扎龙湿地不同生境芦苇功能性状变异及其对土壤因子的响应

物种的遗传特征和外在环境条件的差异共同决定了植物功能性状的表达,植物功能性状可以反映物种对环境条件的适应策略。采用大样本抽样调查与统计分析方法,比较研究扎龙湿地4种生境（盐碱生境、旱生生境、湿生生境和水生生境）芦苇分株和叶功能性状,分析不同生境芦苇功能性状的分异规律及其对土壤因子的响应。结果表明：（1）不同生境芦苇功能性状均表现出中等程度变异。其中分株和叶性状均以盐碱生境最低（P<0.05）,分株及除叶面积和比叶面积以外的叶性状均以水生生境最高;株高和株重在种群内的变异系数为15.96%-48.61%和38.65%-87.82%,种群间的变异系数为46.58%和66.39%;叶性状在种群内的变异系数为13.21%-72.37%,种群间的变异系数为26.46%-57.03%;（2）不同生境芦苇功能性状间存在协同变化特征。芦苇的株高、株重、叶长、叶宽、叶面积和叶重之间均呈极显著正相关关系（P<0.01）,比叶面积与其他性状的相关性因生境不同存在一定变化;（3）不同生境芦苇的原位土壤因子表现出异质性特征,芦苇功能性状的变异是含水量、pH、有机质和速效氮等土壤因子综合作用的结果。其中含水量、有机质和速效氮为正向驱动,而pH为负向驱动。因此,芦苇通过自我调节功能性状更好地适应不同的生存环境,局域尺度不同生境的土壤因子是引起芦苇功能性状产生分异的导因。     

Changes in Endogenous Fatty Acids and Lipid Synthesis Associated with Copper Pollution in Fucus spp

Fatty acid synthesis from [¹⁴C]acetate was studied in the brownalgae, Fucus serratus and Fucus vesiculosus, which had beencollected from sites polluted by run-off from old copper mines.Algae collected from areas exposed to copper in situ showedchanges in the pattern of fatty acids labelled in vitro withan increase in oleate labelling and a decrease in palmitatelabelling in both species. The endogenous fatty acid patternsfor algae from polluted sites also differed from those fromunpolluted sites. Algae from sites polluted by copper containedmore oleate than samples from non-polluted sites. In addition,there were decreases in the polyunsaturated fatty acids -linolenate,octadecatetraenoate and docosapentaenoate for copper-exposedalgae. These differences are discussed with regard to the possiblemetabolic site of copper's action and to the relative toleranceof Fucus spp. to high environmental dissolved copper levels. Key words: Fucus spp., Copper pollution, Fatty acid synthesis     

Genomic pattern of adaptive divergence in Arabidopsis halleri, a model species for tolerance to heavy metal

Pollution by heavy metals is one of the strongest environmental constraints in human-altered environments that only a handful of species can cope with. Identifying the genes conferring to those species the ability to grow in polluted areas is a first step towards a global understanding of the evolutionary processes involved and will eventually improve phytoremediation practices. We used a genome-scan approach to detect loci under divergent selection among four populations of Arabidopsis halleri growing on either polluted or nonpolluted habitats. Based on a high density of amplified fragment length polymorphism (AFLP) markers (820 AFLP markers, i.e. ~1 marker per 0.3 Mb), evidence for selection was found for some markers in every sampled population. Four loci departed from neutrality in both metallicolous populations and thus constitute high-quality candidates for general adaptation to pollution. Interestingly, some candidates differed between the two metallicolous populations, suggesting the possibility that different loci may be involved in adaptation in the different metallicolous populations.     

