催青温度对家蚕二化性品种丙酮酸脱氢酶激酶基因(BmPDK)表达的影响

丙酮酸脱氢酶激酶(PDK)在生物体的新陈代谢中具有重要的生理功能。为了探讨家蚕(Bombyx mori)PDK基因的表达特性,用蛾区半分法将二化性家蚕品种的活化越年卵(丙2期)分别以常温(25℃)光照和低温(15℃)黑暗催青,通过实时荧光定量PCR技术检测分析2种温度催青处理后家蚕不同发育阶段和不同组织的BmPDK表达水平。常温光照催青区BmP-DK的表达水平表现出发育时期和组织差异:胚胎发育阶段BmPDK在己4期的表达水平最高,其次是戊2、己3和己5期;幼虫发育阶段BmPDK的表达水平在蚁蚕期极显著高于其它龄期,5龄期在卵巢和精巢的表达水平高于其它组织;蛹期BmPDK的表达水平比其它发育时期低;成虫期的表达水平与胚胎发育末期相当,其中雌蛾的脂肪体和卵巢中BmPDK的表达水平较高。推测BmPDK在家蚕胚胎发育末期及产卵过程中有重要作用。催青温度影响BmPDK在家蚕各发育时期及卵巢组织中的表达水平:胚胎发育阶段戊2期BmPDK的表达水平为常温催青区显著高于低温催青区,己3～己5期常温催青区BmPDK的表达呈低-高-低的趋势,而低温催青区则呈上升趋势;蚁蚕期BmPDK表达水平为低温催青区极显著低于常温催青区;蛹期和成虫期卵巢中,常温催青区BmPDK的表达水平极显著高于低温催青区。催青温度对二化性家蚕BmPDK的表达的影响主要出现在胚胎戊2期、胚胎己3期～蚁蚕期、蛹期、成虫期。     

Plant lignin and nitrogen contents control carbon dioxide production and nitrogen mineralization in soils incubated with Bt and non-Bt corn residues

Bt (Bacillus thuringiensis) corn is reported to produce lignin-rich residues, compared to non-Bt (NBt) corn, suggesting it is more resistant to decomposition. As the Bt gene is expressed selectively in stem and leaf tissue, it could affect lignin distribution in corn, which naturally has greater lignin content in roots than in stems and leaves. Our objective was to evaluate the effects of corn plant components, the Bt gene and elevated-lignin inputs on decomposition. Roots, stems and leaves from Bt corn and NBt corn isolines enriched with ¹³C and ¹⁵N were finely ground and mixed separately with soil, then incubated at 20 °C for 36 weeks. The effect of elevated lignin on decomposition was tested by adding a commercial lignin source (indulin lignin) to half of the samples. In addition to weekly CO₂ analysis and regular measurement of N mineralization, the degree of lignin degradation was evaluated at 1 and 36 weeks from the acid to aldehyde ratio (Ad/Al) of vanillyl and syringyl lignin-derived phenols. The CO₂ production and N mineralization was lower in root-amended soils than stem- and leaf-amended soils. The Bt genetic modification increased CO₂ production from stem-amended soils (P < 0.05) and decreased N mineralization in root-amended soils. The ¹³C and ¹⁵N results also showed more residue-C and -N retained in soils mixed with NBt stem residues. After 36 weeks leaf- and stem-amended soils with indulin lignin had a lower Ad/Al ratio and were less degraded than soils without exogenous lignin. In conclusion, plant lignin and nitrogen contents were good predictors of CO₂ production and N mineralization potential. Corn roots decomposed more slowly than aboveground components emphasizing the importance of recalcitrant root residues in sustaining the organic matter content of soil.     

