On the Nature of the Soaking Injury of Phaseolus vulgaris Seeds

Phaseolus vulgaris L. seeds are often killed or show signs ofsevere injury after they have been soaked in water for periodsexceeding a very few hours. But all ill effects can be largelyor completely prevented by any one of the following: (a) removingthe testa before or after soaking; (b) thorough or even partialdrying of the soaked seed; (c) draining the seed after cuttingoff its end portion; (d) treatment of the seed with hydrogenperoxide before, during, or after soaking. Air bubbled throughthe soaking water can aggravate the injury. By contrast, injuryfrom soaking can be prevented if oxygen has free access to theinterior of the seeds until they have imbibed about one-thirdof the water required for germination.It is suggested that,despite microbial complications at a later stage, the soakinginjury is caused at a critical early stage of germination bya deficient oxygen supply to the interior of the soaked seed,because during soaking the cavity between the cotyledons isflooded with an excess of water which remains trapped unlessforcibly removed.     

Effects of Heavy Metals on Stomatal Movements in Broad Bean Leaves

How do heavy metals affect stomatal movements and whether water channels are involved in stomatal movements was investigated in broad bean (Vicia faba L.) leaves. Three-week old fully expanded leaves were harvested. Leaf epidermis was peeled off and soaked in the Mes–KOH buffer containing the salts of heavy metals. Stomatal aperture was measured under the microscope. The tested heavy metal ions, such as Hg²⁺, Pb²⁺, Zn²⁺, and La³⁺, partly inhibited stomatal opening in light or closing in darkness at submillimolar concentrations, while K⁺, Na⁺ and Mg²⁺ had no visible effects on stomatal movements. As compared to La³⁺, Hg²⁺ affected stomatal movements more significantly. Stomatal movements were almost completely inhibited under a combined Hg²⁺ and La³⁺ treatment. Apparently, La³⁺, a Ca²⁺ channel blocker, inhibits the changes in the cytosolic Ca²⁺ concentration in guard cells, thus affecting stomatal movements. The inhibitory effect of Hg²⁺ on stomatal movements may be explained by the inhibition of water channels. Like Hg²⁺, Zn²⁺ and Pb²⁺ interfered with stomatal movements. It is concluded that heavy metals at submillimolar concentrations inhibit stomatal movements. They may affect water fluxes through guard cell membranes in different ways, i.e., Hg²⁺, Pb²⁺, and Zn²⁺ inhibit water channels, whereas La³⁺ block ion channels. Water channels may be involved in stomatal movements by regulating water fluxes and play a dominant and primary role in stomatal movements.     

Identification of Glucosinolates in Seeds of Three Brassicaceae Species Known to Hyperaccumulate Heavy Metals

Plants from the Brassicaceae family are known to contain secondary metabolites called glucosinolates. Our goal was to establish by LC/MS the glucosinolate profile of seeds of three Brassicaceae species known to hyperaccumulate heavy metals. We investigated Alyssum fallacinum auct. non Hausskn ., Iberis intermedia Guers ., and Noccaea caerulescens (J. Presl & C. Presl ) F. K. Mey . Our results indicate that A. fallacinum seeds contain glucoiberin and glucoibervirin, which had not been previously identified in this plant. Furthermore, we report for the first time the presence of glucoiberin, glucoibervirin, glucotropaeolin, and sinigrin in I. intermedia. We have detected for the first time glucoconringiin in N. caerulescens. In addition, glucosinalbin, 4‐hydroxyglucobrassicin, and glucomoringin were also detected.     

菜豆病程相关蛋白基因在重金属胁迫下的表达分析

为探讨植物抗重金属的分子机理 ,差别筛选了 Hg Cl2 胁迫的菜豆 ( Phaseolus vulgaris L.)叶片 c DNA库 ,分离出一个重金属胁迫响应基因 Pv SR4克隆 .c DNA和氨基酸序列分析表明 Pv SR4编码一种细胞内病程相关蛋白 ,该蛋白具有 RNase活性 .Northern blot分析表明 Pv SR4基因在正常生长条件下的叶片中不表达 ,重金属 ( Hg、Cd、As、Zn和 Cu等 )和水杨酸能强烈地诱导其基因的表达 ,受伤也能促进该基因的转录 ,而热胁迫几乎没有调节作用 .推测 Pv SR4蛋白在诱导植物的抗逆性和抵抗重金属胁迫方面有重要作用     

