沙生濒危物种霸王的高频植株再生研究

实验选用霸王无菌苗的茎尖、子叶、下胚轴和胚根作为材料,研究霸王不同外植体的离体培养技术。结果表明,霸王茎尖是诱导丛生芽的良好外植体,而子叶、下胚轴和胚根是诱导愈伤组织的良好外植体;霸王茎尖的最适增殖培养基是:MS+6-BA 5.0 mg·L-1+NAA 1.0 mg·L-1;最适生根培养基是:MS+IAA 1.5 mg·L-1;最适愈伤组织诱导培养基是:MS+6-BA 1.0 mg·L-1或MS+6-BA 1.0 mg·L-1+NAA 0.5 mg·L-1。沙质基质为霸王组培苗过渡的最佳基质。     

氯吡苯脲对红砂愈伤组织诱导和增殖的影响及响应面法优化

以红砂的一年生苗嫩茎为外植体,添加不同浓度的氯吡苯脲（CPPU）、6-BA和NAA,进行愈伤组织诱导试验,得出红砂愈伤组织诱导的最佳培养基为1/2MS+CPPU 0.1 mg·L-1+NAA1 mg·L-1。利用响应面分析法,设计CCD中心组合试验,对CPPU和NAA两个因素进行优化,得出愈伤组织最佳继代培养基为1/2MS+CPPU 0.1195 mg·L-1+NAA1.1 mg·L-1,在此条件下,实际增殖率可达到4.7414,为理论预测值的99.15%,愈伤组织的最适继代周期为30 d左右。利用响应面分析法可优化红砂愈伤组织继代培养基,得到理论最佳配方,验证结果表明该方法科学、高效。     

珍稀泌盐植物长叶红砂(Reaumuria trigyna)愈伤组织诱导及增殖

以珍稀泌盐植物长叶红砂(Reaumuria trigyna)成熟种子和不同发育阶段幼苗的不同部位为外植体,对其愈伤组织诱导和增殖进行了系统研究。结果表明:在添加3.0mg·L-12,4-D、1.0mg·L-1 NAA、0.5mg·L-1 6-BA、30g·L-1蔗糖和6.0g·L-1琼脂,pH为5.8的MSO培养基中,出愈率达70%以上,生长量高于其他培养基,是该植物愈伤组织诱导的最佳培养体系;7d下胚轴和25d的幼苗较适合愈伤组织诱导,可形成淡黄色疏松愈伤组织,且褐化程度相对较低;适宜的继代周期为30~40d,随着传代次数增加,愈伤组织颜色变淡,生长速度加快;NaCl浓度为50mmol·L-1和100mmol·L-1时促进愈伤组织生长,盐浓度过高则导致其生长受抑,甚至死亡。     

红砂愈伤组织适应盐胁迫的渗透调节机制研究

测定在不同盐胁迫下红砂愈伤组织中几种渗透调节物质的累积量,研究盐胁迫下红砂的渗透调节机制。研究结果表明, 在盐胁迫下,红砂愈伤组织的相对生长率随着盐浓度的增加先升高后降低。红砂愈伤组织具有很强的耐盐能力,低于100 mM NaCl处理可促进红砂的生长,大于100 mM NaCl处理,则会抑制红砂生长。红砂愈伤组织中脯氨酸、甘氨酸甜菜碱、类黄酮和海藻糖在盐胁迫下大量累积,是红砂渗透调节能力改善的积极反应,也是红砂耐盐性强的体现和重要原因。     

