The Experts below are selected from a list of 6417 Experts worldwide ranked by ideXlab platform
Gilbert Neuner - One of the best experts on this subject based on the ideXlab platform.
-
Frost Resistance in alpine woody plants
Frontiers in Plant Science, 2014Co-Authors: Gilbert NeunerAbstract:This report provides a brief review of key findings related to Frost Resistance in alpine woody plant species, summarizes data on their Frost Resistance, highlights the importance of freeze avoidance mechanisms, and indicates areas of future research. Freezing temperatures are possible throughout the whole growing period in the alpine life zone. Frost severity, comprised of both intensity and duration, becomes greater with increasing elevation and, there is also a greater probability, that small statured woody plants, may be insulated by snow cover. Several Frost survival mechanisms have evolved in woody alpine plants in response to these environmental conditions. Examples of tolerance to extracellular freezing and freeze dehydration, life cycles that allow species to escape Frost, and freeze avoidance mechanisms can all be found. Despite their specific adaption to the alpine environment, Frost damage can occur in spring, while all alpine woody plants have a low risk of Frost damage in winter. Experimental evidence indicates that premature deacclimation in Pinus cembra in the spring, and a limited ability of many species of alpine woody shrubs to rapidly reacclimate when they lose snow cover, resulting in reduced levels of Frost Resistance in the spring, may be particularly critical under the projected changes in climate. In this review, Frost Resistance and specific Frost survival mechanisms of different organs (leaves, stems, vegetative and reproductive over-wintering buds, flowers and fruits) and tissues are compared. The seasonal dynamics of Frost Resistance of leaves of trees, as opposed to woody shrubs, is also discussed. The ability of some tissues and organs to avoid freezing by supercooling, as visualized by high resolution infrared thermography, are also provided. Collectively, the report provides a review of the complex and diverse ways that woody plants survive in the Frost dominated environment of the alpine life zone.
-
dehydration and osmotic adjustment in apple stem tissue during winter as it relates to the Frost Resistance of buds
Tree Physiology, 2013Co-Authors: Manuel Pramsohler, Gilbert NeunerAbstract:In deciduous trees, measurement of stem water potential can be difficult during the leafless period in winter. By using thermocouple psychrometry, osmotic water potentials (Ψo; actual Ψo: Ψo(act); Ψo at full saturation: Ψo(sat)) of expressed sap of bark and bud tissue were measured in order to test if the severity of winter desiccation in apple stems could be sufficiently assessed with Ψo. Water potentials were related to Frost Resistance and freezing behaviour of buds. The determination of Ψo reliably allowed winter desiccation and osmotic adjustments in apple stem tissue to be assessed. In winter in bark tissue, a pronounced decrease in Ψo(act) and Ψo(sat) was found. Decreased Ψo(sat) indicates active osmotic adjustment in the bark as observed earlier in the leaves of evergreen woody plants. In terminal bud meristems, no significant osmotic adjustments occurred and dehydration during winter was much less. Osmotic water potentials, Ψo(act) and Ψo(sat), of bud tissue were always less negative than in the bark. To prevent water movement and dehydration of the bud tissue via this osmotic gradient, it must be compensated for either by a sufficiently high turgor pressure (Ψp) in bark tissue or by the isolation of the bud tissue from the bark during midwinter. During freezing of apple buds, freeze dehydration and extra-organ freezing could be demonstrated by significantly reduced Ψo(act) values of bud meristems that had been excised in the frozen state. Infrared video thermography was used to monitor freezing patterns in apple twigs. During extracellular freezing of intact and longitudinally dissected stems, infrared differential thermal analysis (IDTA) images showed that the bud meristem remains ice free. Even if cooled to temperatures below the Frost-killing temperature, no freezing event could be detected in bud meristems during winter. In contrast, after bud break, terminal buds showed a second freezing at the Frost-killing temperature that indicates deep supercooling. Our results demonstrate the applicability of thermocouple psychrometry for the assessment of winter desiccation in stem tissues of deciduous trees and corroborate the finding that dormant apple buds survive by extra-organ freezing and do not deep supercool. In addition, they indicate that significant changes of the Frost-survival mechanism can occur during the apple bud development in spring.
