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A-F, Poales: A-B. Typhaceae: A. Typha minima, rhiz, CC, endo BGVepifl, bar= 650μm, inset endo CBs, BGVepifl bar = 80μm. B. T. latifolia, rhiz CC, BGVepifl, endo, bar= 650μm; T. glauca, right inset, endo SL, SR7Bbrfld bar = 80μm, T. angustifolia, left inset, LSCWs, BABepifl, bar = 80μm. C. Juncaceae: Juncus effusus, rhiz CC, endo, BGVepifl bar= 650μm, upper inset both endo and exodermis ADbrfld, bar = 100μm; lower inset only endo CBs, ADbrfld, bar = 50μm. D. Cyperaceae: Eleocharis montevidensis, rhiz CC, endo, BGVepifl, bar= 170μm, inset, Cyperus alternifolius, endo BGVepifl, bar = 120μm. E-F. Poaceae: E. Phalaris arundinacea, rhiz CC, endo, BGVepifl, bar= 270μm, inset endo CBs BGVepifl; bar = 110μm. F. Phragmites australis, rhiz, no endo Berepifl, bar= 350μm. G. Commelinales: Pontederiaceae: Pontederia cordata, rhiz CC, BABepifl, bar= 600μm, inset endo BABlcf, bar = 80μm. H-I. Zingiberales: H. Cannaceae: Canna sp., rhiz CC, endo, BGVepifl, bar= 400μm, inset endo CBs, BVGepifl, bar = 100μm. I. Marantaceae: Thalia dealbata, rhiz CC, BTBOepifl, bar= 700μm, inset endo CBs, suberin lamellae, BTBOepifl, bar = 100μm.
Source publication
A sampling of angiosperms across a broad spectrum of families and generas was done to determine if angiosperms from the ANA grade basal angiosperms to the Zingiberales of the monocots and Apiales of the eudicots had an endodermis with demonstrable Casparian bands in shoots because the literature has a paucity of demonstrable images, especially for...
Contexts in source publication
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... French and Tomlinson (1981c, page 720, Fig. 21) noted an endodermis in A. calamus and A. gramineus, only the figure of A. gramineus revealed light micrograph images of CBs. Keating (2003) showed the central cylinder of the rhizome, and Lux et al. (2017, page 132-133, Fig. 67) illustrated a monostelic stem with endodermis and CBs in a brightfield ...
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... Poales: For the Typhaceae of the Poales, members of Typha (T. minima Fig. 6A and inset; T. latifolia, Fig. 6B), had a monostele with an endodermis of CBs surrounding a central cylinder of VBs and fundamental tissue; SL (Fig. 6B right inset, T. glauca) and U-shaped LSCWs ( Fig. 6B left inset, T. angustifolia) eventually characterized this endodermis. This was also seen in the Juncaceae (Juncus, Fig. 6C, upper inset, acid ...
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... Poales: For the Typhaceae of the Poales, members of Typha (T. minima Fig. 6A and inset; T. latifolia, Fig. 6B), had a monostele with an endodermis of CBs surrounding a central cylinder of VBs and fundamental tissue; SL (Fig. 6B right inset, T. glauca) and U-shaped LSCWs ( Fig. 6B left inset, T. angustifolia) eventually characterized this endodermis. This was also seen in the Juncaceae (Juncus, Fig. 6C, upper inset, acid digestion at lower ...
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... Poales: For the Typhaceae of the Poales, members of Typha (T. minima Fig. 6A and inset; T. latifolia, Fig. 6B), had a monostele with an endodermis of CBs surrounding a central cylinder of VBs and fundamental tissue; SL (Fig. 6B right inset, T. glauca) and U-shaped LSCWs ( Fig. 6B left inset, T. angustifolia) eventually characterized this endodermis. This was also seen in the Juncaceae (Juncus, Fig. 6C, upper inset, acid digestion at lower magnification with remnant endodermis and exodermis to right; lower inset, higher magnification of wavywalled CB remnants). In the ...
