Seed micromorphology and its taxonomic evidence in subfamily Alsinoideae (Caryophyllaceae)

Micromorphological study of some Salsola species (Amaranthaceae) in Iran and its systematic significance using scanning electron microscopy

Using scanning electron microscopy (SEM), six Salsola species from Iran were examined for their epidermis, seed, and fruit micromorphology. Among them were S. brachiata from section Heterotricha, S dendroides, S. incanescens, and S. orientalis from section Caroxylon, S. kali from section Kali, and S. turcomanica from section Physurus. Epidermal cells are divided into three types. There were diamond, irregular, and polygonal cells, as well as straight and undulated walls. Studied species of Salsola have smooth or sculptured fruit surfaces, and there are three main types of fruit surface ornamentation. There is a significant difference between these species based on the type of hair and density of the fruit. Seed shape and color have little systematic significance. The seed epidermis is composed of polygonal, elongated polygonal, irregular, and diamond cells. Although polygonal and irregular testa cells are most common, their size and shape can provide additional information and useful diagnostic characteristics at both specific and infraspecific levels. For taxonomic separation, the current study provides novel insights at micromorphological levels. RESEARCH HIGHLIGHTS: This article reports halophyte are shown as models for adaptation to extreme habitats. These plants are placed among the ecological communities of xerophytes. Here, for the first time, the microstructural analysis of Salsola has been investigated. Additionally, it provides new insights into plant species' response to extreme conditions, as well as possible adaptation strategies at the micromorphological level.

Infraspecific Variation in Silene Seed Tubercles

The seeds of many species in the order Caryophyllales exhibit surface protuberances called tubercles. While tubercle shape and distribution have often been proposed as taxonomic criteria, paradoxically, their description has primarily relied on adjectives, with quantitative data on tubercle width, height, and other measurements lacking in the literature. Recently, a quantitative analysis of seed surface tubercles based on tubercle width, height, and curvature values (maximum and average curvature, and maximum to average curvature ratio) was proposed and applied to individual populations of a total of 31 species, with 12 belonging to Silene subg. Behenantha and 19 to S. subg. Silene. Tubercles were classified into two categories: echinate and rugose. Echinate tubercles exhibited higher values of height and curvature, and lower width, and were more prevalent in species of S. subg. Behenantha, while the rugose type was more abundant in S. subg. Silene. This work explored infraspecific differences in tubercle size and shape. For this, measurements of tubercle width, height and curvature were applied to 31 populations of eight species of Silene. Significant differences between populations were observed for most of the species examined. A particular tubercle type, previously described as umbonate or mammillate, was identified in S. nocturna seeds, characterized by high curvature values.

Seed morphology of Hypericum (Hypericaceae) in China and its taxonomic significance

The seed morphology of 40 taxa within the genus Hypericum (Hypericaceae) from China, representing 9 sections of the genus, was examined using both Light and Scanning Electron Microscopy to evaluate the taxonomic relevance of macro- and micro-morphological features. Details articulating variation in seed size, color, shape, appendages, and seed coat ornamentation are described, illustrated, and compared, and their taxonomic importance is discussed. Seeds were generally brown in color and cylindric-ellipsoid to prolonged cylindric in shape. Seed size displayed wide variation, ranging from 0.37-1.91 mm in length and 0.12-0.75 mm in width. Seed appendages were observed as a characteristic morphological feature. Seed surface ornamentation has high phenotypic plasticity, and four types (reticulate, foveolate, papillose, and ribbed) can be recognized. In general, seed color and shape have limited taxonomic significance. However, some other features represent informative characters that can be used efficiently in distinguishing the studied taxa at the section and/or species levels. The findings illustrate that considerable taxonomic knowledge can be obtained by investigating the seed features of Hypericum, and the use of Scanning Electron Microscopy can reveal inconspicuous morphological affinities among species and play a role in taxonomic and systematic studies of the genus Hypericum. RESEARCH HIGHLIGHTS: Macro- and micro-morphological features of seeds of 40 Hypericum taxa from China were examined using Light and Scanning Electron Microscopy, providing the first broad study regarding seed morphology for Hypericum from China. Details and variations of seed size, shape, color, surface ornamentation, and appendages are fully presented. Seed features and their variation have important taxonomic significance at the section and/or species levels within Hypericum.

