Evidence for silicon as a prevalent elemental component in pollen wall structure

1974 ◽  
Vol 52 (10) ◽  
pp. 2171-2174 ◽  
Author(s):  
Richard E. Crang ◽  
Georgiana May
Keyword(s):  
Tapetal Cell ◽  
Dry Weight ◽  
Pollen Wall ◽  
Wall Structure ◽  
Elemental Silicon ◽  
Pollen Ontogeny ◽  
Elemental Component ◽  
High Degree

Lychnis alba pollen possesses 0.73–0.79% elemental silicon (dry weight), and levels at least as high as in pollen exines have been indicated in tapetal orbicules upon maturation. Even higher levels of elemental silicon (1.30–1.37%) were recorded from Impatiens sultanii pollen. This may indicate that silicon is an important elemental component of exine materials characteristic of many types of pollen, in which silicate compounds may aid in the high degree of pollen resistance to geological weathering, microbial decay, and acetolysis treatments. Further, the data for the incorporation of silicon in L. alba pollen in this report support the concept that exine materials are derived from tapetal cell secretions during pollen ontogeny.

scholarly journals THE FINE STRUCTURE OF ACANTHAMOEBA CASTELLANII (NEFF STRAIN)

1969 ◽  
Vol 41 (3) ◽  
pp. 786-805 ◽  
Author(s):  
Blair Bowers ◽  
Edward D. Korn
Keyword(s):  
Golgi Complex ◽  
Cyst Wall ◽  
Matrix Material ◽  
Acanthamoeba Castellanii ◽  
Dry Weight ◽  
Amorphous Layer ◽  
Wall Structure ◽  
Weight Protein ◽  
Granular Matrix ◽  
Mature Cyst

Encysting cells of Acanthamoeba castellanii, Neff strain, have been examined with the electron microscope. The wall structure and cytoplasmic changes during encystment are described. The cyst wall is composed of two major layers: a laminar, fibrous exocyst with a variable amount of matrix material, and an endocyst of fine fibrils in a granular matrix. The two layers are normally separated by a space except where they form opercula in the center of ostioles (exits for excysting amebae). An additional amorphous layer is probably present between the wall and the protoplast in the mature cyst. Early in encystment the Golgi complex is enlarged and contains a densely staining material that appears to contribute to wall formation. Vacuoles containing cytoplasmic debris (autolysosomes) are present in encysting cells and the contents of some of the vacuoles are deposited in the developing cyst wall. Lamellate bodies develop in the mitochondria and appear in the cytoplasm. Several changes are associated with the mitochondrial intracristate granule. The nucleus releases small buds into the cytoplasm, and the nucleolus decreases to less than half its original volume. The cytoplasm increases in electron density and its volume is reduced by about 80%. The water expulsion vesicle is the only cellular compartment without dense content in the mature cyst. The volume fractions of lipid droplets, Golgi complex, mitochondria, digestive vacuoles, and autolysosomes have been determined at different stages of encystment by stereological analysis of electron micrographs. By chemical analyses, dry weight, protein, phospholipid, and glycogen are lower and neutral lipid is higher in the mature cyst than in the trophozoite.

Fine structure in the red algae - II. The structure of the cell wall of Rhodymenia Palmata

1959 ◽  
Vol 150 (941) ◽  
pp. 447-455 ◽  
Keyword(s):  
Cell Wall ◽  
Chemical Treatment ◽  
Amorphous Matrix ◽  
Dry Weight ◽  
Wall Structure ◽  
X Ray Diffraction ◽  
X Ray ◽  
Floridean Starch ◽  
Thin Sectioning ◽  
Paper Chromatographic Separation

