茄子(Solanum melomgena L.)根系糖苷生物碱对5种蔬菜作物的化感效应及相关分析

利用生物碱指示剂鉴定了茄子(Solanum melomgena L.)根系分泌物和腐解液中糖苷生物碱(glycoalkaloid)的存在,并采用超声波技术提取茄子根系糖苷生物碱,探讨了茄子根系糖苷生物碱对5种蔬菜作物的化感效应及其相关性.结果表明,糖苷生物碱抑制了3种茄科蔬菜种子的萌发和幼苗生长,且随着生物碱提取液浓度的升高,化感抑制作用显著增强,而不同浓度的生物碱提取液对大白菜(Beussica pekinensis)和菜豆(Phaseolus vulgaris)种子萌发和幼苗生长呈现"低促高抑"的双重浓度效应;随着生物碱浓度升高,茄科蔬菜萌发种子中丙二醛(MDA)含量和质膜透性逐渐上升,3种保护酶活性逐渐下降,大白菜和菜豆萌发种子中三种保护酶活性呈先升高后降低的趋势,高浓度的糖苷生物碱同样导致MDA含量和质膜透性的显著增加;对于不同种类的蔬菜,生物碱的化感效应主要通过不同抗性生理指标分别作用于种子萌发和幼苗生长,其中对种子萌发的作用要显著大于幼苗生长.     

外源ABA对不同品种辣椒种子萌发的影响

以4种辣椒种子为试验材料,研究了不同浓度ABA(0~100 mg/L)对种子萌发的影响.结果表明:低浓度ABA对种子的发芽势和发芽率没有显著影响,高浓度ABA极显著抑制种子的发芽势和发芽率,辣椒品种(系)不同,种子萌发对ABA浓度的敏感性也不同.不同浓度ABA溶液极显著降低了种子的发芽指数,随着ABA浓度的增加,对发芽指数的抑制程度逐渐加强,种子的发芽起始时间也被推迟,浓度越高,萌发延迟天数越多.ABA溶液极显著抑制种子胚根和胚轴的分化和生长,ABA浓度越高,抑制程度越强.图6,表1,参17.     

2.4 二氯酚对作物幼苗生长抑制及对氧化酶同工酶的影响

用不同浓度的2.4二氯酚溶液处理高梁、玉米、小麦、西红柿和芥菜种子后,对种子萌发除西红柿外基本无明显影响,对根系及幼苗生长不同作物中反应不同,芥菜对2.4二氯酚不敏感,而在其它四种作物中,根系及幼苗生长严重受抑.过氧化物酶同工酶的变化与根系及幼苗生长受抑存在一定的相关性,因此,这种酶似乎可以作为一种生化指标供检测作物受氯酚毒害用.40ppm的2.4二氯酚已可引起作物根系及幼苗生长受抑,因此用含氯酚污水灌溉作物时,其氯酚浓度应控制在40ppm以下.     

不同粒径的聚乙烯微塑料对玉米和黄瓜种子发芽和幼苗生长的影响

近年来,微塑料（MPs）对土壤生态系统的污染和危害备受关注。聚乙烯（PE）微塑料对农作物生长发育的影响主要聚焦于粒径和浓度效应,但粒径和浓度的交互作用对植物的生长的影响知之甚少。该研究通过发芽试验和盆栽实验探究了3种粒径（13、58、178μm）PE微塑料在不同质量分数（0、0.1%、0.5%、1%、2%）下对玉米（Zea mays L.）和黄瓜（Cucumis sativusL.）种子发芽、幼苗生长及根系形态的影响。结果表明,3种粒径的PE微塑料均不同程度地降低了玉米和黄瓜种子的发芽势和芽长,种子活力指数下降;对于幼苗生长,除了0.1%的PE13显著增加了玉米株高,0.1%和0.5%的PE13显著增加了玉米根体积和根表面积外,3种粒径的PE均不同程度地抑制了玉米和黄瓜幼苗的生长。双因素方差分析结果显示PE粒径、质量分数和二者交互作用均显著影响玉米种子的发芽,且质量分数效应更显著,而PE对黄瓜种子发芽仅存在质量分数效应;PE对玉米幼苗的株高、黄瓜地下部鲜质量和干质量以及玉米的根尖数具有更显著的粒径效应。RDA分析结果也显示,PE对玉米和黄瓜种子的萌发、幼苗的生长和黄瓜的根系形态存在显著...     

