Authors: AZZA EL-HADIDY, ASMAA OLWEY, SALAH EL-NAGGAR
Abstract: Genus Heliotropium L. (Boraginaceae s.l . ) is one of the difficult taxonomic complexes. The validity of phenetic investigations is often questioned in contrast to the modern phylogenetic approaches. In this study, 120 different populations of 17 Heliotropium taxa were analyzed, using 169 macro- and micromorphological characters to assess the phenetic relationships between taxa. The macromorphology of all parts of the studied taxa (vegetative, floral, and fruit) was investigated, along with some micromorphological characters including indumentum and anatomy. The most significant characters were calyx asymmetry, corolla color and lobe shape, anther connation in young flowers, staminal connective tissue prolongation, shape of stigma, shape of leaf blade, petiole, and venation. Ten different types of trichomes were recognized and organized into four general categories: a) glandular hairs; b) eglandular branched unicellular hairs (T-shaped, 2-armed hairs); c) eglandular unbranched simple hairs; and d) eglandular unbranched pustular hairs that usually bear cystolith structures. The anatomy revealed two patterns of vascularization in cross-sections of the petioles; the vascular tissue is either arranged in a complete ring or in an arc-shaped pattern. In comparison to the classic infrageneric classification of the genus, our results were in line with the traditional sectional essence. However, numerical analyses revealed the uniqueness of section Orthostachys , which supports upgrading its status to a separate genus ( Euploca ).
Keywords: anatomy, Boraginaceae, Euploca , Heliotropioideae, morphology, numerical taxonomy, trichomes
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