The cell-wall structure of the red alga Rhodymenia palmata has been examined by the methods of X -ray diffraction analysis and electron microscopy, including ultra-thin sectioning. The cell wall is shown to consist of numerous lamellae each of which is made up of unoriented, crystalline microfibrils embedded in an amorphous matrix of other cell-wall constituents. The material can be stretched reversibly up to 100% when wet, and the stretching induces orientation of the microfibrils. The ‘∝ cellulose' fraction, which accounts for only 2 to 7 % of the original dry weight, was isolated chemically and was analyzed by means of hydrolysis and paper chromatographic separation of the resulting sugars, and it was found to be composed of approximately equal quantities of glucose and xylose residues. Chemical treatment of the cell wall was found to cause considerable variations in the X -ray diagrams, which are discussed. It is concluded that the microfibrils contain both glucose and xylose residues in approximately equal proportions and that chemical treatment in this case causes changes in crystallinity of the structural component of the wall. The importance of these findings for the meaning of the term cellulose is discussed. The X -ray diagram of older fronds was found to be complicated by the occurrence of extra rings due to the presence of floridean starch, and the highly elastic properties of the thallus enabled the diagrams of the starch and the cell wall to be separated.

scholarly journals ESTIMATION OF THE PURITY OF PREPARATIONS OF ELEMENTARY BODIES OF VACCINIA

1939 ◽  
Vol 70 (4) ◽  
pp. 379-385 ◽  
Author(s):  
Joseph E. Smadel ◽  
Thomas M. Rivers ◽  
Edward G. Pickels
Keyword(s):  
Dry Weight ◽  
Vaccine Virus ◽  
Elementary Body ◽  
High Degree

A method of estimating the purity of preparations of elementary bodies of vaccinia is described. It depends on the comparison of the number of infective units of virus in a given material with the number of elementary bodies. The latter figure is estimated from the dry weight of the preparation by means of a calculated value for the weight of a single dehydrated elementary body. Values for the ratio of infective units of vaccine virus to elementary bodies varied between 1 : 2.4 and 1 : 9.2 in seven consecutive experiments; the average was 1:4.2. These ratios indicate a high degree of purity of the preparation. Moreover, they indicate that a relatively high percentage of the elementary bodies in the preparations was infective.

Pollen Wall Structure and Cytochemistry in the Seagrass Amphibolis griffithii (Cymodoceaceae)

1982 ◽  
Vol 50 (5) ◽  
pp. 729-732 ◽  
Author(s):  
C. A. McCONCHIE ◽  
R. B. KNOX ◽  
S. C. DUCKER ◽  
J. M. PETTITT
Keyword(s):  
Pollen Wall ◽  
Wall Structure

Variation in pollen wall ultrastructure in New World Senecioneae (Asteraceae), with special reference to Packera

1997 ◽  
Vol 75 (5) ◽  
pp. 730-735 ◽  
Author(s):  
J. F. Bain ◽  
B. S. Tyson ◽  
D. F. Bray
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Chromosome Number ◽  
Special Reference ◽  
New World ◽  
Pollen Wall ◽  
Wall Structure ◽  
Transmission Electron ◽  
Wall Ultrastructure ◽  
Base Chromosome Number

The structure of the pollen wall as revealed by transmission electron microscopy is presented for 34 species representing two subtribes and 12 genera of New World Senecioneae. The genus Packera (=aureoid Senecio), with the exception of Packera zimapanica, is characterized by the helianthoid wall structure. In light of these results, the disposition of the latter species requires review. The genera Robinsonecio and Telanthophora of the subtribe Tussilagininae also possess helianthoid pollen. All other taxa surveyed have senecioid pollen. So far as known no taxa exist within the tribe Senecioneae with a base chromosome number of n = 20 and helianthoid pollen. This suggests that the evolution of Packera may have involved hybridization between members of the two subtribes Senecionineae and Tussilagininae. Key words: Asteraceae, Packera, Senecioneae, pollen, TEM, systematics.

