Doctor of Philosophy / Department of Agronomy / Allan K. Fritz / Heat and drought stress are two of the most significant abiotic stresses limiting wheat production in the Great Plains and worldwide. Introgression of novel tolerance genes from wild relatives is a strategy which presents promise. This study examined both heat and drought tolerance from the tetraploid species Aegilops geniculata (U[superscript g]U[superscript g]M[superscript g]M[superscript g]). Additional screening for heat tolerance was conducted with the US genome species Aegilops peregrina (Hack) and Aegilops kotschyi (Boiss). A comprehensive screening system for drought tolerance was also constructed to evaluate wheat and its wild relatives. Previous reports suggested that Ae. geniculata accession TA2899 was moderately tolerant to heat stress. It had also previously been used to develop a full set of wheat-Ae. geniculata chromosome addition lines in a Chinese Spring background. To identify the chromosome(s) carrying the heat tolerance, all addition lines, as well as wheat check genotypes, were screened for post-anthesis heat tolerance in two growth chamber experiments. No chromosome addition lines were significantly different (p<0.05) from Chinese Spring, and none were found to have superior performance to the positive check cultivars. Forty-five accessions of Ae. peregrina and its close relative, Ae. kotschyi were screened in a post-anthesis heat experiment. A follow-up experiment compared the genotypes in a split-plot temperature treatment with heat and optimal growth chambers. Many accessions were similar to the control genotypes for grain fill duration, and some exceeded the wheat controls for relative chlorophyll index values on Day 12 and Day 16. TA1889 and TA1904, both Ae. peregrina accessions originating from Israel, had a higher grain fill duration across experiments than the best wheat control, and warrant further investigation. Previous reports suggested drought tolerance in Ae. geniculata. After preliminary screenings, six genotypes were selected for advanced screening and compared with three wheat cultivars. The advanced greenhouse screening system was conducted in 152cm tall PVC growth tubes. The experiment measured multiple plant responses, and had a datalogging system automatically collecting water content and matric potential of the growth media. Multiple accessions warranted further investigation, and showed potentially different modes of drought tolerance, with varying levels of stomatal resistance, biomass, and osmotic adjustment.

A degeneração testicular é a mais frequente afecção reprodutiva em machos e leva a queda da qualidade espermática e, consequentemente, da fertilidade. Uma das principais causas é o estresse térmico, sendo caracterizada pelo aumento na produção de espécies reativas ao oxigênio, assim, substâncias antioxidantes podem reduzir os impactos negativos ao sêmen desses animais. A melatonina tem alto fator antioxidante, além de atuar na proteção ao DNA espermático e na regulação da apoptose. O presente estudo teve por objetivo avaliar os efeitos do tratamento exógeno com melatonina de longa ação sobre a recuperação do quadro de degeneração testicular em touros da raça Nelore. Para tal, foram realizados dois experimentos. O experimento 1 foi realizado para definir a dose exógena de melatonina (diluída em veículo oleoso e administrada por via intramuscular) que provocaria aumento por tempo prolongado na concentração sérica da mesma em bovinos. Foram utilizadas nove vacas ovariectomizadas distribuídas em três grupos: Controle (somente veículo oleoso); Melatonina 18 mg/50 kg de peso vivo; e Melatonina 27 mg/50 kg de peso vivo. Foram colhidas amostras de sangue no dia da aplicação e 4, 8, 16 e 24 dias após. A concentração de melatonina foi dosada pela técnica de ELISA. Os dados foram analisados utilizando o software Statistical Analysis System (SAS), pela ANOVA, adicionando-se o fator medidas repetidas no tempo. As probabilidades de interações ao longo do tempo foram determinadas pelo comando RANDOM (PROC GLIMMIX do SAS), com nível de significância de 5%. A aplicação de melatonina intramuscular diluída em veículo oleoso, na concentração