Leaf epidermal micromorphology in Aspidistra (Asparagaceae): diversity and taxonomic significance

Taxonomic implications of leaf morphology and epidermal anatomy for 14 species of Gagea (Liliaceae) from Xinjiang, China

BACKGROUND

Leaf morphology and epidermal characters are important for phylogenetic and taxonomic studies of many plants, but there is currently insufficient data to use them to help distinguish species of Gagea, which is a taxonomically difficult genus mainly due to polyploidy and hybridization. Therefore, leaf morphology and epidermal characters of Gagea were studied to assess the characters that can be used to elucidate the taxonomy and systematics of 14 species of Gagea collected in Xinjiang, China. Using light microscopy (LM), six qualitative and three quantitative leaf epidermal anatomical characters were examined for both the adaxial and abaxial surfaces. Hierarchical cluster analysis (HCA) was employed to reveal the similarities based on leaf morphology and epidermal characters of the investigated species.

RESULTS

Basal leaf of these species can be terete or flat, and it is triangle, flat, or circular in transverse section. Anticlinal wall patterns of the leaf epidermal cells were straight and sinuous, and only three species had epidermal hairs. Shape of long cells varies, ranging from quadrangular to irregular. HCA revealed that the 14 species could be divided into two groups. Group A was arranged into three subgroups (A1, A2 and A3), based on the Euclidean distance of 6.96. Subgroup A1 consisted of three species with indumentum; subgroup A2 had four species with sinuous type anticlinal walls; and subgroup A3 comprised of two species with a fistulose basal leaf. Group B included five species with short cells.

CONCLUSIONS

Leaf morphology and epidermal characters did not differ significantly among populations of the same species in Gagea, whereas they differ significantly among species. Thus, leaf morphology and epidermal characters provide diagnostic information for differentiating G. nigra and G. filiformis; G. altaica, G. jensii and G. alberti, which are morphologically similar species.

Comprehensive Comparative Analyses of Aspidistra Chloroplast Genomes: Insights into Interspecific Plastid Diversity and Phylogeny

Limestone karsts are renowned for extremely high species richness and endemism. Aspidistra (Asparagaceae) is among the highly diversified genera distributed in karst areas, making it an ideal group for studying the evolutionary mechanisms of karst plants. The taxonomy and identification of Aspidistra species are mainly based on their specialized and diverse floral structures. Aspidistra plants have inconspicuous flowers, and the similarity in vegetative morphology often leads to difficulties in species discrimination. Chloroplast genomes possess variable genetic information and offer the potential for interspecies identification. However, as yet there is little information about the interspecific diversity and evolution of the plastid genomes of Aspidistra. In this study, we reported chloroplast (cp) genomes of seven Aspidistra species (A. crassifila, A. dolichanthera, A. erecta, A. longgangensis, A. minutiflora, A. nankunshanensis, and A. retusa). These seven highly-conserved plastid genomes all have a typical quartile structure and include a total of 113 unique genes, comprising 79 protein-coding genes, 4 rRNA genes and 30 tRNA genes. Additionally, we conducted a comprehensive comparative analysis of Aspidistra cp genomes. We identified eight divergent hotspot regions (trnC-GCA-petN, trnE-UUC-psbD, accD-psaI, petA-psbJ, rpl20-rps12, rpl36-rps8, ccsA-ndhD and rps15-ycf1) that serve as potential molecular markers. Our newly generated Aspidistra plastomes enrich the resources of plastid genomes of karst plants, and an investigation into the plastome diversity offers novel perspectives on the taxonomy, phylogeny and evolution of Aspidistra species.

Leaf Epidermal Morphology of Ten Wild Tree Peonies in China and Its Taxonomic Significance

This research reports for the first time the epidermal characteristics of 10 wild tree peonies belonging to the sect. Moutan group. The leaf micromorphology of 10 wild tree peonies—P. qiui, P. decomposita, P. jishanensis, P. ostii, P. delavayi, P. lutea, P. potanini, P. rockii, P. ludlowii and P. cathayana—were investigated by light and scanning electron microscopy. The characteristics of the leaf epidermis were found to be constant at the species level, but variable among species. Patterns of anticlinal walls were slightly wavy to wavy, very wavy, and straight to curved. All studied tree peonies presented stomata only on the abaxial surfaces of the leaves. The stomatal apparatus was elliptical or rectangular. Stomatal density was highest on the abaxial surface in P. qiui (300.25 per mm2), and lowest in P. jishanensiss (198.41 per mm2). Stomatal Index was highest on the adaxial surface of P. potanini (27.30%), and lowest in P. ludlowii (18.35%). Trichomes were observed in four studied peonies, which appeared only on the abaxial surface of the leaves, and three basic types of trichomes were identified. The long conical trichomes were distinctive of P. jishanensis, and the flat-shaped trichomes were characteristic of P. qiui, P. rockii and P. cathayana, and commonly occurred in the intervenous region and leaf veins. Stomatal shape, stomatal density, anticlinal wall patterns and trichomes may be of great value and significance for the classification of wild tree peonies. The principal component analysis showed that the component 1, component 2 and component 3 were the most components and nearly 79% of the observed variation. The key to the identification of wild tree peonies based on trichomes and stomata diversity was provided.