-
how endangered is sexual reproduction of high mountain plants by summer Frosts Frost Resistance frequency of Frost events and risk assessment
Oecologia, 2013Co-Authors: Ursula Ladinig, Gilbert Neuner, Jurgen Hacker, Johanna WagnerAbstract:In temperate-zone mountains, summer Frosts usually occur during unpredictable cold spells with snow-falls. Earlier studies have shown that vegetative aboveground organs of most high-mountain plants tolerate extracellular ice in the active state. However, little is known about the impact of Frost on reproductive development and reproductive success. In common plant species from the European Alps (Cerastium uniflorum, Loiseleuria procumbens, Ranunculus glacialis, Rhododendron ferrugineum, Saxifraga bryoides, S. moschata, S. caesia), differing in growth form, altitudinal distribution and phenology, Frost Resistance of reproductive and vegetative shoots was assessed in different reproductive stages. Intact plants were exposed to simulated night Frosts between −2 and −14 °C in temperature-controlled freezers. Nucleation temperatures, freezing damage and subsequent reproductive success (fruit and seed set, seed germination) were determined. During all reproductive stages, reproductive shoots were significantly less Frost resistant than vegetative shoots (mean difference for LT50 −4.2 ± 2.7 K). In most species, reproductive shoots were ice tolerant before bolting and during fruiting (mean LT50 −7 and −5.7 °C), but were ice sensitive during bolting and anthesis (mean LT50 around −4 °C). Only R. glacialis remained ice tolerant during all reproductive stages. Frost injury in reproductive shoots usually led to full fruit loss. Reproductive success of Frost-treated but undamaged shoots did not differ significantly from control values. Assessing the Frost damage risk on the basis of summer Frost frequency and Frost Resistance shows that, in the alpine zone, low-statured species are rarely endangered as long as they are protected by snow. The situation is different in the subnival and nival zone, where Frost-sensitive reproductive shoots may become Frost damaged even when covered by snow. Unprotected individuals are at high risk of suffering from Frost damage, particularly at higher elevations. It appears that ice tolerance in reproductive structures is an advantage but not an absolute precondition for colonizing high altitudes with frequent Frost events.
-
summer Frost Resistance and freezing patterns measured in situ in leaves of major alpine plant growth forms in relation to their upper distribution boundary
Plant Cell and Environment, 2004Co-Authors: D Taschler, Gilbert NeunerAbstract:Summer Frost Resistance and ice nucleation temperatures for 33 alpine plant species were measured in situ to avoid the shortcomings of laboratory tests. Species were selected to investigate the relationship between plant stature and upper distribution boundary, and Frost Resistance and freezing patterns. The species tested in situ were on average 1.1 K ( ± ± ± 0.2, SE) Frost hardier than in laboratory tests. Frost Resistance (LT 50 ) ranged from - 4.5 to - - 14.6 ∞ ∞ ∞ C and appeared insufficient to protect against air temperature minima, corroborating reports of natural Frost damage. All species tolerated extracellular ice formation (recorded at 1.9 ± 0.2 ∞ C; E1). Initial Frost damage occurred at average temperatures 4.9 K below E1. In 64% of the species a second exotherm (E2) and Frost damage were recorded between - - 3.7 and - 9.4 ∞ C. In the highest ranging species E2 was not detectable. Frost Resistance increased with increasing upper distribution boundary (0.4 K per 100 m), corresponding well with the altitudinal decrease in air temperature minima. No relationship between plant stature and Frost Resistance was found. Graminoids were significantly Frost hardier than other growth forms. Frost survival at high altitudes will depend not only on altitudinal increase in Frost Resistance but also on freezing avoidance strategies, snow cover protection and a high recuperation capacity.