Morphological, Anatomical and Physiological Responses Related to Differential Shoot vs. Root Growth Inhibition at Low Temperature in Spring and Winter Wheat

Several morphological, anatomical and physiological changesand their relationship with differential root vs. shoot growthinhibition at low temperature (5°C) were studied in springand winter wheat cultivars. Root:shoot ratios, expressed eitheras a function of root and shoot fresh weight or as a functionof root and leaf areas, increased at low temperature and thisincrement was more pronounced in spring cultivars than in winterones. Although winter cultivars developed relatively smallerroot systems at 5°C, this characteristic was counterbalancedby a lower stomatal frequency and increased thickness of epidermalcell walls in leaves unfolded at this temperature, relativeto spring cultivars. Likewise, at 5°C a decrease in theosmotic potential of shoots and roots was observed in parallelwith sugar accumulation; this decrease was more marked in wintercultivars. These results indicate a differential morpho-anatomicaland physiological plasticity of winter and spring cultivarsduring development at low temperature. The possible associationbetween these changes and plant water economy at low temperaturesis discussed. Copyright 2001 Annals of Botany Company Spring wheat, winter wheat, Triticum aestivum, low temperature, root:shoot ratio, root surface area, stomatal frequency, osmotic potential     

Histochemical Localization of Phenolic Deposits in Leaf Blades of Eragrostis racemosa

The distribution of phenolic deposits in the leaves of Eragrostisracemosa from different habitats was investigated during cultivationunder uniform environmental conditions. The plants retainedtheir leaf phenolic distribution pattern over a period of 8months. Plants from dry habitats had phenolic inclusions inboth epidermal layers, whereas phenolic deposits were absentor only occurred in the abaxial epidermal layers of plants occupyingmoist habitats. Eragrostis racemosa, narrow-heart love grass, Poaceae, phenolic deposits, epidermis, histochemistry, anatomy     

Anatomical responses of leaves of Black Locust (<Emphasis Type="Italic">Robinia pseudoacacia</Emphasis> L.) to urban pollutant gases and climatic factors

This study investigates responses in the leaf anatomy of Black Locust (Robinia pseudoacacia L.) to the atmospheric pollutants, SO₂, NO₂ and O₃ and climate in Tehran. The anatomical variables studied include thickness of the leaf lamina and of its main constituent tissues and the length and density of stomata. We present evidence that, in response to urban air pollution, the spongy mesophyll layer is thinner, the upper cuticle of the leaf thicker and stomatal density and the ratio of palisade parenchyma to spongy parenchyma are increased. Similar responses were also detected in relation to a climatic gradient. Stomatal density and thickness of the leaf lamina and of its mesophyll layer were all higher under warmer drier conditions. This overlap in anatomical response to two very different suites of environmental variables may reflect a functional overlap between mechanisms designed to restrict water loss in dry climates and those that minimize the uptake of toxic gases in polluted habitats.     

Allometry ofUrtica urens in polluted and unpolluted habitats

The allometry ofUrtica urens (small nettle), an important medicinal plant in many countries, growing in an area near pollution sources and an area away from pollution sources was determined. The allometric coefficients were determined for nonlinear relationships between plant height, stem width, root length, petiole length, leaf dry weight, petiole dry weight, leaf length, leaf width, leaf area and specific leaf area. The slopes of the linear equations were determined for the above parameters. The results showed that there is a difference in the allometry of different parts ofU. urens growing in these two areas. Air pollutants reduced the plant height, stem width, root length and petiole length and increased leaf parameters. The same pattern of growth was reflected by comparing the slopes of the straight lines of the parts of the plants growing in the two areas.     

Diversity and divergence in Cistus salvifolius (L.) populations from contrasting habitats

Cistus salvifolius L. is a widespread Mediterranean shrub, occurring over a wide range of environments. Given the degree of habitat differentiation, and geographic isolation of some populations, adaptation to local conditions and hence population divergence might be expected to have occurred. To test this hypothesis morphology and allozyme diversity was measured in 13 populations collected from contrasting habitats around the Mediterranean. Leaf morphology (length, width and petiole length) and internode length varied widely between populations. Leaf width and internode length were negatively correlated with longitude, and leaf length was negatively correlated with mean rainfall. All populations were polymorphic at all allozyme loci studied, and no populations showed significant difference between levels of expected and observed heterozygotes. Allelic diversity (Hs) within populations was high, and populations from the more extreme sites showed no decrease in diversity or predominance of rare genotypes, suggesting there is little selection for characters favouring survival in local conditions. Some populations from highly contrasting habitats, in terms of rainfall, appeared to be genetically similar. However, there were differences between some populations, in areas less than 1 km apart, which have similar geography and climate. Results suggest that the C. salvifolius populations examined may not be as adapted to local environmental conditions as expected. Periodic fires, gene flow, and environmental heterogeneity may all help maintain genetic diversity and hinder adaptation.     