根癌农杆菌(Agrobacterium tumefaciens)介导的马铃薯高效遗传转化体系筛选及优化

马铃薯是重要的块茎类作物,根癌农杆菌(Agrobacterium tumefaciens)介导的遗传转化方法是马铃薯基因工程育种的重要技术,研究其遗传转化体系和转化效率有助于提高分子育种效率。针对利用根癌农杆菌介导的2种外植体遗传转化马铃薯普通栽培品种,通过筛选获得最佳转化体系和转化率。以4种马铃薯普通栽培品种(Favorita、Shepody、Atlantic、甘农薯2号)的茎段和试管薯薄片为受体材料,对根癌农杆菌介导的不同遗传转化体系的分化率和转化率进行分析。结果表明:Favorita、甘农薯2号和Atlantic茎段经S2(MS;6-BA 2.5mg·L~(-1),2,4-D0.6mg·L~(-1),Carb 400mg·L~(-1),Kan 50mg·L~(-1))和M2(MS;6-BA 2.5mg·L~(-1),IAA 0.25 mg·L~(-1),2,4-D0.25mg·L~(~(-1)),Carb 400mg·L~(-1),Kan 50mg·L~(-1))培养后获得的转化率显著高于其他培养基。Favorita茎段最大转化率显著高于试管薯薄片转化率;甘农薯2号和Shepody试管薯薄片转化率显著高于茎段转化率。茎段转化体系的最佳诱导愈伤培养基为S2,最佳分化培养为基为M2。Favorita适合采用茎段转化体系,甘农薯2号和Shepody适合采用试管薯薄片转化体系。不同品种的愈伤组织诱导培养基和分化培养基的差别主要是由基因型差异引起的,在提高遗传转化效率中应该针对品种进行转化体系的筛选。     

NaCl胁迫下红砂愈伤组织中主要离子累积特征的研究

盐胁迫下植物对Na+、K+、Ca2+、Cl-的选择性吸收代表了植物对盐胁迫的适应性。以荒漠植物红砂为材料,研究不同浓度NaCl胁迫对红砂愈伤组织Na+、K+、Ca2+、Cl-含量的影响。结果表明,NaCl胁迫下红砂组织相对生长率随着盐浓度的增加先增加后下降, 100 mM处理时达到最大;K+、Ca2+含量下降,Na+和Cl-含量升高,变化幅度随NaCl浓度的增加而增大。红砂愈伤组织具有很强的耐盐能力,低浓度NaCl处理可促进愈伤组织的生长,对Na+、K+、Ca2+、Cl-的吸收选择性提高,有利于避免离子代谢紊乱,减轻NaCl胁迫的伤害;在较高浓度下盐胁迫会对植物的生长造成一定的抑制。可见,离子平衡是红砂组织耐盐性的重要机理之一。     

利用响应面法优化野生白刺(Nitraria sibirica)茎段增殖培养基

为了提高野生白刺(Nitraria sibirica)组培过程中的增殖系数,以野生白刺的无菌苗幼嫩茎段为外植体,利用响应面法对白刺茎段增殖诱导试验进行优化。在添加不同激素浓度NAA、IBA、IAA与6-BA组合的单因素增殖诱导试验基础上,根据CCD中心组合试验设计原理,采用2因素5水平的响应面法,对挑选出的6-BA和IBA两个因素浓度进行优化,得出增殖诱导最佳培养基为MS+6-BA(0.22mg·L-1)+IBA(0.55mg·L-1)。在此条件下,实际增殖系数可达到3.90。优化后的培养基使得增殖系数从之前单因素实验所得最高增殖系数3.63提高到了3.90。为野生白刺组培方面稳定增殖以及后续在组培环境下与锁阳接种研究提供了保障。     

强抗旱胡麻新品种陇亚11号组织培养技术优化研究

针对胡麻组织培养中胚状体诱导率低、植株再生和生根困难等问题,以强抗旱胡麻优良新品种陇亚11号为实验材料,从培养基配置、外植体筛选、生根培养等方面开展系统研究,并进行相关技术优化,为胡麻组织培养技术提供一套更加适用的优化方案。结果表明,NAA与6-BA互作,诱导的愈伤组织深绿、致密、团状性好,玻璃化和疏松透明现象较少,二者浓度的变化对胚状体的诱导率平均值和最大值以及成苗率平均值等均高于优化前,其中MS+NAA（1.0 mg·L-1）+6-BA（0.5 mg·L-1)的培养基胚状体诱导率、成苗率均为所有处理中最高;NAA与PP333互作,生根率、平均生根数、平均根长均有明显的提高,其中1/2MS+AC(0.05%)+NAA(0.5 mg·L-1) +PP333（0.001 mg·L-1）的培养基生根效果最好,该培养基上培养的试管苗,根上发生较多的侧根和不定根,有利于幼苗吸收土壤中的水分和无机盐,提高移栽成活率。虽然优化后的培养基使胚状体的诱导率和成苗率均有明显增加,但通过胚状体分化的植株比率仍然偏低,与实际生产中的要求还有一定差距,不利于大量的繁殖移栽,仍需进一步探索研究。     