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... Poales: For the Typhaceae of the Poales, members of Typha (T. minima Fig. 6A and inset; T. latifolia, Fig. 6B), had a monostele with an endodermis of CBs surrounding a central cylinder of VBs and fundamental tissue; SL (Fig. 6B right inset, T. glauca) and U-shaped LSCWs ( Fig. 6B left inset, T. angustifolia) eventually characterized this endodermis. This was also seen in the Juncaceae (Juncus, Fig. 6C, upper inset, acid digestion at lower magnification with remnant endodermis and exodermis to right; lower inset, higher magnification of wavywalled CB remnants). In the Cyperaceae, endodermis was present in ...
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... of Typha (T. minima Fig. 6A and inset; T. latifolia, Fig. 6B), had a monostele with an endodermis of CBs surrounding a central cylinder of VBs and fundamental tissue; SL (Fig. 6B right inset, T. glauca) and U-shaped LSCWs ( Fig. 6B left inset, T. angustifolia) eventually characterized this endodermis. This was also seen in the Juncaceae (Juncus, Fig. 6C, upper inset, acid digestion at lower magnification with remnant endodermis and exodermis to right; lower inset, higher magnification of wavywalled CB remnants). In the Cyperaceae, endodermis was present in Eleocharis ( Fig. 6D) and Cyperus ( Fig. 6I inset); typically rhizomes develop endodermis with LSCWs. In the Poaceae, the genus, ...
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... 6B left inset, T. angustifolia) eventually characterized this endodermis. This was also seen in the Juncaceae (Juncus, Fig. 6C, upper inset, acid digestion at lower magnification with remnant endodermis and exodermis to right; lower inset, higher magnification of wavywalled CB remnants). In the Cyperaceae, endodermis was present in Eleocharis ( Fig. 6D) and Cyperus ( Fig. 6I inset); typically rhizomes develop endodermis with LSCWs. In the Poaceae, the genus, Phalaris, has well-defined endodermis in its rhizomes ( Fig. 6E and inset). Many grasses had no stem endodermis (e. g., Phragmites, Fig. 6F, Table 1). Among the Poales, for Typha, Typhaceae, McManus et al. (2002, page 491 Fig. 1M; ...
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... eventually characterized this endodermis. This was also seen in the Juncaceae (Juncus, Fig. 6C, upper inset, acid digestion at lower magnification with remnant endodermis and exodermis to right; lower inset, higher magnification of wavywalled CB remnants). In the Cyperaceae, endodermis was present in Eleocharis ( Fig. 6D) and Cyperus ( Fig. 6I inset); typically rhizomes develop endodermis with LSCWs. In the Poaceae, the genus, Phalaris, has well-defined endodermis in its rhizomes ( Fig. 6E and inset). Many grasses had no stem endodermis (e. g., Phragmites, Fig. 6F, Table 1). Among the Poales, for Typha, Typhaceae, McManus et al. (2002, page 491 Fig. 1M; page 492, Fig. 2A, G, H, I) ...
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... with remnant endodermis and exodermis to right; lower inset, higher magnification of wavywalled CB remnants). In the Cyperaceae, endodermis was present in Eleocharis ( Fig. 6D) and Cyperus ( Fig. 6I inset); typically rhizomes develop endodermis with LSCWs. In the Poaceae, the genus, Phalaris, has well-defined endodermis in its rhizomes ( Fig. 6E and inset). Many grasses had no stem endodermis (e. g., Phragmites, Fig. 6F, Table 1). Among the Poales, for Typha, Typhaceae, McManus et al. (2002, page 491 Fig. 1M; page 492, Fig. 2A, G, H, I) demonstrated CBs, SL, and LSCWs; for Juncus and other genera of the Juncaceae, Cutler (1969, pages 9, 20, 26) noted that there was "an endodermoid layer, ...