de 18 mg/50 kg de peso vivo, provocou aumento estável por oito dias na concentração sérica de melatonina em bovinos. No experimento 2 foi avaliado o tratamento com melatonina sobre a degeneração testicular em touros, utilizando a dose estabelecida no experimento 1. A degeneração testicular foi induzida pela colocação de bolsas insuladoras testiculares por 96 horas. Foram utilizados 22 touros da raça Nelore distribuídos em 4 grupos: CON - touros não induzidos à degeneração testicular e não tratados (n=5); DT - touros induzidos à degeneração testicular e não tratados (n=6); ME - touros não induzidos à degeneração testicular e tratados com melatonina exógena (n=5); e DTME - touros induzidos à degeneração testicular e tratados com melatonina exógena (n=6). Foram realizadas colheitas de sêmen e sangue semanalmente, iniciando-se duas semanas antes da colocação das bolsas testiculares; no dia da retirada; e por mais 11 semanas após. Foram analisadas as características clínicas, tais como perímetro escrotal, consistência testicular, homogeneidade testicular (presença de pontos hipercóicos) e hemodinâmica do parênquima e plexo pampiniforme e índice de resistência vascular. As características seminais avaliadas foram volume, concentração, motilidade e vigor subjetivos, análise computadorizada dos espermatozoides, membranas plasmática, acrossomal e mitocondrial, morfologia espermática, peroxidação lipídica e bioquímica do sêmen. O plasma sanguíneo foi utilizado para avaliar a peroxidação lipídica e componentes bioquímicos (proteína total, albumina, GGT, AST, ALT, creatina quinase, triglicérides, colesterol, HDL, BHB e NEFA). Os dados foram analisados utilizando o software SAS, pela ANOVA, adicionando-se o fator medidas repetidas no tempo. As probabilidades de interações ao longo do tempo foram determinadas pelo comando RANDOM (PROC GLIMMIX do SAS), com nível de significância de 5%. A insulação provocou queda na consistência testicular, motilidade, integridade das membranas plasmática e acrossomal e no potencial de membrana mitocondrial, bem como aumentou os defeitos espermáticos e a peroxidação lipídica. O tratamento com melatonina não mostrou influência sobre as características clínicas; contudo, apresentou melhora no vigor (p=0.05), na motilidade total (p=0.05) e no potencial mitocondrial (p=0.003) 15 dias após a aplicação da melatonina. Além disso, a melatonina diminuiu os valores de HDL, colesterol e BHB. O tratamento da degeneração testicular em touros (28 dias após a insulação) utilizando melatonina exógena em veículo de liberação lenta, na dose de 18 mg/kg, é eficiente em melhorar características de vigor, motilidade e potencial mitocondrial espermático. / Testicular degeneration is the most frequent reproductive affection in males and leads to a decrease in sperm quality and, consequently, fertility. One of the main causes is heat stress, being characterized by the increase in the production of reactive oxygen species, thus, antioxidant substances can reduce the negative impacts to the semen of these animals. Melatonin has a high antioxidant factor, besides acting in the protection of sperm DNA and in the regulation of apoptosis. The present study aimed to evaluate the effects of exogenous treatment with long acting melatonin on the recovery of testicular degeneration in Nellore bulls. Therefore, two experiments were conducted. Experiment 1 was performed to define the exogenous dose of melatonin (diluted in oily vehicle and administered intramuscularly) which would cause a prolonged increase in serum concentration of melatonin in cattle. Nine ovariectomized cows were divided into three groups: Control (only oily vehicle); Melatonin 18 mg/50 kg of body weight; and Melatonin 27 mg/50 kg of body weight. Blood samples were collected on the day of application and at 4, 8, 16 and 24 days after administration. The melatonin concentration was measured by ELISA. The data were analyzed using the Statistical Analysis System (SAS) software, by ANOVA, adding the factor repeated measures in time. The probabilities of interactions over time were determined by the RANDOM command (PROC GLIMMIX from SAS), with a significance level of 5%. The