Effect of high temperatures in the pre-blooming and blooming periods on ovule formation, pollen grains and yield of ‘Granada’ peach

2009 ◽  
Vol 122 (1) ◽  
pp. 37-44 ◽  
Author(s):  
Gilmar Antônio Nava ◽  
Genei Antônio Dalmago ◽  
Homero Bergamaschi ◽  
Rafael Paniz ◽  
Rinaldo Pires dos Santos ◽  
...  
Keyword(s):  
High Temperatures ◽  
Pollen Grains ◽  
Ovule Formation

Effects of high temperatures on mature pollen grains in wild and cultivated maize accessions

Euphytica ◽  
1991 ◽  
Vol 55 (3) ◽  
pp. 203-207 ◽  
Author(s):  
V. A. Lyakh ◽  
A. N. Kravchenko ◽  
A. I. Soroka ◽  
E. N. Dryuchina
Keyword(s):  
High Temperatures ◽  
Pollen Grains ◽  
Mature Pollen

Lipopolysaccharide Embedded within the Exine of Pollen Grains

1975 ◽  
Vol 33 ◽  
pp. 572-573 ◽  
Author(s):  
J. R. Rowley
Keyword(s):  
High Temperatures ◽  
Oral Presentation ◽  
Pollen Grains ◽  
Carboxyl Groups ◽  
Organic Base ◽  
Anionic Sites ◽  
Basic Dyes

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.

scholarly journals The suppression of meiosis and the origin of diplochromosomes

1940 ◽  
Vol 128 (851) ◽  
pp. 170-185 ◽  
Keyword(s):  
High Temperatures ◽  
Pollen Grains ◽  
Chiasma Formation ◽  
Pollen Grain ◽  
Developmental Processes ◽  
Wall Formation ◽  
Internal Development ◽  
First Case ◽  
Diploid Pollen ◽  
New Type

The effects of abnormal temperatures on the meiotic divisions in various plants have been investigated by Sax (1937), Straub (1938), Matsuura (1937) and others. The effects which they have described arise in two ways: (1) by prevention of the pachytene pairing and subsequent chiasma formation in the chromosomes, and (2) by inhibition of the action of the spindle. In the first case we have a development very similar to that described in numerous hybrids, which can be adequately understood in terms of the irregular behaviour of univalents. They may, for instance, give rise to restitution nuclei at the end of the first division, and divide equationally at the second to give diploid pollen grains (Sax on Rhoeo 1936, and Tradescantia 1937). The suppression of the spindle gives rise to similar effects in the pollen grains. Separation of the bivalents and wall formation are affected so that diploid and tetraploid grains are formed as well as many unbalanced types. The present paper gives an account of a new type of derangement produced by high temperatures. In addition to the upset of developmental processes external to the chromosomes, as in the above cases, the internal development of the chromosomes is affected, so that a nucleus at early diplotene changes directly into a pollen-grain resting nucleus.

Resolution of Channels in the Exine by Translocation of Colloidal Iron

1971 ◽  
Vol 29 ◽  
pp. 352-353
Author(s):  
John R. Rowley
Keyword(s):  
Phosphate Buffer ◽  
Pollen Development ◽  
Osmium Tetroxide ◽  
Pollen Grains ◽  
Deionized Water ◽  
Colloidal Iron ◽  
Fixed Material ◽  
Epilobium Angustifolium ◽  
Untreated Material ◽  
Microspore Mitosis

The morphology of the exine of many pollen grains, at the time of flowering, is such that one can suppose that transport of substances through the exine occurred during pollen development. Holes or channels, microscopic to submicroscopic, are described for a large number of grains. An inner part of the exine of Epilobium angustifolium L. and E. montanum L., which may be referred to as the endexine, has irregularly shaped channels early in pollen development although by microspore mitosis there is no indication of such channeling in chemically fixed material. The nucleus in microspores used in the experiment reported here was in prophase of microspore mitosis and the endexine, while lamellated in untreated grains, did not contain irregularly shaped channels. Untreated material from the same part of the inflorescence as iron treated stamens was examined following fixation with 0.1M glutaraldehyde in cacodylate-HCl buffer at pH 6.9 (315 milliosmoles) for 24 hrs, 4% formaldehyde in phosphate buffer at pH 7.2 (1,300 milliosmoles) for 12 hrs, 1% glutaraldehyde mixed with 0.1% osmium tetroxide for 20 min, osmium tetroxide in deionized water for 2 hrs and 1% glutaraldehyde mixed with 4% formaldehyde in 0.1M cacodylate-HCl buffer at pH 6.9 for two hrs.

In situ REM imaging of surface processes on ceramic bulk crystals from 300 to 1670 K in a conventional TEM

1991 ◽  
Vol 49 ◽  
pp. 660-661
Author(s):  
Z. L. Wang ◽  
J. Bentley
Keyword(s):  
High Temperatures ◽  
Image Resolution ◽  
Atomic Processes ◽  
Crystal Surfaces ◽  
Beam Radiation ◽  
Surface Areas ◽  
Transmission Electron ◽  
Reflection Electron Microscopy ◽  
Gas Reactions

Studying the behavior of surfaces at high temperatures is of great importance for understanding the properties of ceramics and associated surface-gas reactions. Atomic processes occurring on bulk crystal surfaces at high temperatures can be recorded by reflection electron microscopy (REM) in a conventional transmission electron microscope (TEM) with relatively high resolution, because REM is especially sensitive to atomic-height steps.Improved REM image resolution with a FEG: Cleaved surfaces of a-alumina (012) exhibit atomic flatness with steps of height about 5 Å, determined by reference to a screw (or near screw) dislocation with a presumed Burgers vector of b = (1/3)<012> (see Fig. 1). Steps of heights less than about 0.8 Å can be clearly resolved only with a field emission gun (FEG) (Fig. 2). The small steps are formed by the surface oscillating between the closely packed O and Al stacking layers. The bands of dark contrast (Fig. 2b) are the result of beam radiation damage to surface areas initially terminated with O ions.

Freeze-substitution of rye grass and ragweed pollen grains

1990 ◽  
Vol 48 (3) ◽  
pp. 686-687
Author(s):  
Liza B. Martinez ◽  
Susan M. Wick
Keyword(s):  
Cell Function ◽  
Pollen Grains ◽  
Freeze Substitution ◽  
Cell Types ◽  
Rapid Freezing ◽  
Rye Grass ◽  
Acrylic Resins ◽  
Allergenic Proteins ◽  
Cold Embedding ◽  
Structural Preservation

Rapid freezing and freeze-substitution have been employed as alternatives to chemical fixation because of the improved structural preservation obtained in various cell types. This has been attributed to biomolecular immobilization derived from the extremely rapid arrest of cell function. These methods allow the elimination of conventionally used fixatives, which may have denaturing or “masking” effects on proteins. Thus, this makes them ideal techniques for immunocytochemistry, in which preservation of both ultrastructure and antigenicity are important. These procedures are also compatible with cold embedding acrylic resins which are known to increase sensitivity in immunolabelling.This study reveals how rapid freezing and freeze-substitution may prove to be useful in the study of the mobile allergenic proteins of rye grass and ragweed. Most studies have relied on the use of osmium tetroxide to achieve the necessary ultrastructural detail in pollen whereas those that omitted it have had to contend with poor overall preservation.

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