快速干燥对黄皮胚轴贮藏寿命及抗氧化酶活性的影响

以黄皮种子离体胚轴为材料 ,研究了快速干燥对胚轴贮藏寿命的影响及与抗氧化酶活性的关系。未经脱水的胚轴在 15℃贮藏 12 8d仍具有较高的存活率和活力指数。快速脱水 1.5和 3.0h后胚轴的存活率和活力指数并未因脱水而下降 ,但它们在 15℃贮藏的寿命分别只有 8和 2d。未经脱水胚轴的抗氧化酶(SOD、POD、CAT)活性在贮藏过程中能较好地保持 ,但经快速脱水后其抗氧化酶活性在贮藏过程中则迅速下降 ,脱水时间越长 ,酶活性在贮藏过程中的下降就越快。     

Bioremediation and Biorestoration of a Crube Oil-Contaminated Freshwater Wetland on the St.Lawrence River

Biostimulation by nutrient enrichment and phytoremediation were studied for the restoration of an acutely stressed freshwater wetland experimentally exposed to crude oil. The research was carried out along the shores of the St. Lawarence River at Ste. Croix, Quebec, Canada. The research determined the effectiveness of fertilizer addition in enhancing the biodegradation rates of residual oil. It further examined the rate at which the stressed ecosystem recovered with and without the addition of inorganic fertilizers and the role of nutrients in enhancing wetland restoration in the absence of healthy wetland plants. Chemical analysis of integrated sediment core samples to the depth of oil penetration within the experimental plots indicated that addition of inorganic nutrients did not enhance the disappearance of alkanes or PAHs. In surface samples, however, hydrocarbon disappearance rates were higher when the metabolic activity of wetland plants was suppressed by the removal of emergent plant growth. These results suggest that oxygen limitation plays a major role in preventing rapid biodegradation of hydrocarbons in anoxic wetland sediment.     

Bioavailability to Fish of Sediment PAH as an Indicator of the Success of In Situ Remediation Treatments at an Experimental Oil Spill

A weathered medium crude oil was applied to experimental plots of Scirpus pungens (Three-square Bulrush) in a freshwater wetland to determine the efficacy of strategies for shoreline oil spill bioremediation based on nutrient enrichment (bioremediation) and plant growth (phytoremediation). Plots were unoiled, oiled with no added nutrients, or oiled with repeated applications of phosphate and nitrate fertilizers. Following initial treatments, the experimental plots were raked to simulate the activity of wave action on oil penetration, and plants in one fertilized plot were cut repeatedly. The sediments were sampled at regular intervals for 15 months after oiling, and the loss of oil was assessed by 4-day laboratory tests of polynuclear aromatic hydrocarbon (PAH) bioaccumulation by trout, as demonstrated by increases in activity of liver cytochrome P450 (CYP1A) enzymes. Oil alone, oil mixed with sediments in the lab, and oiled sediments from treated plots all induced CYP1A activity relative to untreated controls, indicating the presence and bioavailability of PAH. Induction did not vary with nutrient treatments, but declined by 80% within 15 months of oiling, and chemical analyses indicated equivalent losses of hydrocarbons in sediment. These results demonstrate that bioavailable PAHs persisted in measurable quantities for at least 1.25 years following oiling, and that stimulation of plant growth did not affect the rate of oil disappearance. The controlling factors were likely weathering and sediment movement.     

Bioremediation of Polyaromatic Hydrocarbon-Contaminated Sediments in Aerated Bioslurry Reactors

Treatment of dredged sediments contaminated by polyaromatic hydrocarbons (PAHs) is a significant problem in the New York/New Jersey (NY/NJ) Harbor. 0.5 m³-scale slurry-phase bioreactors were used to determine whether bioaugmentation with a PAH-degradative bacterial consortium, or with the salt marsh grass S. alterniflora, could enhance the biodegradation of PAHs added to dredged estuarine sediments from the NY/NJ Harbor. The results were compared to biodegradation effected by the indigenous sediment microbial community. Sediments were diluted 1:1 in tap water and spiked to a final concentration of 20 mg/kg dry weight sediment of phenanthrene, anthracene, acenaphthene, fluorene, fluoranthene, and pyrene. The sediment slurry was then continuously sparged with air over 3 months. In all bioreactors a rapid reduction of greater than 95% of the initial phenanthrene, acenaphthene, and fluorene occurred within 14 days. Pyrene and fluoranthene reductions of 70 to 90% were achieved by day 77 of treatment. Anthracene was more recalcitrant and reductions ranged from 30 to 85%. Separate experiments showed that the sediment microbial communities mineralized ¹⁴C-pyrene and ¹⁴C-phenanthrene. PAH degradation, and the number of phenanthrene-degrading bacteria, were not enhanced by microbial or plant bioaugmentation. These data demonstrate that bioaugmentation is not required to effect efficient remediation of PAH-contaminated dredged sediments in slurry-phase bioreactors.     