application of intramuscular melatonin, diluted in oily vehicle at the concentration of 18 mg/50 kg of live weight, caused stable increase for eight days in the serum concentration of melatonin in cattle. In experiment 2 was evaluated melatonin treatment on testicular degeneration in bulls, using that dose assessed in the experiment 1. Testicular degeneration was induced by the placement of testicular insulation bags for 96 hours. Twenty two Nelore bulls were distributed in 4 groups: CON - bulls not induced to testicular degeneration and untreated (n = 5); DT - bulls induced to testicular degeneration and untreated (n = 6); ME - bulls not induced to testicular degeneration and treated with exogenous melatonin (n = 5); and DTME - bulls induced to testicular degeneration and treated with exogenous melatonin (n = 6). Semen and blood samples were collected weekly, starting two weeks before the placement of testicular bags; on the day of removal; and for another 11 weeks thereafter. Clinical characteristics such as scrotal perimeter, testicular consistency, testicular homogeneity (presence of hypercoic points) and parenchyma and pampiniform plexus hemodynamics and the vascular resistance index were analyzed. The seminal characteristics evaluated were subjective volume, concentration, motility and vigor, computerized analysis of spermatozoa, plasma, acrosomal and mitochondrial membranes, sperm morphology, lipid peroxidation and biochemistry of semen. Blood plasma was used to evaluate lipid peroxidation and biochemical components (total protein, albumin, GGT, AST, ALT, creatine kinase (CK), triglycerides, cholesterol, HDL, BHB and NEFA). Data were analyzed using the SAS software by ANOVA, adding the factor repeated measures in time. The probabilities of interactions over time were determined by the RANDOM command (PROC GLIMMIX from SAS), with a significance level of 5%. Insulation caused reduction on testicular consistence, motility, integrity of plasma membranes, integrity of acrosome, mitochondrial potential, as well as increased sperm defects and lipid peroxidation. Treatment with melatonin showed no influence on clinical characteristics, however, showed improvement in vigor (p = 0.05), total motility (p = 0.05) and mitochondrial potential (p = 0.003) 15 days after melatonin application. Besides that, melatonin decreased HDL, cholesterol and BHB values. The treatment of testicular degeneration in bulls (28 days after insulation) using exogenous melatonin in a slow-release vehicle, at a dose of 18 mg/kg, is efficient in improving sperm characteristics of vigor, motility and mitochondrial potential.

Although dark coat color in dogs has been theorized as a risk factor for thermal stress, there is little evidence in the scientific literature to support that position. We utilized 16 non-conditioned Labradors (8 black and 8 yellow) in a three-phase test to examine effects of coat color on thermal status of the dog. Rectal, gastrointestinal (GI), surface temperature, and respiration rates measured in breaths per minute (bpm), were collected prior to (Baseline – phase 1) and immediately after a controlled 30-minute walk in an open air environment on a sunny day (Sunlight – phase 2). Follow up measurements were taken 15 minutes after walking (Cool down – phase 3) to determine post-exposure return to baseline. No effect of coat color was measured for rectal, gastrointestinal, surface temperature, or respiration (P > 0.05) in dogs following their 30-minute walk. Temperatures increased similarly across both coat colors (rectal 1.88 °C and 1.83 °C; GI 1.89 °C and 1.94 °C) for black and yellow dogs respectively during the sunlight phase (P > 0.05). All temperatures and respiration rates decreased similarly across coat colors for rectal (0.9°C and 1.0 °C) GI (1.5 °C and 1.3°C) for black and yellow dogs respectively (P>0.05). Similarly, sex did not impact thermal status across rectal, gastrointestinal, surface temperature or respiration rates measured (P > 0.05). These data contradict the commonly held theory that dogs with darker coat color may experience a greater thermal change when compared to dogs with a lighter coat color exposed to direct sunlight.

