Intergeneric Comparison of Staminal Trichomes in the Tribe Ipomoeeae (Convolvulaceae)

Hairs or trichomes distributed on the base of filaments in the morning glory family, known as staminal trichomes, differ from those found on other plant parts and have been recognized for their taxonomic value for over a century. In this study, our aim was to investigate the appearance of staminal trichomes in the tribe Ipomoeeae Hall. f., a significant tribe within the family Convolvulaceae, and assess their taxonomic implications. Micromorphological examinations were conducted using clearing techniques on 73 taxa from seven out of eight genera within the tribe, and the data were analyzed using factor analysis of mixed data (FAMD). The results show that, among all examined taxa, only two species lacked staminal trichomes. Glandular staminal trichomes were the most common type observed, and they were the only type observed in Ipomoea, Paralepistemon, Rivea, Stictocardia, and most Argyreia species. Nonglandular staminal trichomes were restricted to Astripomoea, Lepistemon, and some Argyreia taxa. The glandular trichomes in Ipomoea exhibited the largest variation and overlapped with other glandular trichome-bearing genera. However, genera with nonglandular trichomes were readily distinguishable from each other. Both glandular and nonglandular trichomes were basically composed of a stalk and apical cell, yet they varied in shape, size, density, and distribution pattern. This study provides a detailed examination and application of microscale features, emphasizing the significance of micromorphology in plant taxonomy.