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Diversity of Pappus structure in some tribes of the Asteraceae
Abstract and Figures
The structures of pappus in 52 species belonging to 30 genera of the subfamilies Mutisioideae, Carduoideae,
Pertyoideae and Cichorioideae have been studied critically with the help of both light microscope and SEM.
The number of studied species in each tribe is indicated in parentheses: Mutisieae (l), Dicomeae (l), Pertyeae
(2), Cardueae (12), Lactuceae (15), Vernonieae (18), and Arctoteae (3).
Pappus structures can be divided into four categories with the pappus elements consisting of l) scales, 2)
bristles, 3) crowns, or coronas, and 4) awns. Combinations of and modifications within the groups occur
in the family, e.g., bristles may be smooth, barbellate or plumose. In ths taxa studied, pappus bristle is the
most prevalent type, whereas true
, coronate type is essentially absent. Pappus may be homomorphic or
heteromorphic; eithef ananged in one, two or three rowsl .either persistent or caducous. Sometimes the apical
part of the pappus is especially significant for distinction of tar<a (e.g., Sonc'hus spp.) or the-basal part of
the pappus is different in ray and disc cypsela (e.g., Hypochaeris glabra). Vascular traces are not usually
visible within the pappus structure, but are noted in Arclotis and' Catananche.
The role of pappus structure in the evolutionary context is briefly discussed. A table based on the present
survey presents the exomorphic variation of pappus and its possible evolutionary pathways.
Keywords : Pappus structure; Asteraceae; Gichorioideae s. lat.
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... The taxonomic usefulness of seed and fruit morphology is variable between plant groups; however, compared with many vegetative and floral structures, seed coat and fruit morphology show very low phenotypic plasticity and less affected by environmental conditions (Barthlott 1984;Zorić et al., 2010). Achenes of Asteraceae have a variety of shape, size, pappus, ribbing pattern and surface sculpturing, representing useful taxonomic tools for classification and delimitation of various taxa from species to tribal level (Zhu et al., 2006;Kreitschitz & Vallès, 2007;Mukherjee & Nordenstam, 2008;Savadkoohi et al., 2012;Roque & Funk, 2013;Zhang et al., 2013;Akcin & Akcin, 2014;Bona, 2015;Behjou et al., 2016;Ghimire et al., 2016;Karanovic et al., 2016;Şirin et al., 2017;Ozcan & Akinci, 2019). In Egypt, Asteraceae contributes about 10.3% (nearly 333 taxa) of the flora of Egypt (Boulos, 2009); while it contributes 13% of the flora of the Northwestern Mediterranean coast of Egypt (126 species belong to 70 genera). ...
... Morphological data from the pappus are taxonomically useful for assessing relationships among species and have helped to reveal evolutionary relationships among and within genera of Asteraceae (Mukherjee & Sarkar, 2001;Semple & Hood, 2003Semple, 2006;Abid & Zehra, 2007;Abid & Qaiser, 2007Mukherjee & Nordenstam, 2008;Bona, 2015;Şirin et al., 2017). It may also contribute to the wind-dispersal of the seeds (Azuma, 2006;Stille et al., 2016). ...
THIS STUDY aimed to characterize the external morphology of achenes of the 74 taxa belonging to 51 genera and four subfamilies of Asteraceae from the Northwestern Mediterranean coast of Egypt. By using light microscopy, 26 quantitative and qualitative morphological characters were recorded. Among the studied taxa, achene symmetry, hairiness, surface topography, hilum position, presence or absence of pappus and pappus type were found significant diagnostic characters for delimiting the taxa. Two main groups were identified based on the presence or absence of hardened fruiting involucre. Four types and four subtypes were recognized: (1) Achene di- or trimorphic per capitulum, (2) Achene monomorphic and lacking pappus, (3) Achene monomorphic, with coroniform or auriculate pappus, (4) Achene monomorphic, with pappus. A description, photographs and identification keys were provided to assist in identification. Despite the taxonomic significance of achene exomorphology characters on the generic and specific level for the recognition of the different studied taxa of Asteraceae, no mutual link was shown between the taxonomic division of the family into subfamilies and tribes except for few cases.
