Evaluation of Cold Resistance and Semi-lethal Low Temperature(LT_(50))of Nine Pear Cultivars

[Objectives]To evaluate the cold resistance and semi-lethal temperature of pear cultivars,and provide a theoretical basis for the regional extension and breeding of cold-resistant pear cultivars.[Methods]Nine pear cultivars were used to study the changes in relative conductivity and cell injury rate of pear branches under low temperature stress,and the semi-lethal temperature(LT_(50))of pear branches was analyzed by fitting Logistic equation.[Results]The relative conductivity and cell injury rate of pear branches took on the trend of slow increase,rapid increase,and slow increase the decrease of treatment temperature.The LC_(50) of the nine pear cultivars were as follows:Nanguo pear-33.9℃,Wanyu-32.3℃,Red D Anjou-31.8℃,Jinfeng-31.3℃,Wujiuxiang-29.2℃,20 th Century Pear-29.1℃,Hanxiang-35.1℃,Yuluxiang-27.9℃ and Korla Fragrant Pear-29.2℃.[Conclusions]The semi-lethal temperature could reflect the cold resistance of pear trees,and Wanxiang had better cold resistance.The evaluation of cold resistance and semi-lethal temperature of pear cultivars can provide theoretical basis for regional extension and breeding of cold-resistant pear cultivars.

Effects of Chitosan and Salicylic Acid on Cold Resistance of Litchi under Low Temperature

This paper focused on the effect of spraying chitosan and salicylic acid to Litchi under low temperature stress conditions.The physiology and biochemistry of litchi were studied as well.Results showed that the appropriate concentration of chitosan and salicylic acid treatment could effectively reduce injury caused by low temperature to litchi,compared with water control,chlorophyll,proline,soluble protein content of litchi after treatment and the activity of protective enzyme increasing significantly.However,the accumulation of resistance could significantly be improved.Furthermore,when 1 000 mg/L chitosan combined with 50 mg/L salicylic acid,the litchi acquired the best cold resistance capability.

Role of CaCl_(2) in Cold Acclimation-Induced Freezing Resistance of Populus tomentosa Cuttings

Populus tomentosa cuttings were treated with 1mmol·L -1 , 5mmol·L -1 , 10mmol·L -1 or 15mmol·L -1 of CaCl 2 for 1\|7 d, respectively, for studying the effects of different concentrations of CaCl 2 on freezing resistance. Results indicated that 10?mmol·L -1 of CaCl 2 has greater effect than other concentrations on the enhancement of freezing resistance, and the optimum time of pretreatment was 5?d. In addition, cuttings used for cold acclimation at -3℃ were pretreated with or without 10?mmol·L -1 of CaCl 2, 3?mmol·L -1 of Ca 2+ chelator EGTA, 0 05?mmol·L -1 of CaM antagonist CPZ or 0 1?mmol·L -1 of Ca 2+ channel inhibitor LaCl 3 The changes in CaM and freezing resistance of all cuttings were investigated. The results showed that cold acclimation at -3℃ increased CaM content and decreased the minimum temperature for 100% survival. The CaCl 2 pretreatment enhanced the effect of cold acclimation and obviously increased CaM content and decreased the minimum temperature for 100% survival, but this effect was strongly inhibited by the EGTA, CPZ or LaCl 3 It is concluded that the effect of CaCl 2 on freezing resistance is associated with its concentration and time of pretreatment, Ca 2+ CaM may be involved in the induction of freezing resistance of the cuttings.

