Exine Of Pollen Grains Research Articles

Новая форма Geranium transbaicalicum (Geraniaceae) из Восточного Забайкалья

A new form Geranium transbaicalicum Serg. subsp. transbaicalicum f. albiflorum Troshkina is described from the East Transbaikalia. The new form differs from the type form of G. transbaicalicum in the color of petals, the length of sepals and their awns, and from G. transbaicalicum subsp. turczaninovii also in the character of pubescence of the sepals, as well as the structure of the surface of the exine of pollen grains. Diagnostic characters of G. transbaicalicum f. transbaicalicum, G. transbaicalicum f. albiflorum, G. transbaicalicum subsp. turczaninovii (Serg.) Peschkova are given in the Table and in the Figure.

Analysis of pollen fertility of coenopopulations of the genus Alyssum L. in the Southern Urals

This study analyzed the fertility of two species of petrophytic genus Alyssum – A. obovatum and A. tortuosum in populations in the Southern Urals. The study examined linear sizes of pollen grains, pollen fertility, and populationcomparisons in contaminated and non-polluted habitats. We found that pollen fertility remains high in natural populationsof species, although pollen fertility level of A. tortuosum was slightly lower compared to A. obovatum. In a contaminatedhabitat, a thickening of the exine of pollen grains was found.

Ультраструктурні особливості пилкових зерен видів роду Arctium L. (Asteraceae Bercht. & J.Presl.)

The plants of the Arctium genus are generally characterized by the similarity of morphological characteristics and the absence of clear diagnostic criteria, which complicates the visual recognition of taxa. In order to determine the plants under our investigation, it is important to attract additional features; therefore, we have studied the exines of pollen grains of species of the genus Arctium of the flora of Ukraine. Pollen grains for the research were collected from the plants of the collection fund of medicinal plants of the laboratory of medical botany of the M.M. Hryshko National Botanical Garden. As a result of palynomorphological studies of four species of the genus Arctium using a scanning electron microscope (SEM), it was found out that the shape of the pollen grains varies from ellipsoidal ( A. lappa, A. minus, A. tomentosum ) to rounded-ellipsoidal ( A. nemorosum ). The maximum sizes of pollen grains are characteristic of A. tomentosum and A minus . The outline of the studied pollen species are three-lobed from the pole, broadly elliptical from the equator, meanwhile in A. lappa , A. nemorosum , A. minus species, the plicae are long, with clear edges, and in of A. tomentosum , their edges are poorly defined; the ori are sharp, equatorially stretched. It was revealed that the surface sculpture of pollen grains in A. lappa is tuberculate (covered with perforations at its base), in A. nemorosum and A. tomentosum it is spinose (thorns without perforation), in A. minus it is spinose (thorns at the base are covered with perforations). The texture of the exine of pollen grains is predominantly intrareticulate in A. lappa , A. nemorosum , A. minus species; while in A. tomentosum it is maculate. The size of the bases of the thorns of pollen grains in A. tomentosum is the smallest, in A. lappa it is the greatest, the height of the thorns is the smallest in A. nemorosum and the largest in A. tomentosum . It was discovered that the widest base in the thorns of pollen grains are found in A. lappa , the narrowest ones are in A. tomentosum . The detected palynomorphological features of pollen grains of the studied species may have diagnostic value and may be used as additional criteria for identifying the species of the genus Arctium .

Saccharomyces cerevisiae Fermentation Effects on Pollen: Archaeological Implications

Pollen is the reproductive agent of flowering plants; palynology is utilized by archaeologists because sporopollenin, a major component in the exine of pollen grains, is resistant to decay and morphologically distinctive. Wine, beer, and mead have been identified in the archaeological record by palynological assessment due to indicator species or due to a pollen profile similar to that recovered from honey, a common source of sugar in a variety of fermented beverages. While most palynologists have assumed that pollen grains are resistant to alcoholic fermentation, a recent study in food science implies that pollen is a yeast nutrient because pollen-enriched meads produce more alcohol. The experiment presented here explores the potential distortion of the pollen record through fermentation by brewing a traditional, pollen-rich mead with Saccharomyces cerevisiae. In this experiment, the pollen grains did not undergo any discernible morphological changes nor were distorted in the pollen profile. Any nutrition that the yeast garners from the pollen therefore leaves sporopollenin intact. These results support palynological research on residues of alcoholic beverages and confirms that the fermentation process does not distort the pollen profile of the original substance. The paper concludes with the potential and limits of palynological study to assess fermentation within the archaeological record.