Phenotypic Characterization of <i>Oryza nivara</i> (Sharma <i>et</i> Shastry) Collected from Different Ecological Niches of Sri Lanka

Information on the genetic diversity of wild rice species in Sri Lanka is relatively meagre, though it plays a key role in crop improvement programs of cultivated rice (Oryza sativa L.). The present study was carried out to identify the morphological variation pattern of the wild populations of O. nivara in Sri Lanka. Seven populations (P1 to P7) collected from different agro-ecological regions were characterized in a common garden based on nine morphological traits. The findings revealed a high level of phenotypic variation between populations when compared to within a population. The most variable traits were the flag leaf panicle neck length (FLPNL) and flag leaf angle (FLA), whereas the least variable trait was the flag leaf length (FLL). Box plots clearly illustrated the large differentiation of phenotypic traits in the entire distribution of wild rice populations. The cumulative values of the two principal components, i.e., FLPNL and FLA, explained 58.7% of the total variance. Populations from similar natural habitats clustered together. The P7 was adapted to intercept more sunlight by increasing flag leaf width (FLW) and FLA to compete with weeds and other shrubs. P2 and P5 were the most closely related populations representing approximately similar ecological conditions of the dry zone. The P3 population from the intermediate zone showed a vigorous plant growth with the highest plant height, culm girth and awn length (P < 0.05). Knowledge of such morphological diversity would facilitate designing conservation strategies and basic information for the proper utilization of wild resources in rice genetic improvement.     

Enhanced reproductive success revealed key strategy for persistence of devastated populations in Himalayan food‐deceptive orchid,Dactylorhiza hatagirea

Anthropogenic disturbances adversely affect populations of rare and endemic plants, resulting in reduction of their population size and performance. Among different plant groups, deceptive terrestrial orchids are vulnerable and possess greater extinction risks because of rarity in occurrence. To understand the response of food‐deceptive terrestrial orchids to disturbances, we selected Dactylorhiza hatagirea as our representative species, which is endemic to Himalaya, and studied its natural populations. This species is rare for being habitat specific, pollination limited and threatened in its natural habitats. We tested the hypothesis that disturbances lead to reduction in population size and plant performance of food‐deceptive terrestrial orchids. For assessing the impact of disturbance, two contrasting groups, heavily devastated (HD) and lightly devastated (LD), were identified on the basis of frequency and intensity of disturbance (harvesting of plant for tubers) by interviewing local people, medicinal plant extractors and shepherds. HD sites, in comparison to LD sites, were found to have smaller population sizes, but showed an increase in plant growth traits (plant height, specific leaf area, leaf N and specific shoot length). Similarly, plants at HD sites were found to have invested less in inflorescence (inflorescence size, inflorescence length, inflorescence length fraction and flowers per length), but despite that showed higher reproductive success. This was a clear indication of enhanced performance of its populations driven by disturbances. Our findings suggested that food‐deceptive species in small populations tend to reduce the probability of population extinction and have the capability to recover rapidly if conserved in time.     

Kudzu (Pueraria montana): History,Physiology, and Ecology Combine to Make a Major Ecosystem Threat

Kudzu, Pueraria montana (Lour.) Merr. variety lobata (Willd.) was introduced into the United States at the 1876 Centennial Exposition in Philadelphia, PA. Subsequently, it was planted widely to reduce soil erosion by the Soil Erosion Service and Civilian Conservation Corp. Over 85 million seedlings of kudzu were provided to landowners by government agencies in the southeast in the first half of the 20th century. In 1953, kudzu was removed from the list of approved plants for erosion control, in 1970 it was officially labeled a weed, and in 1997 it was placed on the Federal Obnoxious Weed List. Its rapid elongation rates, high leaf area indices, high photosynthetic rates, and frequent rooting at stem nodes make kudzu an aggressive competitor with native shrubs and trees. Estimates are that kudzu currently covers 3 million hectares throughout the eastern United States and is spreading by 50,000 ha per year. Despite widespread anecdotal statements, little quantitative information is available regarding the ecological effects of kudzu. The ability of kudzu to overtop and shade forest trees, fix atmospheric nitrogen, and emit isoprene suggest that it may have substantial effects on native forest biodiversity, forest nitrogen cycles, watershed nitrogen saturation, freshwater eutrophication, and regional air quality. Kudzu's growth rate increases strongly in response to increased CO₂, and without the constraint of allocation to woody tissue this response may increase the competitive dominance of kudzu as atmospheric levels of CO₂ increase. This fact, combined with its sensitivity to cold temperatures, implies that kudzu may increase its range in future warmer, high-CO₂ environments. The lack of quantitative investigations on the ecological effects of kudzu is a severe impediment to our understanding of its current and future effects on native plant and animal communities and forest ecosystems.     