Quantitative Analysis of Seed Surface Tubercles in Silene Species

In the Caryophyllaceae, seed surfaces contain cell protrusions, of varying sizes and shapes, called tubercles. Tubercles have long been described in many species, but quantitative analyses with measurements of size and shape are lacking in the literature. Based on optical photography, the seeds of Silene were classified into four types: smooth, rugose, echinate and papillose. Seeds in each of these groups have characteristic geometrical properties: smooth seeds lack tubercles and have the highest values of circularity and solidity in their lateral views, while papillose seeds have the largest tubercles and lowest values of circularity and solidity both in lateral and dorsal views. Here, tubercle width, height and slope, maximum and mean curvature values and maximum to mean curvature ratio were obtained for representative seeds of a total of 31 species, 12 belonging to Silene subg. Behenantha and 19 to S. subg. Silene. The seeds of the rugose type had lower values of curvature. Additionally, lower values of curvature were found in species of S. subg. Silene in comparison with S. subg. Behenantha. The seeds of S. subg. Behenantha had higher values of tubercle height and slope and higher values of maximum and average curvature and maximum to mean curvature ratio.

Comparison of Seed Images with Geometric Models, an Approach to the Morphology of Silene (Caryophyllaceae)

Seed morphological description is traditionally based on adjectives, which originated from the comparison with other shapes, including geometric figures. Nevertheless, descriptions based on this feature are not quantitative and measurements giving the percentage of similarity of seeds with reference figures are not available in the literature. Lateral views of Silene seeds resemble the cardioid and cardioid-derived figures. Dorsal views, nonetheless, resemble ellipses and derivatives, allowing seed shape quantification by comparison with defined geometric figures. In this work, we apply already-described models as well as new models to the morphological analysis of 51 Silene species. Our data revealed the existence of a link between lateral and dorsal models. Lateral models closed in the hilum region (models LM2 and LM4) were associated with those convex models of the dorsal seed views (DM1-DM4, DM10). Lateral models more open around the hilum region adjusted to seeds characterized as dorso canaliculata type better, i.e., to those geometric models with partial concavities in their dorsal views. The relationship between lateral and dorsal models, as well as between the models to their utility in taxonomy, is discussed.

Frequency and spectrum of M2 mutants and genetic variability in cyto-agronomic characteristics of fenugreek induced by caffeine and sodium azide

Trigonella foenum graecum L. (Fenugreek) is a valuable medicinal plant cultivated for decades for its therapeutic characteristics. Still no pronounced improvement concerning wild form was accomplished as it is a self-pollinating crop. Induced mutagenesis is encouraged as a remarkable tool on this plant to circumvent the genetic bottleneck of cultivated germplasms. As a result, novel allelomorphic combinations for short-term agronomic attributes were developed. Fenugreek cultivar Pusa Early Bunching, selected for the present experiment, was mutagenized with five doses (0.2%, 0.4%, 0.6%, 0.8%, and 1.0%) of caffeine and sodium azide (SA) to evaluate its impact on the qualitative and quantitative traits of M₁ and M₂ generation conducted in a Complete Randomized Block Design (CRBD), replicated five times during 2019-2020 and 2020-2021, respectively. The frequency of induced phenotypic variations was assessed in M₂ progenies, resulting in the identification and isolation of a broad spectrum of mutants with altered phenotypes. Mutagenic effectiveness and efficiency were found to be maximum at lower concentrations of the mutagen treatments and highest in SA, followed by caffeine. Various morphological mutants with modified characters were observed at different concentrations in M₂ generation. The spectrum of mutations was wider in SA than in caffeine, as caffeine produced 51 while SA produced 54 individual mutants under seven major categories. The maximum frequency of morphological mutants was associated with leaf, followed by plant size, plant growth habit, pod, seed size, seed shape, and seed color. Morphological and structural variations in the guard cells of stomata and seeds were observed through scanning electron microscopy. The variations created in the economically important traits may enrich the genetic diversity of this plant species. Moreover, these morphological mutants may serve as a source of elite genes in further breeding programs of fenugreek.