甲胺磷对土壤中磷酸酶和脱氢酶活性的影响

报道了土壤中施入不同浓度有机磷杀虫剂甲胺磷（ｍｅｔｈａｍｉｄｏｐｈｏｓ）后对土壤磷酸酶和脱氢酶活性的影响。结果表明：甲胺磷对脱氢酶和３种磷酸酶的活性均有不同程度的抑制。其抑制强度和作用时间随浓度升高而加剧和延长，但随着时间的推移，这种抑制作用逐渐消失，并产生微弱的刺激效应。甲胺磷对土壤酸性磷酸酶活性的影响大于中性和碱性磷酸酶。初步讨论了酶活性与微生物生长的变化情况。     

奥曲肽对人结肠癌细胞生长增殖抑制作用的研究

目的:研究不同浓度生长抑素类似物奥曲肽对人结肠癌SW480细胞生长增殖的抑制作用.方法:体外培养人结肠癌SW480细胞;MTT比色法测定不同浓度奥曲肽抑制SW480细胞增殖作用,以效价强度最高者为最佳抑制浓度;然后,平皿集落形成法测定奥曲肽抑制体外培养SW480细胞的锚定依赖性生长作用.结果:不同浓度奥曲肽对SW480细胞增殖活性具有不同程度的抑制作用,在10-10 M-10-8M(mol/L)浓度范围内呈剂量依赖性,其中10-8M为最佳抑制浓度;奥曲肽对SW480细胞锚定依赖性生长具有明显的抑制作用,并呈浓度依赖性.结论:奥曲肽能抑制体外培养人结肠癌SW480细胞生长增殖,并在一定范围内呈浓度与时间依赖性.     

玉米幼苗根系形态对芘污染的响应

采用盆栽试验探讨了玉米（Zea mays L.）根系形态学参数（根质量长度、根质量面积、根质量体积、根平均直径及不同根直径等级分布）对不同浓度芘污染胁迫的响应。较低浓度芘可适当地刺激玉米的生长,高浓度芘处理抑制了玉米的生长,并且抑制作用随芘处理浓度的提高而增强;芘对玉米根系的影响要大于对茎叶的影响。不同浓度芘处理下玉米根系形态学参数发生了显著的变化,与对照相比,芘处理下根直径显著降低,根质量长度、根质量面积和根质量体积显著增大,且随芘处理浓度的提高其效应更显著。     

甲胺磷对土壤中磷酸酶和脱氢酶活性的影响

报道了土壤中施入不同浓度有机磷杀虫剂甲胺磷（ｍｅｔｈａｍｉｄｏｐｈｏｓ）后对土壤磷酸酶和脱氢酶活性的影响。结果表明：甲胺磷对脱氢酶和３种磷酸酶的活性均有不同程度的抑制。其抑制强度和作用时间随浓度升高而加剧和延长，但随着时间的推移，这种抑制作用逐渐消失，并产生微弱的刺激效应，甲胺磷对土壤酸酶活性的影响大于中性和碱性磷酸酶。初步讨论了酶活性与微生物生长的变化情况。     

紫茉莉β-谷甾醇对镉处理的浓度响应及其化感效应

外来入侵植物紫茉莉(Mirabilis jalapa)对镉(Cd)具有一定的富集能力,但对其他植物也会产生化感效应,其植株体内已被检测到甾醇类物质,对其他植物的种子萌发和幼苗生长会产生不同程度的影响。虽然有关紫茉莉对作物化感效应方面已有一些研究,但大多是在非重金属污染条件下进行,有关Cd处理下紫茉莉化感效应的报道甚少。采用室内水培法研究不同Cd浓度处理下外来入侵植物紫茉莉根系分泌物对黄豆和玉米的化感效应,以及紫茉莉植株和根系分泌物中化感物质β-谷甾醇含量和Cd处理下外源添加不同浓度β-谷甾醇(0、0.125、0.5、1、2 mg·L^-1)对黄豆和玉米的化感效应。结果表明,不同Cd浓度处理下,紫茉莉根系分泌物会对2种作物产生化感抑制作用,但对黄豆的抑制作用高于玉米。紫茉莉根部β-谷甾醇含量显著高于茎、叶;根部β-谷甾醇含量在高浓度Cd处理下显著减少,其根分泌物中β-谷甾醇含量则显著增加。Cd处理下外源添加0.125 mg·L^-1β-谷甾醇时,黄豆和玉米种子发芽及幼苗生长均受到显著抑制,其他β-谷甾醇处理浓度对玉米幼苗生长则表现为促进作用,黄豆则...     

