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Digitale Medien

Chemical agents that inhibit pollen development: effects of the phenyl-cinnoline carboxylates SC-1058 and SC-1271 on the ultrastructure of developing wheat anthers (Triticum aestivum L. var Yecora rojò) (1993)

Schulz, P. J. ; Cross, J. W. ; Almeida, E.

Springer

Sexual plant reproduction 6 (1993), S. 108-212

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ISSN: 1432-2145

Schlagwort(e): Wheat pollen ; Chemical hybridizing agents ; Male sterility ; Ultrastructure

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie

Notizen: Summary Phenylcinnoline carboxylate compounds SC-1058 and SC-1271 cause complete male sterility in wheat when applied at suitable dosages at the pre-meiotic stage of anther development. Anthers from treated and untreated plants were compared using light and electron microscopy from the pre-meiotic stage through the formation of nearly mature pollen. Overall anther development is gradually slowed in treated plants and pollen development is generally arrested in the late prevacuolate or early vacuolate microspore stage, although the first pollen mitosis does sometimes occur. The sporopollenin-containing exine walls are thinner, and show abnormally developed foot and tectum layers with sparse connecting baculi. Microspore cytoplasm degenerates and the cells eventually collapse. At the early, prevacuolate, free microspore stage treated tapetal cells hypertrophy, expanding into the locule. They contain abnormally large vacuoles that appear to form from the fusion of secretory vesicles, and some vacuoles contain electrondense deposits. The sporopollenin-containing orbicular wall and Ubisch bodies are retarded in their development and are structurally deformed. Acetolysis of whole anthers and of thick sections shows that the sporopollen-in-containing structures of treated materials are greatly reduced in thickness and are less rigid than in the control. We conclude that application of these compounds causes interference with the secretory function of tapetal cells which supplies sporopollenin cell-wall polymers to the exine of the microspores and to the tapetal orbicular wall and associated Ubisch bodies. Interference with the tapetal secretion of other nutrients required for microspore development is strongly suggested.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00227655

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Digitale Medien

Chemical agents that inhibit pollen development: tools for research (1991)

Cross, J. W. ; Ladyman, J. A. R.

Springer

Sexual plant reproduction 4 (1991), S. 235-243

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ISSN: 1432-2145

Schlagwort(e): Male sterility ; Pollen ; Anther ; Gameto cides ; Chemical hybridizing agents

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie

Notizen: Summary Several unrelated compounds are known to selectively inhibit the development of the male gametophyte. When applied at suitable dosages to plants at the appropriate stages of anther development, these substances block the formation of fertile pollen. The affected stage of pollen development is characteristic of the specific chemical structure of the compound, ranging from effects on microspore meiosis to the formation of pollen defective in the ability to germinate or fertilize. The range of effects mediated by these substances, and by known male-sterile mutants, indicates that microspore development has several critical phases that are particularly sensitive to fatal inhibition. We propose that chemical inhibitors of pollen development deserve attention as tools for elucidating the regulation of pollen development.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00200541

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Digitale Medien

Finite element analysis of heat transfer and flow problems using adaptive remeshing including application to solidification problems (1991)

Lewis, R. W. ; Huang, H. C. ; Usmani, A. S. ; [weitere]

Chichester [u.a.] : Wiley-Blackwell

International Journal for Numerical Methods in Engineering 32 (1991), S. 767-781

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ISSN: 0029-5981

Schlagwort(e): Engineering ; Engineering General

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Mathematik , Technik allgemein

Notizen: An error estimation technique for adaptive finite element analysis of heat conduction problems is described. The performance of this technique is demonstrated using a two-dimensional steady-state linear benchmark problem with a known analytical solution. A transient non-linear heat conduction problem involving solidification is then solved as a typical practical application. Some preliminary investigations for error indicators in flow problems are presented.

Zusätzliches Material: 10 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/nme.1620320408

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Digitale Medien

A finite element model for the simulations of mould filling in metal casting and the associated heat transfer (1992)

Usmani, A. S. ; Cross, J. T. ; Lewis, R. W.

Chichester [u.a.] : Wiley-Blackwell

International Journal for Numerical Methods in Engineering 35 (1992), S. 787-806

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ISSN: 0029-5981

Schlagwort(e): Engineering ; Engineering General

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Mathematik , Technik allgemein

Notizen: The flow associated with the pouring of molten metal into moulds has been modelled based upon certain simplfying assumptions. A finite element based Navier-Stokes equation solver has been used to analyse the flow. The velocities obtained from the Navier-Stokes equation solver are used to advect a pseudo-concentration function for modelling the free fluid front. A simple problem with a known analytical solution is solved first to test the model. Subsequently, several more examples of varied geometrical configuration are modelled to demonstrate the applicability of the proposed model. The Taylor-Galerkin method has been used to model the heat transfer during filling due to its advection dominated nature.

Zusätzliches Material: 12 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/nme.1620350410

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