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... magnification of wavywalled CB remnants). In the Cyperaceae, endodermis was present in Eleocharis ( Fig. 6D) and Cyperus ( Fig. 6I inset); typically rhizomes develop endodermis with LSCWs. In the Poaceae, the genus, Phalaris, has well-defined endodermis in its rhizomes ( Fig. 6E and inset). Many grasses had no stem endodermis (e. g., Phragmites, Fig. 6F, Table 1). Among the Poales, for Typha, Typhaceae, McManus et al. (2002, page 491 Fig. 1M; page 492, Fig. 2A, G, H, I) demonstrated CBs, SL, and LSCWs; for Juncus and other genera of the Juncaceae, Cutler (1969, pages 9, 20, 26) noted that there was "an endodermoid layer, but sometimes cells have U-shaped wall thickening and mark off ...
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... Zingiberales:Pontederia (Commelinales, Pontederiaceae, Fig. 6G and inset), Canna of the Zingiberales, Cannaceae (Fig. 6H and inset), and Thalia (Zingiberales, Marantaceae, Fig. 6I and inset) had monosteles. In Pontederia and Canna the endodermis had only CBs whereas in Thalia CBs were usually associated with SL ( Fig. 6I inset, visible on inner and outer tangential walls in most cells of ...
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... Zingiberales:Pontederia (Commelinales, Pontederiaceae, Fig. 6G and inset), Canna of the Zingiberales, Cannaceae (Fig. 6H and inset), and Thalia (Zingiberales, Marantaceae, Fig. 6I and inset) had monosteles. In Pontederia and Canna the endodermis had only CBs whereas in Thalia CBs were usually associated with SL ( Fig. 6I inset, visible on inner and outer tangential walls in most cells of ...
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... Zingiberales:Pontederia (Commelinales, Pontederiaceae, Fig. 6G and inset), Canna of the Zingiberales, Cannaceae (Fig. 6H and inset), and Thalia (Zingiberales, Marantaceae, Fig. 6I and inset) had monosteles. In Pontederia and Canna the endodermis had only CBs whereas in Thalia CBs were usually associated with SL ( Fig. 6I inset, visible on inner and outer tangential walls in most cells of ...
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... Zingiberales:Pontederia (Commelinales, Pontederiaceae, Fig. 6G and inset), Canna of the Zingiberales, Cannaceae (Fig. 6H and inset), and Thalia (Zingiberales, Marantaceae, Fig. 6I and inset) had monosteles. In Pontederia and Canna the endodermis had only CBs whereas in Thalia CBs were usually associated with SL ( Fig. 6I inset, visible on inner and outer tangential walls in most cells of ...
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... Schweingruber et al. (2011, pages 346-349) illustrated endodermis without demonstrable CBs around individual VBs in Primula species, as a monostele in Cyclamen with secondary growth, and in L. thyrsifloraSchweingruber et al. (2020, page 211, Fig. 3) labeled an endodermis but without showing CBs. However, De Micco and Aronne (2012, page 8, Fig. 6g, n) demonstrated CBs in rhizomes of Primula ...
Citations
... La ecorregión Esteros del Iberá está formada por un sistema de esteros, bañados, lagunas someras y cursos de aguas interconectados (Neiff, 2004). En la revisión de su flora, Arbo & Tressens (2002) con tallos erectos o postrados; que crecen en cuerpos de agua como lagunas y esteros, terrenos húmedos e inundados, como llanuras aluviales, suelos arenosos y pantanosos (Sculthorpe, 1967;Cook, 1974;Sosa et al., 2018aSosa et al., , 2018bSosa et al., 2021). ...
... Se destaca la presencia de una capa de endodermis en B. dubia, B. monnieri y en B. salzmannii, carácter descrito anteriormente para B. monnieri donde se menciona además la presencia de un periciclo de 1 o 2 capas en el tallo, carácter que tiende a ser común en las raíces de las plantas, pero en los tallos no es habitual (Varshney et al., 2017). Sin embargo, se observó en los tallos de B. caroliniana, donde se considera que la endodermis del tallo es un rasgo distintivo de las plantas acuáticas o de humedales, derivadas de ancestros terrestres, donde su presencia en las plantas de la base de algunas líneas de angiospermas sugiere que puede haber estado presente al principio de la evolución de las angiospermas (Seago, 2020). Wu et al. (2022) investigaron las características anatómicas e histoquímicas que permitían que Plantago fengdouensis ...
