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Cypselae in Dahlia and Hidalgoa (Asteraceae: Coreopsideae): anatomical and morphological differences
Abstract
A number of morphological vegetative, floral, pollen, and fruit characters differ between the taxa of Dahlia and Hidalgoa. This study compares morphological and anatomical characters of the cypselae in Dahlia and Hidalgoa, identifying variations of potential taxonomic value to assess whether they should be treated as independent taxa. Cypselae of two species of Hidalgoa and fifteen species of Dahlia were analyzed using optical and scanning electron microscopy. In Hidalgoa, phytomelanin is positioned in the space between the outer and median mesocarp, forming a continuous smooth layer. A multiplicative pericarp was also identified in Hidalgoa, a rare feature in Asteraceae, in which the parenchyma cells of the mesocarp are thickened and sclerified at maturity. Vascular bundles in Hidalgoa are observed only in the ribs, and the largest awns of cypselae were identified in these species. In contrast, the cypselae in Dahlia displayed morphological uniformity, with the typical pericarp of the tribe Coreopsideae; theonly variation in Dahlia is that a few species possess exocarp cells with well developed secondary walls. The phytomelanin layer in Dahlia is discontinuous and spiny. The anatomical attributes of cypselae in Hidalgoa are similar to those of taxa in other tribes or alliances in Asteraceae.
... In addition, comparative studies of the attributes of cypselae in several tribes in Asteraceae have identified traits of taxonomic importance that can help further our understanding of the evolutionary history of this family (Marques et al. 2022). Some examples of these characters include exocarp cells with pigmentation (Mukherjee & Sarkar 2001), variation in the number of layers of the mesocarp and cell layer arrangement of the sclerenchyma and parenchyma (Julio & Oliveira 2009, Batista & De Souza 2017, Sánchez-Chávez et al. 2023, orientation of the exocarp cells (Jana & Mukherjee 2018), presence of phytomelanin with characteristic patterns and morphology (Pandey et al. 2014, Freitas et al. 2015, Sánchez-Chávez et al. 2023, and striations in the pericarp wall (Tadesse & Crawford 2014). The objective of this study is to document anatomical and palynological attributes of Dicranocarpus parviflorus not yet recorded and compare them along with macromorphological characters with those of other genera in Coreopsideae such as Dahlia and Hidalgoa to better understand how closely related these taxa are. ...
... In addition, comparative studies of the attributes of cypselae in several tribes in Asteraceae have identified traits of taxonomic importance that can help further our understanding of the evolutionary history of this family (Marques et al. 2022). Some examples of these characters include exocarp cells with pigmentation (Mukherjee & Sarkar 2001), variation in the number of layers of the mesocarp and cell layer arrangement of the sclerenchyma and parenchyma (Julio & Oliveira 2009, Batista & De Souza 2017, Sánchez-Chávez et al. 2023, orientation of the exocarp cells (Jana & Mukherjee 2018), presence of phytomelanin with characteristic patterns and morphology (Pandey et al. 2014, Freitas et al. 2015, Sánchez-Chávez et al. 2023, and striations in the pericarp wall (Tadesse & Crawford 2014). The objective of this study is to document anatomical and palynological attributes of Dicranocarpus parviflorus not yet recorded and compare them along with macromorphological characters with those of other genera in Coreopsideae such as Dahlia and Hidalgoa to better understand how closely related these taxa are. ...
... The anatomy of the cypselae in taxa in Coreopsideae has demonstrated uniform morphology (Pandey & Singh 1982, Julio & Oliveira 2009, Batista & De Souza 2017, Sánchez-Chávez et al. 2023, with some exceptions in Fitchia Hook.f. (Pandey et al. 2014), Hidalgoa (Sánchez-Chávez et al. 2023), and now in Dicranocarpus. ...
Dicranocarpus is a monotypic genus endemic to the Chihuahuan Desert with atypical attributes among species of tribe Coreopsideae. Phylogenetic position of Dicranocarpus parviflorus has been controversial. A molecular phylogeny showed that the taxon was closely related to Dahlia; however, further analyses with a wider sampling of Dahlia, also including Hidalgoa, identified the genus in a more distant clade. The objective of this study is to gather anatomical attributes from the cypselae as well as palynological characters along with macromorphology to determine whether Dicranocarpus shares characters with these genera in Coreopsideae. Our results show that although the pollen of D. parviflorus does not possess attributes that distinguish it from the rest of the tribe Coreopsideae, they were useful to confirm its membership in the tribe. The cypselae anatomy identified that D. parviflorus has characters of taxonomic value that differentiate this species from the rest of the Coreopsideae. The three most significant novel characters in Dicranocarpus were in the outer mesocarp, consisting of tracheoidal-like cells forming irregular rows up to 250 μm in length, an aerenchyma in the middle mesocarp, and the lack of phytomelanin and calcium oxalate crystals. Furthermore, the results of the phytomelanin patterns in the studied taxa highlight the need for further anatomical studies of the cypselae to fully understand the evolution of phytomelanin deposition in the tribe Coreopsideae and even in the Heliantheae Alliance. Macromorphological, palynological and anatomical attributes of the cypsela in Dicranocarpus were not shared with Dahlia. Moreover, the sexual condition of the disc and ray florets shared with Hidalgoa has evolved independently in lineages of Asteraceae.
