A COMPARATIVE MORPHO-ANATOMICAL STUDY OF ALBIZIA ADIANTHIFOLIA (SCHUM.)W.F. WIGHT AND ALBIZIA CHEVALIERI HARMS. (FABACEAE-MIMOSOIDEAE)
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 inpr 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.