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DIAPHRAGMS AND AERENCHYMA IN SCIRPUS VALIDUS
Abstract
After the short-lived apical meristem ceases activity, a basal intercalary meristem produces all new tissues in the aerial internode of Scirpus validus Vahl. These include extensions of the original vascular system and of the original partitioning walls as well as new vascular bundles and new walls which are produced in a predictable pattern. Diaphragms begin to differentiate well within the intercalary meristem. At first their cells are indistinguishable from those that will become the aerenchyma, but they undergo segmentation and form packets of daughter cells. Such continued mitotic activity allows the diaphragms to expand with the increasing girth of the stem above the intercalary meristem. Aerenchyma cells between the diaphragms become stellate by being stretched as the cells of the vertical partitions divide and enlarge in and above the intercalary meristem.
... The volume between these partitions increases as the cylinder cells divide and enlarge (Evans, 2003). It has been previously reported that the diaphragms of aerenchyma originate from mother cells in the intercalary meristems of aerial internodes of Scirpus validus and in the leaves of other aquatic plants (Kaul, 1971(Kaul, , 1973Schussler and Longstreth, 1996). Diaphragms often perforate across the air compartments and can exhibit a marked cell dimorphism from surrounding tissues (Kaul, 1971(Kaul, , 1973. ...
... It has been previously reported that the diaphragms of aerenchyma originate from mother cells in the intercalary meristems of aerial internodes of Scirpus validus and in the leaves of other aquatic plants (Kaul, 1971(Kaul, , 1973Schussler and Longstreth, 1996). Diaphragms often perforate across the air compartments and can exhibit a marked cell dimorphism from surrounding tissues (Kaul, 1971(Kaul, , 1973. Diaphragms have also demonstrated functions other than that of supporting stem and cross bundles. ...
... Diaphragms have also demonstrated functions other than that of supporting stem and cross bundles. For example, some diaphragms are photosynthetic (Stant, 1967), carrying laticifers (Stant, 1967) storing tannins (Kaul, 1971), and preventing internal flooding when stems are damaged (Snow, 1914;Soukup et al., 2000). ...
The development of aerenchyma in the petiole of Sagittaria trifolia L. was studied by means of light-microscopy, scanning electron microscope, transmission electron microscope and immunofluorescence, focusing on the formation of intercellular spaces in diaphragms and its relationship with the organization of cortical microtubule arrays. A complex and organized honeycomb-like schizogenous aerenchyma formed by cylinders and vascular diaphragms was observed in the petiole of S. trifolia at different developmental stages. Cell division was the primary factor contributing to the increased volume of air spaces at early stages, while cell enlargement became the primary factor at later stages. The cortical microtubules localize at the sites where intercellular spaces and the secondary cell walls will be formed or deposited during the formation of intercellular spaces by the separation of diaphragm cells. Cortical microtubules were observed at the boundary of diaphragm cells and the fringes of intercellular spaces at later developmental stages where cell expansion occurs rapidly. These observations support the hypothesis that reorganization of cortical microtubule arrays might be related to the formation of air spaces in diaphragms and are involved in the deposition of secondary cell walls.
... Changes in the size of the lacunae, as also recorded by Martins & Scatena (2015) and Santos & Esteves (2004) and presence or absence of small lateral air lacunae do not alter the general architecture of the aerenchyma (spongy simple and mixed, septate with or without vascular bundle in the center) that can be used as a taxonomic character. The architecture of the spongy aerenchyma, present in most of the species analyzed, is considered an efficient adaptation for supporting aerial organs due to the extensive compartmentalization, which provides force and reserve of air at the same time (Williams & Barber 1961;Kaul 1971). ...
... In Eleocharis spp., it is observed that in the four aerenchyma patterns, each air column is associated with at least one vascular bundle and, in general, the number of air lacunae coincides with the number of vascular bundles, especially in the spongy patterns. Kaul (1971) in describing the aerenchyma of the culm of Scirpus validus Vahl (Cyperaceae), recorded a pattern in the distribution of vascular bundles similar to the spongy mixed, here registered for Eleocharis spp, differing, however, by the presence of vascular bundles in the diaphragms. ...