This study looked at the effects of different extraction protocols on the biochemical properties of compost extract (CE) and its effect on the growth of Dahlia pinnata Cav. (dahlia), Consolida ajacis (L.) Schur (delphinium), and Centaurea cyanus L. (cornflower). Composted green waste (CGW) extract was prepared at compost-to-water ratios of 8:1, 8:2, 8:3, and 8:4, employing preservation methods of sterilization and refrigeration, or direct refrigeration. Sterilized CE with compost-to-water ratio of 8:3 exhibited superior biochemical properties (pH value, electrical conductivity, nutrient contents, and enzyme activities). The stem width, root length, flower number, root-shoot ratio, and total chlorophyll contents of dahlia cultivated in the optimal CE significantly increased by 33%, 44%, 115%, 110%, and 28%, respectively; the stem width, root length, flower number, root-shoot ratio, and total chlorophyll content of delphinium in the optimal CE greatly increased by 39%, 25%, 76%, 31%, and 31%, respectively; the stem width, root length, flower number, root-shoot ratio, and total chlorophyll content of cornflower in the optimal CE remarkably increased by 29%, 27%, 108%, 44%, and 17%, respectively. Therefore, the results indicated that CE at a compost-to-water ratio of 8:3, coupled with sterilization and refrigeration effectively promoted plant growth, offering a superior alternative to CGW.
Hidalgoa and Dahlia are two closely related genera in Asteraceae, tribe Coreopsideae whose limits need to be clarified. Pollen morphology has been useful for delimitation at the genus level in this family. To better define these genera, the morphology of pollen grains was observed and measured using light and scanning electron microscopy. The pollen grains of 25 species of Dahlia and Hidalgoa were acetolyzed and analyzed. Pollen is tricorporate in most of the species studied, although in a few species in Dahlia , grains were found to be hexacolporate. The most outstanding differentiating characters among species of Dahlia and Hidalgoa are colpus length (greater in Hidalgoa ) and shape of spines (conical in Hidalgoa ). In addition, lalongate ora are larger in Hidalgoa than in Dahlia . A PCA analysis of thirteen pollen characters, identified species of Hidalgoa in a discrete group and Dahlia cuspidata as an outlier. These distinctive attributes in pollen morphology support the idea that pollen morphology is useful for delimitation at the generic level in the Dahlia clade. Further evidence from other sources, genetic or anatomical, might contribute to demarcating Dahlia and Hidalgoa , and provide insight into the family’s evolutionary history.
Phytomelanin is a mechanically hard, blackish, and inert substance rarely found in plants. In Asteraceae, this substance was historically associated with the Heliantheae alliance, but recent studies have observed it in unrelated groups as Heterocoma and Wunderlichia. During a taxonomic investigation, we found phytomelanin in cypselae of Lychnophora salicifolia an unusual feature in Vernonieae previously found only in Heterocoma. Furthermore, phytomelanin fills the intercellular spaces of the sclerenchymatic outer mesocarp in L. salicifolia. Our results doubt the (syn)apomorphy status in Heterocoma, suggest the phytomelanin may have not the same evolutionary significance in Lychnophorinae as in other tribes and proposes new perspectives for evolutionary studies in Asteraceae.
The sunflower family, Asteraceae, comprises 10% of all flowering plant species and displays an incredible diversity of form. Asteraceae are clearly monophyletic, yet resolving phylogenetic relationships within the family has proven difficult, hindering our ability to understand its origin and diversification. Recent molecular clock dating has suggested a Cretaceous origin, but the lack of deep sampling of many genes and representative taxa from across the family has impeded the resolution of migration routes and diversifications that led to its global distribution and tremendous diversity. Here we use genomic data from 256 terminals to estimate evolutionary relationships, timing of diversification(s), and biogeographic patterns. Our study places the origin of Asteraceae at ∼83 MYA in the late Cretaceous and reveals that the family underwent a series of explosive radiations during the Eocene which were accompanied by accelerations in diversification rates. The lineages that gave rise to nearly 95% of extant species originated and began diversifying during the middle Eocene, coincident with the ensuing marked cooling during this period. Phylogenetic and biogeographic analyses support a South American origin of the family with subsequent dispersals into North America and then to Asia and Africa, later followed by multiple worldwide dispersals in many directions. The rapid mid-Eocene diversification is aligned with the biogeographic range shift to Africa where many of the modern-day tribes appear to have originated. Our robust phylogeny provides a framework for future studies aimed at understanding the role of the macroevolutionary patterns and processes that generated the enormous species diversity of Asteraceae.
Dahlia mixtecana (Asteraceae, Coreopsideae) is described and illustrated as a new species endemic to western Oaxaca, Mexico. This taxon is related to Dahlia sect. Dahlia and Dahlia sect. Entemophyllon. However, based on the current evidence available and the current system of infrageneric groups, it does not appear possible to assign the new species with confidence to any taxonomic section. The description of the new species is presented with distribution maps, illustrations, photographs, discussions on the taxonomic relationship and an identification key to the sections and species of Dahlia occurring in Oaxaca and species in Dahlia sect. Entemophyllon related to D. mixtecana.
Asteraceae are one of the largest families of angiosperms and comprise > 1700 genera and 24 000 species currently in 13 subfamilies. However, despite recent and continuous improvement regarding their classification, little is known about their embryological diversity, especially in some of the early-diverging subfamilies including Stifftioideae and Wunderlichioideae. These subfamilies were previously considered to be similar, sharing several external features such as anther appendages, pollen grains, pappus bristles and cypsela trichomes. Ontogenetic and anatomical studies could reveal deeper levels of homology and expand the features of interest for the systematics of the family. Also, the lack of knowledge of the early-divergent subfamilies precludes the reconstruction of evolutionary trends in Asteraceae and Asterales. Here, we compared the anthers, ovaries, ovules, fruits and seeds of two Stifftia spp. and two Wunderlichia spp. to identify possible evolutionary trends. Our results show that embryology in these genera is similar, with slight differences in pollen grain ornamentation, types and distribution of ovary trichomes, antipodal persistence, pericarp tissue organization, occurrence of phytomelanin in the fruit wall, the form of the carpopodium, shape and lignification of carpopodial cells, form and distribution of pappus bristles, and lignification patterns of exotesta cells. The results also demonstrate novelties for the family, including Basic-type anther wall development and trichomes on the inner ovary epidermis of W. mirabilis, funicular trichomes in both Stifftia spp., and funicular stomata and phytomelanin in the pericarp of both Wunderlichia spp. Therefore, our data support Stifftioideae and Wunderlichioideae as distinct but closely related subfamilies. The results also open new perspectives on how anther, ovary and fruit evolved in the family. The occurrence of a Basic-type anther wall in early-divergent subfamilies may represent a symplesiomorphy or apomorphy for the family. This will depend on how the anther develops in the subfamilies related to Wunderlichioideae and Stifftioideae. Vascularization of the ovary was different from that previously known in the family and throws doubts upon its origin. Phytomelanin is a rare substance in plants, found only in seeds of most families of Asparagales and fruits of some Asteraceae; it had previously been found in fruits of Heterocoma (Cichorioideae) and some Asteroideae. We detected phytomelanin in Wunderlichia, indicating that presence of this substance has evolved independently three times in the fruits of the family.
