Micromorphological differentiation of Korean Disporum species using light and scanning electron microscopy

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

The genus Ajuga is widely distributed in temperate to subtropical regions, and four species are currently recognized in Korea (A. decumbens, A. multiflora, A. nipponensis, and A. spectabilis), but epidermal anatomical differences across these species have never been described. A comparative study of the leaf micromorphological characteristics of Korean Ajuga species was performed using light microscopy (LM) and scanning electron microscopy (SEM) to elucidate their taxonomic usefulness and to assess leaf micromorphological diversity. Considerable diversity in epidermal and stomatal anatomy was observed across Korean Ajuga species. Species had both hypostomatic or amphistomatic leaves, with anomocytic, anisocytic, diactyic, or actinocytic stomatal complexes. Guard cell length across species ranged from 17.66 ± 0.57 μm to 32.50 ± 2.38 μm and correlated with genome size. Abnormal stomata were frequently observed in three species (A. decumbens, A. multiflora, and A. nipponensis) but not in A. spectabilis. Three types of glandular trichomes were found: peltate in all species, short-stalked in all species, and long-stalked glandular trichomes in A. multiflora. Among the investigated leaf micromophological characters, trichome type, epidermal cell shape, and stomatal morphology were all taxonomically informative traits at a species level. RESEARCH HIGHLIGHTS: A comprehensive micromorphological description of the leaf surface is provided for Korean Ajuga species using scanning electron microscopic (SEM) and light microscopic (LM) analyses. The diverse range of stomatal development and the occurrence of polymorphic stomatal types are documented for the first time in Korean Ajuga species. The great diversity in stomatal and trichome morphology in Korean Ajuga species are taxonomically useful traits for species identification.

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

BACKGROUND

Chromosome number and genome size changes via dysploidy and polyploidy accompany plant diversification and speciation. Such changes often impact also morphological characters. An excellent system to address the questions of how extensive and structured chromosomal changes within one species complex affect the phenotype is the monocot species complex of Barnardia japonica. This taxon contains two well established and distinct diploid cytotypes differing in base chromosome numbers (AA: x = 8, BB: x = 9) and their allopolyploid derivatives on several ploidy levels (from 3x to 6x). This extensive and structured genomic variation, however, is not mirrored by gross morphological differentiation.

RESULTS

The current study aims to analyze the correlations between the changes of chromosome numbers and genome sizes with palynological and leaf micromorphological characters in diploids and selected allopolyploids of the B. japonica complex. The chromosome numbers varied from 2n = 16 and 18 (2n = 25 with the presence of supernumerary B chromosomes), and from 2n = 26 to 51 in polyploids on four different ploidy levels (3x, 4x, 5x, and 6x). Despite additive chromosome numbers compared to diploid parental cytotypes, all polyploid cytotypes have experienced genome downsizing. Analyses of leaf micromorphological characters did not reveal any diagnostic traits that could be specifically assigned to individual cytotypes. The variation of pollen grain sizes correlated positively with ploidy levels.

CONCLUSIONS

This study clearly demonstrates that karyotype and genome size differentiation does not have to be correlated with morphological differentiation of cytotypes.

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

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.

Implications of foliar epidermal micromorphology using light and scanning electron microscopy: A useful tool in taxonomy of Korean irises

The genus Iris L., comprising approximately 210 species, is one of the most species-rich genera in the family Iridaceae. In this study, the first comprehensive leaf micromorphological characters of Korean irises were studied using light and scanning electron microscopy. Our objective was to evaluate the foliar micromorphological characteristics (namely epidermal cells, stomata types, and guard cell size) of Korean Iris taxa in a systematic context. All the investigated Korean Iris taxa had amphistomatic or hypostomatic leaves with anomocytic stomatal complexes. Guard cell length varied among species, ranging from 24.8 μm (I. rossii) to 56.0 μm (I. domestica). Although the presence of papillae on the outer periclinal wall is not of taxonomic significance, leaf margin pattern, guard cell size, and sunken stomata type were useful for species-level identification of Korean Iris species. The occurrence of polymorphic stomatal types was reported here for the first time, and the correlation between genome size and epidermal guard cell length was discussed.

Leaf epidermal morphology of Asparagaceae of Taiwan and its systematic significance

The current study analyzed the epidermal morphology of Asparagaceae in detail and assessed its systematic importance. At the familial level, no consistent characteristics were found, but anticlinal wall and stomata morphology provided systematic information of different tribes, especially Ophiopogoneae and Polygonateae. In Ophiopogoneae, Liriope and Ophiopogon had similar epidermis, which implying a close relationship between them, and was also supported by related studies. The leaves of Polygonateae exhibited rounded and undulate anticlinal wall. Polygonatum arisanense var. formosanum had a rounded anticlinal wall, whereas other species exhibited undulate anticlinal walls. Different epidemis of Po. arisanense var. formosanum supported the variety treatment of Po. arisanense. The intergeneric relationship was also interpreted based on the anticlinal wall and stomata. Therefore, the epidermis could provide the systematic value of Asparagaceae. The present study also revealed the linkage of stomata and habitat types, though the adaptative significance of epidermal traits needs further study.