Eleocharis (Cyperaceae) includes more than 300 species of perennial or annual herbs, frequently found on poorly drained soils. The species are morphologicaly similar, and the taxonomy is difficult because their vegetative and reproductive structures are very reduced. Previous study on the stem architecture in the subgenus Limnochloa showed that anatomical features help in the interpretation of the evolution, taxonomy and ecological aspects of the group. Our objectives were to add new characters from the stem (= culm) structure, to explore the characters in a greater number of Eleocharis species, representatives of the other subgenera, and add these data in a new phylogenetic analysis with molecular data. The study covered 68 species obtained from herbaria and fixed material. In addition to the stem architecture, the internal organization of the tissues, the cross-section format, the presence or absence of stretched cells in aerenchyma air gaps and the plant size were included in the morphological analysis. Our data confirm that spongy aerenchyma pattern is the ancestral condition while the mixed and septate patterns occurred independent and punctually. Only the cross-section format was variable among specimens while the other characters were uniform and relevant for taxonomic use.
... Moreover, in the freeze-fractured palisade mes-ophyll of a young bean leaf, the cell walls lining the gas spaces are concave toward the space (Jeffree et al. 1986). Similar space shapes occur in the diaphragms of the shoot internodes in the Scirpus validus (Kaul 1971) or Sagittaria trifolia leaf petiole (Liang et al. 2008). Such cell walls that are bending into the cell lumen cannot be brought under tensile stress by turgor and their growth is likely to be driven by the in-plane wall tension originating from swelling stress (Hejnowicz 2011). ...
... As a result, the spaces enlarge and become elongated in the radial direction (Sego et al. 2005). The arms of the developing stellate aerenchyma cells of the stem internodes in Scirpus are most likely stretched by vertically oriented plates of cells (partitions) in which there are unmatched cell elongations and divisions (Kaul 1971). ...
In this chapter, we discuss various cases of cell and tissue wrinkling or folding from the perspective of a putative mechanism of their formation—tissue folding in the contractile roots; cell or meristem surface folding in phyllotaxis generation; the formation of the stomata pore and various types of gas spaces; the development of jigsaw puzzle-shaped epidermal cells; and the wrinkling of cell wall layers after the removal of tensile stress. We also address the biological role of such shaped cells or tissues and the mechanical property or state of the cell wall or tissue that is manifested by its folding or wrinkling. Buckling and differential growth are likely ways to generate folds or wrinkles. The former is an intuitive mechanism from the mechanical perspective, while the latter derives from biology. Some cases of cell or tissue morphogenesis suggest that locally the two mechanisms may simultaneously contribute to the formation of a wavy shape.
... In allied species C. blepahroleptos, braciform cells also were observed in air lacunae [67]. The braciform cells provide structural support to air lacunae as well partake in the gas flow among distinct tissues of aquatic plants [67,[71][72][73][74][75][76]. ...
Cyperus prophyllatus, an endangered new species of Cyperus (Cyperaceae) from an aquatic ecosystem of the Atlantic Forest, Espírito Santo State, southeastern Brazil, is described and illustrated. The spikelet morphology of Cyperus prophyllatus is unique among the c. 950 species of Cyperus in having both a conspicuous spikelet prophyll and a corky rachilla articulation, which remain persistent at the base of the spikelet after disarticulation. Our molecular phylogenetic data support the placement of C. prophyllatus in the C3 Cyperus Grade and more precisely in the clade representing Cyperus sect. Oxycaryum, which also includes C. blepharoleptos and C. gardneri. Anatomical and (micro)morphological analyses corroborate the phylogenetic results, provide a better understanding of ecology and taxonomy, as well as reveal compatibility of structures with survival and dispersion in aquatic environments. A distribution map, table with distinctive characters of allied species, and conservation status are made available.
... The multipurpose character of aerenchyma, including support, was inherent in many descriptions of this tissue, inc1uding the fIrst comprehensive study of diaphragms in aquatic monocotyledons by DUVAL-JOUVE (1873); however, the transport and storage of oxygen were always emphasized as its main functions. KAUL (1971KAUL ( , 1972, in the most-detailed modern anatomical studies of aerenchyma, valued as "most cogent" the view of WILLIAMS & BARBER (1961) that the main function of aerenchyma composed of diaphragms is mechanical stabilization; however he did not develop this concept further. As far as the author is aware, the mechanical importance of the diaphragm aerenchyma has not yet been proven by biomechanical methods. ...
... Hence, the anatomical features of wetland plants with well-developed aerenchyma in the root cortex were described already at the end of the 1800s and at the beginning of the 1900s (Klinge 1879; Plowman 1906;Kükenthal 1909;Wille 1926). During the twentieth century, the root anatomical structures were described in many wetland plants including the rather extreme developments in, i.e., Scirpus and Carex species (Crawford 1910;Kaul 1971;Fagerstedt 1992). In Carex rostrata Stokes, large portions of the root cortex die and the remaining tangential parts of the cell walls form sheetlike structures (Figure 32.2). ...
