Leaf Micromorphological Study of Onosma (Boraginaceae)

Jamshidi, R. and Keshavarzi, M. and Mehrabian, A. R. (2026) Leaf Micromorphological Study of Onosma (Boraginaceae). ACTA BOTANICA HUNGARICA, 68 (1-2). pp. 87-109. ISSN 0236-6495

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Abstract

The genus Onosma L. (Boraginaceae) comprises 235 species worldwide, 47 of which are distributed in Iran, primarily in the Asian and Mediterranean regions. This study investigates the leaf micromorphological characteristics of 12 species within Onosma Section Onosma , subsection Haplotricha , collected from the various areas of Iran, to identify diagnostic traits for species delimitation. Scanning Electron Microscopy (SEM) was employed to examine the adaxial and abaxial surfaces of both cauline and basal leaves. Qualitative and quantitative traits were analysed in detail. Multivariate statistical analyses, including cluster analysis and principal component analysis, revealed two main clusters, illustrating interspecies relationships based on micromorphological traits. Significant variation was observed in setae density, orientation, and ornamentation, with abaxial surfaces generally exhibiting greater ornamentation density. Key diagnostic features, such as setae density, base shape, and ornamentation pattern, were identified as critical for distinguishing among species. Additionally, five distinct basal setae shape types were described, providing refined criteria for species differentiation. These findings underscore the diagnostic value of micromorpho-logical characters in resolving taxonomic ambiguities within Onosma . They also contribute to a deeper understanding of species relationships and evolutionary patterns in the genus.

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