Inheritance of Resistance to The Auxinic Herbicide Dicamba in Kochia (Kochia scoparia)

Weed Science ◽  
2009 ◽  
Vol 57 (1) ◽  
pp. 43-47 ◽  
Author(s):  
Christopher Preston ◽  
David S. Belles ◽  
Philip H. Westra ◽  
Scott J. Nissen ◽  
Sarah M. Ward
Keyword(s):  
Dry Weight ◽  
Inheritance Of Resistance ◽  
Kochia Scoparia ◽  
Susceptible Line ◽  
Degree Of Dominance ◽  
Hand Pollination ◽  
Single Allele ◽  
Seven Generations ◽  
High Degree ◽  
Family Segregation

The inheritance of resistance to the auxinic herbicide dicamba was examined in a kochia population from Nebraska. An inbred, resistant line was developed by selection and selfing over seven generations to ensure any resistance alleles would be homozygous in the parents. An inbred, susceptible line was similarly developed, but without selection. Dose–response experiments with dicamba determined a glyphosate-resistant concentration required to inhibit dry weight accumulation by 50% (GR50) of 45 and 1,331 g ae ha−1for the susceptible and resistant populations, respectively. F1crosses were made between resistant and susceptible inbred individuals by hand-pollination, and the F1plants were selfed to produce F2plants. The F2population was screened with 280 g ha−1dicamba, a rate that could discriminate between susceptible and resistant plants. A total of eight F2families were screened twice. In the first screen, seven F2families segregated in a 3:1 ratio, consistent with a single dominant allele controlling resistance, and in the second screen six F2families segregated in a 3:1 ratio. F2individuals were selfed, the F3progeny were tested with 280 g ha−1dicamba, and the genotype of each F2parent was determined based on F3progeny segregation. F3family segregation was consistent with the F2parents having a 1:2:1 homozygous-susceptible:heterozygote:homozygous-resistant pattern, confirming that resistance to dicamba in kochia is likely conferred by a single allele with a high degree of dominance.

Pollen Wall Structure Using a New Stripping-Sputtering Device for Scanning Electron Microscopy

Grana ◽  
1995 ◽  
Vol 34 (5) ◽  
pp. 325-331 ◽  
Author(s):  
Shengyin Lan ◽  
Zhenxiu Xu ◽  
Tingdong Fu ◽  
Waheeb K. Heneen
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Pollen Wall ◽  
Wall Structure ◽  
Scanning Electron

scholarly journals Weight-to-weight conversion factors for benthic macrofauna: recent measurements from the Baltic and the North Seas

2021 ◽  
Author(s):  
Mayya Gogina ◽  
Anja Zettler ◽  
Michael L. Zettler
Keyword(s):  
Rapid Assessment ◽  
Dry Weight ◽  
Local Data ◽  
Conversion Factors ◽  
Food Web Interactions ◽  
The North ◽  
Reference Information ◽  
Region Data ◽  
The Baltic ◽  
High Degree

Abstract. Estimates of biomass often involve the use of weight-to-weight conversion factors for rapid assessment of dry-weights based metrics from more widely available measurements of wet weights. Availability of standardized biomass data is essential amid research on population dynamics, energy flow, fishery and food web interactions. However, for many species and groups the widely-applicable freely available conversion factors until now remained very rough approximations with high degree of taxonomic generalization. To close up this gap, here for the first time we publish the most detailed and statically robust list of ratios of wet weight (WW), dry weight (DW) and ash-free dry weight (AFDW). The dataset includes over 17000 records of single measurements for 497 taxa. Along with aggregated calculations, enclosed reference information with sampling dates and geographical coordinates provides the broad opportunity for reuse and repurposing. It empowers the future user to do targeted sub selections of data to best combine them with own local data, instead of only having a single value of conversion factor per region. Data can help to quantify natural variability and uncertainty, and assist to refine current ecological theory. The dataset is available via an unrestricted repository from: http://doi.io-warnemuende.de/10.12754/data-2021-0002 (Gogina et al., 2021).

scholarly journals Study On The Steel-Aluminum Plastic Clinching of The Inclined Wall Die