Flooding of native and agricultural lands is a major problem on Earth. On the whole world scale, the land area exposed to flooding is more than 17 million km2 annually. Dramatic floods occur in all continents of our planet and result in an estimated damage of more than U.S. $80 billion annually (Global Register of Major Flood Events; www.dartmouth.edu/~floods/Archives/2005sum.htm). Furthermore, it has been predicted that the global climate change will lead into an increase in the frequency and in the severity of flooding events (Arnell and Liu 2001). Floods are changing the natural patterns of plant distribution and biodiversity (Silvertown et al. 1999), and as most of our food crop species (including some rice cultivars) are intolerant of flooding, waterlogging has a devastating impact on global food production (Normile 2008).
... In J. roemerianus, Juncus maritimus Lam. and Juncus acutus L. these stellate cells form diaphragms and are regarded as a secondary development in the more advanced species (Buchenau 1906). Diaphragms have been found in other water plants (Kaul 1971(Kaul , 1973(Kaul , 1974) associated with air chambers which provide internal ventilation. These diaphragms probably give strength without rigidity (Snow 1914;Williams and Barber 1961). ...
The extensive rhizome development found in Juncus roemerianus makes this species unique among rushes and is a biological feature responsible, in part, for its domination of large tracts of salt marsh. Branching in certain mature plants is distinctly sympodial, while in most it is obscured by precocious development of the continuation bud and appears to be monopodial. Each vegetative unit is composed of a scaly rhizome which grows to varying lengths and then abruptly turns up at the end to become an erect shoot. A continuation rhizome consistently arises from an axillary bud in a ventral scale leaf. Transitional leaves (large scale leaves) accompany development of the erect shoot. Rhizome scales, transitional and foliage leaves are distichously arranged and in the same vertical plane. The culm forms through an elongation of an internode of an erect shoot. Other rhizomes may also arise from buds in the axils of the transitional and foliage leaves. From one to seven terete leaves with a bifacial sheath are produced from the apical meristem of the erect stem. Fibrous roots occur laterally on erect shoots. Non-fibrous roots occur on the ventral surface to the rhizomes. The internal rhizome and root anatomy resembles that reported for most other species of Juncus while the leaf anatomy is very similar to that of Juncus maritimus and Juncus acutus.
... Eles têm a função principal de suportar os feixes vasculares (KAUL, 1971), assim como permitir o fluxo de gases (BRIX, 1992) e impedir que a água circule, uma vez que, a tensão superficial necessita ser rompida para transpassar entre os microporos (ARMSTRONG, 1979). Alguns trabalhos sugerem que os diafragmas teriam uma relevância na resistência das plantas a choques mecânicos, como os que ocorrem por meio da ação do vento e das ondas (SPATZ, 1990) de modo que teriam uma maior lignificação (assim como os tecidos externos), quanto mais as plantas estiverem expostas a esses fatores. ...
... Essas lacunas promovem a oxigenação através de difusão entre órgãos aéreos e submersos, sendo capazes de transportar o O 2 formado durante a fotossíntese nas folhas para outros órgãos da planta, indicando a continuidade dessas lacunas de ar ao longo de todo o vegetal (Nielsen & Orcutt 1996) A presença de células braciformes, que formam o diafragma, limitam as lacunas de ar nos diferentes órgãos das espécies estudadas e além de serem responsáveis pela condução de gases também atuam de forma mecânica em órgãos submersos conforme o que foi demonstrado em outras plantas aquáticas por Sculthorpe (1967), Kaul (1971) e Fahn (1990). ...
We examined the anatomy of roots, rhizomes, leaves, and scapes of Cyperus odoratus L., Oxycaryum cubense (Poep. & Kunth) Lye, and Pycreus macrostachyos (Lam.) Raynal (Cyperaceae-Poales) from temporary lakes in the semi-arid region of Bahia in order to characterize the anatomy and examine structural adaptations to amphibious lifestyle. All species had roots with uniseriate epidermal cells, cortex with exoderm and air canals. The rhizomes had amphivasal or collateral vascular bundles in the vascular cylinder. The leaves had uniseriate epidermal cells with external periclinal cell walls thicker than the inner walls, stomata on the abaxial leaf surface, chlorenchyma alternating with air canals, and collateral vascular bundles. The scapes had uniseriate epidermal cells, fibrous groups distributed peripherally, alternating with chlorenchyma, air canals, and collateral vascular bundles. Oxycaryum cubense differs from Cyperus odoratus and Pycreus macrostachyos by having roots with long hairs; rhizomes and stolons with collateral vascular bundles; leaf blades with acute margins, and lacking Kranz structures in leaves and scapes. Anatomic characters such as the presence of large air canals principally in the roots, bulliform cells on the adaxial face of the leaf epidermis, hypodermis, reduced numbers of xylem vascular elements and little lignification of the cell walls of the different plant organs are considered important features in the adaptation of these amphibious plants that inhabit temporary lakes in the semi-arid region of Bahia state.