Bacterial Growth in the Cold: Evidence for an Enhanced Substrate Requirement

Growth responses and biovolume changes for four facultatively psychrophilic bacterial isolates from Conception Bay, Newfoundland, and the Arctic Ocean were examined at temperatures from - 1.5 to 35°C, with substrate concentrations of 0.15, 1.5, and 1,500 mg of proteose peptone-yeast extract per liter. For two cultures, growth in 0.1, 1.0, and 1,000 mg of proline per liter was also examined. At 10 to 15°C and above, growth rates showed no marked effect of substrate concentration, while at - 1.5 and 0°C, there was an increasing requirement for organic nutrients, with generation times in low-nutrient media that were two to three times longer than in high-nutrient media. Biovolume showed a clear dependence on substrate concentration and quality; the largest cells were in the highest-nutrient media. Biovolume was also affected by temperature; the largest cells were found at the lowest temperatures. These data have implications for both food web structure and carbon flow in cold waters and for the effects of global climate change, since the change in growth rate is most dramatic at the lowest temperatures.     

Ethylene as a Component of the Emanations From Germinating Peanut Seeds and Its Effect on Dormant Virginia-type Seeds

The embryonic axes of Spanish-type peanut seeds that do not exhibit dormancy to any extent were found to produce ethylene during germination. Virginia-type peanut seeds of the extremely dormant variety NC-13 produced low levels of ethylene when imbibed but not germinating. Treatments that released dormancy of NC-13 peanut seeds resulted in increased ethylene production by the embryonic axis. The estimated internal concentration of ethylene in Virginia-type peanut seeds was 0.4 ppm at 24 hr of germination. Fumigation with an external concentration of 3.0 to 3.5 ppm for 6 hr was sufficient to break dormancy of Virginia-type peanut seeds. These results suggest that ethylene is associated with the germination processes of non-dormant seeds and participates in the breaking of seed dormancy of dormant peanut varieties.     

Acetylcholine and Synthesis of Ethylene in Etiolated Bean Tissues

Acetylcholine chloride inhibited ethylene production in etiolated bean tissues and prevented to some extent the IAA-promoted opening of the bean hypocotyl hooks. The results were interpreted on the basis of acetylcholine mimicking the effects of red light on auxin content and ethylene production.     

Lack of Evidence for Sign Epistasis Between Beneficial Mutations in an RNA Bacteriophage

In previous work (Betancourt, Genetics 181:1535, 2009), I propagated three large laboratory populations of an RNA phage (MS2) as they adapted to a controlled laboratory environment. These populations were large enough so that evolution might be expected to be mostly repeatable, but they nevertheless fixed different suites of mutations over the course of the experiment. Here, I investigate one possible explanation for these results: epistasis, in which the effect of a mutation depends on its genetic background, may have prevented populations with different initial substitutions from fixing the same set of subsequent mutations. I show that two mutations that previously occurred in different genetic backgrounds are beneficial on either background. This result suggests that sign epistasis-in which a mutation is beneficial on one background, but deleterious on another-is not the cause of different evolutionary trajectories observed in the Betancourt (2009) experiment. However, they can be explained by either magnitude epistasis-in which mutations have stronger or weaker beneficial effects depending on the background-or by the simultaneous fixation of multiple beneficial mutations. Surprisingly, the large populations of the previous experiment showed less parallel evolution than the small populations of this experiment, which lends support to the fixation of multiple beneficial mutations contributing to the patterns seen in both experiments.     

Systemic Acquired Resistance to Virus Infections and Ethylene Biosynthesis in Asparagus Bean

Systemic acquired resistance (SAR) was induced in asparagus bean following inoculation with tobacco necrosis virus (TNV) or tobacco rattle virus (TRV), viruses that produce a hypersensitive reaction in this plant. SAR was expressed against challenge by TNV as reduction in lesion size, but not as inhibition of viral antigen accumulation. Systemic stimulation of ethylene-forming enzyme (EFA) activity, in the absence of any ethylene increase or 1-aminocyclopropane-1-carboxylic acid (ACC) accumulation, was associated with SAR. Formation of local necrotic lesions was necessary for both induction of SAR and stimulation of EFA, because early removal of inducer leaves prevented both events. SAR was expressed at rather constant level between 7 and 12 days after inducing infection. EFA stimulation declined with time and was no longer detected 7 days after inducing infection. SAR was not expressed against cucumber mosaic virus, that infect asparagus bean systemically. Prior inoculation with TNV or TRV was ineffective to reduce CMV antigen content or to minimize the pathogenic effect of this virus in systemically infected leaves.     

