不同温度盐度下饵料对卤虫生长及体内类胡萝卜素积累的影响

以螺旋藻粉、酵母、酵母+β-胡萝卜素为饵料，分别在不同盐度（10、30、50、70和90）和不同温度（20℃、25℃和30℃）下，探究饵料对卤虫（Artemia sp.）生长及体内类胡萝卜素积累的影响。结果表明：相同温度盐度条件下，投喂螺旋藻粉组卤虫存活率和体长优于其它饵料组；养殖第10d，在温度25℃下投喂螺旋藻粉组和酵母组卤虫均在盐度30时有最大平均体长（7.5mm，5.9mm），而投喂酵母+β-胡萝卜素卤虫在盐度10时平均体长最大（4.0mm）；在盐度50下各饵料组卤虫平均体长在温度30℃组均显著大于其它温度组（P < 0.05）。养殖第15d，在温度25℃下投喂螺旋藻粉组卤虫在盐度30时存活率（93.7%）最高；在盐度50下投喂螺旋藻粉组卤虫存活率在温度20℃（94.0%）和25℃（92.0%）均显著大于30℃组（P < 0.05）。投喂螺旋藻粉各组卤虫抱卵率显著大于其它饵料（P < 0.05），且随盐度或温度升高而逐步增大。对养殖15d卤虫体内类胡萝卜素检测表明，各饵料组卤虫均只检测到海胆酮和角黄素，未检测出β-胡萝卜素、β-隐黄质、玉米黄质和虾青素。投喂螺旋藻粉卤虫总类胡萝卜素含量显著高于其它组（P < 0.05），且随盐度升高呈下降趋势，盐度10组最高（46.25μg/g）；随温度升高呈先上升后下降趋势，温度25℃组最高（46.28μg/g）。综上所述，投喂螺旋藻粉的卤虫生长最好，卤虫可以将β-胡萝卜素转化成海胆酮和角黄素，温度升高会降低卤虫存活率，加快卤虫生长、性成熟及类胡萝卜素代谢；盐度过高或过低会降低卤虫存活率和生长速度，但是高盐可以促进卤虫性成熟，且消耗体内类胡萝卜素。     

Abrupt shift in subsurface temperatures in the tropical pacific associated with changes in El Nino

Radiocarbon (14C) content of surface waters inferred from a coral record from the Galapagos Islands increased abruptly during the upwelling season (July through September) after the El Nino event of 1976. Sea-surface temperatures (SSTs) associated with the upwelling season also shifted after 1976. The synchroneity of the shift in both 14C and SST implies that the vertical thermal structure of the eastern tropical Pacific changed in 1976. This change may be responsible for the increase in frequency and intensity of El Nino events since 1976.     

热带玉米耐低氮性状的遗传变异

采用６个国际玉米小麦改良中心的热带玉米自交为亲本,按Ｇｒｉｆｆｉｎｇ方法２组配成双列杂交,在高氮和低氮条件下对各主要性状进行鉴定,并估算其遗传参数。结果表明,从高Ｎ到低Ｎ,籽粒产量降低程度最大,降减系数（ＲＩ）达０．４８４５,与叶绿素含量降低程度几乎一致。自交系间和杂交组合间在产量的降解系数上明显的遗传差异。低氮条件下,籽粒产量、穗行数、百粒重、穗长、单株穗数、穗位以下绿叶数、雌雄开花差期、穗位叶     

自然降温对不同生长期甘蔗生理生化指标的影响

【目的】为研究甘蔗的抗寒、耐寒机理提供理论依据。【方法】以桂糖28号（GT28）和新台糖22号（ROC22）为材料,测定自然降温条件下,新植苗期、宿根苗期、新植伸长期和新植成熟期等不同生长期甘蔗叶片丙二醛（MDA）含量、过氧化物酶（POD）活性、脯氨酸（Pro）和可溶性蛋白（SP）含量等生理指标。【结果】自然降温条件下,相同的生长时期,两个品种POD活性、MDA和SP含量变化基本一致,均为新植苗期〉宿根苗期〉新植伸长期〉新植成熟期;相同生长时期,GT28叶片MDA含量低于ROC22,ROC22叶片POD活性比GT28高,GT28的Pro和SP含量均高于ROC22。【结论】通过分析甘蔗新植苗期生理指标,可以在很大程度上评价甘蔗成熟期的抗寒性。     

Photoinduced DNA-protein cross-links and bacterial killing: a correlation at low temperatures

The increased sensitivity of Escherichia coli to killing by ultraviolet irradiation when frozen and the variation in this sensitivity as a function of the temperature during irradiation have been correlated with changes in the amount of DNA that was cross-linked to protein by ultraviolet light. These variations in sensitivity to killing do not correlate with the production of thymine dimers.     

