Dairy calves require nutrients for maintenance and growth, but in cold weather, the body alters physiologic processes to control body temperature through thermogenesis, which increases its requirements. In this regard, it is important a better understanding of how different feeding managements act in the calf thermogenesis, performance and health when raised in temperatures below thermoneutral conditions. Based on that, two studies were performed. The first study evaluated thermoregulation, performance and blood metabolites in thirty newborn calves fed 10%, 15% or 20% BW of colostrum. At 24h of life, calves were placed in a temperature-controlled chamber at 10ºC for 150 min. After the cold challenge, calves were individually housed in ambient temperature facilities (26.8 ± 5.9°C) until weaning. Calves given 15% or 20% of BW as colostrum exhibited increased thermoregulatory responses during cold challenge and increased immunity responses during preweaning. The second study compared performance and production cost of 75 calves fed milk replacer (MR) or whole milk (WM) and a traditional starter (TS) or an alternative starter (AS) during low environmental temperatures (1.4 ± 9.2°C). Calves were assigned to one of five treatment groups in a 2 x 2 + 1 factorial. The first treatment was a negative control (NC), 4 L/d of MR from d1 to 49; 2L/d of MR from d 50 to 56 of the study and ad libitum TS (commercial texturized ration). The others four treatments were a high rate (HR) of MR or WM (6L/d from d 1 to 7, 8 L/d from d 8 to 35, 4L/d from d 36 to 42, and 2 L/d from d 43 to 49 of the study) and ad libitum AS (cracked corn from d 1 to 21, low protein grower from d 22 to 28, high protein grower from d 29 to 49 of the study) or TS. After weaning, animals were maintained in group hutches in the same environment until 12 weeks of life. Restricted liquid feeding provided higher economic efficiency. However, the final BW was higher for calves fed HRTS. In addition, feeding calves higher volumes of WM increased growth and decreased morbidity. Besides, replacing commercial TS with an AS in high rate of nutrition presented minimal impact on performance. / Bezerros leiteiros necessitam de nutrientes para mantença e crescimento, contudo, em baixas temperaturas, o corpo altera os processos fisiológicos para controlar a temperatura corporal por meio da termogênese, aumentando a exigência. Neste sentido, se torna importante uma melhor compreensão de como diferentes manejos alimentares atuam na termogênese, no desempenho e na saúde de bezerros criados em temperaturas abaixo das condições de termoneutralidade. Com base nisso, dois estudos foram realizados. O primeiro estudo avaliou a termorregulação, o desempenho e os metabólitos sanguíneos de trinta bezerros recém nascidos alimentados com 10%, 15% ou 20% de colostro em porcentagem de peso corporal. Vinte e quatro horas após o nascimento, os bezerros foram colocados em uma câmara de temperatura controlada a 10°C por 150 min. Após o desafio do frio, os bezerros foram individualmente alojados em instalação à temperatura ambiente (26,8 ± 5,9°C) até o desaleitamento. Bezerros que receberam 15% ou 20% de colostro exibiram aumento das respostas termorreguladoras durante o desafio pelo frio e aumento das respostas de imunidade durante o aleitamento. O segundo estudo comparou o desempenho e os custos de produção de 75 bezerras alimentadas com sucedâneo (S) ou leite (L) e uma ração tradicional (RT) ou uma ração inicial alternativa (RA) durante baixas temperaturas ambientais (1,4 ± 9,2°C). As bezerras foram designados para um dos cinco tratamentos em fatorial 2 x 2 + 1 O primeiro tratamento foi o controle negativo (CN), 4 L/d de S do d1 ao 49; 2L/d de S do d 50 ao 56 do estudo e RT ad libitum (ração comercial texturizada). Os outros quatro tratamentos foram alta taxa (AT) de S ou L (6L/d do d 1 ao 7, 8 L/d do d 8 ao 35, 2L/d do d 36 ao 42, e 1 L/d do d 43 ao 49 do estudo) e RA ad libitum (milho quebrado do d 1 ao 21, ração de crescimento com baixa proteína do d 22 ao 28, ração de crescimento alta proteína do d 29 ao 49 do estudo) ou RT. Após o desaleitamento, os animais foram mantidos em baias coletivas até 12 semanas de vida. Dieta líquida restrita promoveu maior eficiência econômica. No entanto, o peso final foi maior para bezerras alimentadas com ATRT. Adicionalmente, alimentar bezerras com maior volume de L aumentou o crescimento e diminui morbidade. Além disso, substituir RT comercial por uma RA em altas taxas de nutrição apresentou mínimo impacto no desempenho.

