Regional differences in aspen (Populus tremuloides Michx.) seedling response to an established nursery protocol     

Howe  Alexander A.  Landhäusser  Simon M.  Burney  Owen T.  Long  James N.  Mock  Karen E. 《New Forests》2020,51(2):367-378

New Forests - In seedling-based reforestation operations, seed source is known to be an influential variable affecting outplanting success. Adaptive variation among seed sources may also be an...  相似文献   

Survival of soil bacteria during prolonged desiccation     

M. Chen  M. Alexander 《Soil biology & biochemistry》1973,5(2):213-221

A determination was made of the kinds and numbers of bacteria surviving when two soils were maintained in the laboratory under dry conditions for more than half a year. Certain non-spore-forming bacteria were found to survive in the dry condition for long periods. A higher percentage of drought-tolerant than drought-sensitive bacteria was able to grow at low water activities. When they were grown in media with high salt concentrations, bacteria generally became more tolerant of prolonged drought and they persisted longer. The percent of cells in a bacterial population that remained viable when exposed to drought stress varied with the stage of growth.  相似文献   

Mechanisms of persistence of low numbers of bacteria preyed upon by protozoa     

M. Habte  M. Alexander 《Soil biology & biochemistry》1978,10(1):1-6

Tetrahymena pyriformis cultures were maintained when transferred serially in solutions containing 10⁵ to 10⁷Klebsiella pneumoniae cells.ml^?1, bacterial numbers that were observed to persist in the presence of protozoa. The number of cells of one strain of K. pneumoniae surviving predation in solution was essentially the same in the absence of an alternative prey as in the presence of a second K. pneumoniae strain. Toxins deleterious to protozoa did not appear as the animal consumed the bacteria. T. pyriformis reduced the abundance of Escherichia coli from about 10⁸ to 10⁶.ml^?1. but the latter number persisted for 15 days; however, in solutions containing chloramphenicol, the abundance of E. coli fell to 590 cells. ml^?1 in 15 days. In solutions containing the antibiotic, T. pyriformis reduced the Rhizobium sp. population from more than 10⁶ to less than 10³ cells in 10 days and K. pneumoniae from more than 10⁸.ml^?1 to zero in 18 days. An appreciable decline in abundance of these bacteria did not occur in the antibiotic-amended liquid free of protozoa. T. pyriformis did not greatly reduce Rhizobium sp. numbers when both were added to irradiated soil, but the predator caused the bacterial population to decline from 4 × 10⁸ to fewer than 10⁵.g^?1 in 16 days in chloramphenicol-treated soil. Colpoda sp. inoculated with Rhizobium sp. into soil sterilized by autoclaving only reduced the prey abundance from 10⁹ to 10⁸.g^?1, but the protozoan caused the bacterial population to fall to about 100.g^?1 in 15 days in the presence of the antibiotic. The population of Rhizobium sp. added to nonsterile soil dropped from in excess of 10⁸ to 6 × 10⁶.g^?1 in 29 days. but it declined to 550. g^?1 in the same period when chloramphenicol was also introduced. It is concluded that the ability of these bacteria to maintain themselves in solution and in soil is governed by their capacity to reproduce and replace the cells consumed by predation.  相似文献   

Formation of volatile organic products in soils under anaerobiosis—I: Metabolism of glucose     

J.A. Adamson  A.J. Francis  J.M. Duxbury  M. Alexander 《Soil biology & biochemistry》1975,7(1):45-50

A simple trapping procedure for concentration of volatile organic compounds present in a head space and the subsequent analysis of the retained compounds by combined gas chromatographymass spectrometry is described. The procedure was used to study the organic metabolites evolved from various soils when they were amended with glucose and incubated under argon. A number of organic acids, alcohols, aldehydes and esters were evolved during a 4 week period. Less than 10 per cent of the added carbon was recovered as organic compounds, which was largely due to poor recovery of volatile organic acids from soil. Some implications of the observations to microbial ecology are discussed.  相似文献   

Preliminary physiological studies on cowpea rhizobia     

N. Okafor  M. Alexander 《Soil biology & biochemistry》1975,7(6):405-406

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Sympathetic Ganglion Cells in Ventral Nerve Roots. Their Relation to Sympathectomy     