科尔沁沙地不同生境土壤氮矿化/硝化作用研究

利用顶盖埋管原位培育法测定了科尔沁沙地不同生境（丘间低地、固定、半固定、半流动和流动沙丘）土壤氮素矿化/硝化速率的月际动态及净矿化/硝化量。结果表明：①沙地土壤无机氮主要以NO^-₃-N的形式存在,各类生境土壤NH⁺₄-N平均含量比NO^-₃-N低58.2%~79.7%;②土壤氮素矿化/硝化速率随植被与土壤条件的恶化呈现递减的趋势,从丘间低地到流动沙丘,净矿化速率分别为61.0、43.4、29.1、5.3 mg·m^-2·d^-1和2.7 mg·m^-2·d^-1,净硝化速率分别为61.8、46.2、30.1、6.2 mg·m^-2·d^-1和3.4 mg·m-2·d-1;③从丘间低地到固定、半固定、半流动和流动沙丘,矿化氮总量分别减少28.8%、52.3%、91.4%和95.5%,硝化总量分别减少25.3%、51.3%、90.0%和94.5%;④不同类型生境土壤净硝化氮占净矿化氮的比例都为100%,表明沙地土壤中植物可利用氮素易于淋溶或氨挥发损失。     

盐胁迫下红砂愈伤组织的抗氧化能力与耐盐性研究

通过测定不同梯度盐胁迫下红砂愈伤组织中超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶（CAT）的活性,以及丙二醛(MDA)含量和细胞膜透性,探讨了红砂抗氧化能力与耐盐性的关系。结果显示:随着盐胁迫浓度增加,红砂愈伤组织中MDA 含量比对照增加0.84%~51.03%,SOD、POD和CAT活性分别比对照提高9.83%~51.98%、26.4%~140.2%和44.74%~216.34%。表明红砂可以通过上调SOD、POD和CAT等保护酶的活性来响应盐胁迫,并以此降低盐胁迫诱导的膜脂过氧化程度,从而提高其耐盐性。     

Analysis of Winter and Summer Glacier Mass Balances

Seasonal mass balance components b_w (winter balance) and b_s (summer balance) as well as c_t (total accumulation) and a_t (total ablation), can be used directly to infer climate variables. In contrast, a_c (net balance of the accumulation area) and a_a (net balance of the ablation area), and b_a or b_n (annual or net balance) can not. The traditional Alpine system of observations of a_c and a_a , however, can be converted to true seasonal values b_w and b_s if both pairs of components are simultaneously observed for some years, because a correlation between the two pairs of components exists. We analyzed b_w and b_s data and their mean, standard deviations and ratios of these to the corresponding net or annual balances for 50 glaciers with relatively long records representing different regions in the northern hemisphere. We also investigated correlations between seasonal components. A negative correlation between b_w and b_s exists at many glaciers. About two-thirds of the glaciers show insignificant correlations (?0.3 < r < 0.3), implying independence of summer and winter balances. In a few unusual cases the correlations are positive. These different correlations, or lack thereof, may offer insight into feedback conditions that must exist in this climate-related system. The correspondence of the b_w and c_t , and b_s and a_t , appears to depend largely on the relative amounts of summer snowfall, a function of their climatic environment expressed as [α = (b_w+b_s)/2]. The contribution of variability of b_s to the net balance increases markedly with decreasing values of α. The variability of b_w and b_s , and therefore the net balance, has been increasing with time; whether this is due to an increase in climate variability or to other causes is not clear. It appears that b_w has been increasing with time at the highest altitudes, but b_s has been increasing more rapidly especially at low altitudes; the many-glacier average net balance is becoming more negative.     

