Taxonomic Significance of Seed Morphology in Veronica L. (Plantaginaceae) Species from Central Europe

In this study, 1159 seeds of 29 Central European species of the genus Veronica were analyzed based on scanning electron microscopy images. The species belonged to nine subgenera: Beccabunga, Chamaedrys, Cochlidiosperma, Pellidosperma, Pentasepalae, Pocilla, Pseudolysimachium, Stenocarpon and Veronica, following the newest phylogenetic classification of the genus. Nine measured characteristics of seeds and nine ratios were analyzed statistically using ANOVA followed by post hoc testing, cluster analysis and discriminant analysis. In most cases, the results were not congruent with the contemporary classification of the genus. Examinations of qualitative seed features by scanning electron microscopy included the cochlidiospermous or discoid seed type, the seed shape, the general sculpture of the seed coat surface, the sculpture of anticlinal and periclinal walls and some species-specific traits such as the presence of the epidermal appendix. All these features, apart from seed shape, were useful to distinguish all subgenera and some species within subgenera: Beccabunga, Chamaedrys, Pellidosperma, Pocilla (only V. filiformis) and Veronica. The identification key based on the seed micromorphological features was prepared.

Micromorphological Characteristics of Fruit Surfaces of Some Usable Species of the Genus Valeriana (Valerianaceae) Among Ukrainian Flora

The micromorphological features of the fruit surfaces of nine species of Ukrainian flora, namely Valeriana tuberosa L., Valeriana tripteris L., Valeriana rossica P. Smirn., Valeriana stolonifera Czern., Valeriana grossheimii Worosch, Valeriana sambucifolia Mikan fil., Valeriana officinalis L. s. str., Valeriana wolgensis Kazak. [ Valeriana officinalis var. nitida (Kreyer) Rostanski], and Valeriana simplicifolia (Rchb.) Kabath, were examined. Depending on the presence and localization of pubescence on the surface of the fruit, three groups of species were distinguished: those with glabrous fruits, those with fruits pubescent only on the adaxial side, and those with fruits pubescent on both sides. Scanning electron microscopy revealed the additional characteristics of the fruits (microsculpture of the fruit surface, shape of cuticular formations on the surface of the outer periclinal walls of epidermal cells and on the surface of hairs, and structure of the stomatal complex), which were useful for the identification of the species. At the supraspecific level, the revealed features of the fruit surfaces somewhat overlapped and could be used to identify series and sections only as additional features. Based on the studied samples from herbarium material (KW), V. officinalis var. nitida was considered synonymous with V. wolgensis since there were no micromorphological differences between their fruits. The detailed micromorphological characteristics of the fruit surfaces of all the studied species can be used for further comparative morphological investigations of different aerial parts to identify stable features independent of geographic and ecological conditions.

Appearance of phenotypic plasticity of leaves in psammophyte Corynephorus canescens during flooding

The results of the study of the leaf structure in psammophyte Corynephorus canescens, which grew under controlled conditions and flooding using the methods of light microscopy, scanning electron microscopy, and laser confocal microscopy, are presented. This study revealed common and distinctive signs of morphological and anatomical parameters of C. canescens leaves in the phase of vegetative growth. Among the common features were the shape and size of the leaf laminas, hypostomatic type of the leaf, isolateral structure of the parenchyma, the thick-walled epidermis, and the bilayered hypodermis. Among the distinctive features were the signs of the destruction of cells in the photosynthetic parenchyma, change in their shape with the formation of protuberances at the cells’ poles, and almost doubling area of the aerenchyma in C. canescens leaves under flooding conditions. Scanning electron microscopy showed the similarity of ultrastructure and density of trichomes on the adaxial surface, excepting the formation of cuticular wax structures on the epidermal surface of the leaves in flooded plants. The subcellular localization of silicon inclusions was studied for the first time. The presence of amorphous and small crystalline silicon inclusions in the periclinal walls of the main epidermal cells and amorphous silicon inclusions in leaf trichomes was established. An increase in the relative silicon content along the trichomes in the leaves’ epidermis after flooding was revealed. It was assumed that the phenotypic plasticity of C. canescens, is realized through the increasing area of aerenchyma in leaves and increasing silicon content in trichomes. Such plasticity helps to optimize both the oxygen balance of plants and water balance in flooded plants, thus increasing the species’ resistance to prolonged flooding.