The Outline of Seed Silhouettes: A Morphological Approach to Silene (Caryophyllaceae)

Seed morphology is an important source of information for plant taxonomy. Nevertheless, the characters under study are diverse, and a simple, unified method is lacking in the literature. A new method for the classification of seeds of the genus Silene based on optical images and image analysis has recently been described on the basis of morphological measurements of the lateral seed views. According to the outline of their silhouettes, seeds from 52 species (49 of Silene and three related species) were classified in three groups: smooth, rugose and echinate, revealing remarkable differences between these groups. This methodology has been applied here to 51 new species, making a total of 100 species of Silene analyzed so far. According to our data, a new group was described, termed papillose. The results showed morphological differences between the four mentioned seed groups, with reduced values of circularity for dorsal and lateral seed views in the papillose and echinate groups and reduced values of solidity in the papillose seeds. The method was applied to the analysis of individual as well as to average seed silhouettes and some of the differences between groups were maintained in both cases.

Seed variability of Sisymbriumpolymorphum (Murray) Roth (Brassicaceae) across the Central Palaearctic

This study presents the results of investigation of the micromorphology and variability of Sisymbriumpolymorphum seeds collected in 49 localities in the core range and isolated populations of Central Europe, Eastern Europe and Central Asia. In addition, we compared the ultrastructure of the seeds of S. polymorphum with that of the closely-related species S.loeselii and S.linifolium. The seeds were measured with a stereoscopic microscope and a biometric programme (ImageJ) and micromorphological studies were performed by scanning electron microscopy (SEM). The seed variability showed intraspecific stability of the ultrastructure and low variability of metric features within the studied range. Studied species showed differences in the ultrastructure, which will be valuable for diagnostic purposes. We present and describe, for the first time, the ultrastructure of S.polymorphum seeds.

SEM observations on the vegetative plant parts of Acantholimon riyatguelii Yıldırım (Plumbaginaceae), a local endemic restricted to gypsum habitats

Acantholimon riyatguelii Yıldırım is a local endemic restricted to gypsum habitats. SEM observation on roots, stems and leaves of A. riyatguelii presented detailed information of ultrastructural properties which described this species adaptations to specific conditions of gypsum habitats. This study showed that A. riyatguelii leaves which are amphistomatic exhibited strong xeromorphic adaptations reflecting numerous stomata, surface hairs, thick cuticle (∼10 µm) and advanced palisade. The xeromorphic stomata in the leaves of the A. riyatguelii growing in aridty areas are in the form of deep cavities under the epidermis. Mesophyll cells had a somewhat rounded shape and placed rather regularly in the mesophyll. Some crystal deposits were observed at stomata and inside the mesophyll cells. In the root, xylem was in the form of pentarch along with the phloem observed among the protoxylems and the periderm was ca. 100 µm thick. In the stem, the centre of the stem was filled with large xylem vessels and five bundles of phloem tissue distributed around the xylem. The ultrastructural properties of A. riyatguelii, a gypsophyte species, were given for the first time in this study at Turkey and revealed detailed descriptive ultrastructures which could serve as a source of information and reference. Finally, this study offers new and interesting avenues to interpret ultrastructural features that allow gypsophiles to tolerate drought and atypical mineral soils.

Micromorphological considerations on Alyssum nezaketiae Aytaç & H. Duman (Brassicaceae), endemic to gypsum habitats from Turkey: An electron microscopic study

Alyssum nezaketiae is a local endemic species in gypsum habitats of Çankırı province in Turkey. In this study, I used field collected specimens of A. nezaketiae in a scanning electron microscopy examination of vegetative and reproductive structures of A. nezaketiae. The objective of the study was to investigate the micromorphological properties that define the species and that represent its adaptation(s) to the extreme environmental conditions posed by gypsum habitats. The epidermis had one to two rows at transverse sections of leaf and stem. Cortex was composed six to eight rows parenchyma cells at stem. A number of adaptations to xeric habitats were observed, including: dense silvery lepidote hairs on leaves and stems, small leaves, stomata on the lower surfaces of the leaves occurring in stomatal crypts, intense lignification in the central cylinder of the stems, and bundles of sclerenchyma in the pith region of stems. These can be interpreted as gypsophytic characteristics associated with physiological drought. Micromorphological properties of plant parts are discussed in relation to environmental conditions and possible constraint factors occurring in these gypsum habitats. Furthermore, these micromorphological studies contribute important taxonomic characters that are needed to help identify a species whose habitat is under threat from a variety of human activities.

