Abstract
Several related yellow-flowered houseleek species which occur on the Balkan Peninsula are divided into two complexes: Sempervivum ciliosum (S. ciliosum, S. jakucsii, S. klepa, S. octopodes, and S. galicicum) and the S. ruthenicum complex (S. ruthenicum, S. leucanthum, S. kindingeri, and S. zeleborii). Due to strong phenotypic plasticity and a limited number of studies, it is difficult to assert at this point whether all the above species are well defined in the taxonomic sense. Detailed studies of the epidermal structures have not been conducted for any of the species in either complex. The aim of this study was to investigate the degree of variability of the epidermal structures together with their potential usefulness for the taxonomic characterization of the species studied. A total of 18 quantitative characters of the epidermal structures of the adaxial and abaxial surfaces of the rosette leaves were analysed within 16 populations. In all species, the epidermal cells are polygonal or irregularly shaped, with straight or sinuous anticlinal walls, while the rosette leaves are amphistomatic with anisocytic stomata. Simple biseriate multicellular glandular trichomes were found on the adaxial and abaxial surfaces and the margins of the rosette leaves. The results of the descriptive statistics, univariate (ANOVA) and multivariate statistical analysis (CDA, AHC) showed low to high variability in the epidermal cells, guard cells and trichomes. The multivariate analysis showed diversification among the complexes and species. The length of the marginal and apical trichomes of the rosette leaves contributed most to diversification.
Highlights
Sempervivum L. is a member of the family Crassulaceae J.St.-Hil., comprising between 1300 and 1500 leafy and stem succulent herbaceous plants and subshrubs (Berger 1930; ‘t Hart 1997; ‘t Hart et al 2003; Thiede & Eggli 2007; Mort et al 2010)
The type of anticlinal walls varied between the species of the S. ciliosum and S. ruthenicum complexes (Fig. 3, Supplementary Fig. 1)
Hagemann (1986) and ‘t Hart (2002) noted that non-glandular trichomes can be found below the apex of the rosette leaves within the species of the S. ruthenicum complex (S. ruthenicum, S. kindingeri, and S. leucanthum), but their presence was not confirmed in our study
Summary
Sempervivum L. is a member of the family Crassulaceae J.St.-Hil., comprising between 1300 and 1500 leafy and stem succulent herbaceous plants and subshrubs (Berger 1930; ‘t Hart 1997; ‘t Hart et al 2003; Thiede & Eggli 2007; Mort et al 2010). 2007; Karaer et al 2011; Klein & Kadereit 2015) The species of this genus are herbaceous, perennial succulents with monocarpic rosettes which have the outstanding capacity for vegetative reproduction. Based on the latest conspectus of this genus, the reported number of species varies between 40 and 60 (‘t Hart et al 2003; Thiede & Eggli 2007). Some recent studies report the exact number of 46 Sempervivum species (‘t Hart et al 2003; Klein & Kadereit 2015)
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