-
Frost Resistance and ice nucleation in leaves of five woody timberline species measured in situ during shoot expansion
Tree Physiology, 2004Co-Authors: D Taschler, Barbara Beikircher, Gilbert NeunerAbstract:Frost Resistance and ice nucleation temperatures of leaves, from bud swelling until after full expansion, were measured in situ for five major woody timberline species with recently developed field freezing equipment. Frost Resistance determined in situ on leaves of attached twigs was significantly higher than values determined on detached leaves in laboratory tests (e.g., the temperature at which incipient Frost damage was observed (LTi) was 1.2 degrees C higher for detached leaves than for attached leaves of Picea abies (L.) Karst.). Frost Resistance of leaves of all species changed significantly during shoot expansion (e.g., changes of 7.2 and 11 degrees C for Rhododendron ferrugineum L. and Larix decidua Mill., respectively). Expanding leaves (between 0 and 60% of full expansion) were the most sensitive to Frost, with LTi values ranging from -3.4 degrees C in R. ferrugineum to -6.3 degrees C in L. decidua. Among the studied species, P. abies and R. ferrugineum were the most Frost sensitive throughout the shoot elongation period. In situ freezing patterns of leaves of attached twigs also differed from those of leaves of excised twigs. During leaf expansion, two distinct freezing exotherms were always registered in situ. The first freezing event (E1, high-temperature exotherm) was recorded at -1.5 +/- 0.2 degrees C and reflected extracellular ice formation. Exposure of leaves to temperatures at which E1 occurred was, in all cases, noninjurious. The low-temperature exotherm (E2) mostly coincided with Frost damage, except for some stages of leaf expansion in R. ferrugineum and P. abies, indicating that in situ freezing exotherms were not accurate estimators of Frost damage in these species.
Bertil Persson - One of the best experts on this subject based on the ideXlab platform.
-
on the internal Frost Resistance of self compacting concrete with and without polypropylene fibres
Materials and Structures, 2007Co-Authors: Bertil PerssonAbstract:In this article experimental and numerical studies of internal Frost Resistance of self-compacting and normal concrete, with and without fibres, are outlined. For this purpose self-compacting concrete with low water-cement ratio was studied, with varying amounts of filler, crystalline or sedimentary, different pouring pressures and different mixing procedure with two ages at the start of testing. The concrete was frozen twice a day at ±20°C all around the specimen up to 300 cycles. Measurement of length, weight and internal fundamental frequency were performed at the start of testing, at 100 cycles and at 300 Frost cycles. Tests were also carried out on submerged cast self-compacting concrete and on self-compacting concrete with fibres. In reference tests normal concrete was studied in parallel. In general self-compacting concrete behaved well or better than normal concrete to internal Frost except for the submerged cast concrete, where large segregation occurred and low internal Frost Resistance followed. The main reasons for low internal Frost Resistance in submerged applications were probably differences in water-cement ratio in the casting due to cement, water or/and aggregate segregation. Polypropylene fibres in concrete seemed to prohibit the movement of water in the air void system so that a sudden internal collapse occurred before 300 Frost cycles. (Less)
-
internal Frost Resistance and salt Frost scaling of self compacting concrete
Cement and Concrete Research, 2003Co-Authors: Bertil PerssonAbstract:This article outlines laboratory and analytical studies of salt Frost scaling and internal Frost Resistance of self-compacting concrete (SCC) that contains increased amount of filler, different air content, and dissimilar methods of casting. The results were compared with the corresponding properties of normal concrete (NC) with the same water-to-cement ratio (0.39) and air content (6%). The start of the testing was applied at ages of 28 and 90 days. The strength development of the concrete was followed in parallel. Six SCC and two NC were studied. The effects of normal and reversed order of mixing (filler last), increased amount of filler, fineness of filler, limestone powder, increased air content, and large hydrostatic concrete pressure were investigated. The results indicated a substantial improvement of the internal Frost Resistance of SCC as compared to NC. The salt Frost scaling performed more or less in the same way in SCC and in NC. No relationship of Frost Resistance was found to the air-void structure of the concrete.
-
assessment of the chloride migration coefficient internal Frost Resistance salt Frost scaling and sulphate Resistance of self compacting concrete with some interrelated properties
Report TVBM, 2001Co-Authors: Bertil PerssonAbstract:This report describes laboratory and analytical studies of the chloride migration coefficient, D, defined by Tang, the salt Frost scaling, the internal Frost Resistance and the sulphate Resistance of SCC that contains increased amount of filler, different types of casting and different air content.
Atsushi Higashi - One of the best experts on this subject based on the ideXlab platform.