La gran mayoría de las especies de Bacopa (Gratioleae-Plantaginaceae) son plantas macrófitas que presentan una serie de adaptaciones morfológicas, anatómicas y ecofisiológicas en sus órganos vegetativos. Se estudió la anatomía vegetativa de cinco especies de Bacopa presentes en el Iberá y una de humedales del Paraguay. Para el estudio de la anatomía foliar y caulinar se realizaron cortes paradermales y transversales a mano alzada y con micrótomo rotativo a partir de material previamente fijado. Se encontraron diferencias entre las 6 especies de Bacopa analizadas, en la hoja relacionadas a: tipos de tricomas; tipos, distribución y densidad de estomas; y en el tipo de mesofilo. Para el tallo, se caracterizaron dos patrones de aerénquima cortical que se relacionan con los ambientes que habitan las especies y sus adaptaciones al mismo. A modo de conclusión se elaboró una clave dicotómica con caracteres anatómicos vegetativos de las especies de Bacopa que crecen en los humedales.
... An investigation of vascular ontogenies following the present developmental framework reveals distinct categories of vascular variants in both stems and roots of major lineages of seed plants. For instance, there is a striking stele variation in stems of some Nymphaeales (ANA grade) and Gunnerales (core eudicots), including polycyclic eusteles and siphonostele (Seago 2020;Seago et al. 2021). Mature stems of Apocynaceae (asterids, eudicot) have been reported with 'intraxylary phloem', interxylary phloem, successive cambia and non-cylindrical stems (Acevedo-Rodríguez 2015, onwards; Angyalossy et al. 2015), while young stems are described with siphonosteles, bicollateral bundles and/or medullary bundles (Salas et al. 2018;Sathya et al. 2022). ...
Over centuries of plant morphological research, biologists have enthusiastically explored how distinct vascular arrangements have diversified. These investigations have focused on the evolution of steles and secondary growth and examined the diversity of vascular tissues (xylem and phloem), including atypical developmental pathways generated through modifications to the typical development of ancestral ontogenies. A shared vernacular has evolved for communicating on the diversity of alternative ontogenies in seed plants. Botanists have traditionally used the term “anomalous secondary growth” which was later renamed to “cambial variants” by late Dr. Sherwin Carlquist (1988). However, the term “cambial variants” can be vague in meaning since it is applied for developmental pathways that do not necessarily originate from cambial activity. Here, we review the “cambial variants” concept and propose the term “vascular variants” as a more inclusive overarching framework to interpret alternative vascular ontogenies in plants. In this framework, vascular variants are defined by their developmental origin (instead of anatomical patterns), allowing the classification of alternative vascular ontogenies into three categories: (1) procambial variants, (2) cambial variants and (3) ectopic cambia. Each category includes several anatomical patterns. Vascular variants, which represent broader developmental-based groups, can be applied to both extant and fossil plants, and thereby offer a more adequate term from an evolutionary perspective. An overview of the developmental diversity and phylogenetic distribution of vascular variants across selected seed plants is provided. Finally, the evolutionary implications of vascular variants are discussed.
... Sections were then stained-for example, with berberine hemisulfate-for at least 1 h, rinsed, and viewed or counterstained in aniline blue, gentian violet, or toluidine blue O. Or they were stained in fluorol yellow, Sudan red 7B, or Sudan IV for 1 h and phloroglucinol-HCl for 5 min and digested in acid with 65% H 2 SO 4 (but no acid digestion or Sudan red 7B images are shown here). These procedures and treatments were done according to Brundrett et al. (1988Brundrett et al. ( , 1991, Seago et al. (1999), Lux et al. (2005), Zelko et al. (2012), Soukup (2014), or Seago (2020. The sections on microslides were variously viewed using a Zeiss LSM700 bright-field microscope, UV epifluorescence, a 488-nm laser confocal microscope, or differential interference contrast microscopy. ...
