A system incorporating a prototype automatic thermoelectric cooling method with computer-based recording of aphid supercooling points was developed and formed the basis of cold hardiness assessment. Under laboratory culture all developmental stages of Myzus persicae had a mean inherent supercooling potential below -20°C, with first instar nymphs the most cold hardy. When maintained at 5°C, younger instars demonstrated acclimation ability unlike adult aphids, and in an insecticide resistant strain, adults lost cold hardiness. When in contact with surface moisture, the majority of aphids did not experience inoculative nucleation. Sexual morphs of M. persicae possessed supercooling ability comparable with laboratory maintained parthenogenetic morphs; eggs supercooled to below -30°C. Seasonal studies of supercooling ability demonstrated that all aphid stages were most cold hardy in summer. Younger instars showed natural acclimatisation and were cold hardy throughout the year. Overall adults lost cold hardiness as winter progressed, exhibiting bimodal supercooling point distributions in two winters, with distinct high (HG) and low (LG) groups and mean supercooling points of approximately -20°C and -10 oe respectively. Clonal differences and adult age did not account for this pattern. Following experimental starvation at 5°C, first instars of M. persicae maintained extensive supercooling potential but adults exhibited losses of cold hardiness comparable with those in natural overwintering populations, suggesting that feeding may be necessary to maintain adult cold hardiness levels during winter. Subsequent starvation experiments did not reproduce the dramatic losses of cold hardiness implying that the feeding influence was more complex than the availability of food per se. In a series of host transfer experiments the mean supercooling point of Aphis fabae adults could be shifted by over 10°C, increasing when they fed on beans and reduced when transferred back to spindle; the LG (spindle/poor supercoolers) to HG (bean/good supercoolers) shift was more difficult to achieve and suggested a nucleating agent in spindle sap. Trimethylsilyl derivatised carbohydrate extracts of M. persicae and A. fabae were analysed by capillary gas-liquid chromatography. Glucose, glycerol, fructose, mannitol, sucrose, and trehalose were detected in samples of both species, together with trace amounts of unidentified carbohydrates in M. persicae samples. Dulcitol was present in spindle-fed A. fabae only. There was no obvious correlation between carbohydrate content and supercooling ability but high total percentage body carbohydrate levels were revealed and may have a solute effect, enhancing inherent supercooling potential and dependent on carbohydrate-rich sap intake. Laboratory cultured A. fabae were capable of extensive supercooling, as were individuals collected from summer herbaceous hosts; first instars were the most cold hardy. When associated with the primary host, spindle, all aphids showed poor supercooling potential, less than -15°C; overwintering eggs were capable of supercooling to below -30°C and acclimatised in winter. Eggs and oviparae were not subject to inoculative nucleation. Preliminary experiments to relate supercooling ability to mortality at sub-zero temperatures proved inconclusive and were terminated when temperature shock and/or desiccation were thought to have induced premature mortality. The results demonstrate that the cold hardiness characteristics of M. persicae are atypical of those observed in other freezing-susceptible arthropods. It is proposed that continued feeding during mild winters maintains cold hardiness levels in adult M. persicae and this influence may provide a possible explanation for the successful anholocyclic overwintering of this aphid during such winters. Avenues of research to further investigate this proposal are suggested.

No description available.

Thesis (M.S.)--Miami University, Dept. of Zoology, 2007. / Title from first page of PDF document. Includes bibliographical references (p. 17-20).

No description available.