... Nas espécies estudadas neste trabalho, o aerênquima é bem desenvolvido e interceptado por diafragmas transversais. A presença de aerênquima e diafragmas é geralmente observada em plantas que crescem em ambientes aquáticos ou muito úmidos, e não há dúvida sobre a sua importância para a fisiologia da planta, principalmente na maior eficiência das trocas gasosas (Sculthorpe 1967;Kaul 1971;Esau 1977;Fahn 1982). A principal função de um tecido aerenquimatoso altamente compartimentado em plantas aquáticas é a estabilidade mecânica (Williams & Barber 1961). ...
The anatomy of roots, stems, leaves, and scapes of Eriocaulon elichrysoides, Leiothrix fluitans, Paepalanthus obtusifolius, Philodice hoffmannseggii, Syngonanthus caulescens, and Tonina fluviatilis were studied. All species are aquatic Eriocaulaceae that occur in Brazilian ecosystems. This paper aims to describe the anatomical characterization as well as the interpretation of the adaptations related to the environment. These species present roots with spongy and whitish aspect; air storage in the cortex; thin-walled uniseriate epidermal cells; differentiated cortex; uniseriate endodermis, and uniseriate or multiseriate pericycle. L. fluitans, P. obtusifolius, and T. fluviatilis present roots that store and roots that do not store air in the cortex. The stems are aerial or rhizomatous, with or without thickening resulted from the activity of the pericycle. Leaves and scapes present thin-walled epidermal cells, stomata on the abaxial surface, loosely aggregated chlorenchyma, reduced collenchyma, and collateral vascular bundles. The anatomical features observed are those typical of plants of aquatic or wet habitats. They are convergent and occur in different genera of Eriocaulaceae.
... In environments where oxygen availability is a critical factor limiting plant survival, differences in oxygen transport capacity can be important in structuring communities (Brix et al., 1992). In many emergent aquatic plants, the pith cavity of the aerial culms is packed with a variety of lignified tissues that provide mechanical resistance to buckling at the cost of increasing resistance to gas flow (Kaul, 1971;Brix et al., 1992). Other species such as Phragmites australis (Cav.) ...
The response of growth and morphology to water depth (6cm below to 32cm above substrate) and substrate type (sandy versus organic substrates, with NPK added in excess of plant requirements) was studied for Eleocharis sphacelata. Depth and substrate interacted strongly in their effects on structure and growth. In sandy substrates, new culm biomass remained constant with depth, but the morphology changed from a high density of short (0.9m) culms in the deepest treatment. Culm height also increased with depth in the predominantly organic substrates, but the number of culms did not differ significantly and hence culm biomass increased with depth. Allocation to culms increased with depth, and tended also to increase with increasing organic matter content of the substrate. Root growth was strongly correlated with growth of the rhizome material, and rooting depth and root cortical porosity remained high in all treatments. The diameter of the tallest culms was affected by depth, but not substrate, increasing from 7mm in the deepest treatment. This decreased resistance to internal gas flow from 1.57±0.30 to 0.97±0.03Pasmm−2 with increasing depth. In contrast to the three deeper treatments, the short, narrow culms in the shallowest treatment did not produce inflorescences. These responses suggest conflicting demands for minimising resistance to gas transport in deep water, but maximising mechanical strength when the water is shallow or below the substrate surface. Short, narrow culms may limit this species’ competitiveness in shallow water and thus explain its frequent displacement from shallow environments.
... Similar diaphragms have been described that originate from mother cells identifiable in intercalary meristems in aerial internodes of the aquatic species Scirpus validus and in leaves of other aquatics (e.g. Kaul, 1971Kaul, , 1972Kaul, , 1973. In other species, schizogenous aerenchyma may involve less complex structures, where the gas spaces are separated files of cells sometimes only one cell across. ...
