热处理对双孢蘑菇质构特性和成分的影响

为研究热处理对双孢蘑菇质量特性的影响,本试验在75、85、95和121℃条件下分别进行热处理0.5、1、5、10、15和20 min后,测定多酚氧化酶(PPO)活性、总酚含量、色差、质构指标,结合感官评价筛选出最适的热处理温度和时间,并在最适热处理条件下,观察组织结构和挥发性成分的变化。结果表明,双孢蘑菇PPO活性和总酚含量显著下降,总色差(△E)先上升后下降;随着温度的升高和时间的延长,硬度、咀嚼性、弹性和胶粘性逐渐下降,内聚性值先升高后降低;结合感官评价得出最适热处理条件为温度95℃、时间10 min;热处理后双孢蘑菇组织结构疏松、细胞孔隙微增,细胞间持水能力增大,植物香型和蘑菇香型变浓,同时还呈现出微弱的烤香型气味。综上,适当的热处理可增加双孢蘑菇的质构特性并赋予其新的风味。本研究结果为双孢蘑菇的加工提供了理论基础,在最大程度上保证了双孢蘑菇的独特风味。     

脉冲强光处理对双孢蘑菇贮藏品质的影响

为探索脉冲强光(IPL)处理对采后食用菌贮藏品质的影响,本试验以新鲜双孢蘑菇为原料,采用不同强度(28.8、48.0、67.2 mJ·cm^-2)的IPL进行前处理,研究其在25℃贮藏期间生理指标及品质的变化。结果表明,随着贮藏时间的延长,IPL处理能有效延缓双孢蘑菇开伞、质量损失、褐变及脂膜氧化,在一定程度上保持原有硬度。同时,IPL处理可显著抑制双孢蘑菇中过氧化物酶(POD)和多酚氧化酶(PPO)活性(P<0.05),可减缓其总酚和维生素C含量的下降(P<0.05),其中48.0 mJ·cm^-2处理组效果最佳;贮藏第8天,总酚和维生素C含量分别较对照提高39.06%、53.63%。本研究结果为IPL技术在控制食用菌品质方面的应用提供了一定的理论依据。     

高氧气调贮藏下双孢蘑菇品质和抗性物质变化

为探索高氧处理对双孢蘑菇保鲜的效果,该试验研究了体积分数为40%、60%、80% 和100% O2及空气气流连续处理对双孢蘑菇在2℃、12 d 贮藏期间主要品质指标和抗性物质变化的影响。结果表明,高氧处理对可溶性固形物含量无显著影响。60%～100%高氧处理可显著抑制双孢蘑菇硬度的下降、菇肉和菇皮的褐变以及细胞膜透性的增加,60%～100%高氧处理的双孢蘑菇脯氨酸含量低于对照处理,差异显著（p＜0.05）;可溶性蛋白质含量高于对照,差异不显著。总体来看, 高氧处理有效保持了双孢蘑菇的品质。     

双孢菇高氧动态气调保鲜参数优化

为提高双孢蘑菇保鲜效果,在(2±1)℃下采用高氧动态气调方法对双孢蘑菇进行贮藏试验,选取第1阶段不同O_2/CO_2比例的气体组分、换气时间、第2阶段不同O_2/CO_2比例的气体组分作为影响因素,考察双孢蘑菇贮藏过程中总色差ΔE、硬度以及感官品质的变化,对双孢蘑菇的动态气调参数进行优化。研究结果显示,第1阶段O_2比例高于80%时,可显著抑制双孢蘑菇ΔE的上升(P0.05);第2阶段80%O_2+20%CO_2气体组分,可使双孢蘑菇的ΔE显著低于其他处理,硬度显著高于其他处理(P0.05);而换气时间则影响较小。最优的动态气调条件为:第1阶段气体组分100%O_2,第3天换气,第2阶段气体组分80%O_2+20%CO_2,双孢蘑菇的ΔE、硬度值和感官品质评分分别为:19.40、6.84×105 Pa和9.52。将此最优动态气调运用于双孢蘑菇的保鲜,研究发现,与静态气调相比,该动态气调显著抑制了双孢蘑菇的呼吸速率与膜结构的损坏,维持了较高的过氧化物酶、抗坏血酸过氧化物酶活性与较低的多酚氧化酶活性,有效抑制了贮藏过程中的酶促褐变,保持了较高的可溶性蛋白含量,并延长其保鲜期至28 d,提高了双孢蘑菇的耐贮性。     