Leaf epidermal micromorphology defining the clades in Cinnamomum (Lauraceae)

In this study, we sampled 48 species of Asian Cinnamomum covering the species groups that were identified in recent phylogenetic studies and conducted leaf micromorphological observations using both light microscopy (LM) and scanning electron microscopy (SEM). Synapomorphies were determined by means of mapping micromorphological characters on a phylogenetic tree. The results indicate that Cinnamomum exhibits two different types of leaf upper epidermis: Type I has smooth/non-reticulate periclinal walls whereas Type II has reticulate periclinal walls and is unusual in the family Lauraceae. We found that the two types of micromorphological characters are clade-specific, sect. Camphora s.s. possesses Type I leaf upper epidermis, and sect. Cinnamomum s.l. has Type II leaf upper epidermis. Our study also reveals that C. saxatile, a member of sect. Camphora s.l. in the traditional classification, actually has Type II leaf upper epidermis, thus reinforcing the result of a recent molecular phylogeny that has this species in a clade consisting mainly of species of sect. Cinnamomum.

Seed morphology of Portulaca (Portulacaceae) in Cuba and taxonomic implications

Portulaca is the only genus in Portulacaceae and includes ca. 115 species with worldwide distribution. 12 species (one naturalized) occur in Cuba. The taxonomic value of seeds characters for the circumscription of species, by comparing macro- and micromorphological characters, is analyzed. The seeds of Cuban purslanes do not present association patterns between types of undulations of the anticline walls. The relief of their periclinal walls allows the corroborate certain variation in the distribution range of some species. The delimitation of Portulaca species in Cuba using seeds characters, provided as an identification key and descriptions, confirms the taxonomic value of such characters and strengthens the circumscriptions supported by the rest of the plant structures. This is largely given by the standardization of macromorphological terms with a micromorphological basis, the color of the mature seeds and their dimensions.

How Do Trees Grow in Girth? Controversy on the Role of Cellular Events in the Vascular Cambium

Radial growth has long been a subject of interest in tree biology research. Recent studies have brought a significant change in the understanding of some basic processes characteristic to the vascular cambium, a meristem that produces secondary vascular tissues (phloem and xylem) in woody plants. A new hypothesis regarding the mechanism of intrusive growth of the cambial initials, which has been ratified by studies of the arrangement of cambial cells, negates the influence of this apical cell growth on the expansion of the cambial circumference. Instead, it suggests that the tip of the elongating cambial initial intrudes between the tangential (periclinal) walls, rather than the radial (anticlinal) walls, of the initial(s) and its(their) derivative(s) lying ahead of the elongating cell tip. The new concept also explains the hitherto obscure mechanism of the cell event called ‘elimination of initials’. This article evaluates these new concepts of the cambial cell dynamics and offers a new interpretation for some curious events occurring in the cambial meristem in relation to the radial growth in woody plants.

DEFINITION OF ORCHIDS (ORCHIDACEAE) OF THE SOCHI BLACK SEA REGION BY MICROMORPHOLOGICAL CHARACTERISTICS OF SEEDS

According to the results of preliminary studies of the micromorphology of orchids seeds in the Sochi Black Sea region, a key has been compiled to identify 25 species and subspecies from 13 genera by seed. The most valuable features of seed structure for diagnosis were identified from the previously described characteristics: seed shape, its length, the number of cells in testa, their shape in different parts of testa. Limodorum-type seeds have fusiform, linear or balloon-shape and Orchis-type seeds are pear-shaped or club-shaped. The shape of the cells is the same throughout the testa or contrasting one – elongated in the micropylar and medial parts and isodiametric at the chalazal pole. This trait also distinguishes the type of seed. Some genera are characterized by convoluted or smooth anticlinal cell walls. The periclinal walls of the cells have sculptural thickenings of different patterns, or no pattern. This feature consistently characterizes different genera and even species. Frequent or rare stripes of the sculpture, mostly straight or curved, forming gaps at the borders of cells or not – these features are species-specific. Relative sizes, in particular, the ratio of the length of a seed to the length of an embryo, as well as the proportion of sizes of parts of seed coats have great specificity. On the contrary, orientation of the strokes of the sculpture, the presence of suspension residues and the degree of homogeneity of an embryo are not reliable diagnostic features. The key is useful for field researches for studying the distribution of orchids in the period after flowering and until the seeds are completely dispersed.