... For example, Caspary originally termed it a Schützscheide, but De Bary (1884) started the general use of the term "endodermis" for cells in a layer of the innermost cortex that have lignified Casparian bands in transverse and radial cell walls (von Guttenberg 1943;Enstone et al. 2003;Soukup and Tylová 2018). While the term "Casparian strip" is often used, we use "Casparian band" in accordance with Schreiber (1996), Schreiber et al. (1999), Enstone et al. (2003), Schreiber and Franke (2011), Soukup andTylová (2018), andSeago (2020). ...
... The endodermoid and stele-cortex wall are not endodermis with manifest Casparian bands (Soukup and Tylová 2018;Seago 2020). Terms like "starch sheath" and "bundle sheath" for an inner layer of cortex or mesophyll have also been included under endodermis (see discussion by Geldner 2013, pp. ...
... In vascular plants, the lignified, suberized endodermis and exodermis act as apoplastic barriers, restricting watersolute exchange, reducing oxygen loss after submersion, and supporting adaptation to terrestrial environments [10,[27][28][29][30][31][32][33][34][35][36][37]. The exodermis has Casparian bands in the primary walls and has suberin lamellae and/or lignin in the secondary walls [27][28][29][30][32][33][34][35]38]. ...
... The endodermis and the exodermis are key impermeable apoplastic barriers that are common in vascular plant roots [28,29,36,37,[63][64][65][66][67][68]. Apoplastic barriers can be histochemically characterized by the presence of Casparian bands, suberin lamellae, and lignin; these barriers protect tissues from oxygen shortages and inhibit watersolute exchanges [18,23,30,34,35,[69][70][71][72][73][74]. ...
We used brightfield and epifluorescence microscopy, as well as permeability tests, to investigate the apoplastic histochemical features of plant roots associated with ion hyperaccumulation, invasion, and tolerance of oligotrophic conditions. In hyperaccumulator species with a hypodermis (exodermis absent), ions penetrated the root apex, including the root cap. By contrast, in non-hyperaccumulator species possessing an exodermis, ions did not penetrate the root cap. In vivo , the lignified hypodermis blocked the entry of ions into the cortex, while root exodermis absorbed ions and restricted them to the cortex. The roots of the hyperaccumulators Pteris vittata and Cardamine hupingshanensis , as well as the aquatic invasives Alternanthera philoxeroides , Eichhornia crassipes , and Pistia stratiotes, contained lignin and pectins. These compounds may trap and store ions before hypodermis maturation, facilitating ion hyperaccumulation and retention in the apoplastic spaces of the roots. These apoplastic histochemical features were consistent with certain species-specific characters, including ion hyperaccumulation, invasive behaviors in aquatic environments, or tolerance of oligotrophic conditions. We suggest that apoplastic histochemical features of the root may act as invasion mechanisms, allowing these invasive aquatic plants to outcompete indigenous plants for ions.
... the Casparian strip endodermis in roots (Tomescu, 2021). Esau (1953) and Seago (2020) proposed that a Casparian strip in the stem is required to identify an endodermis. However, studies by Van Fleet (1950) have experimentally induced and inhibited the production of Casparian strips, thus indicating the plasticity of this feature. ...
Evolutionary developmental biology (evo‐devo) explores the link between developmental patterning and phenotypic change through evolutionary time. In this review, we highlight the scientific advancements in understanding xylem evolution afforded by the evo‐devo approach, opportunities for further engagement, and future research directions for the field. We review evidence that 1) heterochrony–the change in rate and timing of developmental events, 2) homeosis– the ontogenetic replacement of features, 3) heterometry–the change in quantity of a feature, 4) exaptation– the co‐opting and repurposing of an ancestral feature, 5) the interplay between developmental and capacity constraints, and 6) novelty– the emergence of a novel feature, have all contributed to generating the diversity of woods. We present opportunities for future research engagement, which combine wood ontogeny within the context of robust phylogenetic hypotheses, and molecular biology. This article is protected by copyright. All rights reserved.