褐色双孢蘑菇原生质体制备、再生条件的研究

为了提高褐色双孢蘑菇原生质体产量和再生率,本研究以褐色双孢蘑菇棕秀一号为材料,利用Design-Expert 8.0.6软件进行二次回归分析对褐色双孢蘑菇制备原生质体的条件进行优化。结果表明,原生质体最佳制备条件为溶壁酶1.35%、蜗牛酶7.01%、酶解温度30.4℃、褐色双孢蘑菇菌丝体菌龄8.36 d、酶解时间3.00 h,在此条件下原生质体产量高达4.39×10~7个·mL^-1;当溶壁酶含量为1.32%、蜗牛酶含量为6.96%、褐色双孢蘑菇菌丝体菌龄9.00 d、酶解时间2.97 h、酶解温度31.0℃时,原生质体的再生率最高(15.1%)。利用紫外诱变和化学诱变技术对褐色双孢蘑菇原生质体进行生长特性诱变,筛选获得了18株生长速率提高的突变菌株。本研究为褐色双孢蘑菇在遗传转化、基因组重排、基因编辑技术等后续分子遗传学研究提供了理论基础。     

纳米二氧化硅改性LDPE膜对草莓生理和品质的影响

为了探索纳米二氧化硅改性LDPE膜对草莓的保鲜效果,研究了常规LDPE薄膜和纳米二氧化硅改性LDPE膜对采后草莓贮藏期间生理和品质的影响。研究发现,与对照组相比,纳米二氧化硅改性LDPE膜可抑制草莓腐烂指数的上升,延缓硬度和可滴定酸含量的下降,保持较高的抗氧化相关酶的活性,减少活性氧自由基的积累,保持贮藏后期较高的抗坏血酸和总酚含量。贮藏第14天,纳米二氧化硅改性LDPE膜中草莓的腐烂指数比对照组低42.85%,可滴定酸含量和硬度分别比对照组高7.10%和20.07%,超氧阴离子产生速率和过氧化氢含量分别比对照组低12.75%和14.98%,抗坏血酸和总酚含量分别比对照组高19.09%和8.95%。结果表明,纳米二氧化硅改性LDPE膜有利于保持草莓贮藏品质,其作为草莓保鲜包装具有潜在的应用前景。     

双孢蘑菇护色保鲜技术研究

以双孢蘑菇为试验材料,研究不同的褐变抑制剂对双孢蘑菇保鲜效果的影响，通过正交试验筛选出双孢蘑菇MA贮藏中有利于色泽保持的最适褐变抑制剂配比。研究结果表明，对双孢蘑菇贮藏保鲜效果较好的褐变抑制剂及其浓度为：0.1%的无水亚硫酸钠溶液、0.06%～0.10%的抗坏血酸溶液、0.8～2.6 mmol/L的半胱氨酸溶液；保鲜液最佳配比为2 mmol/L半胱氨酸、0.05%抗坏血酸、0.15%无水亚硫酸钠、浸泡时间8 min。     

腌制加工对不同品种叶用芥菜抗氧化物质含量和抗氧化活性的影响

本试验以4个不同品种叶用芥菜为材料,研究了腌制加工对叶用芥菜抗氧化物质含量(维生素C、总酚、总黄酮)和抗氧化活性(TEAC值和FRAP值)的影响。结果表明:与腌制前相比芥菜中抗氧化物质含量与抗氧化活性都有不同程度的下降。维生素C含量下降最为显著(P<0.01),幅度为40.70%~57.46%,总黄酮含量下降不显著,幅度为2.30%~10.62%,总酚介于二者之间;抗氧化活性的变化在品种间存在较大差异,雪里蕻和金丝芥腌制后抗氧化活性下降幅度未达到显著水平(TEAC 8.49%~10.83%,FRAP 9.03%~14.06%),而笋壳青菜和瘤子芥菜下降幅度达到显著水平(TEAC 14.45%~19.14%,FRAP 28.05%~35.77%,P<0.05)。总酚和总黄酮与抗氧化活性呈现极显著的正相关,总酚与TEAC和FRAP的R2分别为0.9482和0.9395,总黄酮与TEAC和FRAP的R2分别为0.8287和0.9129。维生素C与抗氧化活性的相关性较弱(TEAC,R2=0.2968,FRAP,R2=0.0979),酚类物质在腌制叶用芥菜抗氧化活性中起重要作用。     