ADDITIONAL KEYWORDS: cypselae-fruit anatomy-megagametogenesis-megasporogenesis-microgametogenesis-microsporogenesis-phytomelanin-seed anatomy.
Resumen:
Antecedentes y Objetivos: El género Dahlia (Asteraceae) es nativo de América y México es su centro de diversificación. Dahlia es importante en la horticultura ornamental, su mejoramiento genético ha generado más de 15,000 variedades. México representa la principal fuente de germoplasma, por lo que un estudio sobre su riqueza y distribución geográfica es indispensable. Los objetivos de este trabajo fueron analizar la riqueza de especies de Dahlia en México, su distribución geográfica y evaluar su estado de conservación.
Métodos: Se elaboró una base de datos con 1980 registros georreferenciados, obtenidos de ejemplares de herbario, publicaciones y recolectas de campo. La información fue analizada utilizando Sistemas de Información Geográfica, se estimó la riqueza de especies por división política, tipos de vegetación, regiones, provincias biogeográficas, rangos elevacionales, latitudinales y longitudinales, una cuadrícula de 33 × 33 km
y Áreas Naturales Protegidas.
Resultados clave: Dahlia agrupa 38 especies, todas crecen en México, 35 son endémicas. El género está presente en 26 estados. Hidalgo y Oaxaca tienen el mayor número de especies, seguidos por Guerrero. Jalisco muestra el mayor esfuerzo de colecta. Comúnmente, Dahlia habita en bosques de coníferas y encino. Su rango de distribución abarca desde 24 hasta 3810 m de elevación, pero el mayor número de especies crece entre 2000 y 2500 m. Se encontraron dos áreas de alta riqueza de especies de Dahlia en México; la primera está en el noreste de Querétaro, este de Guanajuato y sureste de San Luis Potosí, en la Sierra Madre Oriental, la otra en el noroeste de Oaxaca, en la Sierra Madre del Sur. Finalmente, 23 especies viven dentro de un Área Natural Protegida. La Sierra Gorda en el estado de Querétaro concentra el mayor número de especies.
Conclusiones: El análisis de la riqueza de especies y su distribución mostró que la mayor diversidad de Dahlia se encuentra en la Zona de Transición Mexicana en las provincias Sierra Madre del Sur y Sierra Madre Oriental.
Palabras clave: biogeografía, dalias, patrones de distribución, Sierra Gorda, SIG.
Abstract:
Background and Aims: The genus Dahlia (Asteraceae) is native to the Americas and Mexico is its center of diversification. Dahlia is important in ornamental horticulture, and breeding programs have generated more than 15,000 varieties. Mexico represents the main source of germplasm; therefore, a study of its richness and geographical distribution is essential. The aims of this work were to analyze the species richness,
geographical distribution and evaluate the conservation status of Dahlia in Mexico.
Methods: A database with 1980 georeferenced observations was elaborated from herbarium specimens, publications and field collections. The information was analyzed using Geographic Information Systems to reveal the estimated species richness by political division, vegetation types, regions, biogeographical provinces, elevational, latitudinal and longitudinal ranges, a grid cell of 33 × 33 km, and Protected Natural
Areas.
Key results: Dahlia consists of 38 species, all growing in Mexico, 35 are endemic. The genus occurs in 26 states. Hidalgo and Oaxaca have the highest number of species, followed by Guerrero. Jalisco has the most records. Commonly, Dahlia grows in coniferous and oak forest. Its distribution ranges from 24 to 3810 m elevation; however, most species are found between 2000 and 2500 m. High species richness occurs in two
areas; the first one is located in the Sierra Madre Oriental including northeastern Querétaro, eastern Guanajuato and southern San Luis Potosí; the second one is in the Sierra Madre del Sur in northwestern Oaxaca. Finally, 23 species grow within the boundaries of a Protected Natural Area, and the Sierra Gorda, state of Querétaro, concentrates the highest species number.
Conclusions: The analyses of species richness and distribution showed that the greatest diversity of Dahlia is found in the Mexican Transition Zone, in the Sierra Madre del Sur and the Sierra Madre Oriental provinces.
Key words: biogeography, dalias, distribution patterns, GIS, Sierra Gorda.
Background and Aims: The genus Dahlia (Asteraceae) is native to the Americas and Mexico is its center of diversification. Dahlia is important in ornamental horticulture, and breeding programs have generated more than 15,000 varieties. Mexico represents the main source of germplasm; therefore, a study of its richness and geographical distribution is essential. The aims of this work were to analyze the species richness, geographical distribution and evaluate the conservation status of Dahlia in Mexico. Methods: A database with 1980 georeferenced observations was elaborated from herbarium specimens, publications and field collections. The information was analyzed using Geographic Information Systems to reveal the estimated species richness by political division, vegetation types, regions, biogeographical provinces, elevational, latitudinal and longitudinal ranges, a grid cell of 33 × 33 km, and Protected Natural Areas. Key results: Dahlia consists of 38 species, all growing in Mexico, 35 are endemic. The genus occurs in 26 states. Hidalgo and Oaxaca have the highest number of species, followed by Guerrero. Jalisco has the most records. Commonly, Dahlia grows in coniferous and oak forest. Its distribution ranges from 24 to 3810 m elevation; however, most species are found between 2000 and 2500 m. High species richness occurs in two areas; the first one is located in the Sierra Madre Oriental including northeastern Querétaro, eastern Guanajuato and southern San Luis Potosí; the second one is in the Sierra Madre del Sur in northwestern Oaxaca. Finally, 23 species grow within the boundaries of a Protected Natural Area, and the Sierra Gorda, state of Querétaro, concentrates the highest species number. Conclusions: The analyses of species richness and distribution showed that the greatest diversity of Dahlia is found in the Mexican Transition Zone, in the Sierra Madre del Sur and the Sierra Madre Oriental provinces.