Container grown perennials are a popular product offered by nurseries and greenhouses and included in their production but little research has been reported on proper overwintering techniques for herbaceous perennials and ornamental grasses. In the first experiment rooted liners of Pennisetum alopecuroides, Pennisetum "Hameln" and Pennisetum "Little Bunny," were potted. Treatments included, utilizing two overwintering covers, two fertilizer rates (low or high) and two substrate moisture contents (wet or dry). Covering with either a double layer of Dewitt N-Sulate™ insulation fabric or a double layer of Dewitt N-Sulate™ insulation fabric and a single sheet of 4 mil white polyethylene plastic on top of the insulation fabric, wet substrate treatments, low fertility rates and combinations of both, improved survival and vigor for all three tested Pennisetum species and cultivars. In the second experiment, rooted liners of P. alopecuroides, P. "Hameln" and P. "Little Bunny," were potted. Treatments included, two transplanting times (young or old), two fertilizer rates (low or high) and two substrate moisture contents (wet or dry) at the UHC and Poplar Ridge Nursery (Montross, VA) (PR). Vigor was improved for P. alopecuroides (at PR) and P. "Little Bunny" (at both locations) with the young transplanting time. In the third experiment, older plant material of P. alopecuroides, P. "Hameln" and P. "Little Bunny," were subjected to fertility treatments of no additional fertilizer or top-dressed at a low, medium or high rate . A high fertility rate reduced survival and vigor for P. "Little Bunny." In the fourth experiment rooted liners of Echinacea purpurea "Hot Papaya," Echinacea purpurea "Milkshake," Gaillardia x grandiflora "Gallo Peach," Heuchera x villosa "Pistache," Heuchera x villosa "Brownies," P. alopecuroides, P. "Cassian," P. "Hameln" and P. "Little Bunny," were potted and overwintered at the UHC or Poplar Ridge Nursery (Montross, VA) (PR) or Riverbend Nursery, Inc. (Riner, VA) (RB). Treatments included, utilizing two overwintering covers, two fertilizer rates (low or high) and two substrate moisture contents (wet or dry). Vigor at the UHC, was reduced with the high fertility rate for E. "Hot Papaya" and H. "Brownies." A double layer of Dewitt N-Sulate™ insulation fabric and white polyethylene plastic on top of the cover, in combination with the wet substrate moisture treatment improved vigor of E. "Hot Papaya."A double layer of Dewitt N-Sulate™ insulation fabric in combination with the wet substrate moisture content and the high fertility rate reduced P. "Cassian" vigor. No overwintering cover reduced P. "Hameln" vigor. No overwintering cover and the high fertility rate reduced P. "Little Bunny" vigor. Vigor at PR was improved with the high fertility rate for E. "Milkshake," G. "Gallo Peach" and H. "Brownies." At RB, a double layer of Dewitt N-Sulate™ insulation fabric in combination with the low fertility treatment and no cover in combination with the high fertility treatment reduced vigor for E. "Milkshake" and P. "Little Bunny," respectively. No cover in combination with the wet substrate moisture treatment reduced vigor for G."Gallo Peach." / Master of Science

The morphological development of Elberta peach fruit buds was studied in relation to their cold hardiness. Morphological development of peach fruit buds was observed beginning with bud differentiation in mid-summer. Flower initiation was essentially complete by September. Growth was slow in the winter months but increased rapidly as anthesis approached. Photomicrographs were taken to substantiate the discussion . Cold hardiness determinations were made from December until anthesis in April. The hardiness level was greatest during December and remained at a relatively high level until rest ended. Hardiness decreased thereafter. Major losses of hardiness occurred just prior to anthesis.

No description available.

Benthic invertebrates inhabiting boreal rivers are exposed to very large seasonal variations in their physical environment. The extremes are in winter when the littoral area freezes solid and in spring when water flow increases rapidly. In the North Swedish river Vindelälven, the invertebrates fell into three main categories according to their seasonal lateral distribution. One category of animals was stationary in the littoral zone and let itselt freeze into the ice, adopting a "take it" alternative. The category consisted of many species belonging to several higher taxa. By overwintering in ice, the animals avoided predation for nearly half the year and they were in the productive littoral at the same time as they thawed out from the ice in spring. On the other hand the animals had to withstand sub-zero temperatures. A typical representative for this category of animals was the semivoltine snail Gyraulus acronicus. It is a less mobile species connected to dense stands of macrophytes, which are found only in the littoral zone of the river. Nearly the whole population was found overwintering successfully enclosed in ice. Its shell and epiphragm could serve as mechanical protection when frozen into the ice. G. acronicus was cold-hardy only during late autumn and early winter, but it could stand prolonged sub-zero exposure during the proper time. A second category of animlas avoided being frozen by performing lateral movements to deeper parts of the river, adopting the Vleave it" alternative. No species tested in this category were found cold-hardy. It consisted of mobile species known to utilize sedimentated detritus which was only found in greater amounts in the littoral zone of the river. In springtime, prior to spring flood peak, these species colonized promptly the former frozen zone. This behaviour was most pronounced in several lentie mayfly species. An extreme case of migratory behaviour was found in the mayfly Pararneletus chelifer which not only moved towards the river bank but continued up into small tributaries. The shoreward movements of mayflies both allowed the nymphs to avoid the high current velocities in the central part of the river during spring flood time and to utilize the food resources in the flooded areas. A third category of animals avoided the ice by living stationary in the sublittoral zone, adopting the "never face it" alternative. This category was dominated by filter feeders. / <p>Diss. (sammanfattning) Umeå : Umeå university, 1982, härtill 5 uppsatser</p> / digitalisering@umu