基于酶动力学方程的双孢蘑菇气调贮藏呼吸速率模型

为了给气调贮藏设计提供理论设计依据,采用酶动力学方程,建立了双孢蘑菇呼吸速率随贮藏时间变化的理论模型;研究了在贮藏温度为5℃、气体体积分数为20%O_2、80%N2的贮藏条件下,贮藏时间对双孢蘑菇采后呼吸速率的影响,并建立了双孢蘑菇呼吸速率随贮藏时间变化的数学模型,模型决定系数R~2为0.9766、0.9331。模型与实测值进行配对T检验差异不显著(P0.05),呼吸速率值的绝对误差小于5 m L/(kg·h),相对误差变化范围为0.06%~24.95%。在已建模型基础上,研究不同贮藏温度(5、10、15、20℃)对已建模型参数的影响,利用Arrhenius方程来描述贮藏温度对果蔬呼吸速率的影响,建立了包含温度和贮藏时间因子的呼吸速率模型,模型决定系数R~2为0.9073、0.9350。验证试验结果表明,模型与实测值进行配对T检验差异不显著(P0.05),呼吸速率值的绝对误差小于17 m L/(kg·h),相对误差变化范围为1.00%~25.25%。该模型可为双孢蘑菇气调贮藏期间呼吸速率的预测及贮藏品质研究提供参考。     

双孢蘑菇片气调干制工艺优化研究

以提高双孢蘑菇片干制质量为目的，采用自制小型气调干燥试验设备，以CO₂、N₂置换部分空气作为干燥介质对双孢蘑菇片进行干制对比试验。采用正交试验方法，分析了不同干燥介质对双孢蘑菇片干制质量的影响。结果表明，在干燥室气体的O₂含量相同条件下，以N₂置换部分空气为干燥介质，可提高双孢蘑菇片的脱水率，干制品褐变度降低、维生素C保存率较高。用均匀试验设计回归分析程序拟合产品的褐变度、维生素C和ADF质量分数随干燥室气体O₂含量、干制温度和干制时间变化的回归方程，置信水平达95%，可用于指导实际生产。     

Soil-profile distribution of primary and secondary plant-available nutrients under conventional and no tillage

Nutrient distributions under no tillage (NT) compared with conventional disk-and-bed tillage (CT) management in the warm, humid region of the southeastern USA need to be assessed so that future placement, quantity, and type of fertilizers can be altered, if necessary, to efficiently match crop demands. We determined soil-profile distributions of pH, N, P, S, K, Ca, Mg, Na, Zn, Fe, Mn, and Cu to a depth of 0.9 m at the end of 8.5 years of continuous CT and NT management on a Weswood silty clay loam (fine, mixed, thermic Fluventic Ustochrept) in southcentral Texas. Most dramatic changes occurred within the 0–0.05 m depth, where soil under NT had lower pH, Fe, and Cu than under CT, but greater P, K, Zn, and Mn. Greater P and K under NT than under CT also occurred below the till-zone (0.15–0.3 m). At a depth of 0–0.3 m, soil under NT contained greater amounts of extractable P, K, Zn, Fe, Mn, and Cu than under CT. Nitrogen fertilization had little effect on nutrient distributions, except resulting in greater extractable K at 0–0.05 m and greater nitrate at 0–0.15 m. Few changes in soil-profile distributions were observed for extractable S, Ca, Mg, and Na. Long-term continuous use of NT on this fine-textured, high-fertility (except for N) soil had no apparent adverse effects on nutrient distributions relative to CT, but enhanced conservation and availability of P, K, Zn, Fe, Mn, and Cu near the soil surface where crop roots proliferate.     