In Asteraceae, subtribe Disynaphiinae comprise c. 50 species distributed among six genera, including the monotypic Acanthostyles, Campovassouria (two species), Disynaphia (16 species), Grazielia (ten species), Raulinoreitzia (three species) and Symphyopappus (14 species). In a recent phylogenetic analysis, the subtribe were shown to be non-monophyletic; to achieve monophyly, D. praeficta would need to be excluded, and Neocabreria malacophylla, N. serrulata (Critoiinae) and Radlkoferotoma cistifolium (Ageratinae) would need to be included. However, there is no strong morphological feature to justify the exclusion of D. praeficta from the subtribe. All other Disynaphia spp. form a clade with Campovassouria. Symphyopappus is also polyphyletic, but all species remain in the subtribe. Thus, the circumscription of the genera traditionally based on morphological features became unclear, and the diagnostic potential of features like the structure of the fruit (called a cypsela) now needs to be re-evaluated in testing the new relationships suggested by molecular data and finding morphological features supporting the exclusion of D. praeficta. The structure of cypselae of all genera of the subtribe was studied using a combination of light and scanning electron microscopy to evaluate its potential for systematics. Our study shows the phytomelanin layer external to the vascular bundles and vascularized pappus were shared by among all species of the subtribe, but including D. praeficta. Features of the cypselae of Disynaphiinae such as the carpopodium, floral disc, pappus outer mesocarp, sclerenchyma, phytomelanin layer, ribs and trichomes are valuable at both generic and specific levels. In addition, the outer mesocarp was an important feature supporting the new relationship in two of four clades proposed in the current phylogenetic framework. Moreover, our results revealed the presence of a multiplicative pericarp only in a few Symphyopappus spp., a rare feature in Asteraceae, which probably evolved independently in the family. Cypsela structure also supports the exclusion of D. praeficta from the subtribe, since the species has several different features when compared with other representatives of Disynaphiinae.
Dahlia calzadana Villaseñor & Redonda-Mart. (Asteraceae, Coreopsideae), a new species from the district of Cuicatlan, state of Oaxaca is described and illustrated. It grows in the ecotone between the seasonal dry tropical forest and the Quercus forest. This new taxon differs from all other known species of Dahlia by its simple, conspicuously petiolate leaves and its white with pink tones ray florets.
Structural features of cypsela are important to certain tribes of Asteraceae; thus, the ontogeny of the fruit (only the pericarp) of 10 weedy Asteraceae species was determined concerning the contribution to increase the knowledge of the fruit development in Asteraceae. The species analyzed are Conyza bonariensis L. (Cronquist.), Cosmos sulphureus Cav., Eclipta alba L. Hassk., Elephantopus mollis Kunth., Emilia sonchifolia L. DC., Galinsoga quadriradiata Ruiz & Pav., Erechtites valerianifolius (Wolf) DC., Parthenium hysterophorus L., Praxelis clematidea (Griseb) R.M. King & H. Rob and Sigesbeckia orientalis L. The mesocarp in the cypsela structure shows variation in the number of layers, the cell layer arrangement of the sclerenchyma and parenchyma, and the presence of phytomelanin that is especially striking. The mesocarp traits of Heliantheae alliance species are homogeneous, and it has been suggested that the derived character phytomelanin may not have the same evolutionary history in species belonging to the same tribe. It is noteworthy that Cichorioideae cypsela has the same general structure as that of Asteroideae.
Studies on seed structure of Asteraceae have received little attention of botanists. Seestructure in Asteraceae is analyzed to evaluate the usefulness of characters in the separation of species through the analysis of nine weedy species. Seeds originate from anatropous, unitegmic and tenuinucellate ovules. The partial collapse of the developing seed coat is a common characteristic in the Asteraceae species studied. The testa consists of crushed and thin-walled cells in almost all of the species studied herein, except for Elephantopus mollis and Parthenium hysterophorus, which showed exotesta cells with U-shaped thickening. The analysis revealed high uniformity in seed characters. © 2015 Eduem - Editora da Universidade Estadual de Maringa. All rights reserved.
Heterocoma is a Brazilian endemic genus resulting from the dismemberment of Sipolisiinae, in which only representatives with fruit containing phytomelanin were included in the genus. As the fruits of Asteraceae are known to be systematically important at various taxonomic levels and Heterocoma fruit has not been described previously, we studied the morphology and anatomy of the cypselas of all species of the genus, comparing them with other fruits in the family containing phytomelanin and evaluating the systematic potential at the specific and tribal levels. The fruits were analysed by scanning electron microscopy (SEM) and light microscopy. The morphological features of the fruit, including the carpopodium, ribs and pappi, varied in the genus and demonstrated potential for species discrimination. The anatomy showed a pattern for the genus with a uniseriate exocarp, the outer mesocarp composed of fibres arranged in several layers, the inner mesocarp composed of several layers of parenchyma, the endocarp, and phytomelanin deposited between the inner and outer mesocarp. This anatomical pattern of phytomelanin deposition differs from that of other Asteraceae with phytomelanin in their fruit. Heterocoma is also the only genus in Vernonieae that has phytomelanin deposition in the cypselas. © 2015 The Linnean Society of London, Botanical Journal of the Linnean Society, 2015, 179, 255–265.