ContentsI Introduction II Schizogenous aerenchyma formation III Lysigenous aerenchyma formation IV Regulators of lysigenous aerenchyma formationV Key questions in lysigenous aerenchyma formation VI Sensing hypoxia; early events in aerenchyma formation VII Ultrastructural changes associated with lysigenous aerenchyma formation VIII Late events in cell death in aerenchyma formation IX Comparative evidence on programmed cell death in aerenchyma formation X Comparison with other abiotic initiators of cell death in plants XI Acknowledgements XII References SummaryAerenchyma – tissue containing enlarged gas spaces – occurs in many plants. It is formed either as part of normal development, or in response to stress (e.g. hypoxia). Two mechanisms of aerenchyma formation have been described; schizogeny, in which development results in the cell separation and lysigeny, in which cells die to create the gas space. While schizogenous aerenchyma provides a fascinating system for study and has been described in detail at a morphological and ultrastructural level, little is known about the molecular genetics of its formation. The ultrastructure and morphology of lysigenous aerenchyma has also been researched in detail, and considerable progress has been made in describing the cell death processes involved, particularly in relation to programmed cell death. Once again, the molecular genetics of the process are not well understood. Aerenchyma is of great importance in crop survival in waterlogging. It is also important in being a major pathway for the release of the global warming gas methane to the atmosphere in flooded soils. Understanding the regulation of its development is therefore a research priority.
... Nas espécies estudadas neste trabalho, o aerênquima é bem desenvolvido e interceptado por diafragmas transversais. A presença de aerênquima e diafragmas é geralmente observada em plantas que crescem em ambientes aquáticos ou muito úmidos, e não há dúvida sobre a sua importância para a fisiologia da planta, principalmente na maior eficiência das trocas gasosas (Sculthorpe 1967;Kaul 1971;Esau 1977;Fahn 1982). A principal função de um tecido aerenquimatoso altamente compartimentado em plantas aquáticas é a estabilidade mecânica (Williams & Barber 1961). ...
Estudou-se a anatomia de raízes, caules, folhas e escapos de Eriocaulon elichrysoides, Leiothrix fluitans, Paepalanthus obtusifolius, Philodice hoffmannseggii, Syngonanthus caulescens e Tonina fluviatilis,espécies aquáticas de Eriocaulaceae que ocorrem em diferentes ecossistemas brasileiros, visando a caracterização anatômica das mesmas e também a interpretação das adaptações ao ambiente. Essas plantas caracterizam-se por apresentarem raízes com aspecto esponjoso e esbranquiçado; acúmulo de ar no córtex; epiderme unisseriada, de paredes finas; córtex externo, mediano e interno; endoderme unisseriada e periciclo unisseriado ou multisseriado. Em L. fluitans, P. obtusifolius e T. fluviatilis foram observadas raízes absorventes com aerênquima e raízes fixadoras sem aerênquima. Caules aéreos ou rizomatosos, com ou sem espessamentos causados pelo periciclo. Folhas e escapos com células epidérmicas de paredes finas, estômatos somente na face abaxial, parênquima clorofiliano frouxo, tecido de sustentação pouco desenvolvido e feixes vasculares colaterais. Essas estruturas anatômicas são típicas de plantas de ambientes úmidos ou aquáticos, e ocorrem de forma convergente em diferentes gêneros de Eriocaulaceae.
Aerenchyma is a characteristic tissue of aquatic plants, characterized by the presence of air lacunae commonly septated by diaphragms. These are formed by one or more layers of stellate cells, which allow for the passage of gases. Most species of Eleocharis grow in wet or flooded soils and have aerenchyma in their aerial stems. However, extensive studies on this structure, which could contribute to ecological and phylogenetic studies of the group, are lacking. This work describes the structure of the diaphragm in the stem of Eleocharis species and investigates the evolution of this characteristic in the genus. Fifty-three species were analyzed under light and scanning electron microscopy. We analyzed the evolution of the characteristics by reconstructing their ancestral states based on the previously published original phylogeny. The diaphragms in Eleocharis vary mainly in the number of layers, cell shape, and cell wall thickness. The typical diaphragm of the genus is composed of three to four layers of stellate cells, with microprojections and secretory cells. The diaphragm of the group’s ancestor had practically the same characteristics as the genus’s typical diaphragm.
Nitrogen limitation of primary production is common in coastal ecosystems. Mangrove trees maintain high levels of nitrogen fixation around their roots. The interior aerial space of mangrove roots, in which atmospheric gas is supplied through lenticels, could be efficient sites for nitrogen fixation.
We measured tidal variations of partial pressure of N2 in root aerenchyma and conducted field experiments using ¹⁵N2 as a tracer to track N2 movement through aerial roots of Avicennia marina. We used the acetylene reduction assay to identify the root parts harboring diazotrophs.
