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21.
GEORGE F. ANTONIOUS JOHN C. SNYDER 《Journal of environmental science and health. Part. B》2013,48(1):43-55
The potential of using phytochemicals from leaves of wild tomato for controlling the two-spotted spider mite, Tetranychus urticae Koch, is explored in this study as a promising alternative to the use of synthetic pesticides. Wild tomato accessions of Lycopersicon hirsutum plants that are not consumed by humans were planted under greenhouse conditions for mass production of leaves. Crude extracts from leaves of three accessions of L. hirsutum, six accessions of L. hirsutum f. glabratum, and one accession each of L. pennellii and L. pimpinellifolium were prepared in chloroform, ethanol and hexane. Two spider mite bioassays, one a measure of antibiosis and the other a measure of repellency, were utilized to determine the acaricidal performance of the crude extracts. The bioassay for antibiosis was a 6-h no-choice test. The bioassay for repellency utilized a ring bioassay. Chloroform leaf extracts of L. hirsutum f. glabratum accessions (PI-251304, PI-134417, PI-134418, and PI-126449) exhibited greatest antibiotic activity on two-spotted spider mites; the hexane extracts exhibited greatest repellency. Extracts from PI-251304, PI-126449, PI-134417, and PI-134418 were especially lethal (chloroform) or repellent (hexane). We investigated differences in chemical composition of the crude leaf extracts that may explain the observed differences in mortality and repellency among the different accessions. Major chemical compounds (α -curcumene, α -zingiberene, trans-caryophyllene, 2-undecanone, and 2-tridecanone) known to have pesticidal efficacy were detected and quantified in the crude leaf extracts using a gas chromatograph (GC) equipped with a mass spectrometer (GC/MS). Lethality of extracts was mainly associated with the presence of high concentrations of 2-tridecanone; repellency of extracts was mainly associated with the presence of trans-caryophyllene. Leaf extracts of L. hirsutum f. glabratum accessions that contain significant quantities of 2-tridecanone and/or trans-caryophyllene could be useful for managing populations of spider mites, which could reduce reliance on synthetic pesticides. 相似文献
22.
The present study was to isolate and identify a potent algicidal compound from extract of Salvia miltiorrhiza and study the potential inhibition mechanism on Microcystis aeruginosa. Column chromatography and bioassay-guided fractionation methods were carried out to yield neo-przewaquinone A, which was identified by spectral analysis. The EC50 of neo-przewaquinone A on M. aeruginosa were 4.68 mg L−1. In addition, neo-przewaquinone A showed relatively higher security on Chlorella pyrenoidosa and Scenedesmus obliquus, with the EC50 values of 14.78 and 10.37 mg L−1, respectively. For the potential inhibition mechanisms, neo-przewaquinone A caused M. aeruginosa cells morphologic damage or lysis, increased malondialdehyde content and decreased the soluble protein content, total antioxidant and superoxide dismutase activity, and significantly inhibited three photosynthesis-related genes (psaB, psbD, and rbcL). The results demonstrated the algicidal effect of neo-przewaquinone A on M. aeruginosa and provided the possible inhibition mechanisms. 相似文献
23.
成都PM2.5与气象条件的关系及城市空间形态的影响 总被引:4,自引:2,他引:2
2013年2月1日至3月20日、2013年7月10日至8月10日对成都市大气中细颗粒物(PM2.5)进行连续监测,同步记录气象数据。将PM2.5质量浓度与城市气象条件进行相关性分析,研究气象条件对PM2.5质量浓度的影响。2月1日至3月20日PM2.5质量浓度平均为147.38μg/m3,7月10日至8月10日平均为50.19μg/m3,大气细颗粒物污染最严重的时间出现在2月1—6日。成都市各气象条件中,PM2.5质量浓度与能见度、风速呈现显著负相关,而与其他气象要素相关性较弱,降水对PM2.5质量浓度影响也很大。改善城市通风有利于成都市大气中PM2.5的稀释和消散。通过建立3D模型并运用计算流体力学(CFD)软件模拟成都市选定的一处密集的建成区域,分析城市空间形态对通风的影响。研究发现,在假设等温的情况下,多层密集的区域对城市通风影响小,而高层对城市通风影响很大,建筑高度相近的街道与风向平行的风速大于与风向成角度的,与风向平行的街道沿线为高层的风速高于沿线为多层的,较大的开敞空间及背景风速更有利于城市通风环境。 相似文献
24.
