A Qualitative Assessment of Leaf Anatomical Variation in Seven Indigofera Species Across Disturbed and Undisturbed Forest and Savannah Habitats in Nigeria

Although leaf anatomy has been used in Indigofera taxonomy, anatomical variation across contrasting ecological and disturbance regimes in Nigeria remains poorly documented. This study assessed qualitative leaf anatomical variation in seven species: Indigofera arrecta, I. hirsuta, I. macrophylla, I. pulchra, I. spicata, I. subulata and I. tinctoria, across disturbed and undisturbed tropical rainforest and savannah habitats. Mature leaves were collected from five individuals per species in each of the four habitat conditions and examined using standard anatomical techniques. Characters assessed included epidermal-cell shape, cuticle, anticlinal wall pattern, trichome type, stomatal complexes, mesophyll organization, and midrib structure and crystal occurrence. The species exhibited distinct anatomical combinations. I. pulchra and I. hirsuta were distinguished by two-armed stellate trichomes, and the remaining species possessed mainly simple unicellular trichomes, with glandular trichomes also present in I. tinctoria. The type of stomata was different among species, while the cuticle development, anticlinal wall pattern, trichome presence and mesophyll organisation were affected by habitat conditions. Savannah and disturbed habitats generally had more obvious cuticles and compact palisade tissues, whereas undisturbed rainforest habitats generally had more extensive mesophyll and undulating anticlinal walls. These results indicate that leaf anatomical characters can be used to support species identification and provide insights into habitat-associated structural variation. However, being a qualitative study, it does not determine the causes or adaptive significance of these differences. The findings provide a baseline for future quantitative and experimental studies of Indigofera leaf anatomy.