The nitrogenase activity and estimated nitrogen fixation through aerenchyma were higher in pneumatophores and absorbing roots than in cable roots. Positive correlations between root nitrogen contents and turnover rates of root nitrogen derived from N2 through aerenchyma suggested that the internal supply of N2 to diazotrophs could be the main source for nitrogen assimilation by A. marina roots.
Our results confirmed that N2 is supplied to diazotrophs through aerial roots and that nitrogen fixation occurs in A. marina roots. The aerial root structures, which occur across families of mangrove plants, could be an adaptation to survival in not only low‐oxygen environments but also tidal flats with little plant‐available nitrogen.
The genus Eleocharis (Cyperaceae, monocotyledons) is characterized by bladeless leaves, which are leaves having only leaf-sheaths. To study the evolutionary process through which Eleocharis species lost their leaf blades, we analyzed the outer morphological and anatomical characters of the representative Eleocharis species, plus species from nine phylogenetically related genera. From the analysis, we recognized eight characters and we optimized their character states on a recent molecular phylogenetic tree. As a result, we recognized five characteristics shared by Eleocharis species as follows: (1) the most apical internode is more than seven times longer than the next apical internode; (2) bladeless leaves having only leaf sheaths; (3) transversely septate aerenchyma in culms; (4) densely and peripherally located, slender, and square timber-shaped fiber bundles in culms; and (5) palisade chlorenchyma in culms. In these characteristics, (2) and (4) are synapomorphies of Eleocharis . These two apomorphic characteristics seemed to be adaptations for inhabiting running waters.
Nitrogen-fixing activity has been observed in the rhizosphere of mangrove ecosystems, suggesting a close mangrove-diazotroph relationship. In regularly flooded soil, however, the pathway by which atmospheric nitrogen reaches the diazotrophs in the rhizosphere is unknown. This study provides evidence that mangrove aerial roots serve as pathways that supply nitrogen gas to the diazotrophs colonizing buried roots. A plastic chamber was attached on the exposed part of a Rhizophora stylosa prop root and 15N2 tracer gas was injected into it. The entire root, including the below-ground part, was collected for analysis of 15N labelling and nitrogenase activity. We detected 15N labelling in buried root materials 2 h after gas injection. Compared with the δ15N contents in root material from an untreated tree, the increment was >10‰ in lateral roots. The nitrogenase activity measured on the other R. stylosa roots was highest in lateral roots, matching well with the results of 15N labelling. Our results indicate that atmospheric nitrogen is taken into aerial mangrove roots through lenticels, diffuses into the buried root system, and is fixed by diazotrophs. The unusual appearance of mangrove aerial roots, which has intrigued researchers for many years, could be a key to the high productivity of mangrove ecosystems.
Classification and phylogeny of the Nymphaeaceae are unresolved. This study provides floral anatomical data that will assist in elucidating generic interrelationships and systematic relationships to other taxa of angiosperms. The floral anatomy of Ondinea purpurea den Hartog subsp. purpurea has been examined utilizing light microscopy. The peduncle possesses stelar vascular bundle complexes and cortical vascular bundles. Cortical bundles terminate within the peduncle. Each bundle complex consists of 2 collateral bundles on the same radius, the inner bundle inverted; 2 protoxylary lacunae occur yet differ in structure and function. Progressing acropetally, the inner xylary lacunae become discrete mesarch strands surrounded centrifugally by a vascular cylinder formed by divisions and anastomosing of the bundle complexes. Together these become the massive receptacular vascular plexus. The plexus provides collateral traces to the floral organs. Each sepal receives 3 traces that separate from the plexus as 1–3 lateral traces. Petals are absent and no vestigial petal traces have been observed. Distally, the plexus forms several large strands of connate gynoecial and androecial traces termed the principal vascular bundles (PVBs). Ventral veins separate from the PVBs and the latter extend acropetally through the outer ovary wall. Branches of the ventrals and PVBs contribute to septal vascular reticula from which each ovule is supplied by one vascular bundle. Each stamen receives 1 trace from branches of the PVBs. The ventrals and PVBs terminate within the carpellary lobes. A comparative anatomical study is offered that supports the inclusion of Ondinea in the Nymphaeaceae sensu stricto.
