Plant species richness in continental southern Siberia: effects of pH and climate in the context of the species pool hypothesis

Aim Many high‐latitude floras contain more calcicole than calcifuge vascular plant species. The species pool hypothesis explains this pattern through an historical abundance of high‐pH soils in the Pleistocene and an associated opportunity for the evolutionary accumulation of calcicoles. To obtain insights into the history of calcicole/calcifuge patterns, we studied species richness–pH–climate relationships across a climatic gradient, which included cool and dry landscapes resembling the Pleistocene environments of northern Eurasia. Location Western Sayan Mountains, southern Siberia. Methods Vegetation and environmental variables were sampled at steppe, forest and tundra sites varying in climate and soil pH, which ranged from 3.7 to 8.6. Species richness was related to pH and other variables using linear models and regression trees. Results Species richness is higher in areas with warmer winters and at medium altitudes that are warmer than the mountains and wetter than the lowlands. In treeless vegetation, the species richness–pH relationship is unimodal. In tundra vegetation, which occurs on low‐pH soils, richness increases with pH, but it decreases in steppes, which have high‐pH soils. In forests, where soils are more acidic than in the open landscape, the species richness–pH relationship is monotonic positive. Most species occur on soils with a pH of 6–7. Main conclusions Soil pH in continental southern Siberia is strongly negatively correlated with precipitation, and species richness is determined by the opposite effects of these two variables. Species richness increases with pH until the soil is very dry. In dry soils, pH is high but species richness decreases due to drought stress. Thus, the species richness–pH relationship is unimodal in treeless vegetation. Trees do not grow on the driest soils, which results in a positive species richness–pH relationship in forests. If modern species richness resulted mainly from the species pool effects, it would suggest that historically common habitats had moderate precipitation and slightly acidic to neutral soils.     

Classification of meadows of the South Siberian uplands and mountains

The classification of South Siberian meadows using the Braun-Blanquet approach was carried out on the basis of a geographically wide-ranging data set from the West Siberian Plain and the Altai-Sayanian mountain systems. Two main phytosociological types of meadows were distinguished within the classMolinio-Arrhenatheretea. The natural Siberian forest meadows were included in the orderCarici macrourae-Crepidetalia sibiricae comprising two alliances (Crepidion sibiricae, Aconito barbati-Vicion unijugae) and 7 associations. The anthropogenic types of dry meadows were included in the European-West Siberian orderArrhenatheretalia, comprising one alliance (Festucion pratensis) and 5 associations. DCA ordination revealed clear differences in the floristic composition of the higher units and in the diagnostic importance of the main ecological and phytosociological species groups.     

基于戴云山固定样地黄山松群落物种组成与结构研究

黄山松是亚热带中部山区主要建群种,研究其物种组成及群落结构对探讨中亚热带植被演替规律具有重要意义。戴云山自然保护区分布有大面积黄山松群落,该研究采用网格布点法,建立86块(25.82 m×25.82 m)共5.7 hm~2固定样地,对样地内黄山松群落的物种组成特征、分布区类型、胸径和树高结构、空间分布格局4个方面特征进行了探讨。结果表明:(1)样地内共出现木本植物32 603株219种,隶属于59科108属。乔灌木优势种有黄山松、马尾松、木荷、肿节少穗竹、岩柃、窄基红褐柃等,其中稀有种和偶见种分别占总物种数的33.79%、25.75%和45.21%、24.66%。(2)在区系分布类型上,热带分布类型的科属多于温带分布类型的科属,热带分布类型中又以泛热带分布类型,温带分布类型以北温带占据最大比例。(3)样地内优势种的胸径分布呈倒"J"型,表明更新状态良好。垂直结构上,各优势种树高为倒"J"型或近似倒"J"型。黄山松和其他优势乔木大部分树高为4~10 m,灌木除短尾越桔0~1 m个体数最多外,其他优势灌木1~2 m个体数最多。(4)经计算,样地内乔灌木各优势种均呈聚集分布,聚集程度有所差异,乔木层黄山松最低,灌木层短尾越桔最低。该研究结果表明戴云山保护区黄山松群落物种组成丰富、更新良好,反映了亚热带高山针叶林的典型特征,其空间分布格局可能与取样方式等因素有关。     

Prd29A及DREB1A的克隆和干旱诱导型植物表达载体的构建与鉴定

从拟南芥中克隆了RD29A基因的启动子(Prd29A)及DREB1M基因的DNA片段,构建Prd29A:DREB1A融合基因,采用合成的接头将该融合基因插入到植物表达载体pBI121中,经鉴定,确认正确.     