La betterave sucrière est la deuxième plante en termes de production de sucre avec 19,6% du sucre produit dans le monde entre 2015 et 2016, derrière la canne à sucre. Cultivée dans les zones tempérées comme le nord de la France et la Belgique, elle est sensible au stress thermique modéré. En effet, une augmentation de 1°C de la température moyenne entraîne une perte de rendement de 29%. Dans le cadre du réchauffement climatique et afin de fournir aux agriculteurs des variétés ayant une meilleure résistance à la chaleur, la compréhension des réponses de la betterave sucrière au stress hyperthermique est nécessaire. Pour cela, une étude des réponses physiologiques et métaboliques a été effectuée avec trois hybrides : un hybride de type sucré avec 18% de sucre dans sa racine, un hybride de type lourd avec un meilleur rendement que la moyenne mais avec seulement 17% de sucre dans sa racine, et un hybride dit « résistant » au stress hyperthermique, ayant le meilleur rendement aux champs avec des températures plus élevées. Alors que la photosynthèse nette n’était pas modifiée en condition de stress, une croissance plus rapide de la rosette a été observée aux stades jeunes pour les trois hybrides. Une approche de modélisation suggère qu’une croissance de la rosette plus rapide contrecarre les effets du stress hyperthermique sur la production racinaire. Cette hypothèse est confirmée par le fait que l’hybride le plus performant a la croissance foliaire la plus rapide. Le stress hyperthermique provoque une forte diminution du stockage transitoire du carbone dans les feuilles matures. Dans les feuilles en cours de développement, le stockage transitoire du carbone, dont la moitié sous forme d’amidon, était seulement maintenu chez l’hybride le plus performant. Un calcul intégrant les besoins en carbone de la croissance foliaire suggère que ce maintien contribue significativement au maintien du rendement chez cet hybride. Par ailleurs, un marqueur putatif de la sensibilité au stress hyperthermique a été identifié lors de cette étude. Au final ce travail a permis de mieux comprendre comment la betterave sucrière répond à l’élévation de la température et ainsi proposer de nouvelles stratégies pour l’amélioration de cette espèce. / Sugar beet is the second largest sugar-producing crop, with 19.6% of the sugar produced in the world between 2015 and 2016, behind sugarcane. Cultivated in temperate zones like the north of France and Belgium, it is sensitive to moderate thermal stress. Indeed, an increase of 1°C in the average temperature leads to a loss of efficiency of 29%. In the context of global warming and in order to provide farmers with varieties with better resistance to heat, an understanding of sugar beet responses to hyperthermic stress is necessary. For this, a study of physiological and metabolic responses was carried out with three hybrids: a sweet-type hybrid with 18% sugar in the root, a heavy-type hybrid with a better yield than average but with only 17% sugar in the root, and a so-called "resistant" hybrid, which has the best yield at higher temperatures. While net photosynthesis was not altered in stress conditions, more rapid growth of the rosette was observed at the young stages for all three hybrids. A modeling approach suggests that faster rosette growth counteracts the effects of hyperthermic stress on root production. This hypothesis was confirmed by the fact that the best performing hybrid had the fastest shoot growth. Hyperthermic stress caused a significant decrease in transient carbon storage in mature leaves. In developing leaves, transient storage of carbon, half as starch, was only maintained in the best performing hybrid. A calculation incorporating the carbon requirement of foliar growth suggests that this maintenance contributes significantly to the maintenance of yield in this hybrid. In addition, a putative marker of hyperthermic stress sensitivity was identified in this study. In the end, this work provides a better understanding of how sugar beet responds to the rise in temperature, thus proposing new strategies for the improvement of this species.

