Adaptive Leaf and Wood Anatomical Traits and Chemical Characteristics of Azadirachta indica and Melia azedarach under Semi-arid Conditions of Northeastern Nigeria

Abstract

A comparative evaluation of anatomical and chemical traits provides important information on the adaptive capacity and ecological performance of woody species growing under semi-arid conditions. The present study investigated the leaf stomatal characteristics, wood tracheary elements, and leaf chemical composition of Azadirachta indica A. Juss. and Melia azedarach L. growing along roadsides in Maiduguri, Borno State, Nigeria. Healthy, approximately 10-year-old trees of both species were selected for the study. The results showed that Azadirachta indica had significantly greater guard cell length (107.1 µm), stomatal length (128.4 µm), and stomatal potential conductance index (31.5) than Melia azedarach. However, the stomatal index was higher in M. azedarach (7.5). Wood anatomical analysis revealed significantly greater fibre length in M. azedarach (864.05 µm), whereas vessel dimensions did not differ significantly between the species. Chemical analysis indicated that A. indica had higher lignin (18.80%), crude fibre (28.26%), cellulose (8.03%), hemicellulose (4.80%), and energy values (3251.5 kcal kg⁻¹), suggesting greater structural investment and biomass quality. The findings indicate that A. indica may possess stronger adaptive characteristics under the semi-arid conditions of Maiduguri through its greater stomatal conductance potential, higher cell-wall component concentrations, and higher calorific value, whereas M. azedarach may provide greater structural support through its longer fibres. These findings provide information relevant to urban forestry, biomass utilisation, and species selection in arid and semi-arid regions.