Cypselar morpho-anatomy is very helpfull for the separation of taxa in fruting stage. For this purpose, three species of the tribe Coreopsideae have been studied to separate the taxa more clearly. Morphologically, cypselas are either homomorphic {Bidens cernua and Cosmos sulphureus) or heteromorphic (Bidens pilosa). In Cosmos sulphureus, pappus is absent. Whereas in others, pappus is present. Pappus is represented by retrosely barbed awn-like structure. In Cosmos sulphureus, stylopodium is enlarged, knobe like structure whereas in the remaining, stylopodia are prominent but not enlarged. In cypselas, carpopodia are symmetric and carpopodial cells are arranged in 1-3 rows. Anatomically, in all die studied cypselas, phytomelanin layer is present in mesocarpic region but discontinuously developed, but except in Cosmos sulphureus where phytomelanin layer is continuous in rib region whereas in furrow region, it is discontinuous. Except in Cosmos sulphureus in other cypselas vellicular cavity exist. Testal layers are made up of crusted layers of parenchyma cells. Based on the aforesaid morpho-anatomical characters, an artificial key has been presented.
Crepis japonica (L.) Benth., Porophyllum ruderale (Jacq.) Cass. and Tridax procumbens L. are weedy species that grow in cultivated fields, roadsides, abandoned fields and open, disturbed spaces in Maringa, Parana state, Brazil. The ontogeny of the fruits and seeds of the 3 Asteraceae species was carried out. The flowers and developing fruits were prepared according to resin inclusion techniques for histochemical tests and scanning electron microscopy. During maturation of the pericarp, processes such as trichome differentiation, tissue sclerification, phytomelanin deposition and breakdown of tissues can be observed. The fruit of C. japonica is entirely lacking in phytomelanin. The seed is only exotestal in C. japonica. Comparative analysis of the pappus and cypsela characters demonstrated that they are efficient in separating species and tribes. The seed coat and embryo may also be useful in the characterization of tribes.
The systematic significance of the morphological structure of achenes in the Himalayan–Tibetan Plateau endemic genera Soroseris, Syncalathium and Parasyncalathium is described and discussed. The achene surface sculpturing of 15 samples representing 13 species of the three genera was investigated using scanning electronic microscopy (SEM) to evaluate inter- and intrageneric relationships of the three genera. Characters such as cell arrangement, shape of the epidermis, type of ornamentation of the outer cell wall and degree of wax development are described. The results show that characters such as the shape of the epidermis and the type of ornamentation of the outer cell wall are distinct between the three genera and useful for species-level classification. Parasyncalathium souliei differs from Syncalathium, in which it has traditionally been placed, in the short, stout beak of the achene and especially in the obscure outline of the epidermal cells and their long acuminate, steeple-like, end walls. Combined with karyological and molecular data, the differences in achene morphology and sculpturing further support our recognition of Parasyncalathium as distinct from Syncalathium. The achene characters are not only useful for assessing relationships, but are also useful for delimiting species. © 2013 The Linnean Society of London, Botanical Journal of the Linnean Society, 2013, 00, 000–000.
Melanins are dark, insoluble pigments that are resistant to concentrated acids and bleaching by oxidising agents. Phytomelanin (or phytomelan) is present in the seed coat of some Asparagales and in the fruits of some Compositae. In Compositae fruits, melanin is deposited in the schizogenous spaces between the hypodermis and underlying fibrous layer. Phytomelanin in Compositae is poorly understood, and there are only speculations regarding the cells that produce the pigment and the cellular processes involved in the secretion and polymerisation of phytomelanin. This report describes the cellular processes involved in the secretion of phytomelanin in the pericarp of Praxelis diffusa, a species with a structure typical of the family. The ovaries and fruits at different stages were fixed and processed according to the standard methods of studies of light microscopy and transmission electron microscopy. Hypodermal cells have abundant rough endoplasmic reticulum and mitochondria, and the nuclei have chromatin that is less dense than other cells. These characteristics are typical of cells that synthesise protein/amino acids and suggest no carbohydrate secretion. The fibres, however, have a dense cytoplasm rich in the Golgi bodies that are associated with vesicles and smooth endoplasmic reticulum, common characteristics of carbohydrate secretory cells. Our results indicate that the hypodermal cells are not responsible for the secretion of phytomelanin, as previously described in the literature; in contrast, this function is assigned to the adjacent fibres, which have an organisation typical of cells that secrete carbohydrates.
Rib numbers have traditionally been used in
identification keys of Eupatorieae. Some species, however,
demonstrate variations in this character much greater than
those registered in the literature, making the use of this trait
controversial. The large variations seen among some species
of Eupatorieae examined in this work were found to be
related to the fact that rib number is more closely associated
with the pressure exerted by neighboring flowers on
the capitulum than with genetic factors. According to our
results, ribs are not a reliable taxonomic character for broad
use in Eupatorieae, being especially inappropriate for
Chromolaena stachyophylla, Praxelis pauciflora, and
Vittetia orbiculata. The association between the occurrence
of vascular bundles and ribs is also discussed, and the
variability seen in some Eupatorieae is analyzed. Our data
indicate that the formation of the ribs on the cypselae is
determined more by the position occupied by the flower on
the inflorescence than by the occurrence of vascular
bundles.
he worry about the indiscriminate use of the terms cypsela and achene for the fruits of Asteraceae has been frequently detached by specialists in this family. The present work was developed aiming to verify the existence of arguments to justify the adoption of a term against the other. After historical and anatomical analysis, we concluded that there is technical basis to consider cypsela and achene as different types of fruits. For Asteraceae, the correct is to call cypsela; achenes are only derived from superior ovaries, as in Plumbaginaceae.
Micromorphological characters of 4 genera (Doellia Sch.-Bip., Laggera Sch.-Bip. ex C. Koch,
Pluchea Cass. and Pseudoconyza Cuatrec.) and 7 specific and infra specific taxa in the tribe
Plucheeae were examined from Pakistan by light and scanning electron microscopes. Cypsela
characters support the taxonomic decisions, as all the taxa are clearly segregated on the basis of
their distinguishable characters except that of the two subspecies of Pluchea arguta.