... In addition, suberized tissues like cork protect the plant organs, roots in particular, against various stresses such as exposure to drought, increased salt concentration, microbial invasion, wounding, and pollutants by heavy metals (Vishwanath et al., 2015). Recently, biological barriers (mainly in roots) were deemed to be a key targets for breeding salt tolerant crops (Cui et al., 2021), however they also might occurs in shoots (Lersten, 1997;Seago Jr, 2020). A well-developed apoplastic barrier might result in an energy-efficient salt adaptation process (Munns et al., 2020). ...
Senescence of plant tissues is a physiologically synchronized process that enables an evergreen or a perennial plant to retrieve, recycle and remobilize nutrients from elder to younger tissues or upcoming seeds. The succulent perennial halophyte S. quinqueflora utilizes this process to discard excess salt being accumulated in outer tissues of their leafy stems. The exact mechanism for salt shedding in this plant, however, remains elusive. In this work we show that the plant develops two distinct types of tissues - an endodermis-like layer (suberized layer, ED), and an additional internal photosynthetic layer (IP) - to enable this process. Their potential roles toward salt-coping strategy were investigated in this study. We show that elevated salinity leads to an accelerated development of the ED, and that its development strongly affected ion partitioning between outer (senescent) and inner (non-senescent) tissues. A positive correlation between the ratio of ED to a bead diameter and the outer to inner concentration of Na+ was observed. These ratios were highest in older (basipetally-located) beads and progressively decreased towards the tip. Furthermore, the Na+/ K+ ratio in inner tissues of bottom beads at highest salinity treatments (800 and 1000 mM NaCl) that showed clear senescence symptoms was ∼1.0, indicative of complete separation of the outer and inner tissues at late developmental stage due to the fully suberized ED multilayer. A dual-sources: dual-sinks model explaining the role of the IP layer in plant adaptation to salinity is presented.
... 34, 35). Most recently, a summary demonstration of endodermis and its Casparian bands around the vascular tissues in species of Gunnera has been done by Seago (2020). ...
... Following the limited illustrations of shoot endodermis and vascular tissues by Seago (2020), the purpose of the present study is to provide a more detailed study of the evidence for endodermis with Casparian bands and the nature of the vasculature of representatives of the six subgenera of Gunnera. This will extend beyond stems to include leaf petioles, leaf lamina where possible, and roots for representative species of Gunnera (Gunneraceae, Gunnerales), at the base of the core eudicots, as per Soltis et al. (2003), Chase et al. (2016), Bacon et al. (2018), Soltis et al. (2018), andStevens (2018). ...
... Among the angiosperms, the genus, Gunnera, has unique anatomical characteristics. The organization and structure of the vascular tissues, or stele, in stems, leaf petioles, and roots stand out from other genera of eudicots and angiosperms (see e. g., Metcalfe andChalk, 1950a, b, 1979;Esau, 1953Esau, , 1977Metcalfe, 1960;Von Guttenberg, 1960;Fahn, 1990;Gifford and Foster, 1989;Schweingruber et al., 2011Schweingruber et al., , 2013Schweingruber and Börner, 2018;Seago, 2020). The occurrence of several stem stelar types -from simple steles which resemble classic monosteles or ectophloic siphonosteles to steles which strongly resemble fern-like amphiphloic siphonosteles/ solenosteles or dictyosteles -alone makes this genus unique, especially for plants at the base of the core eudicots (Soltis et al. 2003(Soltis et al. , 2018Stevens, 2018). ...