Seed morphology and sculpture of invasive Impatiens capensis Meerb. from different habitats

Impatiens capensis is an annual plant native to eastern North America that is currently spreading across Europe. In Poland, due to this plant’s rapid spread in the secondary range and high competitiveness in relation to native species, it is considered a locally invasive species. The microstructure of seeds is an important tool for solving various taxonomic problems and also provides data useful for determining the impact of various environmental factors on the phenotypic variability of species. This issue is particularly important in regard to invasive species which occupy a wide range of habitats in the invaded range. There are few reports on seed size and thus far no descriptions of the seed ultrastructure of I. capensis in the analyzed literature. We present new data on the seed morphology of I. capensis growing in different habitats and conditions in the secondary range of the species. The studied populations differed significantly in each of the investigated traits (seed length, width, circumference, area, roundness, and mass). Our findings showed that anthropogenic disturbances in habitats and some soil parameters (presence of carbonates, potassium, loose sand, and moisture) were statistically significant with various seed sizes and morphology in the studied populations of I. capensis. Moreover, our studies showed maximum seed length (5.74 mm) and width (3.21 mm) exceeding those values given in the available literature. For the first time, we also provide a detailed SEM study of the ultrastructure of the seed coat of I. capensis. There are two types of epidermal cells on the seeds: (a) between the ribs (elongated with straight anticlinal walls, slightly concave outer periclinal walls, and micropapillate secondary sculpture on the edges with anticyclic walls), and (b) on the ribs (isodiametric cells with straight anticlinal walls and concave outer periclinal walls). Unlike the variability of size and weight of seeds, the coat ornamentation has turned out to be a steady feature within the studied secondary range of I. capensis.

Morphological peculiarities of flowers, pollen grains and fruits of Valeriana tuberosa (Valerianaceae)

The results of the study of flowers, pollen grains and fruits of Valeriana tuberosa (sect. Tuberosae, Valerianaceae) are presented. Materials of the National Herbarium of the M.G. Kholodny Institute of Botany, National Academy of Sciences of Ukraine (KW) were studied. The morphological structures of flowers, pollen grains and fruits were examined using both light microscopy and scanning electron microscopy; detailed descriptions of the elements of the flower, pollen grains and fruits were made and their specific features were established. The morphological features of the inflorescence, bracteoles, and the elements of the hermaphrodite flowers have been clarified. The pollen grains of V. tuberosa are 3-colpate, suboblate to subprolate (P/E = 0.85–1.33), medium- or large-sized. Their outline in equatorial view is elliptic, rarely circular, in polar view slightly trilobate or trilobate. Exine sculpture is echinate-microechinate with verrucae. The known and new carpological features are specified. In particular, papillate growth of periclinal walls of exocarp with stroke-shaped, jet and warty cuticular formations of the surface were noted the first time; details of exocarp stomatal system were revealed; features of trichomes and their cuticular structure on fruit wall are described. The obtained data are important additional characters for identification of the species and for the issues of taxonomy and phylogeny.

Seed Morphology of Allium L. (Amaryllidaceae) from Central Asian Countries and Its Taxonomic Implications

We studied seed macro- and micro-morphological characteristics of 48 Allium species (51 accessions) belonging to 24 sections and 7 subgenera. Our taxonomic sampling focused on the central Asian regions of Uzbekistan, Kyrgyzstan, and Mongolia. The seed length ranged between 1.74 ± 0.16–4.47 ± 0.43 mm and width ranged between 1.06 ± 0.08–3.44 ± 0.23 mm, showing various shapes. The irregular and elongated polygonal testa cells occurred in all investigated species. Seed testa sculptures showed high variation in their anticlinal walls associated with different shapes: straight to with U-, S- or Omega-type undulations among the species. The moderately flat to convex periclinal walls with various sized verrucae or granules were found in all investigated taxa. Based on our research, we conclude that seed characteristics such as size, shape, and the seed testa features show their significant variability, revealing key characteristics to support taxonomic relationships and major clades recovered in the molecular phylogeny of the genus Allium. Especially, the anticlinal wall characteristics were highly variable and decisive at the both section and species levels. In addition, widely varied shapes and sizes of the seeds were remarkably effective to distinguish Allium species.