The postglacial recolonization of northern Europe supposedly originated from Western Europe and the Russian Plain, however, recent molecular and macrofossil-based investigations suggest that the history may be more complex than previously thought. This study aims to investigate the genetic diversity and population structure of Scots pine from Scandinavia to Russia to re-evaluate its recolonization history, and to examine whether the pattern of spatial genetic diversity has any adaptive significance. Populations ranging from Norway to Russia were sampled and genotyped using genotyping-by-sequencing. The seedlings were freeze tested to provide an average degree of hardiness for every population. Eight hundred and thirty-two seedlings were analyzed, and 6,034 SNPs were recovered in these individuals after stringent filtering. Population structure was investigated using fastStructure and differentiation between populations was estimated with pairwise FST and analysis of molecular variance (AMOVA) to assess the genetic variability. Genetic diversity was measured as observed heterozygosity, H0, in populations, clusters and overall. Two genetic clusters were detected in the samples, one in Norway and Sweden and one in Russia. These clusters are weakly differentiated (FST = 0.01202) with only 0.66 % variation between them. Highest variation was found within populations (98.8 %) and the overall genetic diversity for all populations was high (Ho = 0.2573). The weak differentiation and high diversity are indicative of extensive gene flow between populations in this species. The composition of the clusters across the sampled area suggests a westward recolonization from the Russian Plain into Scandinavia, and a possible local origin of another polymorphism in Norway and Sweden. No clear relationship between cold hardiness and genetic variation was detected. The clinal variation in cold hardiness reflects local adaptation, and the difference between genetic and phenotypic variation is likely due to epigenetic regulation or polygenic inheritance. More extensive genome scan is needed to understand the genetic basis of local adaptation.