We investigated selected species of the six subgenera of the genus Gunnera (Gunneraceae, Gunnerales, basal core eudicot) in order to confirm and to particularize for this taxon trait specifics on the occurrence of endodermis with Casparian bands in the organs of these representative species and to relate this endodermis to the structure of the vascular tissues. The general presence of endodermis with Casparian bands in stems and the vascular tissue arrangement varying from monostele to complex siphonostele is particularly specific for the genus. Petiolar endodermis was also characteristic and some species even had an endodermis surrounding veins in leaf lamina. Similarity of vascular tissue in stems and petioles in Gunnera species to seedless vascular plants is an interesting structural trait regarding phylogenic position of the genus. Only two species had simple, tetrarch to pentarch root vascular patterns common for eudicots, whereas all others were hexarch to multiple polyarch.
... Barberon 2017). Although an endodermis with CS mainly occurs in roots, it is not uncommon in aerial shoots and leaves (Lersten 1997;Seago 2020) but more often established in subterranean or submersed stems (Dalla Vecchia et al. 1999). In the "rootless" bladderworts, the conductive function of the endodermis has been seemingly transferred from roots into stolons that manifest dynamic developmental processes for roots, shoots, and leaves (Rutishauser 2016(Rutishauser , 2020Reut and Płachno 2020). ...
... Other staining and fluorescence techniques should be applied to improve the identification of CS and to gain insights into their composition (see e.g. Dalla Vecchia et al. 1999;Naseera et al. 2012;Seago 2020). ...
Aims
The carnivorous Utricularia (Lentibulariaceae) has an anatomically simple and seemingly rootless vegetative body. It occupies a variety of wetlands and inland waters and shows a broad range of life forms. Here, we aimed to elucidate structural and functional traits in various hydric conditions. Furthermore, we intended to evaluate morpho-anatomical adaptations in correlation with life forms.
Methods
Morpho-anatomical characteristics typical for hydrophytes of all life forms were investigated by light microscopy on 13 Utricularia taxa, compared to one Pinguicula and two Genlisea taxa, and assessed by multivariate analyses.
Results
Vegetative structures of Utricularia and Genlisea showed reduced cortical, supporting, and vascular tissues. With increasing water table, leaves were thinner, and narrower or dissected, and submerged organs tended to contain chloroplasts in parenchymatic and epidermal cells. In some main stolons, an endodermis with Casparian strips was visible. Large gas chambers, including a novel ‘crescent’ and a special ‘hollow’ aerenchyma pattern, were found in amphibious to free-floating taxa.
Conclusions
The evolutionary transfer of carnivory from aerial to subterranean organs in Genlisea , and even more in Utricularia , coincides with a highly simplified anatomy, which is adapted to a broad variety of hydric conditions and compensates for structural innovations in the uptake of nutrients.
... Additionally, variations in the architecture of the endodermis further broaden the diversity of eustelic vascular architecture (e.g. Seago, 2020). These compounded layers of complexity and diversity have been encompassed in several classification systems (e.g. ...
... This is despite their distinct physiological functions and anatomies, e.g. whether consisting of cells that possess Casparian strips, traditionally associated with endodermal identity (Seago, 2020), or otherwise. Additionally, available evidence suggests that these layers are specified by the same regulatory modules throughout the plant body (reviewed by Tomescu, 2008) and this shared developmental regulation indicates that they may be serially homologous. ...
... An endodermis marked by Casparian strips was thought to be rare in stems with eustelic organization (Esau, 1977). However, such considerations were based on sparse taxon sampling and a recent survey has demonstrated more frequent presence of this anatomical feature across angiosperm diversity (Seago, 2020). Additionally, substantial evidence from anatomy, physiology, and development indicates the presence of a boundary layer that separates two major domains in eustelic axesa central domain that includes vascular tissues (the stele) and an outer accessory domain of ground tissues (cortex) (j and l in Fig. 7) and that provides positional cues crucial for cell fate specification in the establishment of radial patterning. ...
