Emergent plant presence and richness alter competitive interactions between two foating plants

Interactions between two plant species can be infuenced by the presence of other plant species and such an effect may change as the diversity of the other species increases.To test these hypotheses,we frst constructed aquatic communities consisting of 1,2 and 4 emergent plant species and then grew ramets of Lemna minor only,ramets of Spirodela polyrhiza only or ramets of both L.minor and S.polyrhiza within these aquatic communities.We also included controls with ramets of L.minor,S.polyrhiza or both but without any emergent plants.Biomass and number of ramets of L.minor and S.polyrhiza were signifcantly smaller with than without the emergent plants,but they did not differ among the three richness levels.The presence of S.polyrhiza did not signifcantly affect the growth of L.minor,and such an effect was not dependent on the richness of the emergent plant species.Without the emergent plant species,the presence of L.minor markedly reduced biomass(-92%)and number of ramets(-88%)of S.polyrhiza.However,such a competitive effect of L.minor on S.polyrhiza became much weaker in the presence of one emergent plant species(-46%biomass and-39%number of ramets)and completely disappeared in the presence of two or four emergent plant species.Therefore,both the presence and richness of emergent plant species can alter competitive interactions between the two duckweed species.These fndings highlight the importance of species diversity in regulating plant-plant interactions.

The Role of Countermeasures in Mitigating the Radiological Consequences of Nuclear Power Plant Accidents

The countermeasures are the actions that should be taken, after the occurrence of a nuclear accident to protect the public against the associated risks. These actions may be represented by sheltering, evacuation, distribution of stable iodine tablets and/or relocation. This study represents a comprehensive probabilistic study to investigate the role of the adoption of the countermeasures in case of a hypothetical accident of type LOCA for nuclear power plant of PWR （1000 Mw）. The effective doses in different organs, short and long health effects, and the associated risks are calculated with and without countermeasures. In addition, the overall costs of the accident and the costs of countermeasures are estimated which represent our first trials to know how much the proposed accident cost. The results showed that, the area around the site requires early and late countermeasures action after the accident especially in the downwind sectors. For late countermeasures, the duration time of relocation ranged from about two to 10 years. The adoption of the countermeasures increases the costs of emergency plan by 40% but reduces the risk associated the accident.

Plant virology in the 21st century in China:Recent advances and future directions

Plant viruses are a group of intracellular pathogens that persistently threaten global food security.Significant advances in plant virology have been achieved by Chinese scientists over the last 20 years,including basic research and technologies for preventing and controlling plant viral diseases.Here,we review these milestones and advances,including the identification of new crop-infecting viruses,dissection of pathogenic mechanisms of multiple viruses,examination of multilayered interactions among viruses,their host plants,and virus-transmitting arthropod vectors,and in-depth interrogation of plantencoded resistance and susceptibility determinants.Notably,various plant virus-based vectors have also been successfully developed for gene function studies and target gene expression in plants.We also recommend future plant virology studies in China.

Nitrogen removal from summer to winter in a field pilot-scale multistage constructed wetland-pond system

A pilot-scale multistage constructed wetland-pond(MCWP)system with a"pre-ecological oxidation pond,two-stage horizontal subsurface flow constructed wetland(HSCW)and surface flow constructed wetland(SFCW)as the core and postsubmerged plant pond"as the process was used to treat actual polluted river water in the field,and the variation in nitrogen removal from summer to winter was investigated.The results showed that the average total nitrogen(TN)removal efficiency in the MCWP was approximately 40.74%.The significant positive correlation between the daily highest temperature and the TN removal efficiency of the whole system was fitted with a nonlinear curve(R^(2)=0.7192).The TN removal load rate in the HSCWs was 2.7–3.7 times that in the SFCW.The SFCW,which had high-density plants(35 plants/m^(2)),increased the proportion of nitrogen removed by plant harvesting and microbial function.The TN transformed by Iris pseudacorus L.accounted for 54.53%in the SFCW.Furthermore,bacteria completed the nitrogen cycle in the SFCW through a variety of nitrogen removal pathways.This research not only investigated the TN removal performance in an MCWP system but also made it possible to predict the TN removal efficiency according to the daily highest temperature from summer to winter in the field.

Clonal performance of Scirpus yagara in multiple levels of substrate heterogeneity and submergence

Aims Environmental heterogeneity affects the performance of clonal aquatic plants.Few researchers integrated two aspects of heterogeneity into the study of clonal plant ecology.The aims of the present study are to(i)test whether different substrate heterogeneity and submergence exert similar effects on plant performance and(ii)explore the foraging behaviour.Methods In this study,Scirpus yagara was subjected to multiple levels of substrate heterogeneity and submergence.Substrate treatments included one homogeneous substrate and three heterogeneous substrates(two-patch,four-patch and eight-patch).Water level treatments included 0,10 and 30 cm.Traits including ramet number,generation number,leaf number,bulb number,ramet height,culm length,rhizome length,clonal radius,spacer length,spacer thickness,total biomass,biomass of bulbs and biomass per bulb were measured.Important Findings Deeper water levels significantly reduced variables associated with growth such as ramet number,generation number,leaf number and bulb number,while substrate patchiness induced significant variations in traits such as spacer length and spacer thickness.Significant interactive effects of the two factors were found for ramet number,leaf number and spacer length.Scirpus yagara showed colonization towards the lake sediment patch in two-patch and four-patch substrates,and more structures were placed in the lake sediment patch.Especially for the two-patch substrate,all structures occupied the lake sediment patch.Two-sided intrusion was observed in the eight-patch substrate,which induced an even allocation of structures in different patches.The foraging behaviour was correlated with the patch size.