A Comprehensive Study of the Genus Sanguisorba (Rosaceae) Based on the Floral Micromorphology, Palynology, and Plastome Analysis

Sanguisorba, commonly known as burnet, is a genus in the family Rosaceae native to the temperate regions of the Northern hemisphere. Five of its thirty species are distributed in Korea: Sanguisorba officinalis, S. stipulata, S. hakusanensis, S. longifolia, and S. tenuifolia. S. officinalis has been designated as a medicinal remedy in the Chinese and Korean Herbal Pharmacopeias. Despite being a valuable medicinal resource, the morphological and genomic information, as well as the genetic characteristics of Sanguisorba, are still elusive. Therefore, we carried out the first comprehensive study on the floral micromorphology, palynology, and complete chloroplast (cp) genome of the Sanguisorba species. The outer sepal waxes and hypanthium characters showed diagnostic value, despite a similar floral micromorphology across different species. All the studied Sanguisorba pollen were small to medium, oblate to prolate-spheroidal, and their exine ornamentation was microechinate. The orbicules, which are possibly synapomorphic, were consistently absent in this genus. Additionally, the cp genomes of S. officinalis, S. stipulata, and S. hakusanensis have been completely sequenced. The comparative analysis of the reported Sanguisorba cp genomes revealed local divergence regions. The nucleotide diversity of trnH-psbA and rps2-rpoC2, referred to as hotspot regions, revealed the highest pi values in six Sanguisorba. The ndhG indicated positive selection pressures as a species-specific variation in S. filiformis. The S. stipulata and S. tenuifolia species had psbK genes at the selected pressures. We developed new DNA barcodes that distinguish the typical S. officinalis and S. officinalis var. longifolia, important herbal medicinal plants, from other similar Sanguisorba species with species-specific distinctive markers. The phylogenetic trees showed the positions of the reported Sanguisorba species; S. officinalis, S. tenuifolia, and S. stipulata showed the nearest genetic distance. The results of our comprehensive study on micromorphology, pollen chemistry, cp genome analysis, and the development of species identification markers can provide valuable information for future studies on S. officinalis, including those highlighting it as an important medicinal resource.

Comparative Floral and Pollen Micromorphology of Leonurus japonicus and L. macranthus (Lamiaceae)

Floral micromorphology and pollen morphology of two Leonurus (Lamiaceae) species were examined and compared using scanning electron microscopy to evaluate the diagnostic value of these features to facilitate future studies on floral biology and taxonomy. Floral epidermal patterns were similar in both species, with the conical to central-conical epidermal cells on the adaxial side of the lower lip (corolla). Capitate, peltate, scale-like glandular, and non-glandular trichomes were distributed on the surface of the floral organs. Notably, scale-like anther glands and floral stomata were found on the anthers and abaxial side of the calyx, respectively. Pollen grains had bi-reticulate exine with angular primary lumina and rounded secondary lumina. These characteristics provide indirect evidence of a close association between plant-pollinator interactions and effective pollination. In addition, quantitative traits of pollen grains and trichome types on the adaxial side of the lip differed between the two species. These characteristics may have diagnostic and taxonomic value for the genus Leonurus and family Lamiaceae.

Comparative Floral Micromorphology in Mimosa sect. Calothamnos (Fabaceae)

The genus Mimosa L. is well known for its high morphological variability and the presence of taxonomic complexes—groups of taxa that are not adequately circumscribed and are therefore in continuous revision. For this study, we analyzed flowers from 28 different taxa in Mimosa sect. Calothamnos Barneby and five vegetatively similar taxa from Mimosa sect. Mimosa. We observed three calyx shapes and four (glabrous or pubescent) calyx border types, as well as describe glandular trichomes on the calyx border for the first time in section Calothamnos. While the corolla exhibits only two shape types, trichomes on the corolla are much more diverse, as we found one simple and 11 branched trichome types in diverse orientations and dispositions. Given the taxonomic value of trichomes and profuse terminology in different families, we focused on the detailed description of their micromorphology, type, and shape, finding morphological differences between trichome types, which is an easy way to adequately compare them between even unrelated taxa. Our results using trichome types on the corolla are consistent with the original differentiation of sections Calothamnos and Mimosa. Flower micromorphology also provides characters to distinguish species, groups of species, and varieties within section Calothamnos and could be useful in a future taxonomic treatment of the section. We also found that some floral features, such as inflorescence color and stamen fusion, are associated with the characters used in this study.