Effects of Cold Acclimation and CaCl_2 on Total Soluble Protein, CaM and Freezing Resistance of Populus tomentosa Seedlings

Populus tomentosa seedlings used for cold acclimation at -3℃ were pretreated with or without 10?mmol·L -1 CaCl 2, 3?mmol·L -1 of Ca 2+ chelator EGTA, 0 1?mmol·L -1 of Ca 2+ channel inhibitor LaCl 3,and 0 05?mmol·L -1 of CaM antagonist CPZ. The changes in the contents of total soluble protein and CaM, and freezing resistance in all pretreated seedlings in various periods ( viz: following cold acclimation, chilling stress and recovery) were investigated. Results showed that cold acclimation increased the contents of total soluble protein and CaM, and freezing resistance of seedlings, which could be strongly reduced by the pretreatments of EGTA CPZ and LaCl 3 Cold acclimation combined with CaCl 2 pretreatment enhanced the effect of cold acclimation on freezing resistance, and obviously increased the contents of total soluble protein and CaM, reduced the declining degree of the contents of total soluble protein and CaM caused by chilling stress as compared with cold acclimation, augmented the increase in the level of total soluble protein and CaM during the recovery periods. Further analysis found that an increase in total soluble protein content during cold acclimation with or without CaCl 2 pretreatment mainly resulted from the increase in content of heat stable protein in total soluble protein. It is suggested that Ca 2+ calmodulin may be involved in the synthesis of total soluble protein, and the induction of freezing resistance of seedlings.

Cold Acclimation-Induced Changes in Total Soluble Protein, RNA, DNA, RNase and Freezing Resistance in Populus tomentosa Cuttings

The changes in the contents of total soluble protein and RNA, the activity of RNase in leaves and branches of Populus tomentosa cuttings at various periods (viz: cold acclimation, deacclimation, chilling stress and the recovery after chilling stress), and the survival rate and the freezing resistance of cuttings during cold acclimation at -3℃ were investigated. Results showed that cold acclimation not only increased the contents of total soluble protein and RNA, the survival rates and the freezing resistance of cuttings, decreased the activity of RNase, but also reduced the declining degree of total soluble protein and RNA contents, and the increasing level of RNase caused by chilling stress as compared with the controls. In addition, cold acclimation augmented the increase in the level of total soluble protein and RNA, and facilitated the decrease of RNase during the recovery periods. Further analysis found that the DNA content of all treatments kept relative stability at various periods. The changes in total soluble protein, RNA and RNase were closely related to the freezing resistance of cuttings. It appears that the increase of RNA content caused by cold acclimation induced decrease of RNase activity may be involved in the accumulation of total soluble protein and the induction of freezing resistance of cuttings.

The Comparison of Cold-resistance and Quality of Rape

通过对8个品种小白菜型油菜的可溶性糖、维生素C、叶绿素等品质和电导率、产量分析，结果表明，四月慢、五月慢具有较强的抗寒性，产量较高，但四月慢的品质相对较差；青邦油菜、苏州青的综合品质较其它品种好。因此，适合于本地区春季种植的品种是五月慢、青邦油菜和苏州青。

Physiological mechanisms of resistance to cold stress associated with 10 elite apple rootstocks

A study was conducted in attempting to identify the cold-resistant apple rootstocks and to establish a comprehensive evaluation system. In this study, 10 elite apple dwarfing rootstocks(GM256, JM7, M26, M7, SC1, SH1, SH38, SH6, M9, and T337) were employed for the experiment and the following parameters were investigated under different low temperature stress conditions(0, –15, –20, –25, –30, and –35°C): the changes of the relative electrical conductivity(REC), anthocyanin content, protein content, soluble sugar content, soluble starch content, proline content, malondialdehyde(MDA) content, superoxide dismutase(SOD) activity, and peroxidase(POD) activity of the dormant branches. The inflection temperature that could represent the plant tissue semi-lethal temperature(LT) was obtained by the measurements of REC. The LTwas used to evaluate eight other indices. The results showed that there was no significant correlation between LTand POD activity as well as between the soluble sugar, protein and proline contents at 0 and –15°C. Soluble starch content at 0 and –15°C and anthocyanin content at –15–(–30)°C were significantly but negatively correlated to the LT50 and the MDA content at 0–(–20)°C was significantly positively correlated to the LT. Statistical analysis based on principal component analysis and LT50 showed that cold resistant apple rootstocks in the decreasing order from high to low as GM256, SH6, SH38, SH1, SC1, M26, M7, JM7, T337, and M9.

