion stabilizers, soil improvers and as nitrogen fixing species, providers of livestock fodder with a high crude-protein content, medicinal plant, as timber trees and also as providers of water-soluble gum (Allen & Allen, 1981; Lowry et al., 1994; Escalante et al.,1998; Sprent, 2001).
Keay (1989) reported ten Albizia species in Nigeria and gave a brief description of A. adianthifolia and A. chevalieri. The Albizia species reported by Keay (1989) are as follows:
A. zygia (DC.) J.F. Macbr.
A. glabberima (Schum. & Thonn.)Benth.
A. adianthifolia (Schum.)W.F.Wight
A. gummifera & A. gummifera var. ealensis (J.F.Gmel.)C.A.Sm.
A. intermedia De Wild.&T. Durand.
A. malacophylla (A. Rich.)Walp.
A. chevalieri Harms.
A. lebbeck (L.)Benth.
A. ferruginea (Guill.& Perr.)Benth.
A. coriaria Welw. ex Oliver
Rico-Arce et al. (2008) reported twelve Albizia species which are endemic to Mexico and
Central America as follows:
A adinocephala (Donn.) Sm.
A. carbonaria Britton
A. duckeana L.Rico
A. guachapele (Kunth.) Dugand
A. lebbeck (L.) Benth.
A. leucocalyx (Britton &Rose) L. Rico
A. niopoides (Spruce ex Benth.) Burkart
A. occidentalis Brandegee
A. pedicellaris (DC.) L. Rico
A. sinaloensis Britton & Rose
A. tomentosa (M. Micheli) Standl.
A. xerophytica J. Linares
1.1 Origin and Botany of Albizia adianthifolia (Schum.)W.F.Wight FWTA,ED.2,1:502
Albizia adianthifolia is commonly called “flat crown albizia”. It is generally known in Nigeria by different names :“Ayinre bona bona” (Yoruba): “Avu” (Igbo): “Uwoweno laghabor” (Edo): “Sakanchi” (Nupe): “Ugbongbe” (Itsekiri). The specific epithet refers to the resemblance of the leaves, “folia”, to the maidenhair fern, genus Adianthum (Krige, 2007). The synonyms include; A. fastigiata (E.Mey.) Oliv. (1871), A. intermedia De Wild. & T.Durand (1901), A. ealaensis De Wild. (1907), A. gummifera auct. non (J.F.Gmel.) C.A.Sm.(Krige,2007).
It is native to West Africa and introduced in other parts of Africa. Keay (1989) noted its distribution to be widespread in tropical and southern Africa. The habitat is described as secondary forest and farmlands.
The tree is erect, perennial, growing up to 36m high with a girth of 3m and few massive widely spreading branches and a flat crown. Bole is single, usually short and practically without buttresses. The bole is short and crooked due to reaction wood formation but when it grows in a closed forest the bole may be straight. Bark is smooth or rarely (in Nigeria) finely fissured, pale brown to reddish brown or dark grey; slash granular, brown or white exuding a little clear gum. Wood is soft, sapwood whitish or pale yellow and heartwood is pale brown or golden brown and sometimes with a greenish tinge. The wood is moderately light, with a density of 520–580 kg/m³ at 12% moisture content. It dries slowly, but generally with little degrade. The rates of shrinkage are moderate: from green to 12% moisture content 1.7% radial 12% moisture content, the modulus of rupture is 99–136 N/mm², modulus of elasticity 9300 N/mm², compression parallel to grain 52.5–57.5 N/mm², cleavage 11.5 –27.4 N/mm and Chalais-Meudon side hardness 1.9–
2.8. (Lemmens, 2007).
Leaves with a stout finely hairy, common stalk 7.5-20 cm long, usually with 5-8 pairs of equally hairy pinnae 7.5 -10 cm long, 8-17 pairs of leaflets with glands between the upper pairs. Stipules are ovate, about 12 mm long. Flowers (November- April) are described as red or greenish white; in heads up to 2.5 cm excluding the stamens on stout stalks up to 7.5 cm long, with ovate bracts about 6 mm long at the base; the heads collect in conspicuous panicles at the ends of the ends of the shoots; stamen tube 12-25 mm long, greenish or red to pink, the free ends of the filament form turfts about 6 mm long; corollas about 12 mm long. Fruiting usually starts December to May and fruits are brown, finely hairy, not glossy, 10-18 cm long, 2.5 cm broad, rounded at the apex (Keay, 1989).
1.1.2 Ecological Requirements
Albizia adianthifolia grows in a wide range of soil types, most often occurring on sandy soils. It occurs at an elevation of 1000 – 2000 and usually between 250–600 m, though it can occur up to 1700 m above sea level. The tree thrives well on moist soils and in areas with heavy rainfall of 800-2000 mm per annum and forms a symbiotic association with the arbuscular Mycorrhiza fungi, which cause rapid growth of the tree. The nitrogen fixing nodules of the root contain Bradyrhizobium bacteria. This species is tolerant of flooding, drought and acidic soils, and is susceptible to fire and browsers (Krige, 2007).
1.1.3 Pest and Diseases
The seeds suffer a high incidence of pest attack of bruchid beetles, while the heartwood is susceptible to wood borer, marine borer and termite (Lemmens, 2007).
1.2 Origin and Botany of Albizia chevalieri Harms.-FWTA, ED. 2, 1:502.
Albizia chevalieri Harms. is commonly known as ‘‘Silk plant’’, “Silk tree” or “Siris”. In Nigeria, it is commonly called: “Katsari” (Hausa): “Jarieh” (Fula): “Tsagie” (Kanuri). According to Keay (1989) its distribution ranges from Senegal to Niger and to Sudan zone of northern Nigeria and also in east Cameroun. Its habitat is described as dry Savannah.
