Growth of the Icefish Neosalanx pseudotaihuensis (Salangidae) in Xujiahe Reservoir,Central China

The icefish Neosalanx pseudotaihuensis(Salangidae) is a small (to 70mm TL), transparent fish that occurs naturally in central and eastern China. It is commercially important in many lakes and reservoirs, and recently has been introduced into other waters. However, very little is known about its biology including growth. In this paper we studied the population structure and the growth of the icefish in Xujiahe Reservoir (central China) from May 1995 to December 1997. The icefish completed its life cycle within about one year and the population consisted of one cohort. The main growth period was May to December and little growth occurred at other times. Remarkable seasonal and interannual variations in the growth rates were found and these are discussed in relation to food availability, water temperature and fishing activity.     

Nitrogen, macrophytes, shallow lakes and nutrient limitation: resolution of a current controversy?

Geomorphic research across the semi-arid and wet-dry tropics of northern Australia has highlighted the role of the regions’ estuaries as a “canary in the coalmine” for climate variations, with dramatic structural shifts over the Holocene. This behaviour highlights the region’s potential sensitivity to climate change and suggests the need for careful identification and interpretation of dynamics in the tropical and sub-tropical regions. However, analysis of change in these regions requires care, as a number of the basic tools applied to interpreting estuarine change in temperate regions are obscured, invalid or simply unavailable when applied in lower latitudes. This study provides a synthesis from a range of investigations across northern Australia and identifies characteristics to be considered when interpreting or predicting sub-millennial estuarine change in these regions.     

Sediment resuspension dampens the effect of nutrient inputs on the phytoplankton community: a mesocosm experiment study

We sampled four populations of the robustly shelled Pleurocera canaliculata from large rivers and five pleurocerid populations bearing more fusiform shells (nominally P. acuta and P. pyrenellum) from smaller streams in a study area extending from upstate New York to northern Alabama, USA. Gene frequencies at 9 allozyme-encoding loci revealed that each population of P. acuta or P. pyrenellum was more genetically similar to the P. canaliculata population inhabiting the larger river immediately downstream than to any nominal conspecific. Thus, the extensive intraspecific variation in shell robustness displayed by these nine populations has apparently been rendered cryptic by taxonomic confusion. We then employed geometric morphometrics to explore a gradient in shell morphology from the acuta form to the typical canaliculata form in 18 historic samples collected down the length of Indiana’s Wabash River. The shell forms appeared generally distinctive on the major axes yielded by relative warp analysis (increasing robustness and decreasing spire elongation), although some overlap was apparent. MANCOVA returned a significant relationship between multivariate shape variation and stream size, as measured by drainage area. Possible drivers for this phenomenon include an environmental cline in the risk of dislodgement due to hydrodynamic drag and shifts in the community of predators.     

光波/微波组合-EDTA修复COX-2抗原及其在乳腺癌的表达及意义

目的观察不同抗原修复方法及修复液对COX-2抗原表达的影响及其与乳腺癌临床病理特征的关系。方法用光波/微波、高压锅结合枸椽酸缓冲液、EDTA作抗原修复处理,分别用即用型和浓缩型COX-2单克隆抗体对70例乳腺癌石蜡切片进行免疫组织化学染色。结果①光波/微波组合-EDTA、CA修复浓缩型COX-2的阳性率均比即用型COX-2的阳性率高(P0.01)。②高压锅抗原修复处理切片的免疫组化染色阳性率略比光波/微波的免疫组化染色阳性率高,但无统计学意义(P0.05);高压锅抗原修复处理的切片组织结构破坏程度和掉片情况均比光波/微波处理的重;③EDTA修复处理切片的免疫组化染色阳性率明显比用CA修复处理切片的免疫组化染色阳性率高(P0.01)。④COX-2表达水平与淋巴结转移有显著关系(χ2=5.24,P0.05);与年龄、肿瘤大小、组织学类型和分级之间无明显关系(P0.05)。结论用光波/微波-EDTA修复COX-2抗原,浓缩型COX-2抗体标记可明显提高免疫组织化学染色的敏感性,具有定位准确、阳性率高、操作简单、安全、组织结构保存好、不易掉片等优点;COX-2的表达与淋巴结转移显著相关,可作为乳腺癌的预后指标。     