Randall J. Schaetzl L. Keith Hendrie Scott W. Kirsch 《Journal of the American Water Resources Association》1989,25(5):1023-1030
ABSTRACT: Soil water was monitored by neutron scattering in six soils, three each within two drainage catenas in east-central Illinois, over a 15-month time span. The prairie soils have formed in: (1) 76–152 cm of silt loam, eolian sediments (bess) over glacial till (Catlin-Flanagan-Drummer catena), and (2) bess greater than 152 cm in thickness (Tama-Ipava-Sable catena). We characterized the water content of these soils over the total time span and for wet and dry climatic subsets, as an aid to potential irrigation decisions. Soils of the thin bess, C-F-D catena dried out to lower water contents and had greater soil water variability than did the thick bess soils. Under wet conditions, soil water contents in the two catenas were quite similar. Alleviation of surface and subsurface drying via irrigation would thus be more advantageous to yields on the C-F-D soils than on the T-I-S soils. 相似文献
25.
Thompson DM 《Environmental management》2002,29(2):250-265
Habitat-improvement structures on the Blackledge and Salmon rivers date back to the 1930s and 1950s. Forty of these structures
were investigated to determine their long-term impact on channel morphology. These structures include designs that continue
to be used in modern restoration efforts. During the intervening period since these structures were introduced, several major
floods have affected the two channels. The floods include three flows in excess of the 50-year event, including the flood
of record, which has an estimated recurrence interval of almost 300 years. Despite the extreme flooding, many structures were
discovered in varying conditions of operation. Grade-control structures and low-flow deflectors generally create some low-flow
habitat (P = 0.815) but do not produce the depth of water predicted by design manuals (P < 0.0001). Unintended erosion has developed in response to many of the channel modifications especially along the outside of meanders.
In addition, the mode of failure of grade-control structures has created localized channel widening with associated bank erosion.
Meanwhile, cover structures have produced a 30% reduction in streamside vegetation with over 75% less overhead cover than
unaltered reaches. Based on these results, it is important for prospective designers to carefully consider the long-term impacts
of instream structures when developing future channel-restoration projects. 相似文献
26.
27.
In the framework of dynamic morphology theory, the centers of gravity and geometric centers of projections have been determined for the bodies of more than 182 forms of invertebrates, and these data have been used to distinguish four types of dynamic body shapes. It has been demonstrated that specific dynamic types of body shape are characteristic of individual taxa. In addition, there are a group of “transformers,” which may assume any dynamic type of shape, and a group of invertebrates with one predominant dynamic type. 相似文献
28.
The Aging of America's Reservoirs: In‐Reservoir and Downstream Physical Changes and Habitat Implications
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Kyle E. Juracek 《Journal of the American Water Resources Association》2015,51(1):168-184
Reservoirs are important for various purposes including flood control, water supply, power generation, and recreation. The aging of America's reservoirs and progressive loss of water storage capacity resulting from ongoing sedimentation, coupled with increasing societal needs, will cause the social, economic, environmental, and political importance of reservoirs to continually increase. The short‐ and medium‐term (<50 years) environmental consequences of reservoir construction and operation are well known and include an altered flow regime, lost connectivity (longitudinal, floodplain), an altered sediment regime, substrate compositional change, and downstream channel degradation. In general, reservoir‐related changes have had adverse consequences for the natural ecosystem. Longer term (>50 years) environmental changes as reservoirs enter “old” age are less understood. Additional research is needed to help guide the future management of aging reservoir systems and support the difficult decisions that will have to be made. Important research directions include assessment of climate change effects on aging and determination of ecosystem response to ongoing aging and various management actions that may be taken with the intent of minimizing or reversing the physical effects of aging. 相似文献
29.