This study examined the effects of rapid and uncompensable core temperature (Tc) acquisition on cerebral oxygenation and haemodynamics, cerebral neural function, decision-making, and rate and magnitude salivary cortisol appearance. Fourteen male subjects (mean age, 33.6 ± 12.1 years) performed an incremental treadmill exercise test to a termination criterion in a control session (CON) and an experimental session (PPE). The incremental treadmill exercise test protocol included an initial 5-minute stage at 3.5 mph and a 0% grade, the second stage was 5-minutes at 3.5 mph at 4% grade, the third stage was 50-minutes at 3.5 mph and an 8% grade, and the final stage was 1-hour at 3.5 mph and a 12% grade. The Instrumentation included a near-infrared spectroscopy (NIRS) monitor, MUSE EEG monitoring system, Equivital integrated physiological monitoring system, Tc capsules, and salivary cortisol oral swabs and ELISA kit for salivary analysis. Important physiological results were significant differences in the physiological strain index (PSI) at all common points of measurement. Important cerebral oxygenation and haemodynamics results were a plateau in left-side prefrontal cortex (PFC) HbO2 and tHb at roughly Tc 38°C in both CON and PPE, 80% of TTT in CON, and 60% of TTT in PPE. Additionally, there was higher left-side PFC activation during PPE as indicated by a significant decrease in TSI % from start to end of exercise and double the decrease in TSI % per minute in PPE when compared to CON. There were no significant differences during the CON session. An analysis of frontal theta EEG power results showed a significant decrease when comparing pre- and post-exercise values during a Go/No-go test in PPE (F(1,13) = 6.069, p ≤ 0.05)). There was also a significant difference when evaluating incorrect responses between pre- and post-exercise values in PPE (F(1,13) = 12.785, p ≤ 0.01)); these differences were not observed during CON. There was also a difference in the rate of cortisol appearance (CON = 0.002 µg dL-1 min-1; PPE = 0.018 µg dL-1 min-1). In the PPE condition, mean cortisol values between start of exercise and the measurement point associated with Tc 38°C and between the start and end of exercise during PPE were significantly different (F(1,13) = 22.71, p ≤ 0.01). Lastly, there was a significant difference between magnitude of cortisol values at the termination between CON and PPE. These data suggest that rapid and uncompensable Tc acquisition during PPE caused an altered cerebral oxygenation and haemodynamic response in the left-side PFC when compared to CON. The left PFC could be working harder to prevent fatigue in PPE. This could have implications for cognitive processes during and/or following exercise in the heat while wearing PPE. These data also suggest rapid and uncompensable Tc acquisition results in decreased cognitive control. This could have implications for individuals whose occupation requires PPE and critical decision making while experiencing rapid Tc heat storage. Lastly, these results show a difference between PPE and CON in regards to rate and magnitude of salivary cortisol appearance, potentially affecting individuals chronically exposed to acute heat stress. Increased acute cortisol concentration decreases anabolic response, cognitive performance, and mood states. The chronic effects of increased cortisol concentration are many: largely related to atherosclerosis development and subsequent cardiovascular disease. Additional issues include anthropometric, endocrine, metabolic, and haemodynamic disturbances. This study makes a strong argument for the rate of thermal acquisition factor. CON and PPE differences in PSI at all measurement points provides justification and support for the changes in other variables. Rapid and uncompensable Tc acquisition needs to be taken into account, as it potentially puts the lives of employees who wear PPE and those around them at risk. / Graduate