Plasticity in bud demography of a rhizomatous clonal plantLeymus chinensis L. in response to soil water status

We surveyed the bud demography ofLeymus chinensis L plants along a soil-moisture gradient that was caused by a flood in 1998 on the Song-nen Plain in northeastern China. The number of vegetative buds per ramet was influenced by soil water content, with regression curves being quadratic and the opening of the parabola pointing downward. In addition, the optimum regression models for the numbers of rhizomatous buds and tiller buds relative to soil water resulted in a quadratic parabola and exponential curve, respectively. Vegetative buds flourished between August and October, with plants producing more of those buds on flooded plots than on control sites. The number of rhizomatous buds per ramet was much higher than for tiller buds throughout most of the growing season, and production of the former was more apt to be affected by soil water status. This observed superiority of rhizomatous bud production was thought to be a consequence of the whole-plant adjustment that was stimulated by an abnormally high moisture content. It could also be interpreted as a strategy for “escape” from disadvantageous overly wet conditions. Moreover, the position-based preference for bud emergence along the ramets could be an underlying mechanism for selective ramet placement.     

Root Foraging Increases Performance of the Clonal Plant Potentilla reptans in Heterogeneous Nutrient Environments

Background

Plastic root-foraging responses have been widely recognized as an important strategy for plants to explore heterogeneously distributed resources. However, the benefits and costs of root foraging have received little attention.

Methodology/Principal Findings

In a greenhouse experiment, we grew pairs of connected ramets of 22 genotypes of the stoloniferous plant Potentilla reptans in paired pots, between which the contrast in nutrient availability was set as null, medium and high, but with the total nutrient amount kept the same. We calculated root-foraging intensity of each individual ramet pair as the difference in root mass between paired ramets divided by the total root mass. For each genotype, we then calculated root-foraging ability as the slope of the regression of root-foraging intensity against patch contrast. For all genotypes, root-foraging intensity increased with patch contrast and the total biomass and number of offspring ramets were lowest at high patch contrast. Among genotypes, root-foraging intensity was positively related to production of offspring ramets and biomass in the high patch-contrast treatment, which indicates an evolutionary benefit of root foraging in heterogeneous environments. However, we found no significant evidence that the ability of plastic foraging imposes costs under homogeneous conditions (i.e. when foraging is not needed).

Conclusions/Significance

Our results show that plants of P. reptans adjust their root-foraging intensity according to patch contrast. Moreover, the results show that the root foraging has an evolutionary advantage in heterogeneous environments, while costs of having the ability of plastic root foraging were absent or very small.     

Nitrogen deposition weakens plant–microbe interactions in grassland ecosystems

Soil carbon (C) and nitrogen (N) stoichiometry is a main driver of ecosystem functioning. Global N enrichment has greatly changed soil C : N ratios, but how altered resource stoichiometry influences the complexity of direct and indirect interactions among plants, soils, and microbial communities has rarely been explored. Here, we investigated the responses of the plant‐soil‐microbe system to multi‐level N additions and the role of dissolved organic carbon (DOC) and inorganic N stoichiometry in regulating microbial biomass in semiarid grassland in northern China. We documented a significant positive correlation between DOC and inorganic N across the N addition gradient, which contradicts the negative nonlinear correlation between nitrate accrual and DOC availability commonly observed in natural ecosystems. Using hierarchical structural equation modeling, we found that soil acidification resulting from N addition, rather than changes in the plant community, was most closely related to shifts in soil microbial community composition and decline of microbial respiration. These findings indicate a down‐regulating effect of high N availability on plant–microbe interactions. That is, with the limiting factor for microbial biomass shifting from resource stoichiometry to soil acidity, N enrichment weakens the bottom‐up control of soil microorganisms by plant‐derived C sources. These results highlight the importance of integratively studying the plant‐soil‐microbe system in improving our understanding of ecosystem functioning under conditions of global N enrichment.