Aerenchyma gas spaces are important for plants that survive flooding because these spaces provide an internal pathway for oxygen transport to the root zone. The objective of this study was to characterize the development of aerenchyma gas spaces in Sagittaria lancifolia L., a dominant species in freshwater wetlands adjacent to the Gulf of Mexico. Tissue at different developmental stages was collected from hydroponically grown plants, embedded in plastic, and sections were observed with a light microscope. In S. lancifolia roots, lysigeny (cell lysis) produced gas spaces that increased in volume from the root meristem to the most mature root tissue. Shoot aerenchyma occurred in the large petioles of S. lancifolia and through the blade midrib, but not in the laminar portion of the blade. In contrast to the roots, gas spaces in the petiole were formed by schizogeny (cell separation during development). Shoot initials produced cells that formed interlocking cylinders in the cortex and diaphragm cells that bridged the central portion of the cylinders. Division and expansion of both these cell types increased the diameter of the cylinders and created schizogenous gaps between diaphragm layers that produced large gas spaces in mature tissue. Therefore, aerenchyma development occurs by two different processes in S. lancifolia.
The robust emergent leaves of Sparganium eurycarpum and S. americanum are supported by corner fiber masses and large bundle sheaths, but the thin floating leaves of S. fluctuans and S. minimum have only moderate bundle sheaths. In emergent types heavily photosynthetic diaphragms bearing vascular bundles are separated from each other in the leaf compartments by three lightly photosynthetic diaphragms without bundles, but in floating types only every other heavily photosynthetic diaphragm has a bundle. Palisade chlorenchyma occurs only at aerial surfaces—abaxial and adaxial in emergent leaves, but only adaxial in floating leaves. Extra photosynthetic areas are provided in emergent leaves by concentrations of chlorenchyma in limited areas on interior partitioning walls, while the remainder of the walls is translucent. Since only 25 % of the diaphragms are heavily photosynthetic, and the others essentially transparent because of their diffusely distributed chloroplasts and large intercellular spaces, a sieve effect exists which allows even the interior parts of thick emergent leaves to photosynthesize.
Morphogenetic pulsations in the intercalary meristem of the leaf of Typha latifolia (Typhaceae) produce regular alternating sequences of vascular and stellate-celled diaphragms separated at first by rib-meristem derivatives. The collapse of these derivatives in the region of elongation in and above the intercalary meristem, and the separation of the diaphragms from each other, produce a mature compartmentalized leaf, the compartments bridged by porous diaphragms but separated from each other by rigid vascularized partitions.
Three types of diaphragms are produced in regular sequence by the basal intercalary meristem in the leaf of Sparganium eurycarpum Engelm. (Sparganiaceae). They bridge compartments formed by the collapse and disintegration of rib meristem derivatives. The adaptive nature of diaphragms, intercalary meristems, and linear photosynthetic organs is considered for emergent aquatic plants.
Aerenchyma development in Carex rostrata was studied using light and scanning electron microscopy. Specimens were collected at two locations in southern Finland. Examination showed the beginning of aerenchyma development in the cortex of roots at the distance of 30–45 mm from the apex and it was fully developed at 75–90 mm from the apex. First, schizogenous cavities were formed in the cortex, and the sequence continued with a collapse of tangential cell walls in the cortex, leaving radial strands of cells intact and leading to a structure resembling a cobweb in cross section. In the rhizomes some of the radial cell walls disintegrated in the cortex, resulting in radial rows of cells without any tangential connections. No diaphragms were observed in the rhizome. There were no direct contacts between the gas spaces of the roots and the rhizomes. The significance of aerenchyma for metabolic processes is discussed.
A well-developed aerenchyma is a major characteristic of aquatic plants. However, because such tissues are also found in wetland
and terrestrial plants, it is not always possible to use their presence or absence to distinguish aquatic species. Whereas
patterns of aerenchyma in roots have been studied in detail, those of the shoots have not. We collected and tested 110 species
of various aquatic and wetland plants, including ferns (5), basal angiosperms (5), monocots (65), and eudicots (35). Three
common and two rare types of aerenchyma were observed in their roots (three schizogeny and two lysigeny), plus five types
of schizogeny in their shoots. We re-confirmed that, although a well-developed aerenchyma is more common in most organs of
aquatic plants than in wetland plants, this presence cannot be used as strict evidence for the aquatic quality of vascular
plants. Here, aerenchyma patterns were stable at the genus level, and the consistency of pattern was stronger in the roots
than in the shoots. Furthermore, significant trends were verified in several higher taxa, and those consistencies of patterns
partially coincided with their phylogeny.
