Graduate Thesis Or Dissertation

 

A comparative anatomical study of galls caused by the major cecidogenetic groups, with special emphasis on the nutritive tissue Public Deposited

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  • The anatomies of 44 galls are discussed with special attention given to the development, longevity, and tannin content of the nutritive tissues. Within the main section of the thesis, representative galls from the major cecidogenetic groups, with the exception of bacterial and Australian scale galls, are studied. These include galls caused by fungi, nematodes, mites, moths, sawflys, scales, aphids, adelgids, tephritids, cecidomyiids, and cynipids. Three leaf mines are also described. Observations were taken from thin sections (plastic embedment) with a light microscope. The galls are arrayed along a continuum of increasing structural complexity, as judged by the degree of gall tissue differentiation. The sclerenchymatous "protective" zone and nutritive cells are used as indicators of gall complexity and of strength of the gall-former's influence over host plant tissue. Starting with the Fungal galls, then moth and sawfly galls, to the thrips, scale, mites, nematode, cecidomyiid and cynipid galls, one sees greater differentiation of gall tissues, with an increasingly distinct nutritive layer. A scierenchyma zone develops only in in midge and wasp galls. The longevity of the nutritive tissue varies from gall to gall. Generally, the nutritive tissue is maintained in an enriched state for an extended period only in galls caused by cynipids (and perhaps by nematodes). The mites and midges show enriched nutritive cells only in early gall development. No distinctive nutritive tissue occurs in the aphid galls that were studied. Generally, nutritive tissue contains less tanniferous material (as detected by the ferrous sulfate stain) than do either peripheral gall tissues or cells of the leaf. Thus, many gall-formers avoid tannins by directing the development of the cells upon which they feed. The epilogue includes a list of features shared by many galls and by gall-forming organisms. Gall-fparasites. The three appendices include 1) an anatomical study of eight galls on shrubs from the drylands of eastern Oregon (mite, cecidomyiid, tephritid, and moth galls), 2) a discussion of fossil galls and leaf mines as indicators of the age and stability of these co-evolutionary relationships. Two galled acorns from the La Brea Tar pits (Los Angeles, California) are described in this section. Lastly, 3) a discussion of economically important galls is provided. This last appendix addresses the question of why there are relatively few gall-forming insect pests, and includes a discussion of the supposed benignity of insect galls.
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Déclaration de droits
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  • PDF derivative scanned at 300 ppi (256 B&W, 256 Grayscale), using Capture Perfect 3.0, on a Canon DR-9080C. CVista PdfCompressor 3.1 was used for pdf compression and textual OCR.
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