Biology and preliminary host range assessment of two potential kudzu biological control agents

Two insect species from China, Gonioctena tredecimmaculata (Jacoby) (Coleoptera: Chrysomelidae) and Ornatalcides (Mesalcidodes) trifidus (Pascoe) (Coleoptera: Curculionidae), were studied in quarantine in the United States as potential biological control agents for kudzu, Pueraria montana variety lobata (Willd.) Maesen and S. Almeida. Adults of G. tredecimmaculata were ovoviviparous and reproduced throughout the summer, producing offspring that had an obligate adult diapause. In no-choice tests, adult and larval G. tredecimmaculata rejected most of the plant species tested, but consumed foliage and completed their life cycle on soybean (Glycine max L. Merr.) and on a native woodland plant, hog-peanut (Amphicarpaea bracteata L. Fernald), which are in the same subtribe as kudzu (Glycininae). Insects showed similar responses to field- and greenhouse-grown soybean and kudzu foliage, despite measurable differences in leaf traits: field-grown foliage of both plants had greater leaf toughness, higher total carbon content, higher trichome density, and lower water content than greenhouse foliage. O. trifidus adults also rejected most of the plants tested but fed on and severely damaged potted soybean and hog-peanut plants in addition to kudzu. Further tests in China are needed to determine whether these species will accept nontarget host plants under open-field conditions.     

From Asian curiosity to eruptive American pest: Megacopta cribraria (Hemiptera: Plataspidae) and prospects for its biological control

The kudzu bug or bean plataspid, Megacopta cribraria (Fabricius), is native to Asia where it appears to be widely distributed (although the taxonomy is not entirely clear), but is infrequently a pest of legumes. This bug appeared in 2009 in the southeastern United States, where it is closely associated with kudzu, Pueraria montana Lour. [Merr.] variety lobata [Willd.] Maesen & S. Almeida. However, the insect has become a consistent economic pest of soybeans, Glycine max (L.) Merr., and some other leguminous crops in areas where large numbers can build in kudzu, in addition to being a considerable nuisance in urban landscapes where kudzu occurs. The insect has remarkable capacity for movement and has spread rapidly from nine Georgia counties in 2009 to seven states in 2012. Despite being a nuisance in urban areas and a crop pest, high populations of the bug also reduce the biomass of kudzu, which is itself a seriously problematic invasive weed, complicating the status of M. cribraria in its expanded range. Extant predators and a pathogen in the US have been observed attacking kudzu bugs in the laboratory and field, but no parasitism of eggs or nymphs has been observed to date. A single record of parasitism of an adult kudzu bug by a tachinid fly is known from the US, but no other adult parasitism has been observed in the US or elsewhere. Extant enemies may eventually significantly reduce the bug’s populations, but at present native enemies appear to be insufficient for the task, and exotic enemies from the kudzu bug’s native range may offer the best possibility for effective biological control in the US. Based on the available literature, the best option for an importation biological control program appears to be the platygastrid egg parasitoid Paratelenomus saccharalis (Dodd) because of its apparent host specificity, intimate biological linkages with M. cribraria, and wide geographic distribution in the Eastern Hemisphere. Other natural enemies may eventually emerge as good candidates for importation, but at present P. saccharalis appears to be the most promising.     