Comparative taxonomic variation in fruits and seeds' surface morphology among populations of alpine Rosa sericea complex (Rosaceae)

In this research, the fruits and seeds' surface morphological features and their taxonomic significance were determined. Additionally, useful traits for delimitation of taxa of Rosa sericea complex were studied. In this research, three taxa of the complex R. sericea, R. omeiensis, and R. sikangensis have been studied. A total of 41 populations and 130 specimens of seeds, and 35 populations and 168 specimens of fruits from 10 different geographical regions of southwest China have been examined. The surface micro-morphological characters of the seeds have been studied through scanning electron microscopy to distinguish important characteristics of the complex taxa. Forty-four different qualitative and quantitative characteristics were observed. Principal component analysis was used to simplify and elucidate the relationship between the studied characters of different population based on the morphology of fruits and seeds' features. Moreover, the numerical taxonomic characters and their variation with elevation have been studied in these species. The most interesting characters observed on the surface of the seeds were stomata, and trichomes, for which density was more at the dorsal and ventral parts, while rarely present on the lateral parts. The fruits and seeds' surface morphology of the studied species was complicated and some variation in the characters, that is, persistent calyx shape, the shape of fruits and seeds, stomata shape, and trichomes size were found significant for delimitation of taxa in the complex. The purpose of this study is to identify the taxa of R. sericea complex based on fruits and seeds' morphological characters, and identification keys.

Micromorphology and anatomy of fruits of Angelica archangelica L. (Apiaceae) and their intraspecific differentiation

Introduction: Angelica archangelica L. (Apiaceae) has a long history of use as a vegetable and medicinal plant. According to the European Pharmacopoeia, the angelica root (Angelica radix) of only one of the sub-species – Angelica archangelica subsp. archangelica (formerly known as Archangelica officinalis) – is used as a source of plant material with documented medicinal properties. Within this species, there are two subspecies that are difficult to classify unambiguously: subsp. archangelica and subsp. litoralis.

Objective: The aim of this study was to provide a micromorphological and anatomical description of fruits of A archangelica and identify new diagnostic characters useful in subspecies identification.

Methods: A comparative analysis of the sculpture and internal structure of fruits of the distinguished A archangelica taxa was conducted, using scanning electron microscopy (SEM).

Results: Based on the taxonomic characters in the Apiaceae family, micromorphological and anatomical characteristics of A archangelica fruits were prepared. Some of the investigated characters, e.g. verrucose sculpture of the oil duct surface and the presence of hooked hairs, exhibited intraspecific differences. Among the anatomical characters, the variation was related to the number and size of the paraendocarpic oil ducts as well as to the thickness of dorsal and commissural mesocarp.

Conclusion: SEM examination of fruits of A archangelica provided a detailed description of their sculptures and several micromorphological and anatomical characters of potential diagnostic value.

Karyomorphological and SEM studies in newly discovered populations of a critically endangered medicinal plant - Lilium polyphyllum D. Don ex Royle from a high altitude protected area of north-western Himalaya

In this study, new populations of a critically endangered Himalayan herb, Lilium polyphyllum D. Don ex Royle have been reported from Chamba, Himachal Pradesh, India for the first time. Karyotypic, palynological, and spermological studies under the light microscope (LM) and scanning electron microscope (SEM) have been carried out on specimens from these populations with an aim to add more knowledge to the current database of the species. Presently studied individuals depicted a diploid (2x) chromosome count of 2n = 24, which is in confirmation with the previous reports from Kashmir Himalaya. Mitotic study showed a karyotype formula of 2n = 2x = 2m + 2sm + 4st + 16t, that is, 2 metacentric +2 submetacentric +4 acrocentric +16 telocentric chromosomes. LM and SEM observations revealed that the pollen grains are monosulcate, heteropolar, elliptical in polar view, and oblate with reticulate ornamentation. Based on the criteria of number, shape, and arrangement of columellae that form the muri, pollen grains in L. polyphyllum correspond to Martagon type. This is the first SEM based study on pollen grains and seeds of endangered Himalayan white lily. Based on the present ecological data collected we confirm the status of L. polyphyllum to be critically endangered in the study area.