-
influence of firing temperature on Frost Resistance of roofing tiles
Journal of The European Ceramic Society, 2004Co-Authors: Kiyohiko Ikeda, Hyungsun Kim, Koichi Kaizu, Atsushi HigashiAbstract:Abstract In cold districts, prevention against Frost damage of roofing tiles caused by the expansion due to the freezing of water absorbed in the numerous pores in the tile material has becomes a serious problem. It is known that the Frost damage is closely connected to the porosity and water absorbing capacity of the roofing tile. Both the porosity and water absorbing capacity of the material can be controlled by the firing temperature. In this work, in order to examine the effect of firing temperature on the Frost Resistance, tiles fired at different temperatures of 900–1200 °C were fractured by four point bending after applying freezing treatment at low temperatures of −10, −30 and −50 °C. At any firing temperature up to 1100 °C, both fracture stress and fracture toughness increased with the firing temperature, but they dropped above 1100 °C. Furthermore, an obvious decrease in fracture stress with decrease in freezing temperature was observed for the samples fired at 1200 °C. Thus, it was concluded that the roofing tile fired at temperatures of up to 1200 °C forming mullite with a glass phase from the reaction with quartz and feldspar could minimize the Frost damage.
D Taschler - One of the best experts on this subject based on the ideXlab platform.
-
summer Frost Resistance and freezing patterns measured in situ in leaves of major alpine plant growth forms in relation to their upper distribution boundary
Plant Cell and Environment, 2004Co-Authors: D Taschler, Gilbert NeunerAbstract:Summer Frost Resistance and ice nucleation temperatures for 33 alpine plant species were measured in situ to avoid the shortcomings of laboratory tests. Species were selected to investigate the relationship between plant stature and upper distribution boundary, and Frost Resistance and freezing patterns. The species tested in situ were on average 1.1 K ( ± ± ± 0.2, SE) Frost hardier than in laboratory tests. Frost Resistance (LT 50 ) ranged from - 4.5 to - - 14.6 ∞ ∞ ∞ C and appeared insufficient to protect against air temperature minima, corroborating reports of natural Frost damage. All species tolerated extracellular ice formation (recorded at 1.9 ± 0.2 ∞ C; E1). Initial Frost damage occurred at average temperatures 4.9 K below E1. In 64% of the species a second exotherm (E2) and Frost damage were recorded between - - 3.7 and - 9.4 ∞ C. In the highest ranging species E2 was not detectable. Frost Resistance increased with increasing upper distribution boundary (0.4 K per 100 m), corresponding well with the altitudinal decrease in air temperature minima. No relationship between plant stature and Frost Resistance was found. Graminoids were significantly Frost hardier than other growth forms. Frost survival at high altitudes will depend not only on altitudinal increase in Frost Resistance but also on freezing avoidance strategies, snow cover protection and a high recuperation capacity.
-
Frost Resistance and ice nucleation in leaves of five woody timberline species measured in situ during shoot expansion
Tree Physiology, 2004Co-Authors: D Taschler, Barbara Beikircher, Gilbert NeunerAbstract:Frost Resistance and ice nucleation temperatures of leaves, from bud swelling until after full expansion, were measured in situ for five major woody timberline species with recently developed field freezing equipment. Frost Resistance determined in situ on leaves of attached twigs was significantly higher than values determined on detached leaves in laboratory tests (e.g., the temperature at which incipient Frost damage was observed (LTi) was 1.2 degrees C higher for detached leaves than for attached leaves of Picea abies (L.) Karst.). Frost Resistance of leaves of all species changed significantly during shoot expansion (e.g., changes of 7.2 and 11 degrees C for Rhododendron ferrugineum L. and Larix decidua Mill., respectively). Expanding leaves (between 0 and 60% of full expansion) were the most sensitive to Frost, with LTi values ranging from -3.4 degrees C in R. ferrugineum to -6.3 degrees C in L. decidua. Among the studied species, P. abies and R. ferrugineum were the most Frost sensitive throughout the shoot elongation period. In situ freezing patterns of leaves of attached twigs also differed from those of leaves of excised twigs. During leaf expansion, two distinct freezing exotherms were always registered in situ. The first freezing event (E1, high-temperature exotherm) was recorded at -1.5 +/- 0.2 degrees C and reflected extracellular ice formation. Exposure of leaves to temperatures at which E1 occurred was, in all cases, noninjurious. The low-temperature exotherm (E2) mostly coincided with Frost damage, except for some stages of leaf expansion in R. ferrugineum and P. abies, indicating that in situ freezing exotherms were not accurate estimators of Frost damage in these species.
O I Grabelnych - One of the best experts on this subject based on the ideXlab platform.
