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Bibliography: leaves 151-187. / xvii, 187 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Agriculture and Natural Resource Sciences, 1993

Bibliography: leaves 151-187.

The phytohormones auxin and cytokinin control plant development through a complex network of interactions which include synergistic, additive, and opposite effects whose mechanisms are unknown. The auxin-insensitive diageotropica (dgt) mutant provided a tool to dissect the relationship between auxin- and cytokinin-induced responses in tomato. Morphological, physiological, and molecular data support the proposal that auxin and cytokinins control a common set of developmental processes through separate signal transduction pathways which interact downstream from the DGT gene product. Morphological traits of dgt plants, such as reduced root and shoot growth, reduced leaf complexity, and reduced apical dominance were phenocopied by exogenous cytokinin application to wild-type plants, demonstrating that cytokinins and the DGT-mediated auxin response control a common set of phenotypic characteristics. Because the dgt mutation had no detectable effects on the levels of endogenous cytokinins or on the cytokinin sensitivity of whole plants, cytokinins were hypothesized to cause dgt-like effects on plant development through inhibiting auxin-induced responses. This hypothesis was supported by physiological experiments showing that auxin-induced elongation and ethylene synthesis were inhibited in cytokinin-treated wild-type and in untreated dgt hypocotyls. Differences between the effects of cytokinins and the dgt mutation on auxin responses became apparent at the molecular level. Experiments on the auxin-induced accumulation of transcripts for two ACC-synthase genes and one SAUR gene demonstrated that cytokinin treatment selectively reduced the auxin-induced expression of only one ACC-synthase gene, while the dgt mutation inhibited the auxin-inducibility of all three genes. The effects of the dgt mutation were thus more pleiotropic than the cytokinin effects, suggesting that cytokinins inhibit auxin-responses downstream from the DGT gene product. In vitro culture of dgt hypocotyl explants and calli demonstrated shared or interacting signal transduction pathways for auxin and cytokinin in the stimulation of cell division, and independent pathways for the control of organ regeneration and vascular differentiation. / Graduation date: 1997

Thesis (Ph. D.)--University of Wisconsin--Madison, 1968. / Typescript. Vita. Includes bibliographical references.

Tris-soluble protein and total nitrogen of tall and dwarf tomato (Lycopersicon esculentum Mill.) seedlings were determined by the method of Lowry et al. and a modified micro-Kjeldahl direct Nesslerization technique. The tall tomato 'Fireball' differs from the dwarf 'Md. 412-4' in several ways: (1) the tall has more total nitrogen and protein; (2) it exhibits a significant increase in protein during the initial 48-hours of seeds imbibition; (3) it has a higher amount of protein in the roots; (4) the rate of decline of total nitrogen is faster than the dwarf, and (5) the tall tomato is more efficient in the utilization of plant nitrogen and protein. The greater growth of the tall resulted in a more rapid decline in nitrogen. However, in 10-18 day-old seedlings, growth was still rapid while nitrogen and protein did not change appreciably. The tall was more efficient and utilized a lesser amount of nitrogen and protein in the production of a comparable amount of fresh weight. It is suggested that the roots have considerable influence(s) on the growth of the shoot and that the decline in nitrogen and protein is a resultant of growth. It is indicated that the differences in growth may be more dependent on the manner in which nitrogen and protein are utilized rather than their absolute content. / Master of Science

The effects of hormonal chemicals and different genotypes on fruit growth of greenhouse-grown tomatoes (Lycopersicon esculentum Mill.) were examined. Continuous root application of 10nM N⁶-benzylaminopurine in Hoagland's nutrient solution to tomato seedlings of 'Fireball' and 'Red Cherry' significantly delayed anthesis of 'Fireball', but not 'Red Cherry'. Ovary diameter at anthesis, final fruit diameter, and fruit weight of both cultivars were unaffected. Irrespective of treatments, a significant positive correlation was obtained between ovary diameter at anthesis and final fruit diameter. A single foliar application of 0.25mM or 0.37mM β-na-phthoxyaceticacid (βNOA) at the appearance of the first in florescence of ‘Fireball' significantly increased ovary diameter at anthesis, but had no effect on final fruit diameter. Flowers on the second inflorescence of tomato plants treated with 0.37mM βNOA had smaller ovary sizes at anthesis than those of untreated plants. Application of 0.125mM βNOA, and 1µM, 10µM, and 100µM gibberellin A₃ had no significant effect on ovary diameter at anthesis or final fruit diameter. A significant positive correlation was also shown between ovary diameter at anthesis and final fruit diameter of βNOA treated plants. Among the twelve genotypes tested, significant correlations between ovary diameter at anthesis and final fruit diameter were found for 'Fireball', 'Michigan/Ohio Hybrid', and 'New Yorker'. The remaining genotypes showed no significant correlations between ovary diameter at anthesis and final fruit diameter. The average ovary diameter at anthesis (of all the genotypes) was significantly correlated with final fruit diameter, fruit weight, and locule number. / Master of Science

We have studied the effects of exogenous salt on whole plant and suspension culture cells of the halophytic tomato Lycopersicon pennellii. Under low salt conditions (2.9 dS/M) plants showed enhanced (halophytic) growth (107% of control). At moderate (7.5 dS/M) and high (18.5 dS/M) salt levels, salt stress reduced growth to about 78% and 40% of control respectively. Salt-induced changes in root mRNAs were analyzed via two-dimensional PAGE of cell free translation (CFT) products. We have identified 14 proteins whose levels were enhanced by exogenous salt. One of these proteins was unique to low salt induced halophytic growth. This system allowed for discrimination between proteins up-regulated at all salt levels and those up-regulated only during salt stress induced growth reduction. Ten proteins were identified whose levels were reduced by exogenous salt. Once again, one could identify a subset of proteins whose levels were reduced only under salt stressed conditions. Proteins identified in this study are candidates for roles in growth maintaining stress adaptive metabolism in L.pennellii. These data underscore the complexity of the genetic control of salt metabolism in higher plants. The effects of exogenous salt on protein synthesis and accumulation were studied in suspension cultures of L.pennellii. Two salt levels were applied to the cells. Under low salt conditions (LS, 10 mM), L.pennellii cells showed enhanced (halophytic) growth. Under high salt conditions (HS, 50 mM), the cells showed reduced (salt-stressed) growth. Changes in proteins with time were analyzed by a combination of cell free translation, in vivo labeling and total accumulated protein. In vivo labeling studies showed that the pattern of steady state protein synthesis was disrupted shortly after addition of salt. High salt induced greater disruption in the pattern. Over time, the steady state levels of most proteins shifted back towards those of the unstressed-control. However, the level of several proteins remained altered. Analysis of proteins whose levels increased with exogenous salt showed differences in the response patterns that may allow for discrimination between proteins involved in growth maintaining and stress shock responses.

Some ill. mounted. Bibliography: leaves 106-118.