油菜根系分泌物对不同作物幼苗生长的化感效应

在实验室采用发芽试验的方法研究了油菜Brassicacampestris根系分泌物对小麦、油菜、蚕豆和玉米种子活力、幼苗生长发育及生理生化特性造成的化感效应。结果表明,油菜根系分泌物的化感累加作用对不同作物种子发芽率、幼苗芽长、芽质量、根长、根质量、根系活力以及幼芽过氧化物酶(POD)活性和丙二醛(MDA)含量均具有显著影响,其化感效应对小麦的影响程度最弱,其中对小麦的种子发芽率、幼苗根长、芽干物质量、POD活性和根系活力以及各作物幼芽细胞膜的毒害程度均表现出促进作用,而对小麦幼苗其它生长特性以及油菜、蚕豆和玉米幼苗的所有生长特性均表现为抑制作用,表明油菜根系分泌物对不同作物及不同生长特性的化感效应具有不同的选择性。因此,合理搭配油菜作物的间、套、轮作是其夺取优质、高产栽培的关键技术。     

Rapid,recurring, structured survey versus bioblitz for generating biodiversity data and analysis with a multispecies abundance model

A bioblitz inexpensively and quickly generates biodiversity data, but bioblitzes are often conducted with haphazard, unreplicated sampling. Results tend to be taxonomically, geographically, or temporally biased, lack metadata, and consist of lists of observed taxa that do not enable further analyses or correction for imperfect detection. A rapid, recurring, structured survey (RRSS) uses a structured sampling design and temporal and spatial replication to survey randomly selected sites on a conservation property. We participated in a loosely structured bioblitz and a subsequent RRSS at Big Canoe Creek Nature Preserve in Springville (St. Clair County), Alabama (USA) to compare observed richness derived from the 2 survey approaches. The RRSS data structure enabled us to fit models that accounted for imperfect detection to estimate abundances, occupancy probabilities, and habitat associations. The loosely structured bioblitz data could not be used in such models. We present a new integrated multispecies abundance model that we applied to avian RRSS data. Our model extension enables estimation for the community, employs data augmentation to estimate the number of undetected species, and incorporates covariates. The RRSS generated a more comprehensive and less biased list of observed taxonomic richness than the loosely structured bioblitz (e.g., 73 vs. 45 bird species and 104 vs. 63 insect families from the RRSS vs. loosely structured bioblitz, respectively). Models fit to the RRSS data identified seasonal patterns in avian community composition and allowed for estimation of habitat–occupancy relationships for insect taxa. The RRSS protocol has potential for broad transferability as a standardized, quick, and inexpensive way to inventory biodiversity and estimate ecological parameters while providing an outreach opportunity.     

Compliance with and ecosystem function of biodiversity offsets in North American and European freshwaters

Land-use change via human development is a major driver of biodiversity loss. To reduce these impacts, billions of dollars are spent on biodiversity offsets. However, studies evaluating offset project effectiveness that examine components such as the overall compliance and function of projects remain rare. We reviewed 577 offsetting projects in freshwater ecosystems that included the metrics project size, type of aquatic system (e.g., wetland and creek), offsetting measure (e.g., enhancement, restoration, and creation), and an assessment of the projects’ compliance and functional success. Project information was obtained from scientific and government databases and gray literature. Despite considerable investment in offsetting projects, crucial problems persisted. Although compliance and function were related to each other, a high level of compliance did not guarantee a high degree of function. However, large projects relative to area had better function than small projects. Function improved when projects targeted productivity or specific ecosystem features and when multiple complementary management targets were in place. Restorative measures were more likely to achieve targets than creating entirely new ecosystems. Altogether the relationships we found highlight specific ecological processes that may help improve offsetting outcomes.     