Assessing the effectiveness of conservation measures: Resolving the “wicked” problem of the Steller sea lion

“Wicked” problems are those that are complex and that change when solutions are applied. Many conflicts in conservation fall into this category. The study approached the problem of how to constrain the apparent wickedness of a problem in the conservation management of a species by using simple empirical indicators to carry out iterative assessment of the risk to a population and to document how this risk evolves in relation to the addition of new data and the implementation of management actions. Effects of high levels of uncertainty within data and also concerning population structure were examined through stochastic simulation and by exploration of scenarios. Historical trends in the example used, the Steller sea lion, showed rapid declines in abundance in some regions during the 1980s. The current total population is 130,000-150,000 Steller sea lions through Alaska and British Columbia and this number has been stable since about 1990 in spite of regional differences in population dynamics. Regional differences in the sequence of changes in the number of pups and non-pups, suggested that an internal re-distribution of juveniles could have happened between 1980 and 1990. Current productivity also appears close to the long-term mean. Stochastic population projection using various scenarios showed that, based upon this history, the risk of extinction for the population has declined and is below reasonable thresholds for considering the population to be endangered. The trends in risk suggest that management actions taken since 1990 have probably been effective. Consequently, the conservation management objectives for the Steller sea lion are probably being met. The approach provides a mechanism, based upon experience and scenario analysis, for exploring future policy options and may help to constrain the debate amongst stakeholders about the cost-benefit trade-offs associated with different options.     

Enhanced establishment and growth of giant cardon cactus in an eroded field in the Sonoran Desert using native legume trees as nurse plants aided by plant growth-promoting microorganisms and compost

To evaluate the feasibility of long-term desert reforestation technology of mixed vegetation, cardon cactus (Pachycereus pringlei) seedlings from indoor and outdoor nurseries were planted in the field adjacent to one seedling of potential legume nurse trees: mesquite amargo (Prosopis articulata), yellow palo verde (Parkinsonia microphylla), and blue palo verde (Parkinsonia florida). Some of the planting holes were also supplemented with common dairy compost. Additionally, the combinations of legume tree–cactus were inoculated with either a consortium of desert arbuscular mycorrhizal (AM) fungi, plant growth promoting bacteria (PGPB; the diazotroph Azospirillum brasilense Cd, and the phosphate solubilizer Paenibacillus sp.), or a mixture of all. The field experiments were evaluated periodically during 30 months for survival and growth. Cardons reared in an outdoor screen house survived better in the field than those reared in a controlled growth chamber and hardened later outdoors. Association with any legume nurse tree increased survival and enhanced growth of untreated cardons. For cardons growing alone, application of either compost, AM fungi, and all the treatments combined increased survival. For these plants, no treatment affected plant growth during the first 3 months after transplanting. Later, all treatments, except for AM fungi, enhanced plant growth. However, only 2 years after transplanting the enhanced growth effect of AM fungi was also significant. In the presence of the legume nurse trees, transient positive effects on cardon growth were recorded. General evaluation after 30 months of cultivation showed that the treatments positively affected cardon growth when growing alone or in combination only with mesquite amargo but not with the other two legume trees. This study proposes that young legume trees have the capacity to enhance survival and growth of cardon cactus, depending on the legume cactus combination. Additional treatments such as compost or PGPB can either amplify the effect or else attenuate it.     

Karyotypic and genome size variation in Cajanus cajan (L.) Millsp. (pigeonpea) and some wild relatives

Detailed karyotypes and 4C DNA amounts have been studied in five cultivars of Cajanus cajan and 20 species belonging to Cajanus, Rhynchosia, Dunbaria, Flemingia and Paracalyx. C. cajan shows intraspecific variability and its karyotype is most similar to that of C. cajanifolius (sect. Cajanus) in the morphology and number of satellite chromosomes and the lack of any correlation between chromosome size within the complement and asymmetry. Karyotypes of C. lineatus and C. sericeus belonging to sect. Atylia are similar with respect to maximum r-index and the ratio of longest and shortest chromosomes in their respective complements. C. acutifolius (sect. Frutocosa) is distinct in having a very low ratio (1.44) between the longest and the shortest chromosomes, while in C. albicans, C. goensis, C. scarabaeoides (sect. Cantharospermum) there is no chromosome pair with r-index >2.0. C. mollis and C. volubilis (sect. Volubilis) show similarity with regard to ratio between the longest and the shortest chromosomes and a distinct chromosome pair with an arm ratio of 2.7 and C. platycarpus is distinct (sect. Rhynchosoides) in having the smallest ratio (1.36) between the longest and the shortest chromosomes. 4C DNA amounts in Cajanus and Rhynchosia vary between 3.28 pg to 11.69 pg and 4.92 pg to 11.13 pg respectively, while in Dunbaria, Flemingia and Paracalyx these vary between 4.70 and 7:06 pg. In the genus Cajanus karyotypic features and 4C DNA amounts agree with the sectional classification and bring out a close relationship between C. cajan and C. cajanifolius. This is supported by studies based on seed protein patterns, isozyme analysis, trypsin and chymotrypsin inhibitor patterns, RFLP and RAPD data and crossability relationships. A clear relation between DNA amount and abnormalities effecting the extent of pairing and recombination in interspecific hybrids shows the importance of this study in developing future breeding programme involving C. cajan and its wild relatives that are of potential value.     

