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This study aims to investigate the influence of oscillating magnetic fields on the deep supercooling of water and the supercooling storage of fruits. The results showed that by utilizing a 6 mT/50 Hz oscillating magnetic field, water (1 ml) was able to be maintained at -18 °C for 24 h, achieving deep supercooling. Combining magnetic field with oil-sealed water enhanced supercooling compared to oil sealing alone. By adding an oscillating magnetic field, fruits were maintained at a temperature of -5 °C for 12 h. The supercooled samples exhibited a texture and color that were close to those of fresh samples and also experienced a reduction in water loss of up to 30.25% in comparison to frozen samples that were not treated by magnetic field treatment. The proposed method achieved significant supercooling and improved food quality using an easily obtainable type of magnetic field.

Background Vessel‐associated cells (VACs) are highly specialized, living parenchyma cells that are in direct contact with water‐conducting, dead vessels. The contact may be sparse or in large tight groups of parenchyma that completely surrounds vessels. VACs differ from vessel distant parenchyma in physiology, anatomy, and function and have half‐bordered pits at the vessel‐parenchyma juncture. The distinct anatomy of VACs is related to the exchange of substances to and from the water‐transport system, with the cells long thought to be involved in water transport in woody angiosperms, but where direct experimental evidence is lacking. Scope This review focuses on our current knowledge of VACs regarding anatomy and function, including hydraulic capacitance, storage of nonstructural carbohydrates, symplastic and apoplastic interactions, defense against pathogens and frost, osmoregulation, and the novel hypothesis of surfactant production. Based on microscopy, we visually represent how VACs vary in dimensions and general appearance between species, with special attention to the protoplast, amorphous layer, and the vessel‐parenchyma pit membrane. Conclusions An understanding of the relationship between VACs and vessels is crucial to tackling questions related to how water is transported over long distances in xylem, as well as defense against pathogens. New avenues of research show how parenchyma‐vessel contact is related to vessel diameter and a new hypothesis may explain how surfactants arising from VAC can allow water to travel under negative pressure. We also reinforce the message of connectivity between VAC and other cells between xylem and phloem.

Seasonal changes in the accumulation of soluble sugars in extracellular freezing cortical parenchyma cells and deep supercooling xylem parenchyma cells in Japanese white birch (Betula platyphylla var. japonica) were compared to identify the effects of soluble sugars on the mechanism of deep supercooling, which keeps the liquid state of water in cells under extremely low temperatures for long periods. Soluble sugars in both tissues were analyzed by high-performance liquid chromatography (HPLC), and the concentrations of sugars in cells were estimated by histological observation of occupancy rates of parenchyma cells in each tissue. Relative and equilibrium melting points of parenchyma cells were measured by differential thermal analysis and cryoscanning electron microscopy, respectively. In both xylem and cortical parenchyma cells, amounts of sucrose, raffinose and stachyose increased in winter, but amounts of fructose and glucose exhibited little change throughout the entire year. In addition, no sugars were found to be specific for either tissue. Combined results of HPLC analyses, histological observation and melting point analyses confirmed that the concentration of sugars was much higher in xylem cells than in cortical cells. It is thought that the higher concentration of soluble sugars in xylem cells may contribute to facilitation of deep supercooling in xylem cells by depressing the nucleation temperature.