2021 ◽  
Author(s):  
Menghan Wang ◽  
Yifeng Chen ◽  
Yan Han ◽  
Lei Li ◽  
Menglong Du
Keyword(s):  
Finite Element ◽  
Failure Mode ◽  
Flow Characteristics ◽  
Element Model ◽  
Wall Structure ◽  
Steel Sheets ◽  
Neck Thickness ◽  
Joint Quality ◽  
Separation Failure ◽  
High Degree

Abstract Aiming at the problems of low strength and unsatisfactory connection quality of plastic clinching of heterogeneous lightweight materials for the cars body, the Q235 steel sheets, and 5052 aluminum alloy sheets were taken as the research objects, and the inclined wall die for plastic clinching was designed based on the deformation and flow characteristics of sheets in the plastic clinching process. The elastic-plastic finite element numerical simulation and experimental research were used to analyze the plastic clinching process of the inclined wall die, and the failure mode and mechanism of the clinching joints in the shear and peel experiment were deeply studied. The results show that the inclined wall die can effectively increase the interlock value of the joints and reduce the maximum joining force during the clinching process under the condition of ensuring the neck thickness of the joints. When the inclined wall angle α increases from 90° to 100°, the interlock value increases by 38.9%, and the maximum joining force decreases by 8.3%. The influence of inclined wall structure on joint quality can be divided into extrusion stage, radial inflow stage, and stability stage. The comparison between the clinching experiment and the finite element results shows that the two results are in good agreement, which proves that the finite element model of plastic clinching of inclined wall die has a high degree of credibility, and verifies the feasibility of practical application of inclined wall die. Finally, under shear and peel loads, the main failure mode of the joints is separation failure.

scholarly journals DCET1 Controls Male Sterility Through Callose Regulation, Exine Formation, and Tapetal Programmed Cell Death in Rice

2021 ◽  
Vol 12 ◽  
Author(s):  
Riaz Muhammad Khan ◽  
Ping Yu ◽  
Lianping Sun ◽  
Adil Abbas ◽  
Liaqat Shah ◽  
...  
Keyword(s):  
Cell Death ◽  
Programmed Cell Death ◽  
Male Sterility ◽  
Tapetal Cell ◽  
Pollen Wall ◽  
Rna Recognition Motif ◽  
Male Sterile ◽  
Cell Degeneration ◽  
Regulatory Pathways ◽  
Callose Wall

In angiosperms, anther development comprises of various complex and interrelated biological processes, critically needed for pollen viability. The transitory callose layer serves to separate the meiocytes. It helps in primexine formation, while the timely degradation of tapetal cells is essential for the timely callose wall dissolution and pollen wall formation by providing nutrients for pollen growth. In rice, many genes have been reported and functionally characterized that are involved in callose regulation and pollen wall patterning, including timely programmed cell death (PCD) of the tapetum, but the mechanism of pollen development largely remains ambiguous. We identified and functionally characterized a rice mutant dcet1, having a complete male-sterile phenotype caused by defects in anther callose wall, exine patterning, and tapetal PCD. DCET1 belongs to the RNA recognition motif (RRM)-containing family also called as the ribonucleoprotein (RNP) domain or RNA-binding domain (RBD) protein, having single-nucleotide polymorphism (SNP) substitution from G (threonine-192) to A (isoleucine-192) located at the fifth exon of LOC_Os08g02330, was responsible for the male sterile phenotype in mutant dcet1. Our cytological analysis suggested that DCET1 regulates callose biosynthesis and degradation, pollen exine formation by affecting exine wall patterning, including abnormal nexine, collapsed bacula, and irregular tectum, and timely PCD by delaying the tapetal cell degeneration. As a result, the microspore of dcet1 was swollen and abnormally bursted and even collapsed within the anther locule characterizing complete male sterility. GUS and qRT-PCR analysis indicated that DCET1 is specifically expressed in the anther till the developmental stage 9, consistent with the observed phenotype. The characterization of DCET1 in callose regulation, pollen wall patterning, and tapetal cell PCD strengthens our knowledge for knowing the regulatory pathways involved in rice male reproductive development and has future prospects in hybrid rice breeding.

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