Effects of Flooding and Drought on the Anatomy of Paspalum dilatatum

Paspalum dilatatum occupies different topographic positionsin the Flooding Pampa, Argentina. Populations from differentpositions are subjected to various regimes of flooding and drought,both of which may occur in the same growing season. We investigatedthe constitutive and plastic anatomical traits of P. dilatatumpopulations from habitats with contrasting regimes of floodingand drought. Both events affected root and sheath anatomy, andthese effects were similar for clones from different topographicpositions. Flooding increased the aerenchymatous tissue in theroot cortex and the leaf sheaths and decreased the number ofroot hairs per unit of root length. Drought decreased the diameterof root metaxylem vessels, thus lowering the risk of embolismsand increasing water-flow resistance, and increased the numberof root hairs, thereby increasing water uptake ability. In additionto these plastic responses, all clones showed constitutive characteristicsthat may confer an ability to withstand sudden events of floodingor drought: a high proportion of aerenchyma, which may maintainaeration before plastic responses take place; sclerenchyma,which may prevent root and leaf sheath collapse by soil compaction;and a conspicuous endodermis, which may protect stelar tissuesfrom desiccation. Both constitutive and plastic anatomical characteristicsare likely to contribute to the ability of this species to occupywidely different topographic positions and to resist temporalvariations in water and oxygen availability. Copyright 2001Annals of Botany Company Flooding, drought, aerenchyma, vessels, roots, leaf sheaths, anatomy, Paspalum dilatatum Poir     

The distribution of Stigeoclonium tenue Kütz. in South Wales in relation to its use as an indicator of organic pollution

The distribution and frequency of Stigeoclonium tenue Kütz. in some South Wales rivers were studied for 12 months to assess the value of the alga as an indicator of organic pollution. It colonised organically polluted areas at most times of the year, and generally in greater abundance as compared with cleaner stations. Tolerance was observed over a wide range of a number of environmental factors: pH, water temperature, suspended solids content, flow, nitrate, nitrite and ammonia nitrogen, phosphate phosphorus, dissolved oxygen, B.O.D., electrical conductivity, chloride, total hardness, magnesium hardness and calcium hardness. Greatest tolerance was expressed mainly in the spring months when the organism became widely distributed in diverse habitats ranging from organically polluted to fairly clean conditions. Some precautions in the use of S. tenue as an indicator of organic pollution are therefore suggested. In particular, the frequency of the organism should be noted especially in spring, since organic conditions are suspect only when the alga is highly abundant.     

Resource-mediated effects of stream pollution on food absorption of Asellus aquaticus (L.) populations

The role of interactions between chemical perturbations and biological constraints on detritivores occurring in polluted streams were investigated by analysing food absorption variation with stress. Absorption rate and efficiency of four Asellus aquaticus (L.) populations from differently polluted habitats were quantified with respect to the microbial guilds colonizing detritus. A twin tracer method was used. Detritus was microbially colonized in standard conditions and on each stream bottom to control for potential resource-independent variations among individuals. The relationship between length and weight was also determined on a random sample of individuals of each population. Differences of 14.6% in potential absorption efficiency and 11.3% in potential absorption rate were observed between populations from the least and the most polluted habitat. Actual (realized) variations were much stronger: from a minimum of a 60.1% reduction in absorption efficiency to a maximum of 93.8% for the rate. The realized food absorption and the individual weight per length showed the same pattern of variation among populations. This suggested that the availability of energy to isopods in nature was related to stream pollution and resource quality. Bottomup interactions appear to be the most relevant pathway through which chemical water pollution affects the Asellus populations studied. The potential resource-independent variations among individuals are also likely to be explained by temporal cascading of resource-mediated effects.     

Leaf fluctuating asymmetry of common plantain as an indicator of habitat quality

Abstract

Although developmental instability (DI), measured as fluctuating asymmetry (FA), is expected to be positively related to environmental stress and negatively to habitat quality, the pattern found here was the reverse. Developmental instability of leaf traits (leaf width and vein distances within a leaf) was estimated (using two indices of FA: FA₄ and σ_i ²) and compared between three populations of Plantago major L. (Plantaginaceae) from northern Serbia. Two of the populations are from chronically polluted areas (Karaburma & Zemun), while Crni Lug is from an unpolluted, natural area. Results obtained using both FA indices were the same; higher asymmetry levels in the unpolluted area than in the polluted sites, were found for both traits. Between the two polluted sites, FA values were significantly higher in Karaburma site for vein distances within a leaf. Concerning differences in FA₄ values between samples, in two cases, results are similar to those found for σ_i ² values, for vein distances within leaf. These are the first quantitative data on P. major indicating that (i) plants living in the stressful sites are more symmetrical and (ii) leaf FA for plant species with wide ecological distribution such as P. major should be considered as an ‘index of habitat quality.’     