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.

Systematic importance of achene macro-micromorphological characteristics in selected species of the genera Crupina, Jurinea, and Klasea (Asteraceae) from Turkey

This study focuses on the macro-micromorphological achene characteristics of 12 species of the genera Crupina, Jurinea, and Klasea (Asteraceae) using light microscopy and the scanning electron microscopy (SEM). The morphological characteristics of the achenes, including shape, size, color, and surface pattern of achene, and hair structure, length, and color of pappus are studied. The results show that the achene length is between 3 and 8 mm, and its width is between 1 and 4 mm. Pappus is 4-15 mm long and persistent for seven species. SEM analysis shows four different achene surface patterns for the studied species: smooth, undulate, smooth-undulate, and undulate-ruminate. The genus Crupina has darkly colored achenes with yellow, dense firm hairs, and the achene surface pattern is smooth. Triangular and sulcate achenes seem to characteristic for the genus Jurinea. The genus Klasea distinguished from the remaining species studied with its straw-colored and deciduous pappus. Macro-micromorphological characteristics provide effective tools for both generic and intrageneric differentiation for the studied species.

Achene micromorphology and its taxonomic significance in some species in Taraxacum sect. Palustria (Asteraceae)

The genus Taraxacum is one of the largest and taxonomically most complicated apomictic genera. Currently, it is considered to consist of over 2800 species placed within 60 sections. Due to the large number of species, and their uniform morphological design and plasticity of leaves, the identification of plants at the species level is challenging even for specialists. This problem significantly hinders the study of their properties and the rational use of these valuable medicinal and nutritional plants. This paper presents the results of research on the morphology and micromorphology of achenes of 28 Taraxacum species of sect. Palustria and for comparison one species per section of: Erythrosperma, Naevosa, Piesis, and Taraxacum. The achenes were measured with a stereoscopic microscope and a biometric program, and micromorphological studies were performed by scanning electron microscopy. It has been shown that traits associated with achene morphology and micromorphology have a high diagnostic value, allowing us to distinguish sections as well as species within the sect. Palustria. Based on the examined achene features, a dichotomous key for determining the studied species was constructed.

Taxonomic study of subfamily Nepetoideae (Lamiaceae) by polynomorphological approach

The present study is insight into pollen morphology for characterizing species and their utility in the taxonomic separation of certain taxa of subfamily Nepetoideae (Lamiaceae) from Pakistan. The pollen micromorphology of 11 species of the Nepetoideae was analyzed and documented using light microscopy and scanning electron microscopy (SEM) for both qualitative and quantitative characteristics. Most species have hexazonocolpate pollen grains but trizonocolpate and tetrazonocolpate pollen with circular and oval amb were also rarely observed in Mentha spicata. The basic pollen shape in most of the studied species was subspheroidal but prolate grains were also observed in M. spicata, S. coccinea, and S. plebeia. The exine sculpturing of Nepetoideae pollen was taxonomically very informative particularly at subfamily level. Observations of exine sculpturing with SEM revealed various types of pollen grains: reticulate, bireticulate, microreticulate, perforate, aerolate, and gammate. The bireticulate type further subdivided into three subtypes based on the number of secondary lumina in each primary lumen and is characterized by varying characteristics of the secondary reticulum and primary muri. A significant variation was observed in colpus surface ornamentation. The maximum polar diameter was found in O. americanum (58 ± 5.8 μm) and the maximum equatorial diameter observed in O. basilicum (50.25 ± 1.37 μm). Pollen features of the studied species were discussed and compared based on the current taxonomical concepts. The results showed that pollen traits of the subfamily Nepetoideae was found significant to classify the taxa. Furthermore, pollen features provide additional evidence to distinguish macromorphologically similar taxa from each other.