The ontogeny of cypselae and their accessory parts were examined using light and scanning electron microscopy for the species Campuloclinium macrocephalum, Chromolaena stachyophylla, Mikania micrantha, Praxelis pauciflora, Symphyopappus reticulatus, and Vittetia orbiculata, some of these being segregated from the genus Eupatorium. A layer of phytomelanin observed in the fruit appears to be secreted by the outer mesocarp into the schizogenous spaces between the outer and inner mesocarp; its thickness was observed to vary among the different species examined. The bristles of the pappus are vascularized, except in M micrantha, and have cells that are superficially projected and arranged acropetally; in S. reticulatus some of the projections are retrorse and a fracture line on the floral disk that is only seen in this species may indicate a double dispersal process. Numerous differences observed among the cypselae examined here reinforce earlier segregations of the genus Eupatorium sensu lato.
Incluye bibliografía e índice
The Calea teucriifolia group is composed by four species of the tribe Neurolaeneae (Asteraceae). Despite numerous attempts to taxonomically understand this group of species through macromorphological characters, no progress has been made due to the overlapping of these characters. Therefore, we propose to evaluate the taxonomic values of cypselae morphology and anatomy for this group. Studies focused on cypsela have represented an advance, since patterns of phytomelanin deposition, pericarp and pappus morphology have allowed classifications within Asteraceae. Our results demonstrate that the cypselae of the analyzed group have a high morphological uniformity. Hence, cypsela morphology does not have characters that support separation of the species. However, the patterns of phytomelanin deposition in this group represent an anatomical novelty in Calea, and perhaps, in Neurolaeneae. The Calea teucriifolia group has the same deposition pattern observed in the tribe Eupatorieae. New systematic approaches are needed to solve taxonomic questions in the Calea teucriifolia group, and an expansion of the cypsela anatomical studies of the Neurolaeneae genera could demonstrate whether the Eupatorieae phytomelanin pattern of deposition could correspond to an apomorphy for the tribe.
Comparative studies of cypselae from Asteraceae have revealed traits of high taxonomic value. The pappus structure, cypsela shape, indument, pericarp structure and its variations between groups are robust features that help assessing the family's evolutionary history. Systematic knowledge has advanced in the subtribe Lychnophorinae (tribe Vernonieae), and the evolution of specific structures has been debated. Thus, we carried out the first morphoanatomical study of the cypselae in Piptolepis (Lychnophorinae), searching for morphological variations to help classify the group and understand its evolutionary history. Cypselae were studied using scanning electron microscopy and historesin inclusion techniques. Our results showed that collenchymatic tissue in the outer mesocarp in Piptolepis distinguishes it from other Vernonieae studied so far. Furthermore, some pappus characteristics such as type, number of series, duration, and lateral projections, and cypsela features such as shape, presence of crystals in the outer mesocarp and occurrence of carpellary bundles may help identify some closely related species. A vestigial pappus series in Piptolepis shed light on the evolutionary history of genus and Lychnophorinae as a whole.
The aims of this study were to describe and illustrate cypselae of 15 Mexican species of Mutisieae from observations using optical and scanning electron microscopy. The cypselae are heteromorphic with pilose, sericeous or glandular indumentum. The primary sculpture of the surface has two microstructural patterns: reticulate and plicate. The secondary sculpture is striate in 13 taxa, but in two species, Chaptalia estribensis and C. mexicana, differences were found in the secondary sculpture of the external and internal cypselae. The most distinctive anatomical trait is in the epicarp, which has rectangular or square-shaped cells that have a convex periclinal wall in most species of Chaptalia. The mesocarp has vascular bundles with fibers in all species of Chaptalia, but fibers are absent in Adenocaulon, Gerbera and Leibnitzia. In addition, the cells of the mesocarp inner layer have either thick walls or only an anticlinal wall in nine species of Chaptalia. The micromorphological characteristics of the primary or secondary sculpture of the surface, the type of trichomes and the variation they present have taxonomical value for recognizing closely-related taxa, whereas anatomical traits of the mesocarp distinguish Adenocaulon, Gerbera and Leibnitzia from most Chaptalia species.
The development of the phytomelanin layer in the achenes of Ageratum conyzoides (Compositae, Eupatorieae) was studied using light and electron microscopy. At the level of the embryo sac, the young ovary wall contains an outer zone, consisting of an epidermis and two hypodermal layers, and an inner zone, consisting of developing fiber cells and 3–5 layers of parenchyma. A schizogenous space forms between the developing fibers and the inner hypodermis at about the time that the embryo sac is fully organized. At this stage, the developing fibers contain papilla which are outgrowths that connect the fibers to the inner hypodermal cells. After fertilization, phytomelanin accumulates on the cell walls lining this space. Subsequently, by the time the fruit matures, the phytomelanin fills the space completely and forms a solid, black layer. The surface of the inner hypodermis that faces the space forms a mold; the characteristic peglike projections of the mature phytomelanin layer develop by filling the invaginations between the hypodermal cells. During phytomelanin accumulation, abundant smooth endoplasmic reticulum is present in the hypodermis, especially in the outer layer. It is hypothesized that the precursors of the phytomelanin are synthesized in this endoplasmic reticulum and that these precursors migrate into the space where the phytomelanin is polymerized.
Surface and some anatomical characteristics of mature cypselae in four genera and 12 species members of the subtribe Leiboldiinae were analyzed, through light and scanning electron microscopy, with the aims of testing their diagnostic value in the taxonomical delimitation, and for this reason also studied related genera of Vernonieae which corresponds to 13 genera and 15 species grouped in seven subtribes. In addition to performing a detailed description of cypselae surface and anatomical characteristics, their potential taxonomical value is discussed. Most Leiboldiinae have prismatic cypselae, but when combined with the number of ribs and surface characteristics, species or genera can be identified. For example, Stramentopappus has obovate glabrous cypselae without a carpopodium compared with the other members of this subtribe. Bolanosa has a sericeous glandular indumentum, and Leiboldia has glands at the base of the cypselae and reticulate primary sculpture. The species of Leiboldiinae and other subtribes of Vernonieae here studied with crystals have prismatic ones contrary to the ones previously described for the Neotropical Vernonieae that were considered raphides.