Morella cerifera is a rapidly expanding native shrub on the Virginia barrier islands which displaces other native coastal species and may interrupt normal sediment dynamics. Barrier islands are considered stressful environments with low nutrients, high solar load, and frequent drought and salt exposure; facilitation often dominates in stressful environments according to the Stress Gradient Hypothesis. The objective of this project was to understand the importance of species interactions with grasses on the growth and physiology of M. cerifera at the seedling life stage through both field and lab experiments. Grasses provided ~1.3°C insulation to shrubs during winter freeze events and a freezing threshold for M. cerifera seedlings was experimentally found between -6°C and -11°C. Seedlings competed for light with grasses during warm months and grew more where grasses were clipped, revealing a tradeoff between winter insulation and summer light competition. M. cerifera shows evidence of ecosystem engineering at the seedling stage by significantly reducing summer maximum temperatures. This enables rapid expansion of M. cerifera across the landscape. As M. cerifera expands, island migration is altered, leading to decreased island stability and increased erosion. Although seedlings are small and relatively vulnerable, this life stage appears to have significant implications for the ecosystem trajectory and stability of the Virginia barrier islands.

The current rice varieties grown by Australian farmers are susceptible to low temperature events particularly during the reproductive stage of plant development. The best management practices of sowing within the recommended time period and maintaining deep water (20–25 cm) through the microspore development stage only offer limited protection. There is a need to develop more cold tolerant varieties and to do so requires the development of low-temperature screening capacity for the NSW rice breeding program. This study looked at the requirements of adapting a controlled-temperature glasshouse facility to enable screening for tolerance to low temperatures during the reproductive stage of rice development. The investigations were grouped into two areas; 1) the physical aspects of the low temperature facility including the location of plants within the facility and within the tubs used to grow the plants and whether these can influence the reliability of the screening and 2) the biological effects of nitrogen (N) concentration in the plant at panicle initiation (PI) and plant susceptibility to low temperatures, and whether growth stage of the plant relative to PI at the start of low temperature treatment influenced floret sterility. A series of nine experiments were conducted at the Deniliquin Agricultural Research and Advisory Station glasshouse facility using up to five rice varieties selected for their divergence in low-temperature tolerance. One other experiment was conducted in a different facility. The modified glasshouse facility in Deniliquin was effective in providing the targeted screening environment of 27°C day and 13°C night temperature regime. There was however a smaller than expected effect of the low temperature exposure in some of the experiments with sterility following low temperature ranging from 9.9% to 27.7%. There was also a higher than expected level of sterility in the controls (i.e. not exposed to low temperature) with sterility levels up to 58% recorded in one experiment. The causes of these overall effects are not known. Notwithstanding these overall effects there were a number of findings that are important for developing a reliable screening facility. The spatial arrangement of the plants within the low temperature facility effected the level of sterility highlighting the need for experimental design to consider spatial variation. The existence of edge effects was identified within the tubs used to maintain permanent water on the potted plants whereby the outer plants in the tubs were less damaged by the low-temperature treatment. The overall N level in the leaf tissue was low even at the equivalent rate of 250 kg N ha-1 and there was only a very modest and inconsistent response in N concentration at PI to N application rates ranging from 0 to 250 kg ha-1. However, the method of growing the plants in pots and of nitrogen fertiliser application did not alter the N concentration. The concentration was the same when N was added either, on the same day as permanent water application, or three days prior to permanent water application. Also restricting the direction of water movement through the pots and therefore the soil within the pots did not alter the amount of N in the plants at PI. The low plant N concentrations were consistent across two glasshouses in which soil from the same source was used suggesting a soil limitation. A soil test identified that the soil phosphorus (P) was at a level at which plants have responded to P application under field conditions, and the loamy texture of the soil had an associated low cation exchange capacity in comparison to medium to heavy clay soil types commonly associated with rice growing. These factors may have reduced the N retention and uptake and, in part, explain the low injury from the low temperature exposures. In the variety Millin, there was no significant effect of timing of the exposure on sterility until it commenced 12 to 15 days after PI. This is a significant finding for a breeding program that must expose lines of unknown phenological development. It means that even though there are small differences in the rates of development, there is no large effect of this on sterility. However, this response was not seen in the other varieties tested and thus requires further validation. It was difficult to induce repeatable levels of floret sterility in this series of experiments most likely due to the low N concentrations in part due to the properties of the soil used to grow the plants. This highlights the importance of standardising all cultural aspects in order to provide uniform and repeatable screening information. The spatial effects highlight importance of experimental design for effective exposure to low temperature treatments, incorporation of the capacity for spatial analysis in the statistical design, the use of standard variety checks for floret sterility after low temperature treatment, and the determination of N concentration in plant tissue prior to exposure.

