scholarly journals Epidermis structure in Mesembryanthemaceae

Bothalia ◽  
1983 ◽  
Vol 14 (3/4) ◽  
pp. 937-937
Author(s):  
H. -D. Ihlenfeldt
Keyword(s):  
Cell Walls ◽  
Climatic Conditions ◽  
Radiation Balance ◽  
Outer Cell ◽  
Extreme Conditions ◽  
Prominent Feature ◽  
Oxalate Crystals ◽  
Different Types ◽  
Bladder Cells ◽  
Epidermis Structure

The Mesembryanthemaceae, which inhabit the deserts and semi-deserts of Southern Africa, exhibit two very different types of epidermis. The first is characterized by thick outer cell walls encrusted by oxalate crystals, a thick cuticle and thick wax layers. In the second type, the epidermal cells exhibit only very thin outer cell walls, not encrusted by oxalate crystals, a very thin cuticle, and wax layers are poorly developed; the most prominent feature of this type is the occurrence of huge idioblasts often protruding as ‘bladder cells’. With regard to the climatic conditions in the native habitats this type of epidermis must be called ‘abnormal’. Both types of epidermis may form sculptures of three distinct size classes, which are not necessarily homologous. The function of these sculptures is still poorly understood. There is evidence that the sculptures influence the optical properties of the surfaces and thereby the radiation balance (and heat stress) of the leaves.From recent research, it has become evident that the two different types of epidermis are the anatomical expression of two different strategies for survival under extreme conditions. Species with the idioblast type of epidermis exhibit a strategy that might be called ‘opportunistic’. These species have developed a mechanism of gaining water from the atmosphere during the night under favourable conditions. There are indications that the idioblasts are involved in this mechanism.

Gymnomitrion fissum (Gymnomitriaceae, Marchantiophyta) — a new species with fissured leaf surface from China

2017 ◽  
Vol 51 ◽  
pp. 274-280
Author(s):  
A. D. Potemkin ◽  
Yu. S. Mamontov ◽  
N. S. Gamova
Keyword(s):  
New Species ◽  
Cross Sections ◽  
Cell Walls ◽  
Leaf Surface ◽  
Outer Cell ◽  
Sem Images ◽  
Cell Lumen ◽  
A New Species ◽  
Surface Comparison

Study of selected specimens of Gymnomitrion collected by D. G. Long in Yunnan, China, revealed a new species, G. fissum Mamontov et Potemkin, sp. nov., with a fissured leaf surface. Comparison of SEM images of the leaf surface and leaf cross sections shows that the leaf surface of G. fissum is different from that of other known species with a superficially similar leaf surface, i. e. Mylia taylorii, M. verrucosa s. l. and Trabacellula tumidula. It has fissures around the cell lumen rather than grids and perforations. Outer cell walls of Gymnomitrion fissum are much thicker than in Mylia taylorii, M. verrucosa s. l. and Trabacellula tumidula, and their outer layers tend to be partly or completely caducous. G. fissum is related to the group of species assigned to the former genus Apomarsupella.

scholarly journals Constitutive Modeling of the Densification Behavior in Open-Porous Cellular Solids

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2731
Author(s):  
Ameya Rege
Keyword(s):  
Constitutive Model ◽  
Cell Walls ◽  
Compressive Strain ◽  
Pore Collapse ◽  
Compressive Response ◽  
Linear Elastic ◽  
Nonlinear Springs ◽  
Different Types ◽  
Point Of Intersection ◽  
Good Agreement

The macroscopic mechanical behavior of open-porous cellular materials is dictated by the geometric and material properties of their microscopic cell walls. The overall compressive response of such materials is divided into three regimes, namely, the linear elastic, plateau and densification. In this paper, a constitutive model is presented, which captures not only the linear elastic regime and the subsequent pore-collapse, but is also shown to be capable of capturing the hardening upon the densification of the network. Here, the network is considered to be made up of idealized square-shaped cells, whose cell walls undergo bending and buckling under compression. Depending on the choice of damage criterion, viz. elastic buckling or irreversible bending, the cell walls collapse. These collapsed cells are then assumed to behave as nonlinear springs, acting as a foundation to the elastic network of active open cells. To this end, the network is decomposed into an active network and a collapsed one. The compressive strain at the onset of densification is then shown to be quantified by the point of intersection of the two network stress-strain curves. A parameter sensitivity analysis is presented to demonstrate the range of different material characteristics that the model is capable of capturing. The proposed constitutive model is further validated against two different types of nanoporous materials and shows good agreement.