Distribution of applied cadmium in different size fractions of soils after incubation

The size fraction of soils is one of the important factors that influence the retention of heavy metals. The sorptive properties of soils for heavy metals are principally associated with clay and silt-size fractions. Phosphate fertilizers that are applied to highly weathered tropical soils contain a wide concentration range of cadmium (Cd) as an impurity. Tropical soils contain kaolinite and oxides of Al, Fe, and Mn, which have the ability to sorb Cd. However, the distribution of Cd in different size fractions and the chemical speciation of particulate-bound Cd in the clay size fractions when introduced to soil and allowed to incubate at field moisture capacity merits attention. Cadmium was, therefore, applied to selected surface Kenyan soils varying widely in physicochemical properties to investigate its distribution in different soil particle size fractions and the speciation of particulate-bound species in clay size fractions after incubation. The Cd content in different particle fractions was analyzed by graphite furnace atomic absorption technique after HF-HClO₄ digestion. The particulate-bound Cd species were investigated using chemical sequential extraction method. The study showed that clay size fraction of the natural and the Idaho monoammonium phosphate (MAP)-fertilizer or the Cd perchlorate-added MAP chemical reagent-treated soils contained the highest amount of the total Cd. However, silt and sand fractions of the treated soils also retained appreciable amounts of Cd. Speciation studies revealed that metal-organic complex-bound Cd was the most predominant compared to other particulate-bound Cd species in the clay size fractions of the soils treated with Idaho MAP fertilizer or the Cd perchlorate-added MAP chemical reagent. The distribution of total Cd in the different soil particle size fractions and the speciation of particulate-bound Cd in the clay size fractions varied with the soil type. The results indicate that clay size fractions can retain Cd making it less available; however, the influence of farming practices, which affect Cd mobility, should not be overlooked.     

Setting of a procedure for experimental incubation of Pacific oyster (Crassostrea gigas) embryos

Standardized experimental protocols designed to study Pacific oyster (Crassostrea gigas) gamete quality have not been previously published. Gamete sampling variations and confounding effect of interacting factors result in large variations between replicates, decreasing the effects of the studied factors. This work aims at defining a standardized procedure for incubation of oyster embryos designed for experimental purposes.In a first phase, four experiments were developed to improve embryo sampling and handling. They showed that a minimum of 50 embryos must be counted to decrease the variation between counting replicates. For reliable results, sampling must be carried out from 0 to 7 min after a careful agitation of seawater containing embryos (salinity: 35.6‰). Compared to control and a 30 cm one, the D-larval yield of embryos submitted to a 1 m fall was significantly reduced, showing the limited effect of mechanical disturbance on Pacific oyster oocytes survival. Then, maintaining 2.2 million embryos in 250 ml seawater for a two hours period resulted in a decrease of D-larval yield which could not be explained by a decrease of O₂ content and pH of seawater.The second phase of this work included a set of five experiments, defining experimental incubation conditions. A higher larval yield was observed using 1.8 l beakers and 150 l tanks compared to 0.3 ml microtiter plates and 1 l fish egg incubators. Higher larval yields were recorded when embryo density ranged from 5 to 100 ml^− 1, compared to values between 500 and 2000 ml^− 1. Compared to controls (no antibiotic or no presence of light), no changes of D-larval yield were observed by adding 20 ppm chloramphenicol or by maintaining embryos in total darkness. Then, a significant decrease of pH and O₂ content was observed during the incubation period. However, these changes could not be considered as limiting for Pacific oyster embryo development.In conclusion, experimental incubation conditions have been defined in this study: 30 embryos ml^− 1 incubated in 1.8 l beakers without antibiotic and regardless of light intensity, when not higher than 500 lux. The mean coefficients of variation observed between tank replicates ranged from 13.1 to 16.5%. The standardized incubation procedure described in this work will help to study quality variations of Pacific oyster gametes.     

土壤水解酶活性测定方法的研究进展

土壤水解酶直接参与有机物质的矿质化过程,对维持生态系统碳和养分的循环过程起重要作用。但不同研究者和实验室测定过程的差异,常给土壤酶测定方法的选定带来困难。针对这一问题,本文围绕土壤酶活性测定过程中样本贮存方式、酶底物选择以及培养条件等,对近二十多年来的研究成果进行了评述。土壤酶来源广泛,存在形式复杂,直接提取土壤酶还有很大的难度。目前土壤酶活性的测定主要是通过一定量底物在酶催化反应过程中的生成物或剩余物量来实现。基于对硝基酚衍生物为底物的分光比色法,因其成本低廉而被广泛使用。针对国际上未能建立统一的测定方法而导致研究数据之间难以进行比较的现状,作者认为现阶段土壤水解酶测定过程中应注意以下几点:1)尽量采用新鲜土样或短时间低温冷藏的土样;2)酶底物种类的选择应与国际接轨,采用饱和底物浓度使其反应速度接近最大值;3)缓冲液的pH值可与土壤pH值相近;4)4 h内培养的土壤酶,可忽略微生物抑制剂的使用。建议我国在近期内:1)应丰富土壤水解酶种类的研究;2)注重灵敏度高、需样量小以及培养时间短的荧光分析技术的应用;3)在强化典型土壤酶动力学特征研究基础上,尽快规范土壤酶活性的测定方法。     

