Low-Temperature Adaptation of Winter Wheat Seedlings under Excessive Zinc Content in the Root Medium

Russian Journal of Plant Physiology - Cold adaptation of winter wheat (Triticum aestivum L.) seedlings was investigated under excessive zinc content (1000 μM) in the root medium. The ability...     

Sporicidal Activity of Sodium Hypochlorite at Subzero Temperatures

Sodium hypochlorite was an excellent disinfectant at low temperatures. With the addition of ethylene glycol to prevent freezing, hypochlorite solutions at low free available chlorine concentrations, were effective against Bacillus subtilis var. niger spores from 0 to -40 C. The effectiveness of this decontaminant was influenced by temperature, pH, and concentration, with pH 7.2 the optimum for decontamination at all temperatures and concentrations.     

玉米赤霉烯酮在冬小麦短日春化中的作用

应用酶联免疫技术,研究了冬小麦品种燕大１８１７ 在不同光周期条件下,体内内源玉米赤霉烯酮（ＺＥＮ） 和ＡＢＡ 含量的变化。结果表明,冬小麦品种燕大１８１７ 具有短日春化性,苗期经４ 周ＳＤ 处理后转到ＬＤ 下能正常抽穗。ＳＤ 诱导春化的幼苗茎尖和叶片中ＺＥＮ 含量高于未经诱导的ＬＤ 幼苗,而在两种光周期条件下生长的幼苗中ＡＢＡ 含量变化趋势并无明显差异。马拉硫磷（ ＭＡＬ） 抑制ＳＤ 幼苗体内ＺＥＮ 含量高峰的出现,也部分抑制抽穗;外源ＺＥＮ 可部分抵消ＭＡＬ对植株的影响,降低茎尖内源ＡＢＡ 含量,并有促进小麦拔节的作用。说明在冬小麦短日春化过程中,ＺＥＮ 具有促进作用,而ＡＢＡ 没有直接影响。     

Coronatine Alleviates Water Deficiency Stress on Winter Wheat Seedlings

With the aim to determine whether coronatine(COR) alleviates drought stress on wheat,two winter wheat(Triticum aestivum L.) cultivars,ChangWu134(drought-tolerant) and Shan253(drought-sensitive) were studied under hydroponic conditions.Seedlings at the three-leaf stage were cultured in a Hoagland solution containing COR at 0.1 μM for 24 h,and then exposed to 20% polyethylene glycol 6000(PEG6000).Under simulated drought(SD),COR increased the dry weight of shoots and roots of the two cultivars significantly;the root/shoot ratio also increased by 30% for Shan253 and 40% for ChangWu134.Both cultivars treated with COR under SD(0.1COR+PEG) maintained significantly higher relative water content,photosynthesis,transpiration,intercellular concentration of CO2 and stomatal conductance in leaves than those not treated with PEG.Under drought,COR significantly decreased the relative conductivity and malondialdehyde production,and the loss of 1,1-diphenyl-2-picrylhydrazyl scavenging activity in leaves was significantly alleviated in COR-treated plants.The activity of peroxidase,catalase,glutathione reductase and ascorbate peroxidase were adversely affected by drought.Leaves of plants treated with COR under drought produced less abscisic acid(ABA) than those not treated.Thus,COR might alleviate drought effects on wheat by reducing active oxygen species production,activating antioxidant enzymes and changing the ABA level.     

Storage of Porcine Articular Cartilage at High Subzero Temperatures

Objective: Transplantation of osteochondral allograft tissue can treat large joint defects but is limited by tissue availability, surgical timing, and infectious disease transmission. Fresh allografts perform the best but requirements for infectious disease testing delay the procedure with subsequent decrease in cell viability and function. Hypothermic storage at lower temperatures can extend tissue banking time without loss of cell viability and, therefore, increase the supply of allograft tissue. This study investigated the effects of different cryoprotectant solutions on intact AC at various subzero temperatures. Design: 10 mm porcine osteochondral dowels were immersed for 30 minutes in various combinations of solutions [(XVIVO, propylene glycol (51% w/w), sucrose (46% w/w)] cooled to various subzero temperatures (−10, −15, and −20 °C), and held for 30 min. After warming, 70 μm slices were stained with membrane integrity dyes, viewed under fluorescence microscopy and cell recovery calculated relative to fresh controls. Results: Results demonstrated excellent cell recovery (>75%) at −10°C provided ice did not form. Excellent cell recovery (>70%) occurred at −15°C in solutions containing 51% propylene glycol but formation of extra-matrix ice in other solutions resulted in significant cell loss. All groups had <6% cell recovery at −20°C and propylene glycol did not provide a protective effect even though extra-matrix ice did not form Conclusions: These results suggest that extra-matrix ice plays an important role in cell damage during cryopreservation. Excellent cell recovery can be obtained after storage at subzero temperatures if ice does not form. Hypothermic preservation at high subzero temperatures may extend AC storage time in tissue banks compared to current techniques.     