Evaluation of cold resistance of ornamental species for planting as urban rooftop greening

Rooftop gardening or green roof establishment, one of the methods of afforestation for urban greening, has many benefits for the environment, the economy and urban landscapes. Various environmental stresses including heat, strong wind, sunshine and cold prevent most plants from growing well in extensive green roof systems. For the establishment of urban rooftop gardening in Beijing, we evaluated 13 ornamental plant species [Berberis thunbergii ‘Atropurea Nana’, Euonymus fortune （Turcz.） Hand., Viburnum dilatatum Thunb., Cotinus coggygria Scop., Swida alba Opiz., Weigela florida （Bunge.） A. DC., Jasminum nudiflorum Lindl., Euonymus japonicus Thunb., Euonymus japonicus ‘Cuzhi’, Buddleja davidii Franch., Pyracantha fortuneana （Maxim.） Li., Ligustrum lucidum Ait. and Spiraea salicifolia L.] for greening of flat rooftops. We obtained three indices concerning cold resistance, i.e., electrical conductivity of leaves, amounts of soluble sugars and amounts of free proline, providing a theoretical basis for selection of plants fit for roof and balcony greening. The results show that the six species P. fortuneana （Maxim.） Li., B. thunbergii ‘Atropurea Nana’, J. nudiflorum Lindl., E. fortune （Turcz.） Hand., E. japonicus Thunb. and E. japonicus ‘Cuzhi’ are excellent plants for rooftop gardening, judging from their strong ability in cold resistance. Plants such as L. lucidum Ait., C. coggygria Scop. and W. florida （Bunge） A. DC. showed a medium ability in cold resistance. However, these species can be used in roof and balcony greening after intensive management or acclimatization of variety. The ability to resist cold of plants such as W. florida （Bunge） A. DC., S. salicifolia L., V. rhytidophyllum and S. alba Opiz. （Cornus alba L.） was found to be rather weak. Therefore, cold-proof measures are recommended when using these species.

Cross Breeding of Populus and Its Hybrids for Cold Resistance

Populus tomentosa was crossed with P.tremuloidis, P.grandidentata, P.alba×P.grandidentata and P.alba×Ulmuspumila in order to maintain its rapid growth and high wood quality and improve its resistance to cold. Two methods were used to increase the germination rate from 1.5% to 41.1% and the remaining rate from 1.7% to 44.2%. Forty crossing combinations were conducted and 2744 hybrid seedlings were obtained. MX4×P.grandidentata （G-1-58）, MX3×P.tremuloidis （T-44-60）, MX2×P.tremuloidis （1-13-87-37） and MX2×（P.alba×P.grandidentata） were regarded as superior combinations after analysis and selection. Thirty seedlings of these combinations and 11 triploid seedlings identified by counting their chromosomes were selected as super plants.

Comparative Study on the Cold Resistance of Four Cherry Cultivars under Chilling Stress

[Objective] The present study was conducted to evaluate the cold resis-tance of four cherry cultivars under different chil ing stresses. [Method] Four cultivars of Cerasus, Early-mahapphala, Red light, Lapins and Kashgar Kukan were selected as the experimental materials, and the changes of the relative electric conductivity （REC）, proline （PRO） content, malondialdehyde （MDA） content, superoxide dismu-tase （SOD） activity and peroxidase （POD） activity of dormant branches of the four cherry cultivars under low temperature stress were investigated. [Result] The REC of the four cherry cultivars was Kashgar kukan 〉 Red light 〉 Early-mahapphala 〉Lapins, while the MDA content was Kashgar kukan 〉 Early-mahapphala 〉 Red light 〉Lapins, both showed a rising trend in the four cultivars with the aggravating of the low temperature stress. The PRO content, POD and SOD activities of al cultivars were precisely contrary to their REC and MDA content, as al of them exhibited a sequence as Lapins 〉 Red light 〉 Early-mahapphala 〉 Kashgar kukan in al culti-vars, and got a trend of first rising and then declining. [Conclusion] Therefore, our final evaluation of cold resistance of the four cherry cultivars was Lapins 〉 Red light 〉 Early-mahapphala 〉 Kashgar kukan.