Strategies to Reduce Tin and Other Metals in Electronic Cigarette Aerosol

Background

Metals are present in electronic cigarette (EC) fluid and aerosol and may present health risks to users.

Objective

The objective of this study was to measure the amounts of tin, copper, zinc, silver, nickel and chromium in the aerosol from four brands of EC and to identify the sources of these metals by examining the elemental composition of the atomizer components.

Methods

Four brands of popular EC were dissected and the cartomizers were examined microscopically. Elemental composition of cartomizer components was determined using integrated energy dispersive X-ray microanalysis, and the concentrations of the tin, copper, zinc silver, nickel, and chromium in the aerosol were determined for each brand using inductively coupled plasma optical emission spectroscopy.

Results

All filaments were made of nickel and chromium. Thick wires were copper coated with either tin or silver. Wires were joined to each other by tin solder, brazing, or by brass clamps. High concentrations of tin were detected in the aerosol when tin solder joints were friable. Tin coating on copper wires also contributed to tin in the aerosol.

Conclusions

Tin concentrations in EC aerosols varied both within and between brands. Tin in aerosol was reduced by coating the thick wire with silver rather than tin, placing stable tin solder joints outside the atomizing chamber, joining wires with brass clamps or by brazing rather than soldering wires. These data demonstrate the feasibility of removing tin and other unwanted metals from EC aerosol by altering designs and using materials of suitable quality.     

Changes in the Photosynthetic Apparatus of Broad Bean Leaves as Dependent on the Content of Heavy Metals in the Growth Medium

The content of chlorophyll, the rate of O₂ evolution, the slow phase of fluorescence induction, and photoinduced changes in the intensity of electron paramagnetic resonance (EPR) signal I from the reaction center of photosystem I (P⁺700) were studied in leaves of Vicia faba L. grown in 10^–7–10^–3 M aqueous solutions of CdCl₂, SnCl₂, CuCl₂, and MgCl₂. At low concentrations of heavy metal (Cd, Sn, and Cu) chlorides, the content of chlorophyll per fresh weight decreased. However, the rate of O₂ evolution calculated per chlorophyll basis, O₂/(t chlorophyll), increased. High concentrations of heavy metals significantly suppressed plant development and inhibited photosynthetic O₂ evolution. In contrast, plant treatment with MgCl₂ (10^–5–10^–3 M) resulted in an increase in the content of chlorophyll and a stimulation of leaf photosynthetic activity. A positive correlation between the F _M/F _T ratio and O₂/(t chlorophyll) (r = 0.89, P > 0.999) was found. We observed a negative correlation between the values of P/P ₀ of EPR signal I (white/far-red light) and O₂/(tchlorophyll) (r = –0.89, P > 0.999). The data obtained indicate nonspecific and nonmonotone changes in the photosynthetic apparatus of plants treated with heavy metals: low concentrations of heavy metals (10^–7–10^–6 M) stimulated photosynthetic activity, whereas high concentrations (10^–4–10^–3 M) suppressed it.     

Chilling Injury in Cotton {Gossypium hirsutum L.): Light Requirement for the Reduction of Injury and for the Protective Effect of Abscisic Acid

Pretreatment by darkness increased chilling (4°C) injuryin whole cotton (Gossypium hirsutum L.) seedlings and isolatedcotyledonary tissue. Addition of sucrose in the dark periodprevented the effect of darkness. Application of the photosyntheticinhibitor DCMU in light simulated the effect of darkness. ABA(10^–5 M) decreased chilling injury when applied in lightas a pretreatment before the onset of chilling. The same pretreatmentin darkness was almost ineffective, unless sucrose was added.ABA applied in light together with DCMU was ineffective in decreasingchilling injury. Lower light intensity resulted in increasedchilling injury and a decreased effect of ABA in the preventionof chilling injury. The antimicrotubular drug colchicine increased the chillinginjury. Pretreatment with ABA in light decreased the chillingand colchicine injury while the same pretreatment in darknesswas ineffective. These results suggest that a deficiency of a photosyntheticproduct increases the chilling sensitivity of the tissue. ABAapparently increases chilling resistance through a metabolicprocess which depends on photosynthetic activity. ³ Incumbent of the Seagram Chair in Plant Sciences (Received November 20, 1980; Accepted January 31, 1981)     