抗旱性不同的冬小麦幼苗对渗透胁迫的生理效应

抗旱性不同的冬小麦幼苗在渗进胁迫下叶片相对透性、Pro含量和在总游离氨基酸中的Pro比例均增加,但品种间变化幅度有明显差别。在严重胁迫下,抗旱性弱的品种济南13,烟农15和鲁麦5号的叶片相对透性增加大于抗旱性强的品种昌乐5号,秦麦3号和山农587;而Pro含量和在总游离氨基酸中Pro比例的增加小于抗旱性强的品种、叶片Pro累积与RWC呈显著负相关。     

Differential Involvement of the Five RNA Helicases in Adaptation of Bacillus cereus ATCC 14579 to Low Growth Temperatures

Bacillus cereus ATCC 14579 possesses five RNA helicase-encoding genes overexpressed under cold growth conditions. Out of the five corresponding mutants, only the ΔcshA, ΔcshB, and ΔcshC strains were cold sensitive. Growth of the ΔcshA strain was also reduced at 30°C but not at 37°C. The cold phenotype was restored with the cshA gene for the ΔcshA strain and partially for the ΔcshB strain but not for the ΔcshC strain, suggesting different functions at low temperature.Bacillus cereus is a human pathogenic sporulated bacterium which is associated with emetic and diarrheal types of food-borne illnesses (4). B. cereus is widespread in the environment and in a wide range of foods. The growth domains of B. cereus strains range from psychrotrophic to nearly thermophilic and correlate with several phylogenetic clusters (15), which presumably permit B. cereus to colonize many different habitats with different thermal regimes. Many foods are stored refrigerated before consumption, and in such cases, B. cereus has to adapt to low-temperature conditions.B. cereus growth at low temperature takes place with a lag phase which may correspond to an adaptation phase (12). Cold is a stress which dramatically affects membrane fluidity, protein synthesis, and also the topology of nucleic acids (22). When exposed to low temperature, bacteria have to face a transient inhibition of protein synthesis mainly due to the presence of secondary structures in mRNA that are stabilized by cold conditions (16, 19). To overcome the translation interruption, cold-shocked cells synthesize cold-induced RNA helicases, which remove secondary structures from RNA duplexes in the presence of ATP, such as CsdA of Escherichia coli (19) or CshA of Bacillus subtilis (1). csdA and srmB deletion mutants of E. coli showed a cold-sensitive phenotype, and these RNA helicases have been described as involved in the biogenesis of the ribosomal 50S subunit at 20°C (10, 11). RNA helicases could also be involved in the degradation of mRNA by unwinding double-stranded mRNA, thereby allowing the action of RNase (8).We have recently shown that the deregulation of the expression of one RNA helicase gene of B. cereus ATCC 14579 increased the lag phase of B. cereus at a low temperature (7). In this context, our aim was to investigate the role of the five putative RNA helicases present in the genome of B. cereus ATCC 14579 in its adaptation at low temperature, close to the growth limit.     

Motility of Colwellia psychrerythraea Strain 34H at Subzero Temperatures

We examined the Arctic bacterium Colwellia psychrerythraea strain 34H for motility at temperatures from −1 to −15°C by using transmitted-light microscopy in a temperature-controlled laboratory. The results, showing motility to −10°C, indicate much lower temperatures to be permissive of motility than previously reported (5°C), with implications for microbial activity in frozen environments.     