Winter wheat (<i>Triticum aestivum</i> L.), seeded in the fall, cold acclimates when exposed to low fall temperatures. Growth resumes in spring, culminating in early summer harvest. Winter wheat yield is generally 20-25% higher than spring wheat. However, winter damage/kill can reduce its yield. A better understanding of the cold acclimation/tolerance process could help in the development of improved breeding strategies for winter wheat hardiness. Transcriptional activators and specific cold regulated (COR) genes are induced as a result of exposure to low temperatures. Thus, the objective of this study was to determine the quantitative expression of three COR genes (Wcs120, Wcor410 and Wcor14b) and one transcriptional activator (WCBF1) in field-grown wheat using real-time PCR and to establish any association with LT50 (temperature at which 50% of plants are killed). Winter Norstar (vrn-A1/vrn-A1), spring Manitou (Vrn-A1/Vrn-A1) and two near-isogenic lines (Spring Norstar (Vrn-A1/vrn-A1) and Winter Manitou (vrn-A1/vrn-A1), respectively) were used in these studies. Plants were sampled on three dates (Sept. 29, Oct. 12 and Oct. 26) in the fall of 2004. Accumulation of WCBF1 transcripts was highest in Norstar, but in all four genotypes there was an increase in transcripts by the second sampling date, followed by a decline on the third sampling date. Wcs120 transcripts increased from the first to the third sampling date in Norstar, Spring Norstar and Winter Manitou, but increased to the second sampling date and decreased by the third in Manitou. For Wcor14b, generally there was an increase to the second sampling date, followed by a decrease or steady levels on the third. Wcor410 showed a similar pattern, except for Spring Norstar wherein transcript levels increased by the third sampling date. With the exception of Wcor410 in Manitou, the Vrn-A1 locus affected gene expression in all genotypes. However, only Wcs120 expression followed the low-temperature tolerance pattern in these genotypes.

