MACRO AND MICRO MORPHO-ANATOMICAL FEATURES OF SEVEN IPOMOEA L. SPECIES FOUND IN NORTHERN GUINEA SAVANNAH REGION OF NIGERIA

Abstract

Members of the genus Ipomoea pose a wide range of morphological similarities resulting in ambiguity in the
identification of different taxa of the group. This study was carried out to determine the taxonomic significance
of leaf epidermis, stomatal types, stomatal index and trichomes with a view to help in the identification of
different members of the group. The leaves were treated with bleaching agent (Sodium Hypochlorite 3.2% w/v)
for 72 hours to clear the chlorophyll contents; a section of the resulting transparent tissue was then transferred to
a clean glass slide for microscopic examination. From morphological studies of the species, two types of base
angles were found (obtuse and wide-obtuse), the apex shape for all the studied species were straight except for
Ipomoea repens which was rounded. The micro morpho-anatomical study revealed sinuous and polygonal
epidermal cells; stomata were present on the abaxial and adaxial surfaces of all the examined species
(Amphistomatic) except the adaxial surface of Ipomoea purpurea. Two types of stomata were obtained
(Paracytic and Anisocytic), unicellular and non-glandular trichomes were found on both surfaces of Ipomoea
nil, the mean and standard error of mature intercostal epidermal cell length (μm) of abaxial surfaces for all the
examined species ranged from (68.20±4.80 to 118.80±3.30) while adaxial surface was (6.60±3.81 to
130.90±8.59). The stomatal index (SI) ranged from 22.53% to 31.88% and 12.13% to 50.64% on the abaxial
and adaxial surfaces respectively. The length of trichomes was higher (390.50μm) on the adaxial than
(331.10μm) on the lower surface. Cluster analysis was used to generate phenogram which revealed the level of
evolutionary relationships. Ipomoea purpurea appear to be an alien species. Two clades were observed which
emerged separately. Ipomoea aquatica and Ipomoea carnea are sister species and are closely related to Ipomoea
batatas.