乙烯对UV-B辐射诱导蚕豆气孔关闭的调控效应(英文)

UV-B辐射作为一种重要的环境信号影响着植物的生长与发育,它能够调控气孔运动和诱导乙烯产生.该试验利用乙烯生物合成抑制剂和乙烯受体抑制剂处理蚕豆叶片表皮条,结合气孔开度分析和乙烯释放量测定,研究乙烯在UV-B辐射调控表皮条气孔运动中的作用.结果发现,将蚕豆叶片表皮条置于0.8 W·m-2的UV-B辐射下1～4 h,乙烯生成和气孔关闭均被显著诱导,且乙烯释放峰先于气孔关闭的起始;乙烯生物合成抑制剂和乙烯受体抑制剂处理均能显著逆转UV-B辐射诱导的气孔关闭;外源乙烯处理也能模拟UV-B辐射的效应诱导可见光下蚕豆表皮条的气孔关闭.可见,乙烯介导了UV-B辐射诱导的蚕豆气孔关闭.     

The Role of Cytokinins and Ethylene in Bean Cotyledon Senescence. The Effect of Free Radicals

During ageing of bean (Phaseolus vulgaris L.) cotyledons in plants with modified life span the time-course of four cytokinins, ethylene, and the end products of free radical attack, lipofuscin-like pigments (LFP), were studied. UV irradiation shortened cotyledon life span, while epicotyl decapitation prolonged it. In controls, LFP increased at the senescence onset but at the end of life span it returned to the initial level. Ethylene increased more than 3-fold at the time of abscission. The content of individual cytokinins (zeatin, zeatin riboside, isopentenyl adenine, isopentenyl adenine riboside) varied differently during ageing but they did not decreased in any case under level observed in young cotyledons at the time of abscission. UV irradiation resulted in 14-fold increase in LFP concentration at the end. Ethylene increased 8-fold 2 h after irradiation. Individual cytokinins increased after UV irradiation to a different extent and time-course, nevertheless cotyledon life span was shortened. Decapitation induced LFP decrease. On day 13, LFP abruptly increased and than decreased and stayed lowered until abscission. Ethylene was maximum on day 24, at the time of abscission, it was above 200 % of control. Decapitation produced transient decrease in some cytokinins namely zeatin and isopentenyl adenine riboside.     

Chemical Composition of Ceramide and Cerebroside in Azuki Bean Seeds

The enzymic properties of three electrophoretically distinct β-glucosidases, β-glucosidase-1, -2 and -3, from Aspergillus aculeatus No. F-50 were investigated. β-Glucosidase-3 had a low optimum pH of 3.0, but the other two enzymes had optimum pHs of 4.0~4.5. Both β-glucosidase-1 and -2 were potently active not only on soluble cellooligosaccharides, such as cellotriose to cellohexaose, but also on insoluble cellooligosaccharide, of which the average degree of polymerization was 20. On the contrary, β-glucosidase-3 was only slightly active on the insoluble substrate. The combined use of either β-glucosidase-1 or -2 and endo-glucanase remarkably stimulated the hydrolysis of amorphous cellulose, yielding glucose only. But β-glucosidase-3 did not show such a synergistic effect, and the glucose content of the hydrolyzate was only about 60%.     

土壤-水稻系统中重金属复合污染物交互作用及生态效应的研究

1　前　言土壤重金属污染常常是两种或两种以上元素同时作用形成的复合污染 ,如污泥土地利用、污水灌溉等往往是多元素同时进入土壤 植物系统。近十几年来 ,国内外学者特别关注复合污染方面的研究 ,认为元素间的联合作用对作物的产量及元素在作物体内的再分配有着至关重要的影响[1～ 3 ]。同时 ,多元素的联合作用是一个相当复杂的过程。美国Ｗａｌｌａｃｅ等将重金属的联合作用分为协同、竞争、加和、屏蔽和独立作用[4 ,5 ]。多元素相互作用产生的生态效应受多种因素的影响 ,诸如作物的种类、元素的不同组合、元素浓度等。本文探讨了土壤中…