Alexander WF  Kuntz A  Henderson WP  Ehrlich E 《Science (New York, N.Y.)》1949,109(2837):484

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Using genetic methods for analysis of fish meals and feeds employed in Greek mariculture     

Antonis Vlachavas  Nikoleta Karaiskou  Lambros Kokokiris  Foteini‐Izampela Zampeta  Elena Drosopoulou  Alexander Triantafyllidis 《Aquaculture Research》2019,50(1):312-322

Large quantities of high protein fish meals are needed to sustain cultured species and thus the impact to marine ecosystem has been highly discussed. The aim of this study was to apply a PCR‐cloning methodology for a robust insight into the composition of commercial fish meals and feeds for farmed species of the Greek mariculture, assessing the risk posed by aquaculture to marine ecosystems but also the risk posed by commercial fish feeds to the increase in trophic level of species farmed in Greece. 89% of the sequences were identified to species level and only 11% to genus/family level. Overall, a total of 49 taxa were identified (44 fish species/taxon, five non‐fish species/taxon). Even though small pelagic fish like Engraulis sp. were the main portion, a wide range of species constituted the fish meals and feeds. Plant and animal species were also detected as an alternative protein source. Feed products employed in Greek mariculture still contain large portions of fish meals which increase the mean trophic level of farmed species causing a farming up trend. The results emphasize that such molecular methodologies are needed to certify aquafeeds allowing fish feed producers to demonstrate their commitment to sustainable aquaculture.  相似文献   

Mesohabitat associations of the threatened San Marcos salamander (Eurycea nana) across its geographic range          下载免费PDF全文

Peter H. Diaz  Joe N. Fries  Timothy H. Bonner  Mara L. Alexander  Weston H. Nowlin 《水产资源保护:海洋与淡水生态系统》2015,25(3):307-321

Structure—activity relationships of organotin biocides and Ceratocystis ulmi     

George Eng  Stephen P. Coddington  Laura L. Stockton  Alexander D. W. Acholonu 《Pest management science》1989,26(2):117-121

The effect of organotin compounds on the growth of Ceratocystis ulmi, the causative agent of Dutch elm disease, was studied in shake culture. Triphenyltin, (C₆H₅)₃SnX, tricyclohexyltin, (C₆H₁₁)₃SnX, and tributyltin, (C₄H₉)₃SnX, compounds were all effective in the inhibition of C. ulmi in vitro. The anionic group, X, did not play a major role in the inhibitory activities of these compounds, suggesting that the species involved in the inhibition is R₃Sn⁺ or the hydrated cation.  相似文献   

Pain management in horses and farm animals     

Alexander Valverde  DVM  DVSc  DACVA    Cornelia I. Gunkel  Dr. med. vet.  MRCVS 《Journal of Veterinary Emergency and Critical Care》2005,15(4):295-307

Objective: This review discusses the different analgesic drugs and routes of administration used in large animals for acute pain management. General guidelines and doses are given to assist in choosing techniques that provide effective analgesia. Etiology: Noxious stimuli are perceived, recognized, and localized by specialized sensory systems located at spinal and supraspinal levels. Diagnosis: Localizing the source of the noxious stimulus as well as understanding the behavioral aspects and physiological changes that result from such insult is important to adequately diagnose and treat pain. Pain assessment is far from being definite and objective; not only are there species differences, but also individual variation. In addition, the behavioral and physiological manifestations vary with the acute or chronic nature of pain. Therapy: Pain management should include (1) selecting drugs that better control the type of pain elicited by the insult; (2) selecting techniques of analgesic drug administration that act on pathways or anatomical locations where the nociceptive information is being processed or originating from; (3) combining analgesic drugs that act on different pain pathways; and (4) provide the best possible comfort for the animal. Prognosis: Providing pain relief improves the animal's well being and outcome; however, interpreting and diagnosing pain remains difficult. Continuing research in pain management will contribute to the evaluation of the pathophysiology of pain, pain assessment, and newer analgesic drugs and techniques.  相似文献