Ulm, Univ., Diss., 2008.

Thesis (Ph. D.)--Illinois State University, 1979. / Title from title page screen, viewed Feb. 4, 2005. Dissertation Committee: Tsan Iang Chuang (chair), Anthony E. Liberta, Derek A. McCracken, Mathew J. Nadakavukaren, David F. Weber. Includes bibliographical references (leaves 229-234) and abstract. Also available in print.

Thesis (doctoral)--University of Wisconsin--Madison, 1928. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (M.S.)--University of Wisconsin--Madison. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 27-28).

Thesis (M.A.)--University of Wisconsin--Madison, 1935. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

"A major part of the thesis submitted to the Agra University, in the year 1964, for the award of the Ph. D. degree." / Includes index. Bibliography: p. 47-49.

Thesis (M.S.)--University of Wisconsin--La Crosse. / Includes bibliographical references (leaves 80-85).

In the tomato-growing areas in southern Canada, it is desirable to have commercial varieties having the character of being able to set fruit at relatively cool temperatures. Puck a non-commercial variety sets fruit at temperatures between 55° and 65°F. Experiments attempting to identify the mechanism of the desirable character of Puck in terms of pollen viability were done. The tomato varieties, Puck, Bonny Best, Earliana 498, and their reciprocal crosses, were grown both in the field and in greenhouses. Various factors affecting variability in pollen samples and pollen viability determinations, were studied. Experimental results indicated that a sample of pollen taken at anthesis consists of mature, immature, and empty grains. The relative proportions of the three classes of grains depended upon the method of collection used, the time of collection and the location of the pollen source on the plant. The greater the variability in the sample, the larger is the representative sample size required for microscopic examination at a chosen degree of tolerance. The staining technique gave the highest percentages of viable pollen. Low viability percentages were obtained in vitro, and these are attributed to bursting of some of the normal mature grains during pollen tube initiation. A quantitative in vivo procedure of counting pollen tubes by callose fluorescence under ultra violet light, was developed. Variations in the in vivo results can be ascribed to variation in the concentration of pollen growth factor (PGF) which appeared to vary with the number and density of grains used in pollinations. Results showed increased germination percentages when the number of grains used was increased. The most suitable number and density for maximum group effect has not been investigated. The variety Puck gave higher viability percentages than Bonny Best in most cases. Further investigations of the problem would require more precise control of environmental factors during pollen development, and exposure of pollen following anthesis. / Land and Food Systems, Faculty of / Graduate

Previous authors have concluded that hummingbird territorial boundaries would restrict pollen flow. I questioned the validity of this on the time scale of a blooming season for a system in which individual plants remained in flower while the territories surrounding them often changed in size and shape. To determine the effects of hummingbird foraging behavior on pollen flow, I studied six components of a hummingbird-plant pollination system: hummingbird territorial behavior, plant blooming time, foraging flight distances, pollen carry over, other pollinators, and plant breeding systems. Using this information I found I could depict pollen flow between two plants as a function of: 1) The flowering times of the plants. 2) The distance between the plants. 3) The amount of time these plants are surrounded by the same territorial boundaries. 4) The number of plants (or flowers) the bird visits before visiting the second plant. I found that the influence of territorial boundaries on pollen flow is determined not by the boundary of a single territory, but by the influence of all the territorial boundaries surrounding a plant while it is in bloom. Within these boundaries, the probability of pollen being transfered between two plants is a function of the amount of time they are within the same boundary. The length of hummingbird foraging flights is also a major determinant of pollen flow and the predominance of short flights between plants may restrict pollen flow probabilities. The restriction imposed by these short flights may be reduced by 1) long pollen carry over distances and 2) the longer flight distances between a perch and a plant. / Science, Faculty of / Zoology, Department of / Graduate

A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy. Johannesburg, 2015. / External pollen grain morphology has been widely used in the taxonomy and systematics of flowering plants. The eurypalynous family Acanthaceae is a notable example of a group where these pollen diversities have proved useful in determining relationships between taxa. However, internal pollen wall features have received far less attention due to the difficulty of examining the underlying exine from which the external sculpturing is derived. Consequently, internal wall features have thus far not been used in formulating existing classifications. A new technique involving precise cross sectioning or slicing of pollen grains at a selected position, using a focused ion beam-scanning electron microscope (FIB-SEM), was used on 39 species of Acanthaceae to examine the internal pollen wall structure and identify features of potential systematic relevance. Five basic internal wall structures were described in this study. The study also showed that similar external pollen wall features may have distinctly different underlying structures.