-
the tebuconazole based protectant of seeds bunker induces the synthesis of dehydrins during cold hardening and increases the Frost Resistance of wheat seedlings
Journal of Stress Physiology & Biochemistry, 2015Co-Authors: A V Korsukova, O A Borovik, O I Grabelnych, V K VoinikovAbstract:Triazole derivatives are widely used in agriculture for seed protectant of cereals against seed and soil infection. Triazole derivatives can have an effect on the biochemical and physiological functions of plants. The tebuconazole-based protectant of seeds «Bunker» (content of tebuconazole 60 grams per liter, g/L) is a systemic fungicide of preventive and therapeutic action. The effect of the seed treatment by «Bunker» preparation on the shoot growth and cell viability coleoptile, synthesis of dehydrins in shoots and Frost Resistance etiolated winter and spring wheat seedlings has been studied. It has been shown that treatment of winter and spring wheat seed by «Bunker» preparation induces similar concentration-dependent inhibition of the coleoptiles length. At the recommended dose (0,5 liter per tonne of seeds, L/t) growth inhibition was 28 - 30%, at a concentration of 1 L/t - 33 - 36%, at a concentration of 1,5 L/t - 40 - 42%, at a concentration of 3 L/t - 43 - 47%, at a concentration of 4 L/t - 48 - 51% and at 5 L/t - 53 - 56%. The treatment of wheat seed by «Bunker» preparation had no phytotoxic effect on coleoptile cells in any of the studied concentrations, on the contrary, with increasing concentration of preparation observed the increase in cell viability, as measured by recovery of 2,3,5-triphenyltetrazolium chloride. We can assume that having retardant properties, tebuconazole not only inhibits the growth of plants, but also delays their aging. The treatment of seed protectant at a concentration of 1.5 L/t induced synthesis of the dehydrins with molecular masses about 19, 21, 22, 25 and 27 kD in winter wheat shoots and 18,6, 27 and 28,5 kD in spring wheat shoots during cold hardening. Among identified dehydrins the dehydrin of 27 kD is most significantly induced both in winter and spring wheat. The treatment of seed protectant «Bunker» in the same concentration increased the Frost Resistance of winter and spring wheat seedlings. It is supposed that increasing of cold and Frost Resistance of winter and spring wheat caused by seed treatment of the tebuconazole-based protectant may be associated with increase of the abscisic acid content - one of the triggers of the low-temperature adaptation of plants. It is concluded that tebuconazole-based protectant of seeds «Bunker» increases the Resistance of wheat to low temperature, affecting the growth processes and the synthesis of stress proteins.
-
mitochondrial energy dissipating systems alternative oxidase uncoupling proteins and external nadh dehydrogenase are involved in development of Frost Resistance of winter wheat seedlings
Biochemistry, 2014Co-Authors: O I Grabelnych, O A Borovik, E L Tauson, T P Pobezhimova, A I Katyshev, N S Pavlovskaya, N A Koroleva, I V Lyubushkina, Yu V Bashmakov, V N PopovAbstract:Gene expression, protein synthesis, and activities of alternative oxidase (AOX), uncoupling proteins (UCP), adenine nucleotide translocator (ANT), and non-coupled NAD(P)H dehydrogenases (NDex, NDPex, and NDin) were studied in shoots of etiolated winter wheat (Triticum aestivum L.) seedlings after exposure to hardening low positive (2°C for 7 days) and freezing (−2°C for 2 days) temperatures. The cold hardening efficiently increased Frost-Resistance of the seedlings and decreased the generation of reactive oxygen species (ROS) during further cold shock. Functioning of mitochondrial energy-dissipating systems can represent a mechanism responsible for the decrease in ROS under these conditions. These systems are different in their response to the action of the hardening low positive and freezing temperatures. The functioning of the first system causes induction of AOX and UCP synthesis associated with an increase in electron transfer via AOX in the mitochondrial respiratory chain and also with an increase in the sensitivity of mitochondrial non-phosphorylating respiration to linoleic and palmitic acids. The increase in electron transfer via AOX upon exposure of seedlings to hardening freezing temperature is associated with retention of a high activity of NDex. It seems that NDex but not the NDPex and NDin can play an important role in maintaining the functional state of mitochondria in heterotrophic tissues of plants under the influence of freezing temperatures. The involvement of the mitochondrial energy-dissipating systems and their possible physiological role in the adaptation of winter crops to cold and Frost are discussed.