scholarly journals FlsnRNA-seq: protoplasting-free full-length single-nucleus RNA profiling in plants

2021 ◽  
Vol 22 (1) ◽  
Author(s):  
Yanping Long ◽  
Zhijian Liu ◽  
Jinbu Jia ◽  
Weipeng Mo ◽  
Liang Fang ◽  
...  
Keyword(s):  
Single Cell ◽  
Cell Walls ◽  
Large Scale ◽  
Full Length ◽  
Cell Level ◽  
Root Cells ◽  
Rna Profiling ◽  
Different Types ◽  
Long Read ◽  
Single Nucleus

AbstractThe broad application of single-cell RNA profiling in plants has been hindered by the prerequisite of protoplasting that requires digesting the cell walls from different types of plant tissues. Here, we present a protoplasting-free approach, flsnRNA-seq, for large-scale full-length RNA profiling at a single-nucleus level in plants using isolated nuclei. Combined with 10x Genomics and Nanopore long-read sequencing, we validate the robustness of this approach in Arabidopsis root cells and the developing endosperm. Sequencing results demonstrate that it allows for uncovering alternative splicing and polyadenylation-related RNA isoform information at the single-cell level, which facilitates characterizing cell identities.

A freeze-etch study of plant cell walls for ectodesmata

1974 ◽  
Vol 52 (9) ◽  
pp. 2033-2036 ◽  
Author(s):  
N. C. Lyon ◽  
W. C. Mueller
Keyword(s):  
Cell Wall ◽  
Cell Walls ◽  
Leaf Tissue ◽  
Physicochemical Characteristics ◽  
Outer Cell ◽  
Plantago Major ◽  
Plant Cell Walls ◽  
Phaseolus Vulgaris L ◽  
Epidermal Cell Wall ◽  
Outer Cell Wall

Leaf tissue of Phaseolus vulgaris L. and Plantago major L. was prepared by the freeze-etch technique and examined in the electron microscope for the presence of ectodesmata. No structures analagous to ectodesmata observed with light microscopy could be found in freeze-etched preparations of chemically unfixed material or in material fixed only in glutaraldehyde. Objects appearing as broad, shallow, granular areas in the epidermal cell wall beneath the cuticle were observed in leaf replicas after fixation in complete sublimate fixative, the acid components of the sublimate fixative, or mercuric chloride alone. Because of their distribution and location, these objects can be considered analagous to ectodesmata observed by light microscopists. Because these areas occur only in chemically fixed walls and are localized within the walls in discrete areas, their presence supports the contention that ectodesmata are sites in the outer cell wall with defined physicochemical characteristics.

Modern problems of regionalization of territories and human adaptation in regions with extreme natural and climatic conditions

2021 ◽  
Author(s):  
A.L. Maksimov
Keyword(s):  
Environmental Factors ◽  
Environmental Conditions ◽  
Allostatic Load ◽  
Climatic Conditions ◽  
Extreme Conditions ◽  
Human Adaptation ◽  
Nonspecific Resistance ◽  
Key Words Adaptation ◽  
High Level ◽  
Selection Of

The paper considers modern approaches to the zoning of territories and the selection of people for life in extreme environmental conditions, taking into account modern geopolitical challenges. It is shown that it is possible, based on the allostasis concept, to conduct not only the selection of persons with a high level of nonspecific resistance, but also to quantify the degree of extremity of environmental factors using the standard represpiration test. Key words: adaptation, extreme conditions, selection, hypoxia, cold, rerespiration, allostatic load.

scholarly journals Flat Glass or Crystal Dome Aperture? A Year-Long Comparative Analysis of the Performance of Light Pipes in Real Residential Settings and Climatic Conditions

2020 ◽  
Vol 12 (9) ◽  
pp. 3858 ◽  
Author(s):  
Magda Sibley ◽  
Antonio Peña-García
Keyword(s):  
Comparative Analysis ◽  
Flat Glass ◽  
Climatic Conditions ◽  
Long Term Effect ◽  
Different Types ◽  
The Difference ◽  
The Aesthetic ◽  
One Year ◽  
The One

This paper presents the first comparative study of its type of the performance of light pipes with different types of apertures: a flat glass versus a bohemian crystal dome. Measurements were taken at 20-minute intervals over a period of one year in the bathrooms of two newly built identical houses of the same orientation located in Manchester, UK. The comparative analysis of the data collected for both light pipes types reveals that the crystal domed aperture consistently outperforms the flat glass one. Furthermore, the difference in the recorded horizontal illuminance is most marked during the winter months and at the end of the one-year experiment, indicating that the crystal dome has better performance for low incident winter light and higher resistance for the long term effect of weathering and pollution. This study provides strong evidence based on long term real measurements. Such evidence informs architects’ decisions when weighing up the aesthetic considerations of a flat glass aperture versus the higher illumination levels afforded by a crystal dome aperture with higher resistance to weathering and pollution.