Wintering Sasa senanensis, dwarf bamboo, is known to employ deep supercooling as the mechanism of cold hardiness in most of its tissues from leaves to rhizomes. The breakdown of supercooling in leaf blades has been shown to proceed in a random and scattered manner with a small piece of tissue surrounded by longitudinal and transverse veins serving as the unit of freezing. The unique cold hardiness mechanism of this plant was further characterized using current year leaf blades. Cold hardiness levels (LT20: the lethal temperature at which 20% of the leaf blades are injured) seasonally increased from August (-11°C) to December (-20°C). This coincided with the increases in supercooling capability of the leaf blades as expressed by the initiation temperature of low temperature exotherms (LTE) detected in differential thermal analyses (DTA). When leaf blades were stored at -5°C for 1-14 days, there was no nucleation of the supercooled tissue units either in summer or winter. However, only summer leaf blades suffered significant injury after prolonged supercooling of the tissue units. This may be a novel type of low temperature-induced injury in supercooled state at subfreezing temperatures. When winter leaf blades were maintained at the threshold temperature (-20°C), a longer storage period (1-7 days) increased lethal freezing of the supercooled tissue units. Within a wintering shoot, the second or third leaf blade from the top was most cold hardy and leaf blades at lower positions tended to suffer more injury due to lethal freezing of the supercooled units. LTE were shifted to higher temperatures (2-5°C) after a lethal freeze-thaw cycle. The results demonstrate that the tissue unit compartmentalized with longitudinal and transverse veins serves as the unit of supercooling and temperature- and time-dependent freezing of the units is lethal both in laboratory freeze tests and in the field. To establish such supercooling in the unit, structural ice barriers such as development of sclerenchyma and biochemical mechanisms to increase the stability of supercooling are considered important. These mechanisms are discussed in regard to ecological and physiological significance in winter survival.

Xylem parenchyma cells (XPCs) in trees adapt to subzero temperatures by deep supercooling. Our previous study indicated the possibility of the presence of diverse kinds of supercooling-facilitating (SCF; anti-ice nucleation) substances in XPCs of katsura tree (Cercidiphyllum japonicum), all of which might have an important role in deep supercooling of XPCs. In the previous study, a few kinds of SCF flavonol glycosides were identified. Thus, in the present study, we tried to identify other kinds of SCF substances in XPCs of katsura tree. SCF substances were purified from xylem extracts by silica gel column chromatography and Sephadex LH-20 column chromatography. Then, four SCF substances isolated were identified by UV, mass and nuclear magnetic resonance analyses. The results showed that the four kinds of hydrolyzable gallotannins, 2,2', 5-tri-0-galloyl-α,β-D-hamamelose (trigalloyl Ham or kurigalin), 1,2,6-tri-O-galloyl-β-D-glucopyranoside (trigalloyl Glc), 1,2,3,6-tetra-O-galloyl-β-D-glucopyranoside (tetragalloyl Glc) and 1,2,3,4,6-penta-O-galloyl-β-D-glucopyranoside (pentagalloyl Glc), in XPCs exhibited supercooling capabilities in the range of 1.5-4.5°C, at a concentration of 1 mg mL⁻¹. These SCF substances, including flavonol glycosides and hydrolyzable gallotannins, may contribute to the supercooling in XPCs of katsura tree.

Xylem parenchyma cells (XPCs) in larch adapt to subfreezing temperatures by deep supercooling, while cortical parenchyma cells (CPCs) undergo extracellular freezing. The temperature limits of supercooling in XPCs changed seasonally from -30 °C during summer to -60 °C during winter as measured by freezing resistance. Artificial deacclimation of larch twigs collected in winter reduced the supercooling capability from -60 °C to -30 °C. As an approach to clarify the mechanisms underlying the change in supercooling capability of larch XPCs, genes expressed in association with increased supercooling capability were examined. By differential screening and differential display analysis, 30 genes were found to be expressed in association with increased supercooling capability in XPCs. These 30 genes were categorized into several groups according to their functions: signal transduction factors, metabolic enzymes, late embryogenesis abundant proteins, heat shock proteins, protein synthesis and chromatin constructed proteins, defence response proteins, membrane transporters, metal-binding proteins, and functionally unknown proteins. All of these genes were expressed most abundantly during winter, and their expression was reduced or disappeared during summer. The expression of all of the genes was significantly reduced or disappeared with deacclimation of winter twigs. Interestingly, all but one of the genes were expressed more abundantly in the xylem than in the cortex. Eleven of the 30 genes were thought to be novel cold-induced genes. The results suggest that change in the supercooling capability of XPCs is associated with expression of genes, including genes whose functions have not been identified, and also indicate that gene products that have been thought to play a role in dehydration tolerance by extracellular freezing also have a function by deep supercooling.