The tree is erect, perennial and growing up to 30 m in height. Bole is reported as often branching low down to several stems. Bark is pale grey, very soft, deeply fissured into rectangular corky patches which flake off leaving brownish areas beneath. Leaves with all parts covered with very short grey hairs; the common stalk is 7-15 cm long, with 6-15 pairs of slender pinnae 5-7 cm long, each with 12- 20 pairs of leaflets about 1 cm long and 2 mm broad; leaflet is
elongated, the midrib nearer to the upper margin and parallel with it, sharply pointed at the apex, rounded at the base. Flowers (April – May) are described as sweetly scented, reddish, with white stamens; about 30 flowers collect on a globose head on a slender stalk about 6cm long. The fruits of A. chevalieri are similar to those of Acacia macrostachya. Fruiting usually starts around May onwards persisting till the next season’s flowers appear. The fruits are 7-15 cm long by 18 mm broad, pale brown, shortly velvetly and dehiscent. Seed is smooth, brownish, with raphe and a small hillum, laterally compressed, almost circular in outline and may possess hardened vestiges of funiculus. Seed length is about 6.43 – 7.98 mm and 1.65 – 2.35 mm in width. The seed configuration is anatropous and the embryo type is axial – investing.
1.2.1 Ecological Requirements
Albizia chevalieri is a tree of the dry deciduous forest and thrives well on sandy soil, clayey
– humid sand, alluvial terraces, swampy ground, rocky outcrops, clayey – sandy soil, tiger bush (=branded vegetation) and sometimes in small clumps. Growth conditions requires an optimal temperature of 24 – 30oC; soil pH of 5.5 – 6.5; annual rainfall of 600 – 900 mm and well drained soils of moderate fertility (Le Houérou, 1987).
1.2.2 Pest and Diseases
There are no records on the pest and diseases of A. chevalieri. Many rusts belonging to the genera Ravenelia and Uredo are recorded only on Albizia spp. (Gibson, 1975). Sharma and Bhardwaj (1988) reported that leaf rusts caused by Ravenelia spp. are important seedling diseases of Albizia spp. in India.
1.4 Economic Importance
i. The mature wood of A. adianthifolia is reported as of high quality for furniture, carving, tunery, farm implements, fuel wood and charcoal (Lemmens, 2007). While the mature wood of A. chevalieri is used in production of furniture and construction.
ii. The stem and fruits of A. adianthifolia are used in treating Filariasis and as Anodyne (Iwu, 1993). A. adianthifolia and A. gummisera are reported as useful for the treatment of Coccidiosis in poultry in Zimbabwe (Mwawe et al., 2005). Lawal et al. (2010) indicated the use of A. adianthifolia in herbal preparations for the treatment of psychotic disorders in South Western region of Nigeria.
iii. The bark of A. chevalieri is reported to be of medicinal value and is used as laxatives and also in the treatment of diarrhoea and dysentery; and as vermifuges and astringents (Burkill, 1985). A. chevalieri leaves are widely used for the management of Diabetes mellitus by traditional medicinal practitioners in some parts of Nigeria and Niger Republic. Hypoglycaemic effects of the leaves (Saidu et al., 2007) and root (Saidu et al.,
2010) have been reported.
iv. The leaves of A. chevalieri are used as protein and mineral supplements in livestock fodder. Also the stems and bark provide dyes and tannins (Le Houérou, 1987), while the leaves A. adianthifolia are used as livestock fodder and bee fodder (Bhat, 1997).
v. A. adianthifolia and A. chevalieri are important soil improvers, since their root nodules help in the fixation of atmospheric nitrogen in the soil and also help to prevent soil erosion.
1.5 Problem Statement
Albizia adianthifolia and A. chevalieri have been largely described based on external morphological characters found in Keys and Flora manuals.
The use of morphological characters alone is limited and has often resulted in erroneous taxonomic classification in the earlier scientific period.
Morpho-anatomical features of A. adianthifolia (bark, leaf, rachis and root) and A. chevalieri (bark, leaf, rachis, stem and root) have not been researched.
The pollen morphology of A. adianthifolia and A. chevalieri have not been reported.
1.6 Justification
Modern classification relies on a wide range of characters obtained from morphology, systematic anatomy, chemical taxonomy, serotaxonomy, cytology and phylogenetics (Stace,
1991). A classification based on a combination of characters is more likely to be correct than those which rest on one or few characters alone (Metcalfe and Chalk, 1950; Stace, 1991).
Anatomical characters cannot by themselves form the basis of classification but are usually regarded as an extension of and supplement to, those external morphological characters on which classification have been built (Metcalfe and Chalk, 1950). For this reason, the use of anatomical characters alongside morphological characters, and characters obtained from pollen studies for the delimitation of the species will achieve a good taxonomic classification.
Aim and Objectives of the study
i. To examine the morpho-anatomical features of leaf, rachis, stem (bark), flowers, fruit, pollen and root of A. adianthifolia and A. chevalieri.
ii. To assess the taxonomic (pleisomorphic and apomorphic) characters in the two species for the delimitation of the taxa.
iii. To explore the agricultural and functional wood traits of ecological significance of the two species in relation to the environmental conditions prevalent in the study areas.
This material content is developed to serve as a GUIDE for students to conduct academic research
A COMPARATIVE MORPHO-ANATOMICAL STUDY OF ALBIZIA ADIANTHIFOLIA (SCHUM.)W.F. WIGHT AND ALBIZIA CHEVALIERI HARMS. (FABACEAE-MIMOSOIDEAE)
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