In previous work with mouse lines selected for resistance (R) and susceptibility (S) to fescue toxicosis, R mice had higher activities of Phase II liver enzymes glutathione S-transferase and uridine diphosphate glucuronosyl-transferase than S mice. Objectives of this study were: 1. to determine whether selection for toxicosis response had also caused divergence between lines in hepatic Phase I enzyme activity (as assessed by sleep time following sodium pentobarbital anesthesia), 2. to determine whether sleep time differences between lines were modulated by fescue toxins or enzyme inducers in the diet, and 3. to determine whether sleep time differences among individual mice were correlated with the impact of a toxin-containing diet on their post-weaning growth. In experiment 1, five dietary treatments were assigned to 24 male mice in each line: rodent food control, E+ (50% endophyte-infected fescue seed, 50% control), E+P (E+ with 1000 ppm phenobarbital), E- (50% endophyte-free fescue seed, 50% control), and E-P (E- with 1000 ppm phenobarbital). After four weeks on these diets, mice were challenged with a sleep time test. All mice were then switched to a pelleted rodent food diet. Each mouse then received a second sleep time test, a random 1/4 of the population after one, two, three, and four weeks on the standard diet. Results demonstrated that, regardless of dietary treatment, R mice had a shorter sleep time than S mice, suggesting higher activity of liver Phase I microsomal enzymes. Mice that were fed phenobarbital had significantly shorter sleep time than those whose diets did not include this microsomal enzyme inducer. Time interval between the first and second sleep time did not significantly impact the second sleep time, confirming line differences in the absence of toxins and inducers and with advancing age. In experiment 2, male and female R and S mice were fed an E- diet for 2 weeks, then an E+ diet for 2 weeks, followed by a pelleted rodent food diet for 2 weeks. Mice were then administered a sleep time test. Their growth rate response to fescue toxicosis was quantified as the proportional reduction in gain during two weeks on the E+ diet, compared to gain on E- during the previous two weeks. Sleep time was significantly influenced by line but not by sex or the line x sex interaction. As in Experiment 1, S mice slept longer than their R counterparts. The residual correlation between reduction in gain associated with the E+ diet and sleep time was only 0.04. Thus, under these experimental conditions an individual animal's Phase 1 enzyme activity did not predict how severely its growth rate would be depressed by a toxin-containing diet. Based upon these and previous studies, divergent selection for toxicosis response in mice was successful partially by causing divergence between lines both in Phase I and Phase II liver detoxification enzyme activities. If a heritable, practical, and economical criterion could be identified to quantify such differences in livestock species, then selection for toxicosis resistance might contribute to the solution of this important problem for American agriculture. / Master of Science

In previous work, mouse lines were selected for resistance (R) or for susceptibility (S) to fescue toxicosis based upon reductions in post-weaning growth rate caused by an endophyte-infected diet. The first objective of the current experiment was to determine whether long term reproduction of S mice was more severely depressed than that of R mice by the toxic diet. The second objective was to quantify glutathione-S-epoxytransferase (GST) and uridine diphosphate glucuronosyl-transferase (UDPGT) activities in R and S dams form the experiment and to determine whether reproduction during continuous cohabitation and liver detoxification enzyme activities were correlated within line x diet groups. Effects of the toxic diet were detectable within the first litters produced. Reproduction was more seriously influenced by the toxic diet within the S line than within the R line when these measures were compared within four equal time phases. The effects of the toxic diet on reproduction were greatest early in the experiment; by the fourth time phase differences among line x diet groups, with the exception of litter weight, were not significant. Percentage differences in total reproduction were greater between S mice fed the non-toxic diet and S mice fed the toxic diet than those between the R mice fed the non-toxic and toxic diets. Averaged across diets, GST activities were higher in R mice, but UDPGT activities were not significant. Within R line mice, GST was correlated with three reproductive measures, but UDPGT activity was not correlated with reproduction within any line x diet group. / Master of Science

The prevailing conditions in metalliferous soils are usually hostile for plant growth, but some plant species are still able to thrive in these substrates. Festuca arundinacea Schreb. plants were found to thrive on serpentine soils containing high concentrations of Cr and Ni. These plants contained higher concentrations of Ni in their roots than in their shoots. Hydroponic growth experiments with 350 µM and 650 µM Ni singularly and in combination revealed that more Cr was accumulated at the roots. The opposite was the case for Ni. The same experiments showed no difference between plants from serpentine and control soils in terms of growth and metal uptake. Ni was found to be toxic to control Festuca arundinacea plants at concentrations of at least 50 µM. The uptake of Ni in Festuca arundinacea was increased by an increase in the concentration of Ni and a decrease the pH of the substrate.

Diss. (sammanfattning). Uppsala : Sveriges lantbruksuniv. / Härtill 5 uppsatser.