Effect of some fungicide seed treatments on the survival of Bradyrhizobium japonicum and on the nodulation and yield of soybean [Glycine max. (L) Merr.]

Several commercial fungicide seed treatments were evaluated for their possible effect on the survival of Bradyrhizobium japonicum on seeds and on the nodulation and yield of soybeans in a greenhouse and a field experiment. quinolate Pro (carbendazim and oxine copper), Vitavax 200FF (carboxin and thiram), and Monceren (pencycuron) had a small effect or no effect on the survival of B. japonicum and on the nodulation and yield of soybeans. They can thus be considered compatible with soybean seed inoculation. Germipro UFB (carbendazim and iprodione), Apron 35J (metalaxyl), and Tachigaren (hymexazol) decreased B. japonicum survival and the nodulation and yield of soybeans and thus cannot be considered compatible with soybean seed inoculation.     

Einfluss der düngungsmethoden auf die entwicklung von zuckerrübenkrankheiten

Während neunjähriger (1994-2002) Untersuchungen in der Versuchsanstalt Ba?cyny (Fahlerde, Fall-Gleyboden, ausgebildet aus leichtem Lehmboden) wurde der Befall mit Krankheiten an der Zuckerrübe in Abhängigkeit von der Düngungsmethode bewertet. Folgende Methoden wurden angewendet: A - Mineraldünger, B - Stalldung und Mineraldünger, C - Stroh-, Gründung und Mineraldünger, D - Kompostdünger und Biopräparate (ökologische Düngung). Auf den Objekten A, B, C wurden bei konstanter Phosphor-Kalium-Düngung die Stickstoffgaben von 0 bis 180 kg.ha^?1 differenziert. Auf dem ökologischen Objekt D ohne Mineraldünger wurden statt Stickstoff die Biopräparate P₅₀₀ und P₅₀₁ verabreicht. Der geringste Befall von Krankheiten wurde an der Zuckerrübe auf jenem Objekt festgestellt, das mit Kompost und den Biopräparaten gedüngt worden war. Im Rahmen der konventionellen Düngungsmethoden wurde allgemein die höchste Intensität der Krankheiten an der mit Stroh, Gründung und Mineraldünger gedüngten Zuckerrübe beobachtet. Ausnahmen von dieser Regel bildete das Vorkommen von echtem Mehltau und Keimlingsfäule. Auf den Objekten A, B, C nahm die Intensität der Krankheiten mit der Steigerung der Stickstoffgabe zu. Auch die auf Objekt D verabreichten Biopräparate stimulierten die Entwicklung der Krankheiten. The effect of various fertilization methods on the diseases of sugar beet was estimated on the basis of nine-year studies (1994-2002) conducted in the Experimental Production Farm in Ba?cyny on loess-based, sedimentary-gley, light-clay soil. The following fertilization methods were applied: A - mineral fertilization, B - mineral and manure fertilization, C - straw, green manure and mineral fertilization, D - ecological compost and biodynamic preparations fertilization. In the objects A, B and C fertilized with phosphorus and potassium, various doses of nitrogen ranging from 0 to 180 kg/ha^?1 were used. In the ecological object D, where mineral fertilization was not used, biodynamic preparations P₅₀₀ and P₅₀₁ were applied instead of nitrogen. The lowest ratio of the diseases of sugar beet was observed in the object fertilized with the compost and biodynamic preparations. In view of the conventional fertilization methods, generally the highest incidence of diseases was noted in the sugar beet fertilized with straw, green manure and mineral fertilizers. The exception was the occurrence of powdery mildew and the black leg. In objects A, B and C the incidence of the diseases increased with the increase in nitrogen doses. The applied biodynamical preparations in the object D stimulated the development of diseases too.     