O objetivo deste estudo foi avaliar a tolerância ao calor de ovinos de corte das raças Santa Inês, Dorper e Merino Branco através do teste de capacidade termolítica (exposição ao sol). Foram utilizadas um total de 97 fêmeas vazias, com idade média de 3 anos. O estudo decorreu no verão, onde foram registradas as variáveis fisiológicas temperatura retal (TR), temperatura superficial (TS), frequência respiratória (FR), mensuradas depois de duas horas sob a sombra (1), uma hora sob o sol (2), quinze (3) e trinta (4) minutos após a exposição ao sol, e a taxa de sudação (Sud), no tempo 2. Posteriormente foram realizadas observações de comportamento a pasto durante três dias, no período das 11 às 14 horas, para as variáveis: tempo ao sol; tempo em pé; pastejo/alimentação, ruminação e ócio. As médias de TR1 foram semelhantes para as ovelhas Santa Inês e Dorper e superior para as ovelhas Merino Branco (P&lt;0,05). Para TR2, TR3 e TR4 as ovelhas da raça Merino Branco tiveram os maiores valores, seguidos das ovelhas da raça Santa Inês e com os menores aumentos de temperatura retal nas ovelhas da raça Dorper (P&lt;0,05). Estes resultados refletiram na capacidade termolítica individual, sendo menor para a raça Santa Inês (P&lt;0,05). Após exposição ao sol observaram-se diferenças entre as TS, sendo as da raça Merino Branco mais elevadas, seguidas pelas da raça Dorper e da Santa Inês (P&lt;0,05). A raça Merino Branco apresentou as maiores FR, seguida das raças Dorper e Santa Inês, todas diferentes entre si (P&lt;0,05). Todos os animais expostos por uma hora ao sol apresentaram aumento nas TR, TS e FR (P&lt;0,05), e se aproximaram dos níveis encontrados antes da exposição ao sol após trinta minutos de descanso sob a sombra (Santa Inês e Dorper P&lt;0,05; Merino Branco P&gt;0,05). A taxa média de sudação para as ovelhas da raça Santa Inês foi superior a encontrada para as ovelhas da raça Dorper (P&lt;0,05). Houve diferença entre os animais dentro de cada raça (P&lt;0,05), confirmando a hipótese de grande variabilidade entre os indivíduos e diferenças entre as raças. Com relação ao comportamento, as ovelhas da raça Santa Inês continuaram em pastejo mesmo nas horas mais quentes do dia, tendo sido encontrada uma correlação positiva de 0,64 entre a capacidade termolítica individual e o pastejo ao sol, enquanto as ovelhas da raça Dorper preferencialmente permaneceram à sombra devido ao manejo semiconfinado. No presente trabalho o tipo de manejo alimentar influenciou no tempo de uso da sombra. Sob as condições climáticas encontradas no experimento os animais estudados tiveram seus parâmetros fisiológicos alterados devido à exposição ao sol, e os animais das raças Dorper e Merino Branco mostraram maior capacidade termolítica do que os animais da raça Santa Inês, sendo este um fator que pode influenciar na tolerância ao calor individual. / The aim of this study was to evaluate the heat tolerance of three meat sheep breeds, Santa Ines, Dorper and White Merino using Thermolysis capacity test. 97 non pregnant females (3 years old) were used in the study that took place in the summer. Physiological variables as rectal temperature (RT), surface temperature (ST), respiratory rate (RR) were measured after two hours under the shade (1), after one hour under the sun (2), fifteen (3) and thirty (4) minutes after sun exposure, and sweating rate (SR) on time 2. Were also collected behavioral data during three days in the period from 11:00 to 14:00 hours: say in the sun, standing posture, eating, ruminating and idling. RT1 means were equal Santa Ines and Dorper, and greater for White Merino (P&lt;0.05). White Merino also had greater values for RT2, RT3 e RT4, followed by Santa Ines and Dorper (P&lt;0.05). These results reflected the thermolysis capacity, being lower for Santa Ines breed (P&lt;0.05). After sun exposure differences between ST were observed, and greater values were found for White Merino, followed by Dorper and Santa Ines breeds (P&lt;0.05). In the same way, White Merino had the highest RR, followed by Dorper, which had higher RR compared to Santa Ines (P&lt;0.05). All animals exposed to the sun for an hour showed increased RT, ST, RR values (P&lt;0.05), and approached the levels found before exposure to the sun after thirty minutes of rest in the shade (Santa Ines and Dorper P&lt;0.05; White Merino P&gt;0.05). Sweating rate for Santa Ines breed was higher than those found for Dorper breed (P&lt;0.05). There were differences among animals within each race (P&lt;0.05), confirming the hypothesis of great variability among individuals and differences between the breeds. With respect to behavior, Santa Ines ewe grazed even during the hottest hours of the day, and a positive correlation of 0.64 between the individual thermolysis capacity and grazing in the sun was found, while the Dorper ewes remained preferentially under the shade due to the semi-confined management. In the present study, feedin management influenced the time under the shade. Under experimental climatic conditions, the studied ewes had theirs physiological parameters increased due to sun exposure, and Dorper and White Merino breeds showed a greater thermolisys capacity than the animals of the Santa Ines breed, which is a factor that can influence individual heat tolerance.

