Models of shoot formation in plants in light of molecular-genetic data, with representatives of <i>Minuartia</i> s. l. (Caryophyllaceae) as a case study. I. Monopodial models

Molecular phylogeny has gained a crucial role for plant taxonomy in recent years. In some cases sequence comparison of the chloroplasts or nuclear genes and even whole genomes led to novel and unexpected results in taxonomic positions. For example, after publication of phylogenetic data a genus Minuartia s. l. was considered to be a paraphyletic group and subjected to taxonomic revision according to cladistics concepts. As a result, several new genera were identified and some genera were restored including Cherleria L., which includes 19 species. The genus Cherleria is of particular interest due to significant habitual differences in its representatives. Thus, to clarify the relationships between intergeneric taxa a search for new taxonomically significant traits is needed. For these purposes, the biomorphological characteristics of representatives of six model species of Cherleria were studied. In the article the most significant biomorphological characteristics such as the model of shoot formation, the morphology of the cushion, the nature of shoot branching, the presence or absence of specialized vegetative shoots for capturing space, the growth strategy and the structure of the monocarpic shoot are proposed to aid for identification of taxonomic position. Analysis of the biomorphological features of the studied species identified four growth strategies: a) the strategy of centrifugal growth; b) the strategy of centrifugal growth with the rare appearance of radially directed lateral specialized shoots of the semi-rosette type; c) the strategy of vector growth by active branching at the early stages of development, with subsequent “fading” in formation of lateral axes; d) the strategy of vector growth with the help of semi-rosette plagiotropic shoots with the subsequent filling of the internal space of the cushion due to orthotropic rosette shoots. Comparison of molecular phylogeny and biomorphology data allows us to identify biomorphological apomorphies: monopodial plagiotropic-semi-rosette–orthotropic-rosette model of shoot formation with specialized semi-rosette shoots for capturing territory, the presence of dicyclic monocarpic shoots, as well as plesiomorphies: monopodial rosette model of shoot formation, formation of a densely filled cushion, monocyclic, simply arranged monocarpic shoots. Based on these data, we put forward an assumption that for the genus Cherleria the initial model of shoot formation was the monopodial rosette model.