... Also, the pappus is a taxonomically important and useful organ in Asteraceae [11]. Cypsela or achene study has been utilized by many authors successfully for the delimitation of genera and species within the family Asteraceae from different parts of the world such as; [12] study macro and micromorphological characters of cypsela in seven species of tribe Anthemideae [13] study the achene characters of 11 species representing five genera of Anthemideae [14] study the data on morphological, histological and scanning electron microscopic for cypsela of 23 species belonging to nine sub-tribes of the tribe Heliantheae [15] study the structures of pappus in 52 species belong to 30 genera of four subfamilies of Asteraceae by using light and scanning electron microscope [16] study the cypsela morphology for five species of tribe Mutisieae from Pakistan [17] study achene macro and micromorphological characters for five species belong to Senecio jacobaea group [18] study the cypsela morphology of 30 taxa of Lactuca L., Cicerbita Wallr. and Prenanthes L. from Pakistan [19] study the achene wall anatomy and surface sculoturing of 12 taxa belong to genus Launaea Cass from Egypt [20] study the achene surfaces of 31 taxa belonging to the genus Centaurea L. from Turkey [21] study achene surface sculpturing and pappus ultrastructure of 26 Crepis taxa from Turkey and [22] study the achene macro-and micromorphologies characters for 22 taxa of the genus Cota from Turkey by using stereo and scanning electron microscope (SEM). ...
... Long and high magnification was performed to capture the recognized features of the specimen. The terminology of [17,[29][30][31] was adopted to describe the SEM aspects of the achene coat, and the terminology of [15] for pappus types. ...
... was used for photomicrographs digitally taken at the Electron Microscopy Unit at the National Research Centre, Dokki, Egypt. The terminology for the cypsela, abaxial epidermis, and stomata used in this study follows Barthlott [54], Garg and Sharma [55], Mukherjee and Nordenstam [56], and Dilcher [57]. In addition, all morphological characters regarding the leaf, cypsela, and trichomes were documented to create classical keys. ...
... was used for photomicrographs digitally taken at the Electron Microscopy Unit at the National Research Centre, Dokki, Egypt. The terminology for the cypsela, abaxial epidermis, and stomata used in this study follows Barthlott [54], Garg and Sharma [55], Mukherjee and Nordenstam [56], and Dilcher [57]. In addition, all morphological characters regarding the leaf, cypsela, and trichomes were documented to create classical keys. ...
The verification of taxonomic identities is of the highest significance in the field of biological study and categorization. Morpho-molecular characterization can clarify uncertainties in distinguishing between taxonomic groups. In this study, we characterized five local taxa of the genus Cichorium using morphological and molecular markers for taxonomic authentication and probably future genetic improvement. The five Cichorium taxa grown under the Mediterranean climate using morphological traits and molecular markers showed variations. The examined taxa showed a widespread range of variations in leaf characteristics, i.e., shape, type, texture, margin, and apex and cypsela characteristics i.e., shape, color, and surface pattern. The phylogenetic tree categorized the Cichorium intybus var. intybus and C. intybus var. foliosum in a single group, whereas C. endivia var. endivia was grouped separately. However, C. endivia var. crispum and C. endivia subsp. pumilum were classified as a cluster. The recorded variance between classes using the molecular markers SCoT, ISSR, and RAPD was documented at 34.43%, 36.62%, and 40.34%, respectively. Authentication using molecular tools proved the usefulness of a dichotomous indented key, as revealed by morphological identification. The integrated methodology using morphological and molecular assessment could support improved verification and authentication of the various taxa of chicory. It seems likely that the Egyptian chicory belongs to C. endivia subsp. pumilum.
