Foliar Epidermal Studies, Organographic Distribution and Taxonomic Importance of Trichomes in the Family Solanaceae
The leaf epidermal and organographic distribution of trichomes studies were carried out on nine species in four genera in the family Solanaceae. Distinctive anatomical characters which indicate close interrelationship amongst the genera and species include presence of trichomes on leaf epidermal surfaces, petiole, stem, pedicel, sepal and petal surfaces, amphistomatic leaf surfaces, anisocytic to anomocytic stomatal types, polygonal, occasionally irregular epidermal cell shape on the adaxial epidermal surfaces and generally lower number of stomata on the adaxial surface. Some characters can be used to separate the genera within the family and also the species within each genus. These include anticlinal walls on the adaxial and abaxial epidermal surfaces, stomata1 types in addition to the basic anisocytic to anomocytic stomatal complex types. S. nigrum in the genus Solanum has the highest number of stomatal types. Noteworthy is the presence of protrusions on the stomata of the species in the genus Lycopersicon which is absent in the species of the other genera. The different trichome types have differing organographic distributions within the same species and within the same genus in the family. This can be useful in the identification of the species and even their corresponding organs such as leaf, stem, petiole, etc. which would be of interest to pharmacognosists, archaeobotanists, palaeobotanists and agronomists. Capsicum annuum can be separated from C. frutescens and C. chinense on the basis of the organographic distribution of the trichomes. Solanum torvum is the only species in the genus Solanum and in the species of the family Solanaceae studied with stellate non-glandular trichomes on the adaxial and abaxial epidermal surfaces. The spine-like non-glandular trichome type observed in Lycopersicon pimpinellifolium was completely absent in all the plant parts of Lycopersicon lycopersicum cv Roma VF. This can be used to delimit the two species in the genus. The unique bicellular to multicellular stalk glandular trichomes of Nicotiana tabacum, a mono-species genus in Nigeria are reported. They are believed to be responsible for the unique smell that emanates from N. tabacum. The genus Nicotiana is the only genus in the family with multicellular stalk glandular trichomes.