It was hypothesized that technical factors associated with in vitro production (IVP) of embryos may influence rate of blastocyst development of oocytes matured at 38.5 or 41.0 C. To test this hypothesis, a retrospective meta-analysis was performed. Simple linear regression was performed to analyze continuous variables and ANOVA for categorical variables. Interactions among factors and maturation temperature on blastocyst development were analyzed using dummy regression for continuous variables, and using a factorial treatment design and ANOVA for categorical variables. Month of collection was the only variable that impacted responsiveness of ova to heat stress. Independent of maturation temperature, variables that explained most variation in blastocyst development included technician, total number of sliced ovaries per collection, ova number placed per well of oocyte maturation media, oocyte collection time, bull ID, sperm concentration added to ova, and ova age at IVF. The proportion of 8 to 16-cell embryos at time of cleavage assessment was the best predictor of blastocyst development. Results of model selection showed that development of ova matured at 38.5 C was associated with size of the collection, while development of ova matured at 41.0 C was mainly associated with ova age at fertilization. When data for ova matured at 38.5 and 41.0 C were combined, the effect of number of PZ per well on blastocyst development became evident. Use of these findings for optimizing efficiency of IVP procedures would effectively reduce experimental costs related to embryo production and increase laboratory productivity.

Carbon flow into developing ovaries has been reported to be important in seed retention and seed size. Invertase, which cleaves sucrose into glucose and fructose has been shown to be important in rapidly expanding tissue, such as early root growth or during tiller expansion. The manipulation of invertase activity with over-the-top applications of agrochemicals may prevent the detrimental effects of abiotic stress by altering the source/sink relationship. These experiments examined economically important tissues in rice production during critical developmental stages under abiotic stress. Field and greenhouse studies were conducted under normal growing conditions using local management practices. Plants were treated with exogenous chemicals that affect the activity of invertase during the early-grain fill stage on field grown plants. Other plants were exposed to elevated nighttime temperature of 30°C for 4 d using a free-air, infrared heating device in the greenhouse. Rice was also treated at mid- to late-grain fill stage of the main crop to identify the impact of the exogenous chemicals on developing ratoon tiller buds. The activity of soluble acid invertase (SAI), concentrations of glucose, fructose, sucrose, and starch were determined in penultimate leaves, panicles, and main-crop stem segments during ratoon tiller bud expansion, using the enzyme-coupled stoichiometric production of NADH measured spectrophotometrically at 340nm. The results suggest SAI, carbohydrates, and agronomic characters are influenced by exogenous chemicals at the applied rates. The thidiazuron treatment caused an unidentified stress event. The stress was confirmed by increased hexose concentration and the proportion of hexose concentration to sucrose concentration. This stress reduced the main-crop grain yield, but not the ratoon yield or total grain yield. An interaction between the ammonium molybdate treatment and high nighttime temperature was seen in the panicle. The ranked difference was reduced by the high nighttime temperature from the ambient nighttime temperature for the SAI activity, TSC content, starch content, and TNC content. The tested chemicals and rates are not appropriate for commercial rice production because the effect of the exogenous chemicals do not appear to consistently aid rice plants to counteract the detrimental effects of abiotic stress.