土壤中六价铬离子在低温环境中的迁移规律研究

为了探究复合土体中六价铬离子在寒区低温环境中的迁移规律,设置了4个不同土体配合比,掺入不同质量分数的水泥(C),脱硫石膏(S),对标准养护28 d后的复合土体进行上表面、下表面和环境3个方向的降温处理,而后进行电感耦合等离子质谱仪(ICP-MS)和低温核磁共振仪(LT-NMR)实验。结果表明,进行三温降温后的土体温度曲线呈现出先快速下降后缓慢下降的趋势,土体温度通过热传递由表及里传递负温;不同配合比下的土体均呈现两侧边缘处离子浓度高于中心处,随温度降低铬离子浓度增加;T_2弛豫时间的特征峰面积和第一峰值明显减小,所对应的第一峰孔隙区间0.001～0.117μm在-5.4℃至-14.4℃时基本不变,第二峰与第三峰面积减小,结冰量增加;温度对铬离子迁移具有重要影响且结冰量与铬离子浓度相关系数高达0.91;大孔隙的结冰速率远高于中孔及小孔隙,冰透镜体的增加导致了Cr~(6+)的迁移并在低温区聚集。研究表明,低温环境对复合土体中重金属离子迁移有重要影响。     

Trichoderma spp. capable of growing at low temperatures with biocontrol potential

Though there are successful commercial biocontrol products with Trichoderma spp. in many countries including US, Israel and Europe, their usefulness is limited in cold environments such as mid-and northern part of Europe, US and Canada, especially in the late fall, winter and early spring period.Trichoderma isolates capable of growing at low temperatures (5-10℃) and showing good antagonistic properties against plant pathogenic fungi may have therefore both scientific and commercial value.     

Ultraviolet damage to bacteria and bacteriophage at low temperatures

The survival of Escherichia coli B/r WP2 (tryptophan-requiring) from ultraviolet irradiation when suspended in 0.067M phosphate buffer (pH 7) has been studied over the temperature range 22 degrees to -269 degrees C. In unfrozen suspensions there was no appreciable change in sensitivity between 22 degrees and -10 degrees C. The sensitivity in the presence of ice progressively increased by a factor of 7 when the temperature was lowered to -79 degrees C. Between -79 degrees and -196 degrees C the sensitivity decreased to less than four times the sensitivity at 22 degrees C and was not appreciably different at -269 degrees C. Evidence from experiments with bacteriophage T1 and E. coli WP2 HCR(-) (a strain unable to excise thymine dimers) indicates that a new, qualitatively different lesion, less amenable to repair, may replace the thymine dimer in E. coli irradiated at -79 degrees C.     

砷对茶树生长的影响及其在茶树体内的吸收与积累

采用室内水培法,研究3个茶树品种在不同浓度As3 胁迫下的毒害症状和砷胁迫对春梢生长的影响,以及茶树体内各器官对砷的吸收与积累特性。结果表明,当砷胁迫浓度≥1 mg.L-1时,茶树已出现明显的受害症状,砷胁迫对新梢萌发和生长均有显著的负面影响。不同品种耐砷能力有一定差异,福鼎大白茶>名山213>名山131。3个品种对砷的吸收吸附率的大小顺序为:福鼎大白茶>名山213>名山131。各器官中的砷含量随砷处理浓度的增加总体呈大幅升高趋势,并且各器官的砷含量与营养液中的砷胁迫浓度呈显著正相关。砷在茶树体内的分布规律为细根>粗根>主茎>嫩茎>叶片>新梢。当砷胁迫浓度≥1 mg.L-1时,各品种1芽2叶新梢中砷含量>2 mg.kg-1。     

Starch accumulation in shoot-forming tobacco callus cultures

Microscopic histochemical examinations of cultured tobacco callus disclosed a strong correlation between starch accumulation and shoot initiation. The accumulation started before any observable organized development and was heaviest in cells of loci which ultimately gave rise to organ primordia. Treatment of tissue cultures with gibberellin prevented starch accunmulation and organ formation.     