THESES TITLES

The Arctic Bibliography

Struggle for Africa

English Topographic Terms in Florida, 1563–1874

Culture Worlds

Economic Statistics of Texas 1900–1952

Water Requirements Survey, Red River Basin, Texas

Geography from the Air

The Columbus Atlas

Map of Caribbean Oil

Oil in the Soviet Union

Goode's World Atlas

Regional Atlas

World Resource Statistics     

Herbaceous layer development during spring does not deplete soil nitrogen in the Portuguese montado

Nitrogen (N) content in the soil and in the herbaceous biomass were monitored during spring of 2004-2006 to determine how the herbaceous layer development influences soil N availability in the montado ecosystem of southern Portugal. Highest (246.6 ± 52.7 g m⁻²) and lowest (123.2 ± 89.5 g m⁻²) peak biomass occurred in 2006 and 2005 respectively. Total soil N within the top 20 cm soil profile ranged between 0.2 ± 0.1% in February and 0.41 ± 0.2% in May, while available soil N was lowest (5 ± 2 μg g⁻¹soil) in February but increased three-to-five fold in March and was >17.5 μg g⁻¹soil at senescence in May. Significant (p < 0.001) increase in total N in the aboveground pool occurred between February and May. There was however, no decay in soil N content. Instead, the herbaceous vegetation enhanced soil N input and N retention in the ecosystem. Most of the herbaceous plants were annuals with large reserves of organic N at senescence, which returned to the soil as detritus. The herbaceous vegetation is a critical component of the montado that contributes to N recharge and cycling within the ecosystem.     

Sand transport under increased lateral jetting of raindrops induced by wind

Wind tunnel experiments for ‘Raindrop Detachment and Wind-Driven Transport’ (RD–WDT) process were conducted under improved lateral jetting induced by wind velocities of 6.4, 10, and 12 m s^− 1 at nozzle operating pressures of 75, 100, and 150 kPa. Wind-driven rainfalls were also incident on the windward and leeward slopes of 4° and 9° to have a broad variation in the angle of incidence. The objective of this experimental set-up was to distinguish the roles of both impact components of obliquely striking wind-driven raindrops on RD and wind on WDT. Raindrop impact components and reference horizontal wind were quantified by normal (E_tz) and horizontal (E_tx) kinetic energy fluxes and wind shear velocity (u), respectively, to physically model the process of RD–WDT. The results showed, at each level of u, differential sand transport rates by RD–WDT (q_m(RD–WDT)) occurred depending on the magnitude of raindrop impact components, and q_m(RD–WDT) increased as the relative contribution of E_tz increased. Although E_tx was more correlated with q_m(RD–WDT) than E_tz, the extreme increases in E_tx at the expense of E_tz brought about no increases but decreases in q_m(RD–WDT). An RD–WDT model was built under the process of examining the discrete effects of E_tz and E_tx on RD together with u and resulted in a better coefficient of determination (R² = 0.89) than only total kinetic energy (E_t) did alone with u (R² = 0.84). In this study, E_tx was strongly related to u and not to E_tz, which was the principal difference from the previous rainsplash studies, which relied on the compensatory lateral jet development by the compressive pressure build-up at the raindrop–soil interface. Including E_tx in the RD–WDT model both separated the distinct role of each raindrop impact component in RD and improved the performance of u in WDT by better distinguishing its interaction with E_tx, which was not explicitly separated in previous models of RD–WDT.     

