Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1990. / Vita. Abstract. Includes bibliographical references (leaf 45). Also available via the Internet.

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Thesis (Ph.D.) -- University of Adelaide, Dept. of Botany, 1999. / Bibliography: p. 191-200.

Rudbeckia hirta I Marmalade' plants at different leaf numbers were exposed to a (long day) LD photo period in order to quantify the end of juvenility. A quadratic relationship existed between flowering and both the number of leaves the plant possessed and the number of days from onset of LD. The loss of juvenility occurred in the shortest time, 42 days, plants had 15-24 true expanded leaves. The greatest stem height also corresponded to this same leaf number. The number of LD received did not affect ray floret number per inflorescence, scape length and capitulum diameter excluding ray florets. Gaillardia pulchella flowered most rapidly in 49 days, with a minimum of 14-20 expanded leaves as described in a quadratic relationship. Histological studies during evocation indicated an increase in apical meristem widths (120 pm to 224 pm) and heights (21 ~m to 48 pm), an increase of 2 to 5 tunica cell layers, greater corpus organization, and a lower point of primordia attachment with respect to increased doming of the apex all occurring with maturity of the apex. Solidago flexicaulis exhibited a complex (combination) photoperiodic response, requiring an extended LO exposure prior to SO initiation. The last treatment, consisting of 12-week-old-plants transferred from LO to SO, flowered most rapidly in 62 days. Other measured characteristics such as stem length, dry weight of all tissue above and below the soil line, number of basal shoots and main axis leaf number were not different depending on amount of SO induction. There was a difference in the above measured variables, except emerged basal shoots and leaves per main axis, between control LO plants and all averaged SO treated plants. / Master of Science

Bibliography: p. 191-200. / 200 p. : ill. (chiefly col.), map (fold.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Persistence mechanisms of Erodiophyllum elderi are investigated in terms of life history strategies and patchy population theory. / Thesis (Ph.D.)--University of Adelaide, Dept. of Botany, 1999

Bibliography: p. 191-200. Persistence mechanisms of Erodiophyllum elderi are investigated in terms of life history strategies and patchy population theory.

Hybrids are common, being found in about 25% of all plant species, but the isolating barriers which preserve species integrity are poorly studied. I investigated this question in the large New Zealand genus Celmisia Cass. (Asteraceae), which hybridises readily in cultivation, but wild hybrids are relatively rare. My study quantitatively tests four potential reproductive isolating barriers in 12 sympatric species of Celmisia found in the Craigieburn Range, inland Canterbury, New Zealand. I examined two potential prezygotic reproductive isolating barriers (flowering phenology and pollinator specialisation), and two potential postzygotic barriers (pre-dispersal seed predation and hybrid seed germination). I used null models to test whether Celmisia species had temporally segregated flowering times, and found that some Celmisia are temporally segregated and thus less likely to form hybrids. I used experimental pair-wise flowering arrays to observe insect visitation to six different Celmisia species pairs. While I found no difference in the overall pollinator community, several insect families showed preferences for some Celmisia species. Furthermore, I found that subtle floral character differences were driving these insect preferences. In particular, I found scape height to be positively associated with insect visitation with taller Celmisia being favoured over shorter species. Insect preferences did not translate into strong floral constancy, therefore indicating that Celmisia flower visitors are likely to be a weak barrier to hybridisation. I reared a range of insect seed predators from field-collected capitula of the hybrid C. x pseudolyallii and both parent species (C. lyallii and C. spectabilis). There was no overall difference in the number of seed-predators per capitulum between hybrid and parent Celmisia taxa. I collected and sowed seeds from three Celmisia hybrids and their parent species in order to test whether hybrids were less fertile than their parent species. I found no evidence to suggest that the seeds of hybrids had lower germination success than those of their parents. Overall I found evidence for only weak prezygotic reproductive isolation and no evidence for postzygotic isolation in the four barriers I examined in Celmisia.

Although herbivory and other types of plant damage typically are viewed as detrimental to plant survival and performance, vigorous regrowth, greater seed set, and fitness benefits may be possible when damage to the apical meristem, or actively growing stem terminal, is involved. Such damage releases apical dominance, or the hormonal suppression of lateral buds, activates dormant lateral buds, and enables lateral shoots to grow. Since in plants with terminal flowers, each stem may bear a flower, removal of the apical meristem may result in stem bifurcation and ultimately increase the number of flowers and seeds, thereby increasing potential fitness. In the current study, possible overcompensation in response to apical meristem damage caused by simulated herbivory (clipping) and the gall midge Asphondylia borrichiae Rossi and Strong (Diptera: Cecidomyiidae) (galling) was investigated in the native coastal halophyte, sea oxeye daisy Borrichia frutescens (L.) DC. (Asteraceae), in relation to nutrient supplementation. Results suggest a strong correlation between stem count and gall count at the study site; moreover, apical dominance was relatively weak early in the growing season and stronger in short plants that were shaded by taller neighbors later in the season. Results also indicate that overcompensation or even full compensation is an unlikely response to apical meristem damage in B. frutescens. Stem count was similar across all stem treatments, but increased significantly with nutrient supplementation, which all supports weak apical dominance in sea oxeye daisy. Nearly all measures of fitness also were either slightly or significantly lower when clipped and galled compared to plants with stems intact, while seed count responded positively to nutrient supplementation.

Berkheya Ehrh. is a genus of daisies in the tribe Arctotideae, subtribe Gorteriinae with over 80 species, most of which occur in southern Africa. This genus has centres of diversity associated with the montane regions of South Africa, including the Drakensberg Alpine Centre and Mpumalanga escarpment regions. Previous molecular and morphological studies indicate that Berkheya is paraphyletic. I present phylogenies based on nrDNA (ITS; Internal Transcribed Spacer) and cpDNA (psbA-trnH) sequence data analysed with Bayesian Inference and Parsimony. A phylogeny of combined cp- and nrDNA is also presented. These phylogenies are used to assess generic limits and to investigate the biogeographic patterns of Berkheya and its allies. The ITS phylogeny shows five well supported clades of Berkheya, two of which (Clades I and 2) are monophyletic summer rainfall region clades. Clades 3 to 5 are all paraphyletic winter rainfall clades with Cullumia occurring in the third clade, Cuspida occurring in the fourth and Didelta in Clade 5. Both psbA-trnH and combined phylogenies show concordance with the clade distribution shown in the ITS phylogeny. The ITS phylogeny was used to analyse correspondence with Roessler’s (1959) Series. It was found that the phylogeny showed considerable agreement with Roessler’s series, but B. bipinnatifida and B. spinosa of Series Speciosae may require some revision as well as taxa of monotypic series Cruciatae and Angustae. It is suggested that the latter series be merged with Cullumia species to form a single series. Some consideration should be taken to include Didelta species into Series Fruticosae as Didelta occurs in subclade 5b of Clade 5 with other Series Fruticosae taxa. Achene morphology was examined from species from each of the five clades to investigate the relationships of Berkheya and its allies, as well as to determine if there were any consistent achene features for each clade. The structure of surface cells on the fruit, the presence, absence and morphology of twin hairs as well as the structure of the pappus scales were found to be most useful in reflecting phylogenetic relationships within the clades. When compared with the clades of the ITS phylogeny, achene morphology showed consistent characters between taxa occurring in the same clades. As the most comprehensive study involving Berkheya, this phylogenenetic investigation was able to confirm that Berkheya is a paraphyletic genus with Didelta, Cullumia and Cuspida needing to be subsumed into Berkheya. An alternative classification is that taxa of Clade 5 could possibly be erected as an expanded Didelta, separate and sister to Berkheya.