Effect of cold working and sandblasting on the microhardness, tensile strength and corrosion resistance of AISI 316L stainless steel

The aim of this work is to investigate the effect of cold working and sandblasting on the microhardness, tensile strength and corro-sion rate of AISI 316L stainless steel. The specimens were deformed from 17% to 47% and sandblasted for 20 min using SiC particles with a diameter of 500-700 μm and an air flow with 0.6-0.7 MPa pressure. The microhardness distribution and tensile test were conducted and a measurement on the corrosion current density was done to determine the corrosion rate of the specimens. The result shows that the cold working enhances the bulk microhardness, tensile and yield strength of the specimen by the degree of deformation applied in the treatment. The sandblasting treatment increases the microhardness only at the surface of the specimen without or with a low degree of deformation. In addition, the sandblasting enhances the surface roughness. The corrosion resistance is improved by cold working, especially for the highly deformed specimen. However the follow-up sandblasting treatment reduces the corrosion resistance. In conclusion, the cold working is prominent to be used for improving the mechanical properties and corrosion resistance of AISI 316L stainless steel. Meanwhile, the sandblasting subjected to the cold worked steel is only useful for surface texturing instead of improving the mechanical properties and corrosion resistance.

Effects of Mutagens on Antioxidant Enzymes Activity and Cold Resistance of Alfalfa

This study aimed to solve the issues in safe wintering of alfalfa in the north of China. The^(60)Co-γ rays, ultraviolet and EMS were used to mutagenize seeds of 4 cultivars of alfalfa to investigate the effects of mutagens on antioxidant enzymes activity and cold resistance of alfalfa. The results showed that after the mutagenic treatment, the activity of the three kinds of antioxidant enzymes basically showed upward trends.^(60)Co-γ radiation increased the activity of SOD; ultraviolet radiation decreased the activity of SOD; and low-concentration EMS promoted and high-concentration EMS inhibited the activity of SOD. The activity of POD and CAT decreased with the increased radiation dose of^(60)Co-γ, but increased with the increased radiation dose of ultraviolet. The effects of EMS treatment on the activity of POD and CAT differed among different alfalfa cultivars. The concentration of MDA reduced under 30-min, 60-min ultraviolet treatment and 0.4% EMS treatment. According to the subordinate function values of various indices, it could be concluded that 150 Gy of^(60)Co-γ radiation, 90 min of ultraviolet radiation, and 0.4% of EMS were more conducive to improving the cold resistance of alfalfa. This study will provide a theoretical basis for the research on adaptability and cold resistance of alfalfa in rigid cold region and a technical reference for the breeding of high-yield, highquality and cold-resistant alfalfa cultivars.

Development of Hybrid Rice Variety FY7206 with Blast Resistance Gene Pid3 and Cold Tolerance Gene Ctb1

Hybrid rice Fanyou 7206（FY7206）, derived from the cross between a sterile line Fanyuan A and a restorer line Fuhui 7206, was bred by the Rice Research Institute, Fujian Academy of Agricultural Sciences, China. FY7206 was characterized by moderate blast resistance, cold tolerance, as well as wide adaptability, and high yields. The blast resistance results indicated that the frequencies of blast races in race B, race C and the total resistance frequency for FY7206 were 95.5%, 100.0% and 97.2%, respectively. The disease resistance results showed that the leaf blast grade for FY7206 was level 1 and panicle blast was level 5. The indoor spray results indicated that FY7206 was resistant to 11 isolates of Magnorpathe oryzae. The blast resistance of FY7206 might be derived from the high expression of blast resistance gene Pid3. The results for simulated cold resistance in an artificial climate chamber indicated that the cold tolerance for FY7206 was moderate at the booting and flowering stages. The cold tolerance results also indicated that FY7206 could be tolerant to temperatures as low as 10 °C at the seedling stage. The q RT-PCR results showed that the expression of cold tolerance gene Ctb1 in FY7206 was relatively high. These results suggested that FY7206 is a hybrid indica rice variety with good comprehensive characteristics, including blast resistance and cold tolerance.