A palaeo-hydrogeological model for arsenic contamination in southern and south-east Asia

An argument is presented in which areas of natural arsenic contamination of modern groundwaters throughout Asia have a common origin. Arsenic originally accumulated in oceanic ferro-manganoan sediments of the eastern Palaeo-Tethys. This was further concentrated through oceanic crustal extinction in what later became the south-east Chinese accreted mineralised terrain. Proto-Himalayan uplift of this area created the palaeo-drainage systems of the Ganges – Brahmaputra, Irrawaddy, Mekong, and Red Rivers, with consequent headwater erosion of arsenic-rich sediments. Their downstream deposition as immature and easily redistributed Neogene sandstones, silts, and iron-rich clays has created secondary and tertiary reservoirs of adsorbed and authigenic arsenic, from which the current arsenic-rich groundwaters have evolved. Considering river basins within the above palaeo-hydrogeological framework provides a basis for assessing the risk of arsenic in groundwater basins of south and south-eastern Asia.     

Cost‐effective conservation of an endangered frog under uncertainty

How should managers choose among conservation options when resources are scarce and there is uncertainty regarding the effectiveness of actions? Well‐developed tools exist for prioritizing areas for one‐time and binary actions (e.g., protect vs. not protect), but methods for prioritizing incremental or ongoing actions (such as habitat creation and maintenance) remain uncommon. We devised an approach that combines metapopulation viability and cost‐effectiveness analyses to select among alternative conservation actions while accounting for uncertainty. In our study, cost‐effectiveness is the ratio between the benefit of an action and its economic cost, where benefit is the change in metapopulation viability. We applied the approach to the case of the endangered growling grass frog (Litoria raniformis), which is threatened by urban development. We extended a Bayesian model to predict metapopulation viability under 9 urbanization and management scenarios and incorporated the full probability distribution of possible outcomes for each scenario into the cost‐effectiveness analysis. This allowed us to discern between cost‐effective alternatives that were robust to uncertainty and those with a relatively high risk of failure. We found a relatively high risk of extinction following urbanization if the only action was reservation of core habitat; habitat creation actions performed better than enhancement actions; and cost‐effectiveness ranking changed depending on the consideration of uncertainty. Our results suggest that creation and maintenance of wetlands dedicated to L. raniformis is the only cost‐effective action likely to result in a sufficiently low risk of extinction. To our knowledge we are the first study to use Bayesian metapopulation viability analysis to explicitly incorporate parametric and demographic uncertainty into a cost‐effective evaluation of conservation actions. The approach offers guidance to decision makers aiming to achieve cost‐effective conservation under uncertainty.     

Threats to intact tropical peatlands and opportunities for their conservation

Large, intact areas of tropical peatland are highly threatened at a global scale by the expansion of commercial agriculture and other forms of economic development. Conserving peatlands on a landscape scale, with their hydrology intact, is of international conservation importance to preserve their distinctive biodiversity and ecosystem services and maintain their resilience to future environmental change. We explored threats to and opportunities for conserving remaining intact tropical peatlands; thus, we excluded peatlands of Indonesia and Malaysia, where extensive deforestation, drainage, and conversion to plantations means conservation in this region can protect only small fragments of the original ecosystem. We focused on a case study, the Pastaza‐Marañón Foreland Basin (PMFB) in Peru, which is among the largest known intact tropical peatland landscapes in the world and is representative of peatland vulnerability. Maintenance of the hydrological conditions critical for carbon storage and ecosystem function of peatlands is, in the PMFB, primarily threatened by expansion of commercial agriculture linked to new transport infrastructure that is facilitating access to remote areas. There remain opportunities in the PMFB and elsewhere to develop alternative, more sustainable land‐use practices. Although some of the peatlands in the PMFB fall within existing legally protected areas, this protection does not include the most carbon‐dense (domed pole forest) areas. New carbon‐based conservation instruments (e.g., REDD+, Green Climate Fund), developing markets for sustainable peatland products, transferring land title to local communities, and expanding protected areas offer pathways to increased protection for intact tropical peatlands in Amazonia and elsewhere, such as those in New Guinea and Central Africa which remain, for the moment, broadly beyond the frontier of commercial development.     