Pollination success in three tropical dry forest orchid species from Mexico: insights from floral display, visitation rates, and flower micromorphology

Background: Despite long-lasting efforts to disentangle the drivers of orchid pollination, pollination success in tropical dry forest orchids remains largely unknown. Questions and hypothesis: How successful are pollination in three tropical dry forest orchids? How is pollination influenced by floral display and floral rewards (as suggested by floral micromorphology)? We hypothesized a positive effect of floral display on pollinia removal and deposition rates. Studied species: Barkeria whartoniana (C. Schweinf.) Soto Arenas, Clowesia dodsoniana E. Aguirre, and Cyrtopodium macrobulbon (La Llave & Lex.) G.A. Romero & Carnevali. Study site and dates: Nizanda (Oaxaca), Mexico; flowering periods of 2013 and 2014. Methods: We calculated pollinia removal and deposition rates, identified floral visitors and analyzed flower microstructure to search for structures potentially producing rewards. Floral display was measured through number of open flowers, and number and length of inflorescences, and its effect on pollination success was assessed through linear modeling. Results: Pollinia removal rates were higher than deposition rates, and floral display was related to pollination success in C. dodsoniana only. Visitation rates were low for the three species and most visitors were not true pollinators. The three species possess potentially secreting structures, but for B. whartoniana and C. macrobulbon these rewards are likely part of the pollinator deception mechanism. Conclusions: The generalized low pollination success implies the need for high population densities of both interacting parts. We emphasize the need for integrated evaluations of different aspects of the plant-pollinator interaction.

Comparative floral surface micromorphology helps to discriminate between species of Paphiopedilum (Orchidaceae: Cypripedioideae) from Peninsular Malaysia

The floral micromorphology of critically endangered Paphiopedilum Pfitzer [P. barbatum (Lindl.) Pfitzer, P. callosum var. sublaeve (Rchb.f.) P.J.Cribb and P. niveum (Rchb.f.) Stein] were analyzed concerning either infrageneric taxonomy or physioecological demands. The first two species are phylogenetically close and superficially identical but occur with distinct phytogeographical distributions in the region. The third species is a phylogenetically distant congener that inhabits limestone areas in the northern part of Peninsular Malaysia. Using scanning electron microscopy (SEM), we investigated the surface of the dorsal sepal, synsepal, lateral petals, pouch or labellum, and staminode. Amongst the investigated features were epicuticular waxes, epicuticular ornamentation, trichome distribution and type, pustular glands, and papillae. Our study supports the distinction of P. barbatum from P. callosum var. sublaeve, which belong to subgenus Paphiopedilum, and from P. niveum, a species belonging to subgenus Brachypetalum, a separated monophyletic clade. Comparatively, P. barbatum has Type III non-glandular trichomes on the margin of its lateral petals, which are absent in P. callosum var. sublaeve. Paphiopedilum callosum var. sublaeve and P. niveum are distinguishable from P. barbatum by a confined distribution of papillae. The epicuticular ornamentation and distribution of trichomes on staminode discriminate between P. barbatum and P. callosum var. sublaeve and differentiates them from P. niveum. Compared to P. barbatum and P. niveum, stomata in P. callosum var. sublaeve were superficial with prominently raised guard cells. From the physioecological view, the absence of glandular trichomes, and the low occurrence of papillae and stomata on the floral parts explain the unscented flowers of P. barbatum and P. callosum var. sublaeve. A combination of the features examined is taxonomically valuable for delimitation of the species at the infrageneric level, although the diagnostic characters are far inadequate for a generic taxonomic revision. A study with a more extensive sampling from the three subgenera of Paphiopedilum, including subgenus Parvisepalum, is anticipated to elucidate the level of variation of the analyzed microcharacters. Key Words: physioecological importance, Peninsular Malaysia, subgenus Brachypetalum, subgenus Paphiopedilum, scanning electron microscopy, taxonomic delimitation

Floral micromorphology, histochemistry, ultrastructure and chemical composition of floral secretions in three Neotropical Maxillariella species (Orchidaceae)