A pot experiment was conducted to study the allelopathic effects of initial decomposing leaf litter of Cinnamomum camphora on growth and physiology of Impatiens balsamina. Three leaf litter treatments included 20, 40 and 80 g of C. camphora leaf litter mixed with 8 kg of soil, namely T1, T2, and T3, respectively. In order to test the effect of leaf litter addition on the permeability and ventilation of soil simultaneously, a parallel trial with steamed leaf litter was conducted with the three treatments of the leaf litter. The leaf litter was steamed for 2 d to remove the secondary metabolites as much as possible, dried, and then mixed with 8 kg of soil, namely Z1, Z2, and Z3, respectively. No leaf litter was added in control (CK). The growth parameters of I. balsamina were determined at the 20 d, 60 d, 100 d and 120 d after sowing and the main physiology indicators were determined at the 60 d. The results indicated that: (1) The ground surface diameter and height of I. balsamina were inhibited significantly at 60 d (P < 0.05). Photosynthetic pigments and gas exchange parameters of I. balsamina were inhibited significantly at 60 d, and the inhibition effect was stronger with increased amount of leaf litter addition. The chlorophyll content, Pn and Ls decreased significantly with increased amount of leaf litter (P < 0.05). The activity of superoxide dismutase (SOD) and peroxidase (POD) in leaves of I. balsamina decreased with the increase of leaf litter addition. The content of MDA in treatments T1, T2 and T3 were all higher than that in CK, which indicated that I. balsamina suffered oxidative damage in a certain degree. The content of free proline (Pro) and soluble sugar (SS) in leaves of I. balsamina decreased significantly with the increase of the leaf litter (P < 0.05), while the content of soluble protein (SP) increased. (2) In the parallel trial, 60 d after sowing, no obvious difference was observed between CK and any steamed leaf litter treatment in terms of the morphological and physiological features stated above (P > 0.05). It indicated that the soil physical properties were not greatly influenced by leaf litter addition in the dose interval designed, or that the release of secondary metabolites from decomposing leaf litter was probably a better reason to explain the inhibition of leaf litter treatment to I. balsamina growth. (3)The compound effect (CE) of leaf litter decomposition on I. balsamina was enhanced with increase of the leaf litter, to 0.169, 0.354, and 0.497, respectively, in treatments of T1, T2 and T3. The study indicated that initial decomposition of C. camphora leaf litter in soil reduces the content of photosynthetic pigments, inhibits photosynthetic capacity and resistance physiology of I. balsamina, weakens its adaptability to the environment, and restrains growth of the plant. © 2015, Science Press. All rights reserved. 相似文献
30.
ADRIZAL P. H. PATTERSON R. M. HULET R. M. BATES 《Journal of environmental science and health. Part. B》2013,48(6):1001-1018
A chamber study was conducted to evaluate the growth response and leaf nitrogen (N) status of four plant species exposed to continuous ammonia (NH3) for 12 weeks (wk). This was intended to evaluate appropriate plant species that could be used to trap discharged NH3 from the exhaust fans in poultry feeding operations before moving off-site. Two hundred and forty bare-root plants of four species (Juniperus virginiana (red cedar), Gleditsia triacanthos var. inermis (thornless honey locust), Populus sp. (hybrid poplar), and Phalaris arundinacea (reed canary grass) were transplanted into 4- or 8-L polyethylene pots and grown in four environmentally controlled chambers. Plants placed in two of the four chambers received continuous exposure to anhydrous NH3 at 4 to 5 ppm while plants in another two chambers received no NH3. In each of the four chambers, 2 to 4 plants per species received no fertilizer while the rest of the plants were fertilized with a 100 ppm solution containing 21% N, 7% phosphorus, and 7% potassium. The results showed that honey locust was the fastest-growing species. The superior growth of honey locust among all species was also supported by its total biomass, root, and root dry matter (DM) weights. For all species there was a trend for plants exposed to NH3 to have greater leaf DM than their non-exposed counterparts at 6 (43.0 vs. 30.8%; P = 0.09) and 12 wk (47.9 vs. 36.6%; P = 0.07), and significantly greater (P ≤ 0.05) leaf N content at 6 (6.44 vs. 3.67%) and 12 wk (7.05 vs. 3.51%) when exposed to NH3. Numerically greater leaf DM due to NH3 exposure was also consistently measured in poplar at both sampling periods. Hybrid poplar, as well as honey locust and reed canary grass, deposited 1.5 to 2-fold greater N in their leaves than red cedar tissues as a result of NH3 exposure compared to non-exposed plants. Regardless of the effect of NH3 on foliar color and damage score of the plants, the increase of foliar N content (g 100 g?1 of fresh foliage weight) after NH3 exposure at 6 and 12 wk was 0.45 and 0.87 for grass,1.25 and 1.34 for locust, and 2.67 and 6.09 for poplar. However, only honey locust likely benefited from ambient NH3 as indicated by its consistent leaf color quality and lower damage score, compared with other species that were adversely affected by atmospheric NH3. 相似文献