Biogeochemical records of paleoenvironmental changes in Nainital Lake,Kumaun Himalayas,India

Rapid urbanization and increased tourism around Nainital Lake in the Kumaun Himalayan region in north India has raised concerns about sediment and water pollution. Lead-210 dated sediment cores from the lake represent ~95 years of accumulation and yield a mean sedimentation rate of ~4.7 mm year⁻¹. Total organic carbon (TOC), percent N and S and their atomic C/N and C/S ratios, stable isotopes (δ¹³C, δ¹⁵N, and δ³⁴S), and specific biomarkers (n-alkanes and pigments) were measured in the core. Organic matter is primarily derived from in-lake algal production and TOC flux varies from 1.0 to 3.5 g m⁻² year⁻¹. Sediments are anoxic (Eh −328 to −187 mV) and have low (0.10–0.30 g m⁻² year⁻¹) N, but high (0.37–1.0 g m⁻² year⁻¹) S flux. Shifts in δ¹³C, δ¹⁵N, and δ³⁴S suggest in-lake microbial processes dominated by denitrification and sulfate reduction. The sediments are dominated by short-chain hydrocarbons with low Carbon Preference Index values. The pigments indicate a gradual shift to cyanobacterial domination of the phytoplankton community in recent years. Despite an increase in external input of nutrients, the trophic state of the lake has remained largely unchanged, and the perceived human-induced impacts are limited.     

Geochemistry of waters and brines from the Salinas Grandes basin,Córdoba,Argentina. I. Geomorphology and hydrochemical characteristics

This paper reports on hydrochemical features of diluted waters in the source areas and the brine end-members dominant in the playa of the Salinas Grandes Basin, Córdoba, Argentina. Special emphasis was placed on the study of the relationship between geomorphology and the resulting hydrochemical fractionation. Inflow is from springs and mountain streams which disappear before reaching the saline complex. The playa and intermittent saline lakes are mainly fed by groundwater flow and a few moderately saline and perennial springs. Conversely, ephemeral lakes are fed by atmospheric precipitation and groundwater, whereas small ponds are only fed by atmospheric precipitation. The absence of a clear linkage between geomorphological units and water types was evident in the source areas. Up to four types of water were recognized in a given geomorphological unit. From the sandflat downward towards the playa, the correspondence between geomorphological units and water types was clear, coinciding with a decreased hydrochemical heterogeneity. In this subenvironment, I have recognized two dominant types of water (SO ₄ ^2– –Cl^––HCO ₃ ^– –Na⁺ and Cl^––SO ₄ ^2– –HCO ₃ ^– –Na⁺), which can be considered the original members of the neutral brine in the playa (Cl^––SO ₄ ^2– –Na⁺ where Ca²⁺+Mg²⁺ do not surpass 5 meq per cent), and an intermediate type in the mudflat (Cl^––SO ₄ ^2– –Na⁺ where the contribution of Ca²⁺+Mg²⁺ reaches up to 15 meq per cent). It seems evident that in the zone between the source areas and the sandflat, hydrochemistry is governed by chemical weathering. In stream floodplains and in the distal alluvial plain, close to the saline complex, the increase in water types as well as the increase of HCO ₃ ^– with respect to SO ₄ ^2– , were explained by the mixture of aquifers controlled by the Salinas Grandes-Salinas de Ambargasta fracture. In the saline complex, the more concentrated end-members are the result of evaporation of the two more frequent water-types in the sandflat subenvironment, and salt dissolution of ancient evaporite deposit.     

Nitrogen deposition effects on tissue chemistry and phosphatase activity in Cladonia foliacea (Huds.) Willd., a common terricolous lichen of semi-arid Mediterranean shrublands

In this article we evaluate the potential use of Cladonia foliacea tissue N content, C:N ratio, and phosphomonoesterase (PME) activity as biomarkers of N deposition by means of a field experiment. In order to do this, we continuously added NH₄NO₃ to a semi-arid shrubland at four rates: 0, 10, 20 and 50 kg N ha⁻¹ yr⁻¹ starting in October 2007. Tissue N content and C:N ratios, considered as N stress indicators, significantly increased and decreased, respectively, after 1.5 years. The response found suggests N saturation above 20 kg N ha⁻¹ yr⁻¹. After 2.5 years, extracellular PME activity increased with 20 kg N ha⁻¹ yr⁻¹ and this was attributed to an induced nutritional (N to P) imbalance. Above this threshold, PME significantly decreased as a consequence of the physiological stress caused by extra N. Effects on PME were dependent on the soil properties (pH and Ca and Mg availability) experienced by C. foliacea. PME response suggests a critical load of ∼26.4 kg N ha⁻¹ yr⁻¹ (20 kg N ha⁻¹ yr⁻¹ + background) for this lichen. Further tissue chemistry and PME evaluations in C. foliacea and soil surveys conducted along wide N deposition gradients will confirm the potential use of this species as a biomonitor of N pollution and the importance of soil properties on its ability to respond to atmospheric reactive N.     

