Pollen Morphology as a Useful Taxonomic Tool in Delimiting the Species of Loranthaceae in Nigeria

Abstract

Background and Objective: Pollen grains shape, size, aperture and wall ornamentation have been useful in taxonomic studies of plants especially in resolving relationship or determining variation in a taxa. The Loranthaceae (Mistletoes) are parasitic family with known taxonomic problem of poorly identified species in Nigeria. Pollen grains of fourteen species which spread across six genera of Nigerian Loranthaceae was studied with a view of generating characters that would further help in their identification. Methods: Samples were subjected to standard acetolysis for palynological sample preparation and analysis. Results: Pollen grains are mainly triangular or three-armed in nature with percentage of polar to equatorial axis ranging from 90.69% to 100%. All pollen grains were oblate-spheroidal except the pollen of Helixanthera mannii that was prolate-spheroidal and all the genera had tri-snycolporate pollen grains except pollen grains of Tapinanthus which were tri-colporate. The smallest grains are found in the genus Helixanthera while others range from medium to large in size with H. spathulata having the smallest size of 20.75 µm by 20.75 µm and the largest of 49.00 µm by 52.50 µm in Globimetula mannii. Conclusion: The information obtained from this study do not only add to the already existing information on the family, but the diagnostic characters obtained can be used in conjunction with other characters like morphology and anatomical characters to delimit the species in the family.