Cold acclimation is a complex process where plants acquire increased freezing tolerance following exposure to low, non-freezing temperatures. Microtubules are dynamic components of the cytoskeleton that are essential for plant growth and development, and there are multiple lines of evidence indicating microtubules are involved in the acquisition of freezing tolerance. <p>The organization of microtubules (MTs) was tracked over the course of a cold acclimation period using GFP:TUB6 and fluorescent imaging tools. Experiments found that MTs undergo incomplete, transient disassembly following exposure to acclimating temperatures, which is accompanied by intranuclear tubulin accumulation and followed by MT reassembly. The importance of the observed changes to MT organization was examined with MT disrupting chemicals that caused reduced MT dynamics or induced transient MT disassembly similar to that of cold acclimation. Results of these experiments suggest that MT reorganization is important for cold acclimation, but the disassembly and reassembly do not directly control cold acclimation.<p>MT binding proteins are likely to play a key role in the low temperature response because they control MT activity and organization, participate in low temperature signal transduction pathways, and mediate interactions between various elements of this pathway. By employing a number of proteomics techniques we were able to identify 96 tubulin-binding proteins from untreated and short term cold acclimated Arabidopsis plants. Proteins both known to and predicted to bind to MTs and unexpected MT binding proteins were identified. The identified tubulin binding proteins have a range of cellular functions, including RNA transport and protein translation, stress responses, and functions related to various metabolic pathways, and cell growth and organization. <p>Exposure to low temperatures affected the binding of some of these proteins to MTs with the identified tubulin binding proteins potentially involved in the cold acclimation process and stress response through a number of possible pathways.<p>This study represents the first live cell imaging of MT reorganization in response to low temperatures and the first time microtubule binding proteins from whole plant protein extracts were identified using 1D gel LC-MS/MS analysis.

Cold acclimation is a complex process where plants acquire increased freezing tolerance following exposure to low, non-freezing temperatures. Microtubules are dynamic components of the cytoskeleton that are essential for plant growth and development, and there are multiple lines of evidence indicating microtubules are involved in the acquisition of freezing tolerance. <p>The organization of microtubules (MTs) was tracked over the course of a cold acclimation period using GFP:TUB6 and fluorescent imaging tools. Experiments found that MTs undergo incomplete, transient disassembly following exposure to acclimating temperatures, which is accompanied by intranuclear tubulin accumulation and followed by MT reassembly. The importance of the observed changes to MT organization was examined with MT disrupting chemicals that caused reduced MT dynamics or induced transient MT disassembly similar to that of cold acclimation. Results of these experiments suggest that MT reorganization is important for cold acclimation, but the disassembly and reassembly do not directly control cold acclimation.<p>MT binding proteins are likely to play a key role in the low temperature response because they control MT activity and organization, participate in low temperature signal transduction pathways, and mediate interactions between various elements of this pathway. By employing a number of proteomics techniques we were able to identify 96 tubulin-binding proteins from untreated and short term cold acclimated Arabidopsis plants. Proteins both known to and predicted to bind to MTs and unexpected MT binding proteins were identified. The identified tubulin binding proteins have a range of cellular functions, including RNA transport and protein translation, stress responses, and functions related to various metabolic pathways, and cell growth and organization. <p>Exposure to low temperatures affected the binding of some of these proteins to MTs with the identified tubulin binding proteins potentially involved in the cold acclimation process and stress response through a number of possible pathways.<p>This study represents the first live cell imaging of MT reorganization in response to low temperatures and the first time microtubule binding proteins from whole plant protein extracts were identified using 1D gel LC-MS/MS analysis.

Winter wheat (<i>Triticum aestivum</i> L.), seeded in the fall, cold acclimates when exposed to low fall temperatures. Growth resumes in spring, culminating in early summer harvest. Winter wheat yield is generally 20-25% higher than spring wheat. However, winter damage/kill can reduce its yield. A better understanding of the cold acclimation/tolerance process could help in the development of improved breeding strategies for winter wheat hardiness. Transcriptional activators and specific cold regulated (COR) genes are induced as a result of exposure to low temperatures. Thus, the objective of this study was to determine the quantitative expression of three COR genes (Wcs120, Wcor410 and Wcor14b) and one transcriptional activator (WCBF1) in field-grown wheat using real-time PCR and to establish any association with LT50 (temperature at which 50% of plants are killed). Winter Norstar (vrn-A1/vrn-A1), spring Manitou (Vrn-A1/Vrn-A1) and two near-isogenic lines (Spring Norstar (Vrn-A1/vrn-A1) and Winter Manitou (vrn-A1/vrn-A1), respectively) were used in these studies. Plants were sampled on three dates (Sept. 29, Oct. 12 and Oct. 26) in the fall of 2004. Accumulation of WCBF1 transcripts was highest in Norstar, but in all four genotypes there was an increase in transcripts by the second sampling date, followed by a decline on the third sampling date. Wcs120 transcripts increased from the first to the third sampling date in Norstar, Spring Norstar and Winter Manitou, but increased to the second sampling date and decreased by the third in Manitou. For Wcor14b, generally there was an increase to the second sampling date, followed by a decrease or steady levels on the third. Wcor410 showed a similar pattern, except for Spring Norstar wherein transcript levels increased by the third sampling date. With the exception of Wcor410 in Manitou, the Vrn-A1 locus affected gene expression in all genotypes. However, only Wcs120 expression followed the low-temperature tolerance pattern in these genotypes.