Aerenchyma gas spaces are important for plants that grow in flooded and anaerobic sites or habitats, because these gas spaces provide an internal pathway for oxygen transport. The objective of this study is to characterize the development of aerenchyma gas spaces and observe the porosity in roots of Sonneratia alba. Tissue at different developmental stages was collected from four root types, i.e. cable root, pneumatophore, feeding root and anchor root, of S. alba. In S. alba, gas space is schizogenously produced in all root types, and increases in volume from the root meristem to mature root tissues. The aerenchyma formation takes place immediately, or 3-5 mm behind the root apex. At first, cortical cells are relatively round in cross sections (near the root apex); they then become two kinds of cells, rounded and armed, which combine together, forming intercellular spaces behind the root apex. The average dimensions of cortical cells increased more than 1.3 times in the vertical direction and over 3.3 times in the horizontal direction. At maturity, aerenchyma gas spaces are long tuberous structures without diaphragms and with numerous small pores on the lateral walls. Within the aerenchyma, many sclereids grow intrusively. Root porosity in all root types ranged from 0-60%. Pneumatophores and cable roots had the highest aerenchyma area (50-60%).
The unique vegetative morphology of Cyperus alternifolius with its single elongated internode is ideal for developmental and experimental studies of internodal growth. The elongated internode is established by a primary rib meristem which extends from it to the third or fourth internode of the leaf crown. There is no internal histological differentiation of nodes. A secondary rib meristem, which is initiated later in the subapical region, produces the upper internodes of the leaf crown. Initiation of the secondary rib meristem and the start of extension of the elongated internode are correlated with the appearance of crown buds. The primary rib meristem is confined to a basal intercalary meristem (IM) at an early stage. The IM is mitotically active for many weeks and produces most of the internodal tissues. Quantitative data on percentage of cells dividing and cell length are presented for the IM at various stages of internodal development, Morphogenetic events are correlated with internodal growth. A histological gradient is described in the matured internode. Frequencies of stomates and papillae decrease and ground parenchyma cells shorten markedly toward the base. Epidermal cell length remains relatively constant but decreases in the region of the matured IM. Anatomical data are presented graphically and are correlated with internodal growth.
The numbers and distribution of cell division and the cell lengths have been determined for the various tissues in the intercalary meristem of Eleocharis acuta R. Br. Prodr. Cell divisions are most numerous in the chlorenchyma tissue and fewest in the plate parenchyma. In all tissues examined except the plate parenchyma, cell length is inversely correlated with numbers of cell divisions. The cell divisions which occur in the vascular tissue in the intercalary meristem are regarded as being a part of the intercalary growth and not as a normal development of a procambium. Mature xylem and phloem are seen to be present in the larger vascular bundles right through the meristematic zone, and the xylem trachieds are shown to be conductive. The transverse strands connecting adjacent vascular bundles are considered to be important in the conduction of water.
The development of the intercalary meristem which produces the main internode of the haulm of Eleocharis acuta R. Br. has been examined from its inception to the maturity of the internode.Most of the differentiation of tissues is basipetal but a small region of basifugal differentiation occurs at the base of the internode. The various tissues become distinguishable within the region where cell divisions occur.Elongation is due mainly to cell division until the internode is several millimetres long. and then to both cell division and elongation until cell division ceases at about two-thirds of the mature length. The final third of elongation is due to cell elongation alone.Cell division is greatest in rate and extent when the haulm is approximately one-third of its mature length. Both rate and extent of cell divisions are greatest in the chlorenchyma tissue and least in the place parenchyma.In general the features of the intercalary meristem in E. acuta conform to those of other species.
The morphology of the family is described with particular reference to the size and form of the leaf. The salient anatomical features, presented in detail for the individual genera on pp. 19–41, are discussed in relation to the aquatic environment of the plants and to the taxonomy of the family. Characters of taxonomic significance are too few to be of more than limited diagnostic value within the family, but their full significance becomes apparent when the taxonomic position of the Alismataceae is considered in relation to that of other families of Monocotyledons as well as to the Ranunculaceae amongst the Dicotyledons. The anatomical evidence does not appear to support the commonly held view that the Alismataceae and Ranunculaceae are closely related to one another. In spite of the limited value of taxonomic characters within the family it has been possible to present a numerical evaluation of the affinities between the species. Some measurements of the xylem elements are given and their taxonomic and phylogenetic significance is discussed.
v. 1. General organography -- v. 2. Especial organography
Thesis (Ph. D.)--Académie de Paris, 1891.
Anatomie comparée des vegetaux
- Chatin
1884 Comparative anatomy of the phanerogams and ferns Oxford
- A Debary
Diaphragmes vasculifères des Monocotylédones aquatiques
- Duval-Jouve
Über die Wasserleitungsbahnen in den Wachstumszonen monokotyler Sprosse
- Buchholz M.
Comparative anatomy of the phanerogams and ferns
- A Debary
Organography of plants Oxford
- K Goebel