Tree biomass and soil organic carbon densities across the Sudanese woodland savannah: A regional carbon sequestration study

Mean tree biomass and soil carbon (C) densities for 39 map sheet grids (1° lat. × 1.5° long.) covering the Acacia woodland savannah region of Sudan (10–16° N; 21–36° E) are presented. Data from the National Forest Inventory of Sudan, Harmonized World Soil Database and FAO Local Climate Estimator were used to calculate C densities, mean annual precipitation (MAP) and mean annual temperature (MAT). Above-ground biomass C and soil organic carbon (SOC, 1 m) densities averaged 112 and 5453 g C m⁻², respectively. Below-ground biomass C densities, estimated using root shoot ratios, averaged 33 g C m⁻². Biomass C densities and MAP increased southwards across the region while SOC densities were lowest in the centre of the region and increased westwards and eastwards. Both above-ground biomass C and SOC densities were significantly (p < 0.05) correlated with MAP (r_s = 0.84 and r_s = 0.34, respectively) but showed non-significant correlations with MAT (r_s = −0.22 and r_s = 0.24, respectively). SOC densities were significantly correlated with biomass C densities (r_s = 0.34). The results indicated substantial under stocking of trees and depletion of SOC, and potential for C sequestration. Up-to-date regional and integrated soil and forest inventories are required for planning improved land-use management and restoration.     

长江口潮滩沉积物－水界面无机氮交换通量

对长江口滨岸潮滩7个典型断面三态氮的界面交换通量进行了三年多的季节性连续观测,结果表明无机氮的界面交换行为存在复杂的空间分异和季节变化。NO^-₃-N和NH⁺₄-N的界面交换通量正负变化范围较大,分别介于-32.82~24.13 mmol.m^-2.d^-1和-18.45~10.65mmol.m^-2.d^-1之间;而NOsup>-₂-N的界面交换通量很小,仅为-1.15~2.82 mmol.m^-2.d^-1。NO^-₃-N的界面交换具有明显的上下游季节性时空分异特征,而NH⁺₄-N的界面交换则表现为南北岸季节性时空分异现象。盐度是控制长江口滨岸潮滩NH⁺₄-N界面交换行为的主要因素,而沉积物粒度、水体 NO^-₃-N浓度、沉积物有机质含量、水温和溶解氧含量则以不同的组合方式,共同制约着 NO^-₃-N在潮滩界面交换的时空分异格局。     

Growth response of three globose cacti to radiation and soil moisture: An experimental test of the mechanism behind the nurse effect

Cactus seedlings often establish under nurse plants which modify environmental conditions by increasing moisture and decreasing solar radiation, which may cause beneficial and detrimental effects, respectively, on seedling growth. Three soil moisture treatments (5%, 25% and 60%) and two solar radiation levels (100% exposure=243 μmol m⁻² s⁻¹, and 40%=102 μmol m⁻² s⁻¹) were used in a factorial design to analyze seedling growth response of three rare cactus species (Mammillaria pectinifera, Obregonia denegrii and Coryphantha werdermannii). The variables evaluated were relative growth rate (RGR), root/shoot ratio (R/S), and K (RGR_roots/RGR_shoot), obtained from an initial seedling harvest (6-month-old seedlings) and a final harvest 6 months after treatment application. All three species had slow RGRs (0.002–0.012 g g⁻¹ day⁻¹). O. denegrii had the lowest RGR values, but was the only species for which R/S and K varied with soil moisture. While all seedlings responded markedly to soil moisture, no response was observed to radiation treatments. The latter might have been related to the relatively low solar radiation levels present in the greenhouse. Yet, our results suggest that the main benefit nurse plants offer to seedlings is the increase in soil moisture.