Post-silking nitrogen accumulation and remobilization are associated with green leaf persistence and plant density in maize

Stay green(SG) maize was found to have higher grain yield and post-silking nitrogen(N) uptake(PostN) compared with a non-stay green(NSG) hybrid. To understand the effects of plant density on grain yield(GY) and N efficiency in modern maize hybrids, we compared two modern hybrids(SG hybrid DY508 and NSG hybrid NH101) with similar maturity ratings at three plant densities(45 000, 60 000, and 75 000 pl ha~(–1)) in 2014 and 2015. GY, leaf senescence, dry matter(DM) accumulation,N accumulation, PostN, and post-silking N remobilization(RemN) were analyzed. DY508 and NH101 had similar GY, but DY508 had higher thousand kernel weight(TKW) and lower kernel number(KN) than NH101. Plant density significantly increased GY in the two hybrids. On average, over the two years, plant density improved GY in DY508 and NH101 by 18.5 and 11.1%, respectively, but there were no differences in total dry matter(TDM) and post-silking DM(PostDM) between the two hybrids. Plant density improved leaf N, stem N, and grain N at the silking and maturity stages in 2014 and 2015. DY508 was lower in harvest index(HI), nitrogen harvest index(NHI), and grain N concentration(GNC) than NH101. Grain N in DY508 was 2.61 kg ha~(–1) less than in NH101, and this was caused by lower GNC and leaf RemN. On the average, DY508 was 1.62 kg ha~(–1) less in leaf remobilized N(leaf RemN) than NH101, but was similar in stem remobilized N(stem RemN;2.47 kg ha~(–1) vs. 3.41 kg ha~(–1)). Maize hybrid DY508 shows delayed leaf senescence in the upper and bottom canopy layers in the later stages of growth. The present study provides evidence that the NH101, which has rapid leaf senescence at the late grain-filling stage, has gained equivalent GY and higher leaf RemN, and was more efficient in N utilization.     

Understanding reactivity at very low temperatures: the reactions of oxygen atoms with alkenes

A remarkable number of reactions between neutral free radicals and neutral molecules have been shown to remain rapid down to temperatures as low as 20 kelvin. The rate coefficients generally increase as the temperature is lowered. We examined the reasons for this temperature dependence through a combined experimental and theoretical study of the reactions of O(3P) atoms with a range of alkenes. The factors that control the rate coefficients were shown to be rather subtle, but excellent agreement was obtained between the experimental results and microcanonical transition state theory calculations based on ab initio representations of the potential energy surfaces describing the interaction between the reactants.     

Temperature acclimation: improved sustained swimming performance in carp at low temperatures

At low temperatures, the reduction in mechanical power output of the aerobic muscle forces cold-blooded animals, such as carp, to recruit their rapidly fatiguing anaerobic fibers at relatively slow swimming speeds. Previous experimental data have suggested that changes in the biochemistry and morphology of the aerobic muscle during cold acclimation might increase its output of mechanical power. The present experiments show that, because of these changes, carp can swim faster at low temperature using only their aerobic muscle, which results in an increase in their sustainable swimming speed. By modifying their musculature, cold-blooded animals can achieve some independence from the effects of seasonal changes in environmental temperature.     