Modes of deformation of walled cells

The bewildering morphological diversity found in cells is one of the starkest illustrations of life's ability to self-organize. Yet the morphogenetic mechanisms that produce the multifarious shapes of cells are still poorly understood. The shared similarities between the walled cells of prokaryotes, many protists, fungi, and plants make these groups particularly appealing to begin investigating how morphological diversity is generated at the cell level. In this review, I attempt a first classification of the different modes of surface deformation used by walled cells. Five modes of deformation were identified: inextensional bending, equi-area shear, elastic stretching, processive intussusception, and chemorheological growth. The two most restrictive modes-inextensional and equi-area deformations-are embodied in the exine of pollen grains and the wall-like pellicle of euglenoids, respectively. For these modes, it is possible to express the deformed geometry of the cell explicitly in terms of the undeformed geometry and other easily observable geometrical parameters. The greatest morphogenetic power is reached with the processive intussusception and chemorheological growth mechanisms that underlie the expansive growth of walled cells. A comparison of these two growth mechanisms suggests a possible way to tackle the complexity behind wall growth.

Cytopathology of Anthers and Pollen From Lettuce Plants Infected by Lettuce Mosaic Virus

AbstractThin sections of mature anthers and pollen grains from three lettuce (Lactuca sativa) plants infected with lettuce mosaic potyvirus (LMV) were studied by immunogold labelling. Labelled LMV particles were present externally on the exine of pollen grains from all plants, but were observed internally in the pollen grains from only one plant. Within mature pollen grains the virus particles were associated with the cytoplasmic bundle inclusions typical of infection by potyviruses. The tapetal plasmodium and the epidermal and endothecial layers of mature anthers from all infected plants also contained labelled virus particles, together with pinwheel and bundle inclusions.

Polymorphisme pollinique et polymorphisme génétique

The polymorphism of the exine of pollen grains was studied in different species to determine if it has a genetic component at the intraspecific level. For some species, the results show that significant differences exist between individuals and that the composition of populations can also vary. The authors conclude that the study of pollen polymorphism could increase our understanding of pollen evolution and the mechanisms of pollen – stigma interactions. Key words: polymorphism, pollen, ash, Rumex, iris.

Lipopolysaccharide Embedded within the Exine of Pollen Grains

Recent observations indicate that sporopollenin cannot any longer be considered as the only major component of the exine. Filaments in great numbers are exposed from exines of Lycopodium spores heated to high temperatures and sporopollenin partially dissolved. The filaments have closely spaced anionic sites whereas sporopollenin is composed only of C, H, and O and is without carboxyl groups to explain the basophilia typical of exines. The exposed filaments of Lycopodium spore exines are similar in their resistance to the organic base 2-aminoethanol, reaction to basic dyes, and in morphology to lipopolysaccharide extracted from exines of Epilgbium pollen (Rowley, abst. & oral presentation for Scand. Soc. of E.M., Umea 1973).To isolate lipopolysaccharide (LPS), exines were dissolved in 2-aminoethanol at 130-140°C for 18 hrs. Following dialysis the residue was extracted with 45% aqueous phenol at 65-68°C. The large aggregates of LPS in water were separated from other non-dialysiable substances by ultracentrifugation.

Origin and development of sporopollenin bodies

This paper reports the results of a study of the first beginnings of sporopollenin granules in the cells of the tapetum. The endoplasmic reticulum was observed to be the system responsible for their production, first by the formation of electron-dense bodies (pro-Ubisch bodies). These constitute the nuclei of the sporopollenin granules upon which laminae with the characteristics observed in the exine of pollen-grains are deposited in formation of the young Ubisch bodies. The latter ultimately assume a spherical shape (adult Ubisch bodies), whereupon they seem to be carried by channels across the cytoplasm of the tapetum into the locule of the pollen-sac. The origin, development and possible function of sporopollenin granules are discussed in the light of the theories and observations of other authors and of the writers themselves.

Deposition of Sporopollenin on Lamellae of Unit Membrane Dimensions

THERE are several reports of a lamellar inner part of the exine of pollen grains1–8. The number of species examined is small, but the sampling of plant families is wide enough to conclude that the deposition of sporopollenin in some kind of lamellar form is probably characteristic for at least the inner unornamented part of the exine of pollen grains.