Clausospicula, a new Australian genus of grasses (Poaceae, Andropogoneae)

1991 ◽  
Vol 4 (2) ◽  
pp. 391
Author(s):  
M Lazarides ◽  
J Lenz ◽  
L Watson
Keyword(s):  
Cell Walls ◽  
Transverse Section ◽  
Northern Territory ◽  
Vascular Bundles ◽  
Monotypic Genus ◽  
Prominent Feature ◽  
Abaxial Epidermis ◽  
Diagnostic Characters ◽  
Adaxial Epidermis

Clausospicula, a new monotypic genus from the Darwin and Gulf District, Northern Territory, Australia, is described and illustrated. Its diagnostic characters include cleistogamous spikelets, reduced panicles, racemes and spikelets, and pedicelled spikelets which are poorly developed and deciduous, or suppressed. Also, the glumes of the bisexual spikelet are awned and slightly keeled or without keels. A prominent feature is the extension of the peduncle into an appendage to which the callus of the bisexual spikelet is attached. The epidermis is notable for its distinct costal and intercostal zones, rectangular intercostal long-cells with tessellated, pitted cell walls, stomata inserted beneath the overlapping interstomatals and arranged in definite rows bordering the costal zones, the presence of macrohairs, narrow microhairs 39–46.5 µm long, silica-celllcork-cell pairs with dumbbell-shaped silica bodies costally and butterfly-shaped silica bodies intercostally. The transverse section shows a distinct midrib with the vascular bundles arranged in a conventional arc abaxially and colourless tissue adaxially, and a symmetrically ordered lamina. The primary vascular bundles are accompanied by sclerenchyma as girders abaxially and adaxially; the adaxial epidermis is extensively bulliform and the abaxial epidermis is of bulliform-like cells.

scholarly journals Quantifying Thermal Stress for Sport Events—The Case of the Olympic Games 2020 in Tokyo

Atmosphere ◽  
2018 ◽  
Vol 9 (12) ◽  
pp. 479 ◽  
Author(s):  
Andreas Matzarakis ◽  
Dominik Fröhlich ◽  
Stéphane Bermon ◽  
Paolo Emilio Adami
Keyword(s):  
Thermal Stress ◽  
Sports Medicine ◽  
Olympic Games ◽  
Heat Waves ◽  
Exercise Physiology ◽  
Thermal Conditions ◽  
Climatic Conditions ◽  
Extreme Conditions ◽  
Atmospheric Conditions ◽  
Sport Events

The effect of weather on sport events is largely discussed in the sports medicine and exercise physiology context. It is important, both for event organizers and for medical staff, to know whether the competition is happening at a time and place with extreme weather or in general not appropriate weather and climatic conditions. In order to find out, whether a place or time is appropriate, two factors should be included when establishing the effect of atmospheric conditions on visitors and athletes. These are the main climatic conditions, based on long term data, and the quantification of extreme events, like heat waves. The present analysis aims at determining what kind of data are required for an appropriate quantification of weather and climate thermal stress. For the analysis, indices like Physiologically Equivalent Temperature (PET) and mPET (modified PET) are applied. The advantage of these indices is the consideration of both, thermo-physiological and meteorological factors to provide results and information that can be used for decision making. In this paper, we analyzed the Tokyo area with regards to the upcoming Tokyo 2020 Summer Olympic Games. The results show that this kind of event may not be appropriate for visitors, if it is placed during months with extreme conditions. For Tokyo, this is the period from May to September, when conditions cause strong heat stress to the visitors for the vast majority of hours of the day. A more appropriate time would be the months from November to February or the early morning and the late afternoon hours, when thermally comfortable conditions are much more frequent. The methods that are applied here can quantify the thermal conditions and show limitations and possibilities for specific events and locations. Should the organizers still want to have these competitions organized during these months with extreme conditions, they should promote and propose all possible countermeasures for the spectators, workforce, and athletes.

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