金属抗性促生菌对玉米生长和锌积累的影响

【目的】探讨金属抗性促生菌对锌污染土壤中玉米生长和Zn吸收的影响,为利用微生物缓解重金属对农作物胁迫和减少重金属吸收提供理论依据.【方法】通过盆栽试验研究接种促生菌Ⅱ2R3和Ⅳ8R3是否能够缓减Zn对玉米的毒害作用,减少玉米对Zn的吸收和积累.【结果和结论】促生菌Ⅱ2R3、Ⅳ8R3不仅有很强的抗Zn胁迫能力,而且具有较强地吸附、积累Zn的能力.在中、轻度Zn污染(200和400 mg·kg-1)土壤上,单独接种促生菌Ⅳ8R3促进了玉米的生长;当土壤Zn污染水平达到800 mg·kg-1时,同时接种促生菌Ⅳ8R3+Ⅱ2R3显著促进玉米的生长.单独或同时接种促生菌Ⅳ8R3、Ⅱ2R3使不同Zn污染水平土壤中的有效Zn含量均显著降低.当土壤Zn含量达到800mg·kg-1时,单独接种菌株Ⅱ2R3或同时接种Ⅱ2R3+Ⅳ8R3均显著抑制玉米对Zn的吸收和向地上部转运,而在中、轻度Zn污染(Zn≤400 mg·kg-1)土壤上,3种接种处理对玉米吸收Zn均没有显著影响.表明在高锌污染(800mg·kg-1)土壤中,接种促生菌Ⅳ8R3、Ⅱ2R3能显著抑制玉米对Zn的吸收和向地上部转运;菌株Ⅳ8R3、Ⅱ2R3对玉米生长的影响与土壤Zn污染水平和菌株的性质有关.     

越冬低温及栽期对偏低海拔区当归生长的影响

【目的】探讨偏低海拔区当归苗的越冬温度和成药生长光温对早薹及成药根产量的影响。【方法】采用甘肃漳县当归苗,越冬期按根直径分类后分别进行0和-5℃处理,次年与当地同期、晚15d和晚30d分3个时期进行分期栽植,以观察早薹及成药根农艺性状对越冬温度和分期栽植的反应。【结果】根直径大于0.45cm的当归苗具有明显的早薹现象,根直径为0.55~0.65cm的当归苗早薹高于根直径为0.45~0.55cm的苗,根直径小于0.65cm的同类大小苗经0和-5℃冬储处理及分期栽植后,相同大小的各类苗间早薹差异不明显。当归成药根主根直径、鲜质量和干质量与苗大小成正比,苗大小不同、冬储温度不同形成的侧根数也不同。当归成药根的产量随栽期的延后而减小。【结论】根直径0.65cm以下的当归苗可在0与-5℃温区越冬,偏低海拔区适宜栽植根直径偏小的苗,栽前萌动、栽期严重影响当归的产量,随栽期延后成药根产量减小。     

Leaf herbivores decrease fitness of a tropical plant

Damage by insect herbivores to neighboring individuals of the shrub Piper arieianum in a neotropical wet forest varies greatly. This differential damage has a genetic basis and results in a 2-year decrease in growth, seed production, and seed viability, with larger plants recovering before smaller plants. The results provide evidence that leaf herbivores represent a potentially strong selective force for the evolution of plant defenses.     

Hole-burning spectroscopy and relaxation dynamics of amorphous solids at low temperatures

The magnitude and temperature dependence of most of the properties of amorphous solids are anomalous at very low temperatures ( less, similar1 Kelvin). Phonon-assisted tunneling of a distribution of glassy bistable configurations, or two-level systems, can account for these anomalies. A unified understanding of the low-temperature properties is required for an understanding of the glassy state. Persistent nonphotochemical hole burning of impurity optical transitions allows a glass state to be produced that is thermally inaccessible to the preburn state, and that allows the probing of tunneling dynamics on time scales that range between picoseconds and days. These data combined with recently obtained distribution functions for the two-level systems offer new insights into the tunneling dynamics.     

高直链淀粉水稻的淀粉积累及相关酶活性关系研究

研究高直链淀粉型水稻品种菲优188花后各时间段内籽粒中不同类型淀粉含量和积累速度的变化,以及淀粉合成相关酶活性的变化,结果发现:该品种花后不同时间段内直链淀粉、支链淀粉、总淀粉含量及其相关酶活性均存在极显著差异.直链淀粉和支链淀粉的积累规律相似,均呈Logistic曲线方程式积累,直链淀粉和支链淀粉积累速度随时间的变化规律也相似,且均与淀粉合成酶呈极显著正相关性.     

Conditions for purine synthesis: did prebiotic synthesis occur at low temperatures?

The rate of polymerization of hydrogen cyanide to aminomalononitrile and the tetramer, diaminomalonodinitrile, is quadratic in the total cyanide concentration. Since the reactions form part of a plausible prebiotic purine synthesis and since they compete with hydrolysis, concentration of cyanide may have been important. This may be achieved usefully by cooling to separate out ice.