Genus Inula L. is paraphyletic and heterogeneous with respect to several diverse characters, which makes delimiting taxa difficult. Dittrichia Greuter, Limbarda Adans. and Pulicaria Gaertn. were previously located in different sections within Inula, and subsequently segregated into separate genera. According to the latest molecular phylogenetic analyses based on plastid and nuclear DNA sequence data, supported by morphological and karyological data, it is suggested that type species of genus, Inula helenium L., should be separated from the remaining species to form a separate genus. The goals of this research are to (1) perform comparative micro-morphological and anatomical analysis of fruit and receptacle of species belonging to Inula, Pulicaria, Dittrichia and Limbarda genera in order to estimate their systematic value; (2) define further characters that would be useful in taxonomic delimitation of species that are often misidentified due to their morphological similarities; (3) investigate whether all these characters support the segregation of I. helenium into a separate genus. Using stereoscopic, light and scanning electron microscope, micro-morphological and anatomical characters of cypsela and receptacle were revealed. Cross sections of mature fruit were obtained using cryotechnic procedure. This study pertains to the evaluation of examined characters using correspondence analysis. The species’ characters, as well as those specific to the genera are identified and described. The findings reveal that the organisation of sclerenchyma tissue in a fruit and receptacle characteristics are features that tend to be diagnostic for genera. The results yielded by this study provide valuable criteria for delimitation of taxa belonging to Compositae tribe Inuleae, which are often misidentified due to their morphological similarities. Our results, based on anatomical and micro-morphological characteristics of the fruit and receptacle, also revealed that I. helenium can be distinguished as a separate taxon with equally small percentage of statistical support as Dittrichia, Limabarda and Pulicaria had.
The phytomelanin layer on the pericarp of cypselae (achenes) of many members of traditional Bidens and Coreopsis, both considered polyphyletic, was studied with the help of scanning electron (SEM) and light (LM) microscopes. It is found to be more prominent in taxa kept within Bidens than in Coreopsis. The black ‘peg-like’ phytomelanin found in traditional members of Bidens is also found in some members of Coreopsis. Some traditional members of Coreopsis display distinctive pericarp morphology but lack phytomelanin. The pericarp in Bidens is striated, i.e. it is interrupted by longitudinal bands of parenchyma through which the embryo emerges during seed germination. No striation was found in cypselae of traditional Coreopsis. Emergence of the seed in taxa with this type of pericarp morphology is observed to be by rupturing the carpel wall along the sutures. Characteristic morphology of the phytomelanin layer and other cellular secretions on the pericarp in representative species of these genera and segregates as well as the probable adaptive value of this layer and that of the parenchyma is discussed. Coreopsis sect. Tuckermannia (Nutt.) Blake, C. sect. Pugiopappus (A. Gray) Blake, and C. sect. Euleptosyne (A. Gray) Blake, are elevated to the genus Leptosyne DC., while Coreopsis sect. Electra (DC.) Blake is returned to Electra DC. A key to the segregate genera and the remaining sections of Coreopsis as well as new combinations and synonyms are provided.
Phytomelanin is a hard, brown to black, resistant layer found in the pericarp of cypselae of taxa mostly restricted to eight tribes within the Heliantheae alliance of Compositae (also known as the Phytomelanin Cypsela Clade). Sixty-five species in 8 tribes (34 subtribes) were examined for surface sculpturing of the phytomelanin layer and its systematic import. The features examined were presence/absence of striations (longitudinal interruptions in the phytomelanin layer), and the occurrence and detailed characteristics of spines, pegs, and pores. Striations are seen in some Heliantheae s.s. but they are lacking in others; they are completely absent in Eupatorieae. A majority of taxa in the Heliantheae alliance have spiny phytomelanin surfaces except for Bebbia, Silphium, Ambrosia, and Clibadium, in which the phytomelanin is smooth or irregular. Fitchia possesses only calcium oxalate crystals. Most Eupatorieae are characterized by peg-like projections. Because phytomelanin is absent from most other tribes of Compositae, and since the Heliantheae alliance has been shown from molecular phylogenetic analyses to be highly derived, the occurrence of phytomelanin must be regarded as apomorphic within the family. The principal roles of phytomelanin probably involve adaptations for resistance against desiccation and/or defense against predators.
The capitular and floral morphology and anatomy ofBidens L. andCoreopsis L. were studied. All the North American species ofCoreopsis were studied. Selected species ofBidens from North and South America andCoreopsis from South America were included. The results were compared with previous observations on African species ofBidens (incl.Coreopsis). Emphasis was given to character states of the ray florets, paleae, stylearm apices, outer phyllaries, achenes, and pollen
grains. Some of the character states are unique features ofCoreopsis, e.g., globular and elongately conical receptacles, deltoid outer phyllaries, truncate and indistinctly 3–5-dentate, 3–4-lobed
ray florets, narrowly spathulate paleae, subulate paleae with linear-filiform upper half, hairy and apically 3-cleft paleae,
truncate, convex or shallowly conical stylearm apices with the sweeping hairs limited to the area above the stigmatic surfaces
and the orbicular to circular achenes. The cylindric setaceous pappus bristles so commonly encountered inBidens are unknown inCoreopsis. The pappus bristles inCoreopsis are paleaceous but similar, though thicker ones are also found in African species ofBidens (incl.Coreopsis) with winged achenes. Twin-celled hairs (setulae) with differing degrees of wall thickness are found on the achenes ofCoreopsis sect.Pseudoagarista (Mexico and South America),Coreopsis sect.Pugiopappus (California), AfricanBidens with winged achenes (e.g.,B. prestinaria, B. macroptera) and some North AmericanBidens (e.g.,B. aristosa). Similar sclerotic parenchyma make up the achenial wings of species in both genera. These may be interpreted as homologous
structures, indicating the underlying similarity of these taxa and their derivation from a common ancestral stock.