Effect of the Rht3 dwarfing gene on dynamics of cell extension in wheat leaves, and its modification by gibberellic acid and paclobutrazol

The second leaf of wheat was used as a model system to examinethe effects of the Rht3 dwarfing gene on leaf growth. Comparedto the rht3 wild type, the Rht3allele decreased final leaf length,surface area and dry mass by reducing the maximum growth rates,but without affecting growth duration. Gibberellic acid (GA₃)increased final leaf length and maximum growth rate in the rht3wild type, but was without effect on the Rht3 mutant, whichis generally regarded as being non-responsive to gibberellin(GA). Paclobutrazol, an inhibitor of GA biosynthesis, decreasedfinal leaf length and maximum growth rate in the rht3 wild typeto values similar to those in the untreated Rht3 mutant. NeitherGA₃ nor paclobutrazol affected the duration of leaf growth.The decrease in leaf length was produced by reduction of celllength rather than cell number. The maximum relative elementalgrowth rate (REGR) for cell extension was essentially the samein all treatments, as was the time between the cells leavingthe meristem and achieving maximum extension rate. The differencesbetween the genotypes and treatments were all almost entirelydue to differences in the time taken from the attainment ofmaximum REGR of cell extension to the cessation of extension.This was reflected in the length of the extension zone, whichwas approximately 6–8 per cent of final leaf length. Theeffects of the Rht3 allele, GA₃ and paclobutrazol all appearto be on the processes which promote the cessation of cell elongation. Key words: Cell extension, gibberellin, leaf growth, Rht3 gene, Triticum, wheat     

Biomass Allocation of Erythronium americanum Populations in Different Irradiance Levels

The forest herb Erythronium americanum was collected from threeNew Jersey habitats and grown in 100%, 43%, or 23% glasshouselight to determine if biomass allocation responses to irradiancediffered between populations. Shaded plants had longer petioles,produced fewer runners, and had greater specific leaf areasthan unshaded plants; these responses did not differ significantlyamong populations. All populations produced smaller bulbs whengrown in shade. Over all light treatments, mean leaf area ofplants from a stable, established site was greater than thatof plants from others. In 100 % light, these plants had thegreater bulb growth. The simple architecture of Erythroniummay constrain morphological responses to the light environment. Erythronium americanum(Ker.), forest herb, biomass allocation, light intensity     

Differences in the abundance and distribution of copepods in two estuaries of the Basque coast (Bay of Biscay) in relation to pollution

The abundance and spatial distribution of copepod species werecompared in the euhaline region of the polluted estuary of Bilbao[mean biological oxygen demand (BOD): 49748.05 kg day^–1in 1996] and the unperturbed estuary of Urdaibai. Sampling wasperformed at fixed salinity sites, where data of temperature,dissolved oxygen saturation, particulate organic matter, Secchidisk depth and chlorophyll were also obtained. Differences betweenthe estuaries and within the estuaries for environmental variablesand copepod abundances were tested statistically. The dominantspecies Acartia clausi and Paracalanus parvus differed significantlyin abundance between estuaries, and most of neritic speciesdiminished more drastically with decreasing salinity in Bilbaoby the effect of pollution. The different responses observedamong species in relation to pollution and water desalinationare discussed. The lack of the brackish-water species in Bilbaoindicated that water quality worsening upward the estuary ofBilbao not only limited the penetration of neritic species butalso prevented the development of autochthonous estuarine species.At the outer euhaline region of Bilbao, however, pollution wasfound to be low enough to enhance the development of tolerantneritic species that are favoured under moderate pollution conditions.Results indicate that comparisons of copepod abundances anddistributions with salinity in estuaries may be a useful toolto evaluate the health of the different estuarine pelagic habitats.