Floral morphological adaptations and composition of secretions aim to ensure reproductive success. Maxillariella is part of the largest subtribe of Orchidaceae, and Maxillariella spp. are important components of the orchid flora of the Neotropics. The aim of this paper was to provide a detailed study of the reproductive biology of three morphologically and geographically distinct species: M. sanguinea, M. variabilis and M. vulcanica. For many years, species in this group were considered rewardless, but several studies have revealed that lips of some species may secrete resins. However, most published research has mainly focused on investigating either micromorphology (SEM, TEM, histochemistry) or fragrance composition (GC–MS). In this study, we make the first attempt to investigate Maxillariella flowers in a more comparative manner by combining both aspects. In all investigated species we reported the presence of resins with lipids, sugars and/or proteins, suggesting a potential role as a food reward. Scant quantities of residues indicate that they are produced periodically in small quantities. Chemical analysis revealed significant differences between species, however, the presence of some compounds was constant. Cycloartenal and cycloartenol (main ingredients of resin and wax-like material in some Maxillariinae) were not been found.

Dissection for Floral Micromorphology and Plastid Genome of Valuable Medicinal Borages Arnebia and Lithospermum (Boraginaceae)

The genera Arnebia and Lithospermum (Lithospermeae-Boraginaceae) comprise 25–30 and 50–60 species, respectively. Some of them are economically valuable, as their roots frequently contain a purple-red dye used in the cosmetic industry. Furthermore, dried roots of Arnebia euchroma, A. guttata, and Lithospermum erythrorhizon, which have been designated Lithospermi Radix, are used as traditional Korean herbal medicine. This study is the first report on the floral micromorphology and complete chloroplast (cp) genome sequences of A. guttata (including A. tibetana), A. euchroma, and L. erythrorhizon. We reveal great diversity in floral epidermal cell patterns, gynoecium, and structure of trichomes. The cp genomes were 149,361–150,465 bp in length, with conserved quadripartite structures. In total, 112 genes were identified, including 78 protein-coding regions, 30 tRNA genes, and four rRNA genes. Gene order, content, and orientation were highly conserved and were consistent with the general structure of angiosperm cp genomes. Comparison of the four cp genomes revealed locally divergent regions, mainly within intergenic spacer regions (atpH-atpI, petN-psbM, rbcL-psaI, ycf4-cemA, ndhF-rpl32, and ndhC-trnV-UAC). To facilitate species identification, we developed molecular markers psaA- ycf3 (PSY), trnI-CAU- ycf2 (TCY), and ndhC-trnV-UAC (NCTV) based on divergence hotspots. High-resolution phylogenetic analysis revealed clear clustering and a close relationship of Arnebia to its Lithospermum sister group, which was supported by strong bootstrap values and posterior probabilities. Overall, gynoecium characteristics and genetic distance of cp genomes suggest that A. tibetana, might be recognized as an independent species rather than a synonym of A. guttata. The present morphological and cp genomic results provide useful information for future studies, such as taxonomic, phylogenetic, and evolutionary analysis of Boraginaceae.

Inflorescence Development and Floral Organogenesis in Taraxacum kok-saghyz

Rubber dandelion (Taraxacum kok-saghyz Rodin; TK) has received attention for its natural rubber content as a strategic biomaterial, and a promising, sustainable, and renewable alternative to synthetic rubber from fossil carbon sources. Extensive research on the domestication and rubber content of TK has demonstrated TK’s potential in industrial applications as a relevant natural rubber and latex-producing alternative crop. However, many aspects of its biology have been neglected in published studies. For example, floral development is still poorly characterized. TK inflorescences were studied by scanning electron microscopy. Nine stages of early inflorescence development are proposed, and floral micromorphology is detailed. Individual flower primordia development starts at the periphery and proceeds centripetally in the newly-formed inflorescence meristem. Floral organogenesis begins in the outermost flowers of the capitulum, with corolla ring and androecium formation. Following, pappus primordium—forming a ring around the base of the corolla tube—and gynoecium are observed. The transition from vegetative to inflorescence meristem was observed 21 days after germination. This description of inflorescence and flower development in TK sheds light on the complex process of flowering, pollination, and reproduction. This study will be useful for genetics, breeding, systematics, and development of agronomical practices for this new rubber-producing crop.

Sinosenecio peltatus (Asteraceae, Senecioneae), a remarkably distinctive new species from Guangdong, China

Sinosenecio peltatus (Asteraceae, Senecioneae), a new species from Yangchun County in southwestern Guangdong, China, is illustrated and described. It is distinguished in the genus in the peltate leaves, a character previously never recorded in Sinosenecio. We also report the floral micromorphology, achene surface features and chromosome number of the new species.