Phenotypic of morpho-anatomical characters of selected plant species in adaptation to riparian and upland ecosystems.
The study evaluated the foliar morphological and anatomical responses of fifteen plant species (four trees, seven shrubs and four herbs) having three different habits to two different ecosystems within Obafemi Awolowo University, Ile-Ife. The tree species studied were: Celtis zenkeri Engl.; Funtumia elastica (Preuss) Stapf.; Holarrhena floribunda (G. Don) T. Durand. and Schinz.; Rauvolfia vomitoria Afzel. The shrub species were: Alchornea cordifolia Mull. Arg.; Chromolaena odorata (L.) King and H.E. Robbins.; Cnestis ferruginea Vahl ex DC.; Hedranthera barteri (Hook. F.) Pichon.; Icacina trichantha Oliv.; Rothmannia longiflora Salisb.; Sphenocentrum jollyanum Pierre. The herbs were: Asystasia gangetica (L.) T. Anderson.; Emilia coccinea (Sims.) G. Don.; Guyonia ciliata Hook F. and Synedrella nodiflora (L.) J. Gaertner. This was with a view to providing explanation for the underlining mechanism behind these responses. Exomorphological assessment was carried out on petiole length and leaf area using visual assessments. Anatomical evaluation was conducted on the leaf, petiole and epidermis following standard established protocols and using light microscopy. The epidermal features focused on stomata frequency and size, epidermal cell number, length and width, trichome frequency as well as their length and width. Other characters of leaf tissues investigated include; thickness of the cuticle, epidermis, spongy and palisade mesophyll, while petiole anatomical characters considered were thickness of the epidermis, collenchyma, parenchyma, phloem, and xylem cells along with pith diameter and trichome length. The result revealed that most plant species showed significant (p<0.05) reduction in leaf area and petiole length from riparian to upland ecosystem. However, Rauvolfia vomitoria, Chromolaena odorata, Rothmannia longiflora, Guyonia ciliata and Synedrella nodiflora showed some level of numerical decrease in petiole length but not significantly different (p<0.05) from riparian to upland ecozones. Foliar anatomical data revealed that stomata and trichome frequency, epidermal cell size significantly increased (p<0.05) from riparian to upland ecosystem for most of the species while number of epidermal cell, trichome and stomata size reduced significantly (p<0.05). In addition, significant increase (p<0.05) from the riparian to upland ecosystems occurs in cuticle thickness, epidermal cell, palisade and spongy mesophyll cells except for the lower cuticle. However, tissues of the petiole reduced significantly (p<0.05) from riparian to upland ecosystem except parenchyma cells. The study concluded that Funtumia elastica, Cnestis ferruginea and Synedrella nodifora were the most adapted to the two ecozones among all the species studied in trees, shrubs and herbs respectively. This study further established the usefulness of anatomical studies in explaining the mechanism underlining the observed morphological responses of plants to varying ecosystems specifically in riparian and upland ecosystems