Prospects for control of Pythium damping-off of lettuce with Trichoderma,Gliocladium and Enterobacter spp.

Summary Damping-off of lettuce (Lactuca sativa) caused by Pythium ultimum was studied in pots containing a non-sterile potting mix in the glasshouse. Fifty P. ultimum sporangia g^-1 compost reduced the plant stand to 15% and shoot dry weight to 18%, but this reduction was totally prevented by applying Trichoderma harzianum at 2×10⁵ viable propagules g^-1 potting mix. Gliocladium virens and Enterobacter cloacae also alleviated the damping-off. E. cloacae did not adversely affect the action of the fungal antagonists. The co-existence of the bacterial and fungal antagonists was revealed on the root surface and inner surface of the testa by scanning electron microscopy, indicating the compatibility of the biocontrol agents.     

细菌、真菌及植物氮营养信号研究进展

氮素吸收代谢是所有生物生命活动的核心部分,因此,各种生物对氮的吸收与同化过程都有精细的调节。这种调节依赖于生物对体内氮素状况信号及体外（生长介质中）氮素信号的感受。过去几十年中,在细菌、真菌中已经对氮素营养信号有了较好的研究,而植物中则相对缓慢,但也有了一定的认识。本文重点比较细菌、真菌及植物中氮信号系统的组成,以期为进一步认识植物中的氮信号接受与转导系统提供启示。     

Aircraft operations near concentrations of birds in Antarctica: The development of practical guidelines

Aircraft operations have the potential to disturb and to impact negatively on bird life. A gradient of increasing behavioural response is evident in birds when exposed to increasing aircraft stimulus. The most major disturbance is likely to lead to impacts on the health, breeding performance and survival of individual birds, and perhaps bird colonies. A process of revision to policies on aircraft operations contained in management plans for a number of specially protected areas in Antarctica by the United Kingdom, accompanied by consultations made within the scientific community through the Scientific Committee on Antarctic Research (SCAR) and with operational interests through the Council of Managers of National Antarctic Programmes (COMNAP) resulted in new guidelines being adopted by the Antarctic Treaty Consultative Parties in June 2004. The principal recommendations of the guidelines are that bird colonies should not be overflown below 2000 ft (∼610 m) above ground level and landings within 1/2 nautical mile (∼930 m) of bird colonies should be avoided wherever possible. These guidelines are less stringent and less specific than those that were recommended by the SCAR specialist group on birds, and represent a compromise to accommodate operational needs. While the adoption of clear and consistent guidelines for the operation of aircraft in Antarctica is welcome in that this provides practical advice that is likely to reduce incidences of close aircraft/bird encounters, there remains insufficient knowledge of the interactions between aircraft and birds in Antarctica, and the consequent impacts on individual birds and on bird populations. It is important, therefore, that the guidelines adopted are considered interim, and should be kept under scrutiny with revisions made as new and improved research results appear.     

Potential of wild species for genetic enhancement of some semi-arid food crops

Discovery and incorporation of genes from wild species provide means to sustain crop improvement, particularly when levels of resistance in the cultigens are low and virulent strains of pests and pathogens overcome the host plant resistance. The extent of utilization and the potential of the wild genepool for genetic enhancement were reviewed in five important food crops viz. sorghum, pearl millet, chickpea, pigeonpea and groundnut grown in the semi-arid tropics. Introgression from compatible wild germplasm in the primary gene pool resulted in transfer of new cytoplasmic male sterility systems in pearl millet and pigeonpea, development of high protein, cleistogamous flower and dwarf pigeonpea lines and foliar disease resistant groundnut cultivars. Utilization of wild species in secondary and tertiary gene pools has been generally limited due to sterility, restricted recombination or cross incompatibility. Nevertheless, these species are extremely important as they contain high levels of resistance to several important biotic and abiotic stresses. Several of them, like those belonging to the Parasorghum section and the rhizomatous Arachis species are sources of multiple resistances and hold great promise to sustain crop productivity.