Research Progress of Cold Resistance Mechanism of Cassava

Cassava is vulnerable to frost and snow, so it is suitable for planting in tropical and subtropical region. Low temperature is an important environment factor affecting the growth and development and production of cassava, and the region with annual average temperature below 15 ℃ is not conducive to its normal growth and development. The improvement of cold resistance of cassava can increase the planting area and improve the yield and quality of cassava. In this study, morphological,physiological and biochemical and molecular researches on cold resistance of cassava, as well as the latest research progress,were reviewed in this paper. At the same time, some potential difficulties in the research on cold resistance of cassava were put forward, and the future work focus was also discussed.

Molecular Cloning of a Cytosolic G6PDH Gene from Populus Suaveolens and Its Expression to Improve the Cold Resistance of Tobacco Plants

Glucose-6-phosphate dehydrogenase (G6PDH,EC 1.1.1.49) is the first and main regulated enzyme of oxidative pentose phosphate pathway (OPPP),catalyzing the conversion of glucose-6-phosphate to 6-phospho-gluconolactone and playing important roles in the growth and development of plants. It is preciously reported that the enhancement of freezing resistance of Populus suaveolenscuttings is clear related to the distinct increase in cytosolic G6PDH activity. Here,a 1697 bp cDNA fragment (PsG6PDH) is amplified by RT-PCR from cold-induced total RNA of the freezing-tolerant P. suaveolens. A sequence analysis showed that PsG6PDH coding region had 1 530 bp and encoded 510 predicted amino acid residues. Genomic Southern analysis revealed that the isoform is encoded by a few copies of the gene in the poplar genome. The cloned gene PsG6PDHis cloned into binary vector pBI121 and used to transform tobacco. PCR and Southern blotting results verified integration of this gene into the genome of tobacco. Moreover,cold treatment experiments and membrane defense enzymeactivity analysis confirmed that overexpression of the PsG6PDHgene could enhance the tolerance to cold or frigid stresses in transgenic plants.

A Review of the Methods of Identifying and Testing Plant Cold Resistance

Low-tempemture stress is a major abiotic stress influencing plant growth, economic yield and quality worldwide. Precise and reliable identification and test of plant cold resistance is a foundation for exploring low-temperature damages, cold resistance mechanism of plants, cultivating and innovating quality cold-re- sistant germplasm resources, which is rather important for woody plants because their perennial and large-sized characteristics. Generally, most researches on plant cold-resistant physiology focused on identification and utilization of cold resistance worldwide, and a few on test methods of cold resistance, but cold resistance mechanism has been less reported. Therefore, researches on methods of identifying and testing plant resistance have achieved considerable progress, accumulated much experience and formed characteristics gradually in terms of methodology. Current methods of identifying plant cold resistance include open field/outdoor culti- vation evaluation, cold and frost damage investigation, simulated cold weather, and mathematical model forecast. And the methods of testing plant cold resistance include growth condition test, frozen index investigation, electrolyte leakage, bioelectrical impedance mapping and so on. Synthesizing the methods of identifying and testing plant cold resistance should be a key matter in the present and future researches and application of plant cold resistance physiology, improvement and in- novation of the identification and test will be an important direction of the future researches. Identification and test of plant cold resistance based on genomies, meta- bonomics and proteomics should be the new trend of the researches on physiology and ecology of plant cold resistance.