... It protects the ovary and fruit from predation and is involved in anemochory and zoochory (Mukherjee and Nordenstam 2008 and references therein). Moreover, the structure and arrangement of pappus elements have long been used to delimit tribes, genera and other taxa in Asteraceae (Small 1918;Nesom 1993Nesom , 2000Mukherjee and Nordenstam 2008;Marzinek and Oliveira 2010;Frangiote-Pallone and de Souza 2014;Talukdar 2015;Silva et al. 2018). Interestingly, Shaukat et al. (2004) evidenced that the removal of pappus decreases the final percentage of seed germination due to decreased hydration of the fruits in Vernonia cinerascens Sch. ...
In Solidago, the pappus, a modified calyx, protects ovary and fruit from predation and is strongly involved in anemochory. In this study, we aimed to test the hypothesis that the mechanical removal of pappus decreases the final percentage and speed of seed germination. We examined S. ×niederederi, a natural hybrid between invasive S. canadensis and native S. virgaurea, in comparison to its parental species and S. gigantea. We conducted a 21-day germination test in the laboratory, using 50 fruits with intact pappus and 50 fruits with removed pappus in four replicates, for each taxon. The statistical analysis demonstrated that the final percentage of germinated seeds was remarkably lower in the group of fruits with removed pappus in S. canadensis (p ≤ 0.05) and S. gigantea (p ≤ 0.05). Moreover, the speed of seed germination was also significantly lower after pappus removal in S. canadensis and S. gigantea, based on the Timson’s index (p ≤ 0.05). In the case of S. ×niederederi and S. virgaurea, the hypothesis was rejected. We assumed that the small size of the cypselae could be responsible for the negative effect of pappus removal on seed germination.
... Susanna and Garcia-Jacas, 2009). Within the Carduinae, the pappus bristles exhibit structural features which help in the delimitation of genera (Häffner, 2000;Mukherjee and Nordenstam, 2008). The pappus is formed by scabrate cylindrical bristles in Berardia and Staehelina, plumose or barbellate bristles in the Carduus-Cirsium group, very long plumose bristles in the Cynara group, very long conspicuous plumose bristles in the Jurinea-Saussurea group, and plumose bristles in the Onopordum group (Susanna and Garcia-Jacas, 2009). ...
Comparative micromorphological analyses were conducted on five members of the Xeranthemum group, both perennial (Amphoricarpos exsul and Shangwua masarica) and annual (Chardinia orientalis, Siebera pungens and Xeranthemum inapertum), using scanning electron microscopy (SEM) and SEM coupled with an energy-dispersive spectrometer (SEM-EDS) in order to evaluate whether micromorphological characters correlate with current phylogenies. “Puzzle-like” epidermal cells at the adaxial leaf surface with smooth outer periclinal walls and slightly sinuate anticlinal walls, and lack of weddellite crystals on the involucral bracts are shared by A. exsul and Sh. masarica and Sh. denticulata, while sinuate anticlinal adaxial leaf epidermal cell walls, weddellite crystals on the involucral bracts and an aristato-paleaceous pappus link together Ch. orientalis, S. pungens and X. inapertum. The following traits are probably species-specific: a glabrous adaxial leaf epidermis and cypsela surface, and a plumose-setose pappus in Sh. masarica; a barbate-aristate pappus in A. exsul; irregular shape of cells of the adaxial leaf epidermis with cuticular corrugations, and a papillose cypsela surface in Ch. orientalis; channeled anticlinal borders of adaxial leaf epidermal cells, and wax deposition on the surface of involucral bracts in X. inapertum; and strongly ribbed thickenings of outer periclinal adaxial leaf epidermal cell walls and involucral bracts with a whitish patch of appressed trichomes on their central surface in S. pungens. All of the examined species exhibit vermiform trichomes on the stems and on the abaxial leaf surfaces, adaxial detachment area of cypselae, an asymmetrical carpopodium and direct insertion of the pappus to the pericarp. Our results revealed valuable qualitative characters that facilitate species identification and contribute to a better understanding of relationships between genera. Optimization of these traits onto phylogenetic analyses suggests that some characters found on leaves and involucral bracts are likely due to adaptations of perennial ancestors to xeric habitats.