<p>Kukuruzni plamenac,&nbsp;<em> Ostrinia nubilalis</em>Hb, je insekt umerenog klimatskog područja koji niske&nbsp; zimske temperature preživljava ulaskom u dijapauzu u stadijumu gusenice. Tokom dijapauze gusenice postaju otporne na hladnoću i sposobne&nbsp; da prežive vanćelijsko zamrzavanje telesne tečnosti.<br />Cilj ove teze je bio razumevanje mehanizama otpornosti na niske temperature gusenica&nbsp; <em>O. nubilalis </em>na ćelijskom i molekularnom nivou.<br />Istraživanja su rađena na letnjim, nedijapauzirajućim gusenicama kao i zimskim gusenicama koje su&nbsp; bile izlagane uticaju niskih temperatura u različitim periodima dijapauze. Određivan je režim telesne vode, sadržaj poliola i &scaron;ećera kao mogućih krioprotektora, kao i NMR metabolomički profili. Zbog pretpostavljene uloge atioksidativnog sistema za&scaron;tite (ADS) u procesima vezanim za otpornost na<br />hladnoću određivane su aktivnosti određenih antioksidativnih enzima kao i produkcija H₂O₂i melanina.<br />Rezultati ukazuju da je izlaganje niskim temperaturama kod dijapauzirajućih gusenica praćeno preraspodelom osmotski aktivne (OA) vode na nivou hemolimfe i masnog tela, pri čemu nivo OA&nbsp; opada u hemolimfi, a raste u masnom telu. Nivo osmotski neaktivne vode (OI) ostaje nepromenjen. Nivo glicerola je značajno veći kod dijapazirajućih u odnosu na nedijapauzirajuće gusenice, a njegov nivo se vi&scaron;estruko povećava pri izlaganju niskim temperaturama na sredini dijapauze ukazujući na njegov značaj kao glavnog krioprotektora u ovoj fazi dijapauze. Krajem dijapauze sa<br />niskim temperaturama vi&scaron;estruko se povećava nivo trehaloze, glukoze i fruktoze, a tek neznatnoglicerola.<br />NMR metabolomički profili su potvrdili značaj glicerola u otpornosti na hladnoću, ali i<br />aminokiselina alanina i prolina. U nedijapuzirajućim i dijapauzirajućim gusenicama na 5^oC registrovano je prisustvo putrescina, poznatog markera stresa, a&nbsp; njegova uloga, kao i moguća uloga njegovih daljih metabolita spermina i spermidina tek treba da se ispita. Odgovor ADS-a na niske temperature takođe je zavistan od perioda dijapauze. Na sredini dijapauze, na temperaturi od&nbsp; -3^oC, a ne i na&nbsp; -16^oC, dolazi do povećanja koncentracije H₂O_2&nbsp;i signala melanin radikala, dok aktivnost katalaze i CuZnSOD, ali ne i MnSOD, opada. Kako je glavni izvor H₂O₂mitohondrijalna MnSOD, ovaj enzim je verovatno uključen u regulaciju unutarćelijskog nivoa H₂O₂.<br />Produkcija melanina verovatno je u funkciji odbrane organizma od oksidativnog stresa zbog uklanjanja intracelularnog H₂O_2. Predpostavljamo da je temperatura od&nbsp; -3^oC ključna temperatura za pokretanje adaptivnih&nbsp; mehanizama za otpornost na hladnoću gusenica<em> O.nubilalis</em>. Promene u ADS sa izlaganjem niskim temperaturama nisu primećene na kraju dijapauze.<br />Rezultati ove teze ukazuju da je dijapauza dinamično stanje podeljeno na faze, a sama otpornost na hladnoću dobroregulisana i usklađena sa ukupnim metaboličkim potrebama tokom dijapauze.</p> / <p>&nbsp;European corn borer, <em>Ostrinia nubilalisHb</em>, is insect species of the temperate zone that survives low winter temperatures as a diapausing larva. Diapausing larvae are cold hardy and tolerate the formation of extracellular ice crystals.</p><p>The aim of this thesis was to investigate the cellular and molecular basis of&nbsp; <em>O. nubilalis </em>cold&nbsp;hardiness.</p><p>Thus, our research was focused on the non-diapausing (ND) as well as the diapausing (D) larvae that&nbsp;were exposed to low temperatures during different &nbsp;diapausal phases. Body water management,&nbsp;content of polyols and sugars as well as &nbsp;metabolomic NMR profiles, were assessed. Because of the&nbsp;possible role of the antioxidant defence system (ADS) in insects&rsquo; cold hardiness, antioxidant&nbsp;enzymes activity as well as the content of H₂O_2&nbsp;and melanin was measured.</p><p>Results showed that the exposure of diapausing larvae to low temperatures provokes exchanges of&nbsp;osmotically active (OA) body water between hemolymph and fat body. With low temperatures, OA&nbsp;water was decreased in hemolymph, increased in fat body while the content of osmotically inactive&nbsp;(OI) water was constant.</p><p>The level of glycerol was higher in diapausing compared to non-diapausing larvae, and showed 2-fold increase with the exposure to low temperatures in mid-diapause. This confirmed that glycerol is&nbsp;O.nubilalismajor cryoprotectant in mid-diapause cold hardiness. On the other hand, at the end of&nbsp;the diapause, the content of trehalose, glucose and fructose, except the glycerol, was substantially&nbsp;increased.</p><p><br />NMR metabolic profiling confirmed the importance of glycerol in diapausal cold hardiness as well&nbsp;as implied the importance of alanine and proline. In addition to this, putrescine, a well-know stress&nbsp;marker, were detected in ND and D larvae at 5^oC suggesting that its metabolites, namely sperimine&nbsp;and spermidine, can have potential role in diapause.</p><p>The ADS response to low temperatures differs during diapause timescale. In mid-diapause,&nbsp;exposure of larvae to&nbsp; -3^oC,&nbsp; but not&nbsp; -16^oC, resulted in the elevation of H₂O_2&nbsp;concentration and&nbsp;melanin radical signal. On the other hand, the activity of catalase and CuZnSOD, but not of&nbsp;MnSOD, was decreased. Since the mitochondrial MnSOD is the main source of H₂O2, this enzyme&nbsp;probably regulates the intracellular level hydrogen peroxide. Melanin probably serves as a defence&nbsp;mechanism against oxidative stress while it reduces the level of intracellular H₂O₂. Temperature of -3^oC is probably the &lsquo;trigger temperature&rsquo; for mechanism in adaptation of larvae&nbsp; <em>O.nubilalisto </em>&nbsp;cold.&nbsp;There were no changes detected in ADS during exposure to cold in the end of diapausing period.</p><p>The results of this thesis suggested that the <em>O. nubilalis</em> diapause is rather dynamic state divided into&nbsp;different phases and that the cold hardiness is highly regulated and in accordance with the current&nbsp;metabolic demands of each diapausal phase.</p>