Role of cannabinoid receptors in regulation of cardiac tolerance to ischemia and reperfusion

Coronary artery occlusion (45 min) and reperfusion (2 h) were modeled in vivo in anesthetized artificially ventilated Wistar rats. Total ischemia (45 min) and reperfusion (30 min) of the isolated rat heart were performed in vitro. The selective agonist of cannabinoid (CB) receptors HU-210 was injected intravenously at a dose of 0.1 mg/kg 15 min prior to the coronary artery ligation. The selective CB1 antagonist SR141716A and the selective CB2 antagonist SR144528 were injected intravenously 25 min prior to ischemia. In vitro, HU-210 and SR141716A were added to the perfusion solution at the final concentrations of 0.1 μM prior to total ischemia. Preliminary injection of HU-210 reduced the infarct size-to-area at risk (IS/AAR) ratio in vivo. This cardioprotective effect was completely abolished by SR141716A but remained after SR144528 injection. Both antagonists had no effect on the IS/AAR ratio. Preliminary injection of the K_ATP channel blocker glibenclamide did not abolish the cardioprotective effect of HU-210. The addition of HU-210 prior to ischemia reduced the creatine phosphokinase (CPK) level in the coronary effluent and decreased left ventricular developed pressure. SR141716A alone had no effect on cardiac contractility and CPK levels. These results suggest that cardiac CB1 receptor activation increases cardiac tolerance to ischemia-reperfusion and has a negative effect on the cardiac pump function. Endogenous cannabinoids are not involved in the regulation of cardiac contractility and tolerance to ischemia and reperfusion. ATP-sensitive k_ATP-channels are not involved in the mechanism of the cardioprotective effect of HU-210.     

The changing of cell-free DNA properties of peripheral blood and TCR-mutant cell frequency in individuals exposed to ionizing radiation

Some properties of the cell-free DNA (cfDNA) of peripheral blood plasma were assessed in 153 employees of atomic industry enterprises. The contents of ribosomal repeat (rDNA) and its concentration in plasma increased in cfDNA of the group of persons in comparison with non-irradiated individuals. The contents of satellite III in cfDNA of donors and of irradiated persons do not differ and less than in DNA nucleus. The correlation between cumulative dose of radiation, contents of rDNA in cfDNA and the frequency of lymphocytes bearing mutations at T-cell receptor (TCR) locus was obtained. The definition of three indications in irradiated persons: the contents of ribosomal genes in cfDNA, TCR-mutant cell frequency and concentration of ribosomal genes in blood plasma--may be useful for revealing individuals in organism of which an intensive cell apoptosis takes place and there is an increased probability of carcinogenesis and of progress of disease of immune system.     

Participation of puncta adherentia junctions in the formation of synaptic connections between a dentate fascia graft and the host brain

The fetal dentate fascia of Wistar rats on the 20th day of gestation was heterotopically grafted into the somatosensory neocortex of adult rats. Granule cells of a graft projected their axons (mossy fibers) to the host brain and established synaptic contacts with inappropriate targets. The organization of ectopic mossy fiber synapses was studied by electron microscopy. It was shown that ectopic synapses reproduce the structural determinants of hippocampal giant synapses and induce a subcellular reorganization of postsynaptic neocortex dendrites. Using morphometric analysis, a significant increase was found in the number of discrete puncta adherentia junctions and their total length in ectopic synapses as compared with the control group. The data obtained indicate that puncta adherentia contacts participate in the structural and chemical adaptation of neuronal targets to alien axons growing from transplants.     

Ion-exchange properties of cell walls of red seaweed Phyllophora crispa

Research into ion-exchange properties of cell walls isolated from thallus of red seaweed Phyllophora crispa was carried out. Ion-exchange capacity and the swelling coefficient of the red alga cell walls were estimated at various pH values (from 2 to 12) and at constant ionic strength of a solution (10 mM). It was established that behavior of cell walls as ion-exchangers is caused by the presence in their matrix of two types of cation-exchange groups and amino groups. The amount of the functional group of each type was estimated, and the corresponding values of pK(a) were calculated. It can be assumed that ionogenic groups with pK(a) -5 are carboxyl groups of uronic acids, and ionogenic groups with pK(a) -7.5 are carboxyl groups of the proteins. Intervals of pH in which cation-exchange groups are ionized and can take part in exchange reactions with cations in the environment are defined. It was found that protein was a major component of cell wall polymeric matrix because its content was 36%.     

肿瘤放化综合治疗中的靶向研究

放化疗综合应用是癌症治疗中的常用方法。研究表明,放化疗综合应用可以有效地控制杀伤肿瘤,但过程中对正常细胞的毒副作用严重制约着放化疗的剂量和疗效。如何在有效杀伤肿瘤细胞的同时减轻放化疗综合应用中对正常细胞的毒副作用已经成为探索更好的治疗策略的关键。随着研究的不断深入,各种相关的新药和新治疗思路层出不穷,比如针对肿瘤发生及代谢过程的靶向类新药、用于辐射增敏的新的基因靶点等都已进入研究者的视线。另外,近年来关于肿瘤细胞中药物转运蛋白的研究也为综合治疗靶点寻找提供了一定依据。本文根据当前研究现状,着重总结近年来放化疗综合治疗靶向研究在上述几方面的一些新进展。