Toxicity of Anaerobic Metabolites Accumulating in Winter Wheat Seedlings during Ice Encasement

Ice encasement damages cold-hardened winter wheat without major disruption of cellular organelles. CO₂ accumulates during total ice encasement to higher levels in Kharkov than in less hardy Fredrick wheat. Partial ice encasement and exposure to a nitrogen atmosphere at -1 C allows greater CO₂ accumulation but neither treatment is as damaging as total ice encasement. Lactic acid accumulates to low levels only during the 1st day of encasement and thereafter remains constant. Exposure of plants to a combination of 50% CO₂ and 5% ethanol reduces survival, with a cultivar difference similar to that found in ice-encased plants. Plants in CO₂ and ethanol show a proliferation of membranes and nuclear condensation similar to that in cells of ice-encased plants. Permeability increases markedly in the presence of CO₂ and ethanol, to levels similar to or greater than those of iced plants. Ethanol alone does not increase permeability but in combination with CO₂ raises permeability of the less hardy Fredrick, although not of Kharkov, but reduces survival of both cultivars. A comparison of the endogenous levels of ethanol, CO₂, and lactic acid at the 50% kill point of plants due to ice encasement or due to externally supplied metabolite indicates that only CO₂ accumulates to independently toxic levels. Permeability and ultrastructural evidence suggest that CO₂ and ethanol in combination are the agents reducing plant viability during ice encasement.     

Response of Winter Wheat Seedlings Respiration to Long-Term Cold Exposure and Short-Term Daily Temperature Drops

Russian Journal of Plant Physiology - The effects of a long-term (6-day) exposure to low positive temperature (4°С, LT treatment) and short-term (3 h per a day for 6 days) daily...     

Adaptation to Water Stress in Wheat

Three experiments were designed to investigate to what extent adaptation to water stress take place. Wheat (Triticum aestivum L. cv. Kolibri) was grown in water culture at constant temperature, air humidity, and light intensity. When the plants were 16 days old, the potential of the root medium (ψ_r) was lowered by 1 bar every second day by means of polyethyleneglycol 1500 down to ?4 or ?7 bar and then remained at these levels. As a control one experiment was grown at ?0.7 bar. By regression it was found that when ψ_r was lowered by I bar, osmotic potential in leaf (ψ_π) decreased 1.46 bar, and leaf water potential (ψ_t) 0.68 bar, which mean an increase of turgor of 0.78 bar. At the same time the leaf water content did fall 0.30 g per g dry matter. Specific transpiration rate increased significantly after ψ_r was kept constant, but the increase in area of fresh leaves was strongly reduced due to wilting of old leaves. After an “adaptation” period during which ψ_r remained at ?0.7, ?4, and ?7 bar, respectively, for at least 1 week. ψ_r was altered so as to cover the range from 0 to ?14 bar and ψ_π, ψ_r, transpiration and diffusion resistance in stomata (r_s) were measured. The levels of ψ_π and ψ₁ were lower (more negative) and turgor potential higher in plants grown at low ψ_r. The transpiration in pre-stressed plants showed less sensitivity to the alteration of ψ_r than in the non-stressed plants. The values of ψ_r at which r_s increased greatly, were found to be about ?13, ?15, and ?18 bar for plants grown at ?0.7, ?4, and ?7 bar, respectively.     

Sporicidal Activity of Peracetic Acid and β-Propiolactone at Subzero Temperatures

A method was developed to evaluate and measure the sporicidal activity of peracetic acid (PAA) and β-propiolactone (BPL) at subzero temperatures as low as -40 C. Bacillus subtilis var. niger spores were used as the test organism. Both PAA and BPL were sporicidal at low temperatures, with PAA the more active. The temperature coefficients of the two chemicals are generally low over a range of 20 to -20 C, but increase significantly at temperatures below this. Results showed an initial lag in the PAA death rates that was directly dependent on the temperature. BPL did not show this lag time.     

Evidence for Involvement of at Least Six Proteins in Adaptation of Lactobacillus sakei to Cold Temperatures and Addition of NaCl

Lactobacillus sakei is a lactic acid bacterium widely represented in the natural flora of fresh meat. The aim of this study was to analyze the differences in protein expression during environmental changes encountered during technological processes in which L. sakei is involved in order to gain insight into the ability of this species to grow and survive in such environments. Using two-dimensional electrophoresis, we observed significant variation of a set of 21 proteins in cells grown at 4°C or in the presence of 4% NaCl. Six proteins could be identified by determination of their N-terminal sequences, and the corresponding gene clusters were studied. Two proteins belong to carbon metabolic pathways, and four can be clustered as general stress proteins. A phenotype was observed at low temperature for five of the six mutants constructed for these genes. The survival of four mutants during stationary phase at 4°C was affected, and surprisingly, one mutant showed enhanced survival during stationary phase at low temperatures.     