The stele concept is one of the oldest enduring concepts in plant biology. Here, I review the history of the concept and build an argument for an updated view of steles and their evolution. Studies of stelar organization have generated a widely ranging array of definitions that determine the way we classify steles and construct scenarios about the evolution of stelar architecture. Because at the organismal level biological evolution proceeds by changes in development, concepts of structure need to be grounded in development to be relevant in an evolutionary perspective. For the stele, most traditional definitions that incorporate development have viewed it as the totality of tissues that either originate from procambium – currently the prevailing view – or are bordered by a boundary layer (e.g. endodermis). Consensus between these two perspectives can be reached by recasting the stele as a structural entity of dual nature. Following a brief review of the history of the stele concept, basic terminology related to stelar organization, and traditional classifications of the steles, I revisit boundary layers from the perspective of histogenesis as a dynamic mosaic of developmental domains. I review anatomical and molecular data to explore and reaffirm the importance of boundary layers for stelar organization. Drawing on information from comparative anatomy, developmental regulation, and the fossil record, I propose a stele concept that integrates both the boundary layer and the procambial perspectives, consistent with a dual nature of the stele. This dual stele model posits that stelar architecture is determined at the apical meristem by two major cell fate specification events: a first one that specifies a provascular domain and its boundaries, and a second event that specifies a procambial domain (which will mature into conducting tissues) from cell subpopulations of the provascular domain. If the position and extent of the developmental domains defined by the two events are determined by different concentrations of the same morphogen (most likely auxin), then the distribution of this organizer factor in the shoot apical meristem, as modulated by changes in axis size and the effect of lateral organs, can explain the different stelar configurations documented among tracheophytes. This model provides working hypotheses that incorporate assumptions and generate implications that can be tested empirically. The model also offers criteria for an updated classification of steles in line with current understanding of plant development. In this classification, steles fall into two major categories determined by the configuration of boundary layers: boundary protosteles and boundary siphonosteles, each with subtypes defined by the architecture of the vascular tissues. Validation of the dual stele model and, more generally, in‐depth understanding of the regulation of stelar architecture, will necessitate targeted efforts in two areas: (i) the regulation of procambium, vascular tissue, and boundary layer specification in all extant vascular plants, considering that most of the diversity in stelar architecture is hosted by seed‐free plants, which are the least explored in terms of developmental regulation; (ii) the configuration of vascular tissues and, especially, boundary layers, in as many extinct lineages as possible.
Eleutherococcus senticosus (Araliaceae) is widely used as adaptogen in herbal medicine. Since comprehensive anatomical analysis of its vegetative organs was not available, the present study aimed at providing the reference data on the structure of leaves and roots, under- and aboveground stems of 1–4 year-old plants by means of conventional light microscopy. In the primary structure, roots were di- or triarch, with secretory canals facing protoxylem. Concurrently with cambium initiation, additional pericyclic secretory canals differentiated close to the existing ones. In the root secondary structure, secretory canals were formed in the conductive secondary phloem and maintained in the nonconductive one. Stem primary structure encompassed uniseriate epidermis with scant prickles, primary cortex and stele. Primary cortex was composed of collenchyma, chlorenchyma, ground parenchyma with secretory canals and ca. triseriate starch sheath. In outer stele (pericycle) strands of sclerenchyma fibers (stereids) differentiated, alternated with parenchyma. In the ring of open collateral bundles, cambium became continuous concurrently with (sub)epidermal initiation of phellogen. In the wide pith, ground parenchyma occurred, with a few secretory canals close to protoxylem. Secondary structure stems retained the cortical tissues in the 4th year; new secretory canals appeared in the conductive secondary phloem. The epithelial cells/sheath cells complexes were maintained even in the oldest nonconductive phloem (and in the cortex) in stems of 4 year-old plants, while the successively formed sieve tube-companion cell complexes functioned till the end of the vegetation periods only. The bifacial leaves exhibited shade adaptation in chlorenchyma structure; secretory canals were formed mainly in veins’ phloem.