Aim The pappus is one of the most distinctive features of the genera belonging to the sunflower family, and is an efficient mechanism for dispersion by wind. The pappose Holocheilus (seven species) and the non‐pappose Panphalea (nine species) are two genera of the monophyletic subtribe Nassauviinae (Asteraceae, Mutisieae), which overlap in their areas of distribution. This paper aims to reconstruct the biogeographical histories that shaped the distribution of these two genera, which are phylogenetically and geographically related, but differ in their means of dispersion. Our initial expectation was that the dispersion capability of the pappus should be reflected in more dispersal events in Holocheilus than in Panphalea .
Location South‐eastern Brazil, Paraguay, Uruguay and Argentina.
Methods Morphological data were acquired from the literature and by analysis of specimens. Two cladistic analyses, one for Holocheilus and one for Panphalea , were based on morphological characters, and data matrices were analysed with the Fitch parsimony algorithm of paup . The ancestral distributions were reconstructed using diva ver. 1.1 according to the dispersal–vicariance optimization method.
Results The Paranense‐fields were identified as the most likely ancestral area of Holocheilus and Panphalea . Biogeographical reconstruction of Holocheilus shows several dispersal events from the Paranense‐fields: two ancestral dispersal events to the Yungas, followed by vicariance events (Paranense‐fields/Yungas) and numerous terminal dispersals to the surrounding areas such as Chacoan, Pampean and Espinal. diva reconstruction of Panphalea distribution also shows frequent terminal dispersals, with no vicariant events, from the Paranense‐fields to the other areas: (1) to Espinal, Pampean‐Uruguayan, Pampean‐oriental; (2) to Paranense‐hills; (3) to Pampean‐Uruguayan; and (4) to Paranense‐pine lands.
Main conclusions In the past, both genera probably originated in the Paranense‐fields area, which was subject to the dry and humid cycles of the Quaternary glaciations. Dispersal was the process that predominantly shaped the distribution of Panphalea and Holocheilus , with approximately the same number of dispersal events in both genera, despite differing ranges of dispersion. The main barriers to dispersal were the dry Cerrado and Chaco, the latter promoting vicariance in Holocheilus . The lack of a pappus in Panphalea was a limitation for its dispersion compared with Holocheilus .
1.
The polychromatic staining of plant cell walls by toluidine blue O is described and illustrated.
2.
The effects of various common fixatives and the effects of the pH of the staining solution are evaluated.
3.
Simple and rapid procedures are described for preparing stained temporary mounts of fresh material, or permanent mounts of embedded and sectioned material.
4.
The relationship between the polychromatic staining observed and the lignification of the walls is discussed.
This accessible, comprehensive glossary covers all the descriptive terms for plants that one is likely to encounter in botanical writing, including everything from magazine articles to plant field guides, scientific papers, and monographs. An essential companion, it presents 3,600 botanical terms, accompanied by full definitions and detailed illustrations to aid in identification, all laid out in a clear, easy-to-use fashion. It will be indispensable for plant scientists, conservationists, horticulturists, gardeners, writers, and anyone working with plant descriptions, plant identification keys, floras, or field guides.
This paper surveys common problems associated with the preparation of animal tissues so that natural or artificial surfaces may be studied in the scanning electron microscope (SEM). Problems arise because (1) we need to prepare surfaces free from extraneous solids in solution (e.g. mucus, blood, tissue fluid); (2) surfaces of simple sections generally do not reveal significant information so that other methods of ‘opening up’ internal organization must be developed; (3) we need to remove the preponderant tissue component—water—without significantly altering the remaining structure, which generally has a very low density, is fragile and is non‐conducting.
In the case of natural, free surfaces to soft tissues, isolated cells or cultures the most useful approach seems to be (a) to wash with a suitable isotonic medium; (b) to fix with an aldehyde; (c) to harden with Parducz's (1967) OsO 4 , HgCl 2 fixative.
Artificial surfaces revealing details of internal organization are best prepared by dissecting and ripping aldehyde‐perfused and fixed tissue; the duration of fixation has been found to influence the location of the ripping planes in CNS. Enzymatic digestion may usefully be combined with dissection, but must be conducted before fixation.
Wet tissue surface is least distorted following freeze drying from a non‐polar solvent (e.g. amyl acetate) which has substituted the tissue water. Critical‐point drying requires simple apparatus and is also generally satisfactory, but it does cause some bulk shrinkage.
Specimens are best coated with a combination of carbon and gold to render them conducting: carbon because it is easily scattered and thus tends to cover very rough surfaces, and because it is tough and stabilizes the surface; gold because it is the most convenient heavy metal having high secondary‐electron emission to evaporate.
Dried soft tissues have very low bulk densities, and beam‐penetration artifacts (bulk charging and edge artifacts) are therefore troublesome. These may be limited by working at as low an accelerating beam voltage as can be tolerated to achieve the required resolution. The preparation and examination of stereo‐pair micrographs is recommended as a routine because images can then be interpreted in terms of topography alone, and brightness variations of artifactual or unknown origin can be mentally excluded.
Ed) The Families and Genera of Vascular plants
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G., Nordenstam, B., Oberprieler, Ch., Panero, J.L., Puttock, C., Robinson, H., Stuessy,
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Morfoanatomia comparada e ontogenese do pericarpo de Bidens gardneri Baker e B. pilosa L. (Asteraceae)
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Development and structure of phytomelanin in Coreopsieae (Asteraceae)
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Mathur, R.R., Pandey, A.K., 2020. Development and structure of phytomelanin in
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