Maintenance of Membrane Fluidity during Development of Freezing Tolerance of Winter Wheat Seedlings

Fluidity of membrane lipids of shoot and root tissue and of chloroplasts from young wheat seedlings of contrasting freezing tolerance was investigated by measuring the motion and order parameters after spin labeling. A striking similarity was observed in membrane lipid fluidity of the five cultivars grown at 22 C. After cold hardening by growth at 2 C, a small change in membrane lipid fluidity was observed, but this was not correlated with the development of freezing tolerance, and there was no alteration in the transition temperature of membrane lipids. The results show that neither changes in membrane lipid fluidity nor transition temperature are a necessary feature of cold acclimation in wheat.     

Water Status Changes in Shoots of a Seaweed Ascophyllum nodosum at Subzero Temperatures

The gradient freezing and NMR spectroscopy were used to study the physical state of water in apices of the intertidal seaweed Ascophyllum nodosum at freezing temperatures. In the apices exposed to temperatures below –10°C, two fractions of bound water were revealed. The slow (T₂ 50 ms) fraction of bound water was completely frozen at –25°C, and its freezing rate was temperature-sensitive. This fraction was apparently associated with protoplasmic water and cell-wall polysaccharides. The fast fraction (T₂ < 10 ms) of bound water was presumably due to water-soluble globular proteins. The freezing rate for this fraction depended on neither the temperature nor the amount of water. The presence of unfrozen water in apical cells at –40°C was demonstrated. The role of this water fraction in maintaining the native structure of biomacromolecules and apex survival is discussed.     

Change in Lectin Specificity of Winter Wheat Seedlings in the Course of Infection with Mycoplasms

The activity of soluble lectins in leaves and roots of seedlings of winter wheat (Triticum aestivum L.) cultivar Mironovskaya 808 increased 1 day and 2 days, respectively, after infection with the mycoplasma Acholeplasma laidlawii 118. Analysis of acid-soluble proteins of wheat leaves by PAGE revealed the appearance of 22- and 20-kDa polypeptides, the disappearance of a 14-kDa polypeptide, and an increase in the content of polypeptides with molecular weights of 76, 48, 25, and 18 kDa. The 18-kDa polypeptide is a subunit of wheat germ agglutinin. A change in the activity of lectins may be a nonspecific response of plants to infection with the pathogen.     

Adaptive Changes in ATPase Activity in the Cells of Winter Wheat Seedlings during Cold Hardening

A cytochemical study of ATPase activity in the cells of cold hardened and nonhardened winter wheat (Triticum aestivum L. cv. Nongke No. 1) seedlings was carried out by electron microscopic observation of lead phosphate precipitation. ATPase activity associated with various cellular organelles was altered during cold hardening. (a) At 22°C, high plasmalemma ATPase activity was observed in both cold hardened and nonhardened tissues; at 5°C, high activity of plasmalemma ATPase was observed in hardened tissues, but not in unhardened tissues. (b) In nonhardened tissues, tonoplast and vacuoles did not exhibit high ATPase activity at either 22 or 5°C, while in hardened tissues high activity was observed at both temperatures. (c) At 5°C, ATPase activity of nucleoli and chromatin was decreased in hardened tissues, but not in nonhardened tissues. It is suggested that adaptive changes in ATPase activity associated with a particular cellular organelle or membrane may be associated with the development of frost resistance of winter wheat seedlings.     

干旱条件下冬小麦幼苗根细胞膜脂组成的变化

干旱条件下小麦幼苗根膜脂总脂肪酸含量、磷脂含量及总脂肪酸双键指数均下降,而游离甾醇含量却明显增加,结果导致游离甾醇／磷脂比率上升。用薄层层析法测得小麦根细胞磷脂主要由磷脂酰胆碱(PC)、磷脂酰乙醇胺(PE)、磷脂酰肌醇(PI)及磷脂酸(PA)组成。干旱降低了各种磷脂的含量,但不改变其相对配比。文中讨论了膜脂代谢变化与植物抗旱性的关系。