Parasitic wasps orient to green leaf volatiles

Summary Undamaged plants emit low levels of green leaf volatiles (GLVs), while caterpillar-damaged and artificially damaged plants emit relatively higher levels of certain GLVs. Female braconid parasitoids,Microplitis croceipes, oriented to both damaged plants and to individual GLVs in no-choice tests in a wind tunnel, but seldom oriented to undamaged plants. Female ichneumonid parasitoids,Netelia heroica, also oriented to individual GLVs in a wind tunnel. Males of both wasp species failed to orient to the GLVs. These data show that leaf-feeding caterpillars can cause the release of GLVs, and that parasitic wasps can respond to these odors by flying upwind (chemoanemotactic response), which brings the wasps to their caterpillar hosts. This supports the hypothesis that plants communicate with members of the third trophic level,i.e., plants under herbivore attack emit chemical signals that guide natural enemies of herbivores to sites of plant damage. In this interaction, the GLVs serve as tritrophic plant-to-parasitoid synomones. That parasitoids from two different wasp families oriented to GLVs suggests that the response may be widespread among the Hymenoptera.Mention of a commercial or proprietary product does not constitute an endorsement by the U.S. Department of Agriculture     

Human Influence and Classical Biogeographic Predictors of Rare Species Occurrence

Biogeographic theory predicts that rare species occur more often in larger, less‐isolated habitat patches and suggests that patch size and connectivity are positive predictors of patch quality for conservation. However, in areas substantially modified by humans, rare species may be relegated to the most isolated patches. We used data from plant surveys of 81 meadow patches in the Georgia Basin of Canada and the United States to show that presence of threatened and endangered plants was positively predicted for patches that were isolated on small islands surrounded by ocean and for patches that were isolated by surrounding forest. Neither patch size nor connectivity were positive predictors of rare species occurrence. Thus, in our study area, human influence, presumably due to disturbance or introduction of competitive non‐native species, appears to have overwhelmed classical predictors of rare species distribution, such that greater patch isolation appeared to favor presence of rare species. We suggest conservation planners consider the potential advantages of protecting geographically isolated patches in human‐modified landscapes because such patches may represent the only habitats in which rare species are likely to persist. Influencia Humana y Predictores Biogeográficos Clásicos de la Ocurrencia de Especies Raras     

Seasonal dynamics of macro-algae in the South Lake of Tunis

The macro-algae communities observed in the south lake of Tunis are characterized by the predominance of nitrophilous algae which are in the order of biomass importance:Ulva, Cladophora andEnteromorpha. We have noted seasonal changes of alga distribution. The wind appears to be one of the most important factors influencing this distribution. The total biomass reaches a maximum in the spring. Rapid decomposition of the biomass leads to a severe ecological imbalance, resulting in crises of anoxia and fish death. A restoration project has already started. It aims at removal of contaminated muds and the introduction of a new circulation system. The main objectives of this work were to collect information on the distribution and biomass of the phytobenthic communities as a first step in the constitution of a database for further comparison.     

Patterns and biases of climate change threats in the IUCN Red List

International Union for Conservation of Nature (IUCN) Red List assessments rely on published data and expert inputs, and biases can be introduced where underlying definitions and concepts are ambiguous. Consideration of climate change threat is no exception, and recently numerous approaches to assessing the threat of climate change to species have been developed. We explored IUCN Red List assessments of amphibians and birds to determine whether species listed as threatened by climate change display distinct patterns in terms of habitat occupied and additional nonclimatic threats faced. We compared IUCN Red List data with a published data set of species’ biological and ecological traits believed to infer high vulnerability to climate change and determined whether distributions of climate change‐threatened species on the IUCN Red List concur with those of climate change‐threatened species identified with the trait‐based approach and whether species possessing these traits are more likely to have climate change listed as a threat on the IUCN Red List. Species in some ecosystems (e.g., grassland, shrubland) and subject to particular threats (e.g., invasive species) were more likely to have climate change as a listed threat. Geographical patterns of climate change‐threatened amphibians and birds on the IUCN Red List were incongruent with patterns of global species richness and patterns identified using trait‐based approaches. Certain traits were linked to increases or decreases in the likelihood of a species being threatened by climate change. Broad temperature tolerance of a species was consistently related to an increased likelihood of climate change threat, indicating counterintuitive relationships in IUCN assessments. To improve the robustness of species assessments of the vulnerability or extinction risk associated with climate change, we suggest IUCN adopt a more cohesive approach whereby specific traits highlighted by our results are considered in Red List assessments. To achieve this and to strengthen the climate change‐vulnerability assessments approach, it is necessary to identify and implement logical avenues for further research into traits that make species vulnerable to climate change (including population‐level threats).