Using fluxing technology, molten Fe80P14B6 alloy achieved significant undercooling (ΔT). Experimental results demonstrate that the solidified morphologies of the Fe80P14B6 alloy vary considerably with ΔT. At ΔT = 100 K, the microstructure is dendritic. At ΔT = 250 K, a variety of eutectic morphologies are observed, including a network-like structure near the solidification center, attributed to liquid spinodal decomposition. At ΔT = 350 K, the microstructure exhibits a uniform, random network-like morphology with approximately 50 nm. The mechanical property of the specimens solidified at different ΔT was checked by microhardness test, indicating that the hardness of the specimens increases with the increase in ΔT, reaching a maximum value of 1151 HV0.2.

Considered is a case study for the East Siberian and Chukchi seas on the significance of the super cooled water and intrawater ice crystals for the formation of the ice cover structure. Given are the brief hydro meteorological description of the region under consideration and the description of ice conditions in the seas depending on the coming of heavy Arc tic ice from the north. It is noted that the intensity of the cooling of the surface water layer in autumn-winter time will in crease due to the de crease in the ice cover age of the seas in the case of the further in crease in the ice-free area. This will result in the supercooling of the surface water layer on the large territory and will cause the intensive formation of frazil ice. The accumulation of intrawater (frazil) ice crystals with their possible freezing into solid mass is inevitable in local areas at the new regular contact with supercooled water that favors the in crease in the total thick ness of the ice cover. It is also revealed that super cooled water initiates the freezing (consolidation) of detritus in ice hum mocks and coastal stamukhas. It is demonstrated that supercooling of water in the seas under consideration in autumn and winter takes place through out the shelf zone to the bottom on large areas, but due to lower salinity, the density of this water is in sufficient for taking part in the formation of deep water layers. Therefore, the water of the shelf zone of these seas influences the formation of surface Arctic water only. This distinguishes consider ably the studied processes from those ob served in Antarctic water.

Deep undercooled tissue water, which froze near -40 C, was found in winter collected stem and leaf tissue of the dominant timberline tree species of the Colorado Rocky Mountains, Engelmann spruce (Picea engelmannii (Parry) Engelm.) and subalpine fir (Abies lasiocarpa (Hook.) Nutt.), and in numerous other woody species in and below the subalpine vegetation zone. Previous work on numerous woody plants indicates that deep undercooling in xylem makes probable a -40 C winter hardiness limit in stem tissue. Visual injury determinations and electrolyte loss measurements on stem tissue revealed injury near -40 C associated with the freezing of the deep undercooled stem tissue water. These results suggest that the winter hardiness limit of this woody flora is near -40 C. The relevance of deep undercooling in relation to timberline, the upper elevational limit of the subalpine forest, is discussed.

The low temperature exotherms (LTE) of 1-year-old twigs of Haralson apple (Malus pumila Mill.), shagbark hickory (Carya ovata [Mill.] K. Koch), green ash (Fraxinus pennsylvanica Marsh), honey locust (Gleditsia triacanthos L.), American chestnut (Castanea dentata [Marsh] Borkh.), and red oak (Quercus rubra L.) were determined by differential thermal analysis (DTA). In one type of experiment freezing during a DTA experiment was halted for up to 2.5 hours after part of the supercooled water had frozen at temperatures between -25 and -42 C. Upon resumption of cooling the freezing started within 2 C of the stopping temperature. In a second type of experiment living and dead cells were microscopically observed in the same ray after partial freezing in the DTA apparatus. In another experiment, the LTE persisted even after tangential and radial sectioning of the twig to 0.13 millimeters. In a final experiment the LTE of a single multiseriate ray of red oak had the same shape as the LTE of wood with many uniseriate rays. These experiments confirm that the deep supercooled water in woody xylem or pith freezes in numerous independent events over a span of as much as 20 C. The units which freeze in an event are single cells or small groups of cells. Ice grows very slowly if at all from these units, and water moves very slowly from unfrozen cells to frozen ones. Deep supercooling of ray parenchyma does not require an intact ray.