... Pappus features have been traditionally used to define genera within Asteraceae (Mukherjee & Nordenstam 2008). In Cardueae, the pappus consists of scales or bristles that are directly attached to the pericarp wall in the basal subtribes Cardopatiinae, Carlininae, and Echinopsinae, as well as in Berardia, Staehelina, and genera of the Xeranthemum group of Carduinae. ...
The paper presents micromorphology of the cypselae of Xeranthemum cylindraceum as revealed by scanning electron microscopy (SEM) and their fatty acid composition as determined on a gas chromatograph coupled with a flame ionisation detector (GC-FID). The cypselae are densely hairy, straight, ribbed, narrowly obconical to obovoid. Micromorphological features are as follows: striate-rugose surface; adaxial detachment area; asymmetrical carpopodium; presence of nonglandular, shortly forked twin hairs; and absence of a pericarp crown. The pappus is paleaceous, homomorphic, uniseriate, persistent, and with several wide, scarious, subulate, and apically pinnulate bristles of variable length. Out of 12 fatty acids detected, nine (88.57%) are identified, ranging from palmitoleic (C16:1) to behenic (C22:0) acids. Oleic acid is dominant (55.24%). Unsaturated fatty acids are predominant in the oil (75.02%). The composition of fatty acids in cypselae of the given species is here reported for the first time. The taxonomic value of the analysed characters is briefly discussed.
CV of Prof. Sobhan Kumar Mukherjee, Retd. Professor, Department of Botany,University of Kalyani, Kalyani -741235,West Bengal, India.
Dispersal is an important life history component. Seed settling velocity may be a useful surrogate for the measurement of dispersal ability in wind-dispersed plants, particularly those whose seeds have plumose dispersal structures. I measured settling velocities on seeds of eight species of Asteraceae, including annuals, biennials, and perennials, and including both native and introduced species. The species are Aster exilis, Picris echioides, Chrysopsis villosa, Heterotheca grandiflora, Conyza bonariensis, Sonchus oleraceous, Senecio vulgaris, and Taraxacum officinale. From these data I estimated components of total variation in seed settling velocities due to differences among species, among plants within species, and among inflorescences and seeds within plants. Significant amounts of variability were found at all levels. Contrasts among mean settling velocities showed that the five introduced species have lower settling velocities than the three native species; this result continues to be true when annuals are considered separately from biennials and perennials. Also, over all eight species, annuals have lower settling velocities than biennials and perennials. Variability among species apparently reflects different dispersal “strategies” employed by the species; these different strategies may be correlated with other life-history traits and with ecological characteristics. Variability within species also may have ecological consequences in that such variability may represent an example of risk-spreading.
I made measurements of morphology and settling velocity on seeds of 19 species of wind-dispersed Asteraceae. From the morphological measurements I calculated Reynolds numbers and approximate plume loadings for the species. Diaspore settling velocity increases linearly with the square root of plume loading. This relationship varies among species and among subfamilies, but not among life history types. Reynolds number is highly variable among subfamilies, less so within subfamilies. Diaspores with beaked achenes have significantly lower settling velocities than diaspores with unbeaked achenes, even though beaked and unbeaked achenes do not differ in plume loading or in Reynolds number. Reynolds numbers of all diaspores examined are well above the range in which Stokes' Law applies. I recommend that the use of formulae based on Stokes' Law be curtailed in studies of the relationship between plume loading and settling velocity. The results suggest that many seed characters may have evolved due to selection on dispersal ability. This is in spite of phyletic constraints on morphology reflected in the relative uniformity of Reynolds numbers within subfamilies.
The Eupatorieae and Vernonieae differ in pubescence, leaf insertion, leaf shape and venation, corolla lobe form, anther bases, anther pubescence, endothecial cells, pollen grains, style branches, achene walls, and pappus. The Eupatorieae are related to the Heliantheae in the subfamily Asteroideae, and the Vernonieae are placed close to the Liabeae and Mutisieae in the subfamily Cichorioideae.