La germination et la croissance hétérotrophe sont des phases clés de l'établissement des plantes. Ils sont sous contrôle génétique et affectés par la température. L'objectif de cette thèse est d'analyser la variabilité inter et intra-spécifique de cinq espèces prairiales dans leurs réponses à la température pendant la germination et la croissance hétérotrophe. Trente-deux populations de Lolium perenne, Festuca arundinacea, Dactylis glomerata, Medicago sativa, et Onobrychis viciifolia ont été évalués sous huit températures constantes entre 5 et 40°C.La nouveauté de ce travail vient de la large gamme de températures et le nombre de populations évaluées. Il a été observé que, au sein des espèces, la réaction des populations à la température indique une forte variabilité et des différences significatives. La germination n'a été pas observée à 40°C pour l'une des 23 graminées, l'O. viciifolia germé peu tandis que les variétés de M. sativa ont été peu affectées. La croissance hétérotrophe des 32 populations a été affectée par la température. La croissance des axes fortement fiable ou nulle à 40°C. Les courbes de réponse du taux de croissance maximale de l'axe sont asymétriques en forme de cloche.Des interactions significatives entre la température et la population ont été détectées pour la germination et la croissance hétérotrophe. La germination des populations des sites froids est renforcée par des températures plus chaudes et limité par les plus froids et vice-versa pour les populations chaudes adaptées. / Germination and heterotrophic growth are key phases for plant establishment. They are under genetic control and affected by temperature. The objective of this thesis was to analyse the inter- and intra-specific variability of five pasture species in their responses to temperature during germination and heterotrophic growth.Thirty two populations of Lolium perenne, Festuca arundinacea, Dactylis glomerata, Medicago sativa, and Onobrychis viciifolia were evaluated under eight constant temperatures between 5 and 40°C.The novelty of this work comes from the wide range of temperatures and the number of populations evaluated. It was observed that, within species, the response of populations to temperature shows high variability and significant differences. No germination was observed at 40°C for any of the 23 grasses, O. viciifolia germinated poorly while M. sativa varieties were little affected. Heterotrophic growth of the 32 populations was affected by temperature. The growths of the axes were negligible or lethal at 40°C. Response curves of maximum growth rate of the axis were asymmetric bell-shaped.Significant interactions between temperature and population were detected for germination and heterotrophic growth. Germination of populations from cold sites is enhanced by warmer temperatures and limited by colder ones and vice versa for warm-adapted populations. This study demonstrates that genetic variability does exist within the five studied species. This variability could be exploited to breed new varieties adapted to the future climate.

The Canterbury plains are frequently exposed to summer drought and climate predictions forecast that the severity and frequency of summer drought will increase. The most commonly used pasture grass, perennial ryegrass (Lolium perenne L.), is drought sensitive. One possible method to maintain sward dry matter (DM) production under water stress is to use an alternative grass species such as tall fescue (Festuca arundinacea Schreb.). The objective of this research was to compare summer DM production of monoculture swards of perennial ryegrass and tall fescue under various seasonal drought regimes to study physiological and biochemical drought responses of each species. Data were collected over a period of two-summer seasons, Season One (2006-2007) and Season Two (2007-2008) in an automated rain shelter at Lincoln, Canterbury. Drought treatments included exposure of plants to a spring or autumn drought or a four-weekly "irrigated" drought regime. DM yields of the two species were similar under each watering regime. The control treatment, under non-limiting conditions, has the highest accumulated yield in both Season One and Two for ryegrass (17.1 and 15.7 t DM ha⁻¹) and tall fescue (18.8 and 16.0 t DM ⁻¹) respectively. Spring and autumn drought treatments were similar for the two species in accumulated yield in either season, however the exposure to drought stress returned yields lower than the control. Consistently, the lowest-yielding treatment was the four-weekly irrigated drought, which resulted in an average yield across species in Season One of 10.1 t DM ha⁻¹ and 8.35 t DM ha⁻¹ in Season Two. Growth rates of the swards were calculated using accumulated DM production against accumulated thermal time using a base temperature of 3°C for both species. The control treatments showed a strong linear relationship for both species in both seasons, though Season Two showed a period of approximately 390 °Cd of no growth. Spring growth was similar for all treatments until October when both the spring drought and four-weekly irrigated treatment deviated from the control as water stress commenced. Growth also ceased under autumn drought later in the season. The physiological drought responses between species and among treatments differed. Tall fescue under control conditions had the highest photosynthesis rates of 20.5 µmol CO₂ m⁻² s⁻¹,or 22% higher than ryegrass, whereas the four-weekly irrigated treatment showed no inter-species differences. Differences were also found for other gas exchange parameters. Physiological water use efficiency (phys WUE) in ryegrass was 15% greater than tall fescue in Season Two. Photosynthesis and gas exchange rates against leaf water potential showed declining gas flow in both species across all treatments in response to drying soil conditions and across all irrigation treatments. The osmo-protectant proline was 22% higher in concentration in ryegrass than in tall fescue in Season Two and increased in drought stressed treatments in both seasons. Water stress was found to reduce total chlorophyll concentrations in all treatments and in tall fescue, while little change occurred in the chlorophyll a:b ratio. In conclusion, the findings from this thesis suggest similar DM responses for the two species under drought. The findings suggests that tall fescue performs more as a "water user" under drought conditions, compared with perennial ryegrass, which is more a "water saver." Resonses to the changing environment to a point, before "shuttting up shop" through lower stomatal conductance.