Hypervariable, nuclear-encoded microsatellites were used to (i) estimate genetic effective size (Ne) of red drum spawning over a two-week period in nine brood tanks at a TPWD hatchery; (ii) estimate heritability of early-larval growth and of growth rate and cold tolerance of juveniles; and (iii) test Mendelian segregation and independent assortment of 31 nuclear-encoded microsatellites. Assuming all tanks contributed equally to an offspring population, the maximum (expected) and observed Ne over the nine brood tanks was 43.2 and 27.0, respectively. The estimate of Ne based on observed variation in family size was 19.4. Simulations indicated that over a limited time period the simplest approach to maximizing Ne for a release population would be to utilize equal numbers of progeny from each brood tank. A family (genetic) effect was found to contribute significantly to the variance in early larval growth, juvenile growth rate, and cold tolerance. Estimates of narrow-sense heritability for these three traits were 0.07 +- 0.03, 0.52 +- 0.21 and 0.20 +- 0.10 (two growth intervals measured), and 0.30 +- 0.11, respectively, under the genetic models employed. The relatively low estimate of heritability for early larval growth suggests that genetic improvement for this trait likely would be slow. The heritability estimates for juvenile growth rate and cold tolerance, alternatively, suggest that genetic selection for these traits could be effective. Segregation at all 31 microsatellites fit Mendelian expectations for autosomal loci; a null allele was inferred at two of the microsatellites. Results from pairwise tests of independent assortment demonstrated that 20 of the 31 microsatellites could be placed into seven linkage groups. Additional linkage groups inferred from a prior study increased the number of inferred linkage groups in red drum to nine, with a range of two - five (avg. = 2.78) microsatellites in each linkage group. The remaining 11 microsatellites tested in this study assorted independently from all other microsatellites, suggesting the possibility of 11 additional linkage groups.

Darbo tikslas – nustatyti endogeninių ir egzogeninių veiksnių poveikį žieminio rapso atsparumui šalčiui in vitro ir in vivo. Ginamieji disertacijos teiginiai: 1. Žieminio rapso atsparumas šalčiui didžiąją dalimi lemiamas endogeninio prolino, o ne tirpiųjų sacharidų kiekio augalų audiniuose. 2. Grūdinant ūglius in vitro egzogeniniai priedai (abscizo rūgštis, prolinas, tirtas aminorūgščių kompleksas) maitinamojoje terpėje didina atsparumą šalčiui. 3. In vitro sistemoje L-prolinas ir tirtas aminorūgščių kompleksas atstato atlydžio metu sumažėjusį užsigrūdinimo tvarumą. 4. Endogeninio prolino kiekis yra membranos stabilumo atsparumo šalčiui žymuo ir gali būti naudojamas kuriant atsparius šalčiui genotipus. / Aim of the work – to determine the effect of endogenous and exogenous factors on the cold tolerance of winter rapeseed in vitro and in vivo. Proposition to be defended: 1. Cold tolerance of winter rapeseed mainly determining by content of endogenous proline but not by soluble sugars. 2. Exogenous additives (abscisic acid, proline, amino acids) in nutrient medium increases the cold tolerance of rapeseed shoots in vitro. 3. In in vitro system the abscisic acid, proline and amino acids restore the reduced acclimation which occurs during de-acclimation period. 4. Endogenous proline content is the marker of membrane stability and cold tolerance and may be used to create cold-tolerant genotypes.

No description available.