Comparative analysis of two Korean irises (Iris ruthenica and I. uniflora, Iridaceae) based on plastome sequencing and micromorphology

Abstract

Iris ruthenica Ker Gawl. and I. uniflora Pall. ex Link, which are rare and endangered species in Korea, possess considerable horticultural and medicinal value among Korean irises. However, discrimination of the species is hindered by extensive morphological similarity. Thus, the aim of the present study was to identify discriminating features by comparing the species’ complete plastid genome (i.e., plastome) sequences and micromorphological features, including leaf margins, stomatal complex distribution (hypostomatic vs. amphistomatic leaves), anther stomata density, and tepal epidermal cell patterns. Plastome comparison revealed slightly divergent regions within intergenic spacer regions, and the most variable sequences, which were distributed in non-coding regions, could be used as molecular markers for the discrimination of I. ruthenica and I. uniflora. Phylogenetic analysis of the Iris species revealed that I. ruthenica and I. uniflora formed a well-supported clade. The comparison of plastomes and micromorphological features performed in this study provides useful information for elucidating taxonomic, phylogenetic, and evolutionary relationships in Iridaceae. Further studies, including those based on molecular cytogenetic approaches using species specific markers, will offer insights into species delimitation of the two closely related Iris species.

Comparative microscopic investigations of leaf epidermis in four Ajuga species from Korea

“…While the chromosome number (2n = 32) was consistent in all the Korean Ajuga species, the genome sizes measured in our previous study varied across the species (Choi et al, 2019). Although stomatal size may vary due to environmental stimuli even within an individual plant as reported in other plant groups (Bucher et al, 2017;Casson & Gray, 2008;Choi, Park et al, 2022;Sun et al, 2014;Wang et al, 2015), a positive correlation between guard cell and genome size is well documented in angiosperms (Beaulieu et al, 2008;Knight et al, 2010;Veselý et al, 2012) in agreement with our present study (Figure 5).…”

“…However, the pattern of leaf epidermal anticlinal cell wall can also be closely related to ecological condition as indicated in other plant groups (Moon et al, 2009;Stace, 1965). The surface ornamentation of leaves in this study revealed key diagnostic characters for the differentiation of Korean Ajuga species (Table 1) although, some traits like the pattern of epidermal pavement cells may be plastic, being closely related to ecological conditions such as xeric habitats or ecological conditions including high humidity Choi, Park et al, 2022;Kim et al, 2021;Kong & Hong, 2019;Stace, 1965;Stenglein et al, 2005). Likewise, amphistomatic leaves are commonly found in herbaceous species, but can also be a plastic trait associated with a xerophytic habitat (Parkhurst, 1978), or low light levels under which leaves differentiate (Muir, 2018).…”

“…Detailed SEM examinations were carried out according to the methods described in , Choi, Park et al (2022) and Kim et al (2021). Micrographs of all images were acquired with a SEM with 10Â to 3500Â magnification.…”

“…We have previously characterized considerable genome size variation across Korean Ajuga species and have found that genome size is a useful taxonomic marker (Choi et al, 2019). It is still unknown whether micromorphological and cytological data correlate across the four Korean Ajuga species, as indicated in recent studies in other genera (Chen et al, 2022;Choi, Park et al, 2022;Kim et al, 2021;Park et al, 2022).…”

Does the evolution of micromorphology accompany chromosomal changes on dysploid and polyploid levels in the Barnardia japonica complex (Hyacinthaceae)?

“…The micromorphology of leaf epidermis and characters of pollen grains are often used as a diagnostic character to establish relationships and to de ne major groups in family Hyacinthaceae [41][42][43] as well as other economically important plant families such as Lamiaceae [44], Polygonaceae [45], Melastomataceae [46], Asteraceae [47], Poaceae [48], and Iridaceae [49][50][51]. Speci cally, wax striation and size of stomatal complexes are considered to be important diagnostic value in Hyacinthaceae [41].…”