外植体及培养条件对葡萄不定芽再生的影响

以优良无核葡萄品种莫利莎、皇家夏天为试材,分别从外植体类型、叶片接种部位、接种方式及培养条件等方面进行不定芽再生技术研究。结果表明,2品种葡萄试管苗离体叶片切割后接种较节间和叶柄容易诱导不定芽再生;将叶片切分为叶尖、叶中、叶基部叶块分别接种,其不定芽再生能力没有差异;取自培养30～50d继代苗上的叶片,其不定芽再生效果相同;叶块以近轴面或远轴面接触培养基的接种方式对不定芽再生影响不大,不过叶片远轴面贴近培养基接种,产生的愈伤组织状态较好;25℃左右小幅变温或恒温的条件能诱发2个葡萄品种产生较多的不定芽;葡萄不定芽再生须经黑暗培养或弱光培养,暗培养时间在2周与4周之间再生效果差异不显著。     

Response of soil organic matter dynamics to conversion from tropical forest to grassland as determined by long-term incubation

Understanding soil organic carbon (SOC) responses to land-use changes requires knowledge of the sizes and mean residence times (MRT) of specific identifiable SOC pools over a range of decomposability. We examined pool sizes and kinetics of active and slow pool carbon (C) for tropical forest and grassland ecosystems on Barro Colorado Island, Panama, using long-term incubations (180 days) of soil and stable C isotopes. Chemical fractionation (acid hydrolysis) was applied to assess the magnitude of non-hydrolysable pool C (NHC). Incubation revealed that both grassland and forest soil contained a small proportion of active pool C (<1%), with MRT of ~6 days. Forest and grassland soil apparently did not differ considerably with respect to their labile pool substrate quality. The MRT of slow pool C in the upper soil layer (0–10 cm) did not differ between forest and grassland, and was approximately 15 years. In contrast, changes in vegetation cover resulted in significantly shorter MRT of slow pool C under grassland (29 years) as compared to forest (53 years) in the subsoil (30–40 cm). The faster slow pool turnover rate is probably associated with a loss of 30% total C in grassland subsoil compared to the forest. The NHC expressed as a percentage of total C varied between 54% and 64% in the surface soil and decreased with depth to ~30%. Grassland NHC had considerably longer MRTs (120 to 320 years) as compared to slow pool C. However, the functional significance of the NHC pool is not clear, indicating that this approach must be applied cautiously. An erratum to this article can be found at     

基于灰色预测的模糊神经网络孵化控制系统

提出一种基于灰色预测的模糊神经网络控制策略,并应用在孵化过程控制系统中.运用灰色预测技术对孵化参数进行预测,方便后续控制,而模糊神经网络则控制过程的动态特性,保证孵化参数的精确和稳定控制.仿真结果表明,该系统能在50 s内将被控对象稳定,具有良好的动态和静态特性.     

禽蛋孵化过程的混合智能控制

针对孵化系统具有强耦合、强干扰、大滞后的特点,提出一种混合智能控制算法.前级控制采用前馈补偿解耦控制算法以消除系统主要控制参数的耦合关系,后级控制根据被控制对象工况的不同,选用模糊免疫PID控制算法或模糊控制算法,实现了孵化过程中温度、湿度和含氧量的混合智能控制.实际运行结果验证了该控制算法的有效性.     

鹰嘴龟的养殖技术

在对鹰嘴龟进行一系列研究的基础上,本文系统介绍了鹰嘴龟的生物学特征、生态习性、繁殖、孵化、人工饲养、疾病防治等知识,可为鹰嘴龟自然资源的保护和开发提供参考。