Since plants utilize CO��� as the substrate for photosynthesis, terrestrial plants may be directly affected by increasing levels of CO��� in the atmosphere. Plants native to the sagebrush steppe are predicted to increase in growth in response to elevated CO��� through increased water use efficiency and higher photosynthetic rates. This study examined the interactions between edaphic factors and CO��� in order to determine how species native to the sagebrush steppe may respond to elevated CO���. The objectives of these experiments were to: 1. determine if Sitanion hystrix, Artemisia tridentata ssp. wyomingensis, and Stipa thurberiana alter their growth and physiology in response to CO��� and soil temperature. 2. determine if Sitanion hystrix and Artemisia tridentata ssp. wyomingensis alter their growth and physiology in response to CO��� and water stress. Two experiments were conducted using environmentally controlled chambers. In the first experiment, Sitanion hystrix, Artemisia tridentata and Stipa thurberiana were exposed to ambient (374 ppm) or high (567 ppm) CO��� conditions and low (13��C) or high (18��C) soil temperature. After four months in the chambers, plants were harvested and plant material was divided into shoots, roots, and leaves. Results from the first experiment demonstrated that carbon dioxide and soil temperature modified the growth of these species. Sitanion hystrix increased its shoot and root weights at elevated CO��� when grown under low soil temperatures. Artemisia tridentata had lower plant weights under elevated CO��� and 18 ��C soil temperature than plants grown at ambient CO��� and 13��C. Shoots of Stipa thurberiana were responsive to soil temperature and roots were responsive to CO��� at 18��C. In the second experiment, Sitanion hystrix and Artemisia tridentata were exposed to ambient (371 ppm) or high (569 ppm) CO��� and well-watered or water stressed conditions. Results indicated that there were no interactive effects betweeen CO��� and water stress with respect to plant growth or physiology. CO��� increased water use efficiency in S. hystrix and increased water use efficiency of A. tridentata at the beginning of the experiment but had no interactive effects with water stress on growth or photosynthesis. Results suggested that the effect of CO��� on plant growth and productivity of the sagebrush steppe is dependent upon the soil temperature to which the plants are exposed. Differences between species in their response to CO���, soil temperature, and water stress were also apparent in this experiment. These controlled environment studies should pave the way for field studies in the sagebrush steppe in order to determine if differences in carbon allocation, resulting from changes in CO��� and soil temperature, are realized in the field. Alterations in carbon allocation may potentially alter the competitive relationships between species and influence successional processes in the sagebrush steppe. / Graduation date: 1997

Effects of developmental exposure to chlorpyrifos (CPS) or methyl parathion (MPS) on visuospatial, adaptive fear response, and passive avoidance memory and the signaling mechanisms responsible for these neurocognitive changes were investigated. Using an incremental low dose regimen, rat pups were orally gavaged daily with either corn oil (vehicle), CPS, or MPS from postnatal day 1 (PND1) -PND21. Cholinesterase activity was significantly inhibited with the highest dosages of CPS and MPS for up to 19 days after the last dosages. OP exposure impaired working and reference memory in males whereas in the females, enhancement occurred following CPS exposure. In addition, the adaptive fear response and passive avoidance retention memory was impaired in males whereas differential changes occurred in females. Accordingly, the behavioral deficits observed in males were persistent whereas the enhancement in females was transient. Males were more sensitive to OPs than females in that the medium and high dosages of CPS and MPS produced greater effects in females whereas all dosages of both compounds produced effects in males. Training in the radial arm maze significantly increased protein kinase C gamma (PKC ) expression and activity in the hippocampal membrane fraction of control rats whereas exposure to OPs exhibited a significant decrease in PKC and PKC immunoreactivity in both untrained and trained rats. However, MPS exposed females exhibited a significant increase in PKC expression in the cytosolic fraction but this was not related to improved memory. Reduction of membrane PKC expression and activity and cytosolic PKC expression and activity seemed to be related to visuospatial learning and memory deficits in exposed males but not exposed females. Brain-derived neurotrophic factor (BDNF) gene expression in the hippocampus was significantly increased (60%) in trained control males as compared to untrained control males. In contrast, trained and untrained females exhibited similar levels of BDNF gene expression. However, exposure of both sexes to either CPS or MPS significantly reduced the expression of BDNF in trained rats. In summary, these data indicate that OP exposure induced gender-specific changes in working memory formation and altered PKC isozyme levels/activity and BDNF expression.

No description available.

Typescript (photocopy). / Digitized by Kansas Correctional Industries

Photocopy of typescript. / Digitized by Kansas Correctional Industries

Typescript (photocopy). / Digitized by Kansas Correctional Industries

Call number: LD2668 .T4 1952 J61 / Master of Science

Call number: LD2668 .T4 1964 M43 / Master of Science

Tests were conducted to ascertain whether B chromosomes influence the susceptibility of maize (Zea mays L.) plants to gamma-radiation-induced DNA damage. Isogenic stocks of Black Mexican sweet corn with and without B chromosomes were premeiotically irradiated and DNA damage was assayed by measuring pollen viability. Higher pollen viabilities relative to non-irradiated control plants were consistently obtained in irradiated plants with B chromosomes when compared to irradiated plants without B's. Furthermore, among plants irradiated with 1250R those with one B chromosome produced the greatest proportion of viable pollen and plants with increasing numbers of B's produced progressively less viable pollen. An exophenotypic trait elicited by B chromosomes is also reported. Plants with 5 or more B chromosomes often display an aberrant phenotype characterized by longitudinal white leaf stripes and/or narrow leaves. This phenotype intensifies with increasing numbers of B chromosomes and is the first case of a qualitative exophenotypic trait attributable to B chromosomes reported in maize.

No description available.