Current knowledge indicates that nonthermal muscle metaboreflex activity plays a critical role in the modulation of skin vasodilation and sweating. However, the mechanisms of control have primarily been studied during isometric handgrip exercise in which muscle metaboreceptor activation is induced by a brief post-exercise ischemia of the upper limb. While the reflex increase in mean arterial pressure associated with this period of ischemia is consistent with the activation of muscle metaboreceptors, the change in baroreflex activity may in itself modulate the response. Thus, we sought to understand how these nonthermal stimuli interact in modulating the control of skin perfusion and sweating under conditions of elevated hyperthermia. Furthermore, we examined the mechanisms responsible for the maintenance of arterial blood pressure under varying levels of heat stress during isometric handgrip exercise. Our study findings indicate that the parallel activation of muscle metaboreceptors and baroreceptors during post-exercise ischemia causes divergent influences on the control of skin blood flow and sweating; and these nonthermal stimuli are dependent on the level of hyperthermia. Moreover, we report that heat stress reduces the increase in arterial blood pressure during isometric handgrip exercise and this attenuation is attributed to a blunted increase in peripheral resistance, since cardiac output increased to similar levels for all heat stress conditions. These results provide important insight and understanding into the role of muscle metabo- and baroreflex activity on the control of skin blood flow and sweating; along with further knowledge into the cardiovascular mechanisms responsible for the regulation of arterial blood pressure during hyperthermia.

High temperature stress (HTS) adversely affects reproduction in most plant species studied to date. HTS during flowering may result in an almost total inhibition of seed production in crop plants. Increasing our knowledge of the effects of HTS on seed production will aid the breeding of more thermotolerant crop plants and improve our understanding of the effects of stress on plants. An investigation of the effects of both drought and high temperature stress on the yields of barley, canola, flax, durum and spring wheat in five locations in Saskatchewan over a 25-year period was performed using multivariate analysis. Higher temperatures during June and July, when the plants were flowering, were correlated with reductions in yields of all the crops studied (except barley in June). A positive correlation between yields and precipitation during May and the winter preceding the growing season was observed.<p>In growth chambers, <i>Brassica napus</i> silique and seed production were inhibited during a ramping HTS treatment. This was due to a decrease in pollen germinability rather than a reduction in the number of flowers produced. HTS also caused reductions in megagametophyte fertility and disrupted embryo and/or seed development.<p>Transgenic plants were developed to overcome the effects of HTS on seed production. Two DNA constructs, one with the <i>Arabidopsis thaliana LEAFY</i> (<i>AtLFY</i>) promoter controlling <i>A. thaliana HEAT SHOCK PROTEIN 101</i> (<i>AtHSP101</i>) ORF expression and another with the <i>AtHSP101</i> promoter controlling <i>AtLFY</i> ORF expression, were inserted into <i>B. napus</i>. Other DNA constructs were made, using the constitutively expressed Cauliflower Mosaic Virus <i>35S</i> or the synthetic <i>EntCup4</i> promoters to control expression of the <i>AtHSP101</i> or <i>A. thaliana HEAT SHOCK TRANSCRIPTION FACTOR 3</i> (<i>AtHSF3</i>) ORFs. These constructs were inserted into both <i>B. napus</i> and <i>A. thaliana</i>. Transgenic plants were tested using a ramping temperature regime but were found not to have increased flower thermotolerance. During the manufacture of the DNA constructs it was determined that, in <i>A. thaliana</i>, 573 bp of <i>AtHSP101</i> had been copied between Terminal Inverted Repeats of a <i>Mu-Like Element</i> (<i>MULE</i>). This fragment was named <i>HSP101B</i>. In some transgenic <i>B. napus</i> and <i>A. thaliana</i> lines, containing 2046 bp of the <i>HSP101B</i> upstream regulatory region controlling <i>B</i>-glucuronidase (GUS) expression, cold-inducible GUS expression was observed. Methylation may have a role in control of endogenous <i>HSP101B</i> transcription.