Effects of Exogenous Calcium and Calcium Ion Inhibitor on Cold Resistance of Pistil of Kernel Apricot

With a kernel apricot cultivar Youzhu 07-3 as the test material, the effects of exogenous calcium and calcium inhibitor on the cold resistance of pistils were investigated. In the bud germination and enlargement period, exogenous calcium and calcium ion inhibitor were sprayed to the kernel apdcot trees, respectively. At the full-bloom stage, a certain number of flower branches of kernel apricot were sam- pied and subjected to low-temperature stress indoor, and the soluble sugar content, MDA content, SOD activity and POD activity in the pistils were determined. The results showed that exogenous calcium increased the soluble sugar content, reduced the MDA content and improved the SOD and POD activity in pistils, and it significantly relieved the cold damage to pistils and improved the cold resistance of pistils; while exogenous calcium ion inhibitor showed the opposite effects.

A Study on Cold Resistance of Osmanthus Fragrans Cultivars in Kaifeng, China

Low winter temperature is generally recognized as the chief factor limiting the northward distribution of Osmanthus fragrans. O. fragrans has been cultivated in Kaifeng for nearly two decades, yet little is known regarding how well this plant has adapted to the city＇s cold winter. In a city-wide survey, we periodically examined O. fragrans leaves for visible symptoms of freeze damage, then measured leaf soluble sugar content, leaf electric conductivity, palisade layer thickness/leaf thickness ratio, and spongy layer thickness/leaf thickness ratio of several cultivars. The data thus collected were assessed to determine the cultivars＇ cold resistance levels. Our results indicate that the northward distribution of O. fragrans may be limited primarily by low spring temperatures rather than low winter temperatures. O. fragrans Sijigui and Huangchuan Jingui are the most cold resistant O. fragrans cultivars in Kaifeng, China.

Resistance and Reactance of Monopole Fields Induced by a Test Charge Drifting Off-Axis in a Cold and Collisional Cylindrical Plasma

We study the interaction of a uniform, cold and collisional plasma with a test charged particle moving off-axis at a constant speed down a cylindrical tube with a resistive thick metallic wall. Upon matching the electromagnetic field components at all interfaces, the induced monopole electromagnetic fields in the plasma are obtained in the frequency domain. An expression for the plasma electric resistance and reactance is derived and analyzed numerically for some representative parameters. Near the plasma resonant frequency, the plasma resistance evolves with frequency like a parallel RLC resonator with peak resistance at the plasma frequency pe, while the plasma reactance can be capacitive or inductive in nature depending on the frequency under consideration.

Dynamics of Essential Metal Elements Contents in Winter Oilseed Rape during Cold Acclimation

[Objective]The paper was to investigate the dynamics of essential metal elements（Ca,Mg,Fe,Mn,Zn and Cu）contents in winter oilseed rape（Brassica napus L.）during cold acclimation,and to reveal the effects and mechanisms of essential elements in cold resistance of oilseed rape.[Method]Three varieties with different cold resistance including Zhongshuang No.11（ZS,freezing sensitive variety）,Ganyouza No.1（GY）and Jinyuyou No.1（JYY,freezing tolerant varieties）were used in the study,and the changes of necessary metal elements in these oilseed rapes during cold acclimation were studied.[Result]The concentration of metal elements in oilseed rape had significant changes during cold acclimation,and the difference between varieties was significant.In plant roots,the concentrations of Ca,Mg,Fe,Mn,Zn and Cu were significantly increased,this might because that low temperature made the transpiration decreased,thus blocking the upward transport of elements.In plant shoots,the concentrations of Ca,Mg and Zn were significantly decreased,while the concentrations of Fe and Mn were significantly increased;the change extent of various elements in ZS variety was the largest.[Conclusion]Maintaining the stability of Ca,Mg and Zn concentrations and increasing Fe,Mn and Cu concentrations in plant shoots might be benefit for increasing the cold tolerance of winter oilseed rape.