Increased mortality of Acanthoscelides obtectus by alkane-grown Beauveria bassiana

The effect of alkane-growth induction of theentomopathogenic fungus Beauveria bassiana(Balsamo) Vuillemin (Deuteromycotina:Hyphomycetes), on the ability to kill the beanweevil Acanthoscelides obtectus Say(Coleoptera: Bruchidae), was tested. Adultinsects were sprayed with an 0.01% Tween 20aqueous suspension of 4 × 10⁶ conidia/ml.The performance of fungi grown in complete agarmedium containing glucose as carbon source(FS₀) was compared to that of alkane-grownfungi (FS₁) with n-hexadecane as the onlycarbon source. Mortality increased (p< 0.05) from 22 ± 4.5% to 44 ±11.4% at day 7, and from 26 ± 5.5% to 60± 7.1% 14 days after treatment withFS₀ or FS₁ respectively. The insectepicuticular hydrocarbons were analysed bycapillary gas chromatography (CGC); majorcomponents were saturated hydrocarbons, 27 to29 carbons in length. A variety ofmethyl-branched isomers of C27 were theprevailing structures, and nC27 was the majorstraight chain component. Whole insecthydrocarbons were qualitatively identical tothose of the epicuticular surface. Oleic,linoleic and palmitic acids accounted foralmost 88% of the fungal fatty acids,irrespective of the carbon source used forgrowth; however, the unsaturated/saturatedratio diminished markedly from 4.32(FS₀) to 2.47 (FS₁). These resultsindicate that alkane supplementation of culturemedia might be a tool to improve the virulenceof some mycoinsecticides.     

Gracilaria and its epiphytes: 4. The response of two Gracilaria species to Ulva lactuca in a bacteria-limited environment

The responses of Gracilaria lemaneiformis, an easily epiphytized host,and the relatively resistant G. cornea mutant, to the green alga Ulva lactuca were studied using biculture experiments with and withoutantibiotics. Both Gracilaria species grown with and without U.lactuca showed different levels of growth rate, release of hydrogenperoxide and of halogenated hydrocarbons. These quantitative differencesled to a successful response against Ulva lactuca in the case of G.cornea mutant and to a failure in response in the case of G.lemaneiformis. The response of each Gracilaria species to U.lactuca was qualitatively similar to its response to bacteria. This suggeststhe involvement of oligosaccharide elicitors produced in the presence ofepiphytes and bacteria. A clear Gracilaria inhibition was demonstratedwith extracts of the culture medium. It appears that hydrogen peroxide,halogenated hydrocarbons and oligosaccharides may be components of theinhibitory activity of the extracts. The responses of Gracilaria speciesto the presence of U. lactuca suggest the characterization of adefence response.     

顽拗性黄皮种子脱水过程中活性氧清除酶活性的变化

以正常性种子花生为对照,研究了顽拗性黄皮种子脱水过程中活性氧清除酶、膜脂过氧化作用以及电解质渗漏率的变化。随着含水量的下降,黄皮胚的电解质渗漏率和膜脂过氧化产物丙二醛(MDA)含量均显著增加;当黄皮胚含水量下降至40％后,SOD活性开始急剧下降,而POD和CAT活性在胚含水量下降过程中呈现出缓慢下降的趋势。花生胚在含水量从45％降至14％的过程中,电解质渗漏率没有明显增加,MDA含量只有少量增加;当含水量降至14％后,电解质渗漏率出现少量增加。花生胚脱水初期,活性氧清除酶活性明显增加,并在整个脱水过程中维持较高的水平。以上结果表明顽拗性种子黄皮的脱水敏感性与活性氧清除酶相对活性变化有关。脱水引起黄皮胚活性氧清除酶活性降低,活性氧清除能力下降,膜脂过氧化作用加强,膜透性增大。黄皮胚的膜系统可能是脱水伤害的靶位之一。     

In vitro rescue of isolated embryos of Bactris major jacq. and Desmoncus orthacanthos mart., potentially useful native palms from the Yucatan Peninsula (Mexico)

Summary Bactris major and Desmoncus orthacanthos are native palms from the Yucatan Peninsula which could be used as substitutes for rattan. When their seeds were germinated in vivo and in vitro they proved to be highly recalcitrant. Therefore, the culture of isolated embryos was studied as an alternative means of producing planting material for nurseries. It was found that the in vitro germination of the isolated embryos was gradually reduced by storage, falling to zero by 5 wk. However, isolated embryos from freshly collected seeds germinated at ∼100% frequency. The presence of the endosperm, whether still attached to the embryos or separated from them but in direct contact with the nutrient medium, greatly reduced germination in both species. High concentrations of abscisic acid (ABA, 100 μM) only slightly diminished it, suggesting a different cause for the observed endosperm-induced inhibition. This embryo rescue method permits the production of sufficient plants for in vitro micropropagation and the establishment of experimental plots to evaluate the full potential of these materials.