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61.
Deep soil heterogeneity and fine root distribution in forests and pastures of eastern Amazonia 总被引:2,自引:1,他引:1
Little is known about deep soil heterogeneity, or its relationship with fine root distribution. Beneath a mature, closed-canopy forest of eastern Amazonia, and the pastures and secondary forests that are derived from this forest, soil soft spots and hollow chambers occur to at least 9 meters depth. We measured the vertical distribution of these soil patches, and compared chemical characteristics, mycorrhizal infection, and root density of soil soft spots with the surrounding matrix of more homogeneous soil. Soil soft spots and chambers varied little with depth, but occupied the greatest soil volume (0.8 to 1.2%) from 4 to 6 m depth in the mature forest. Soft spots had lower pH, P availability and arbuscular mycorrhizal infection, and higher K availability than surrounding soil. Root length density was 2 to 15 times higher in soft spots than in surrounding soil. In the pastures, roots were found only in soil soft spots at depths of >3 m. Pastures and secondary forest had more soil chambers in the upper meter of soil than mature forest, but were otherwise indistinguishable in their patterns of deep soil heterogeneity. Soil soft spots may be vestiges of cutter ant nest chambers, while hollow chambers are cutter ant chambers and root channels. Chambers may act as conduits for root penetration and water penetration to deep soil.Abbreviations AM
arbuscular mycorrhizae
- RLD
root length density (root length per unit of soil volume) 相似文献
62.
Angela Lombardi Michele Saviano Flavia Nastri Ornella Maglio Marco Mazzeo Carlo Pedone Carla Isernia Vincenzo Pavone 《Biopolymers》1996,38(6):683-691
In the present paper we describe the synthesis, purification, and single crystal x-ray analysis of the cyclic pentapeptide cyclo-(Pro-Phe-Phe-β-Ala-β-Ala). This compound crystallizes in the orthorhombic space group P212121 from methanol and adopts in the solid state an unusual conformation characterized by a cis β-Ala5-Pro1 peptide bond and by an intramolecular hydrogen bond stabilizing a C11- and a C12-ring structure. The C11, structure contains the Phe3 and the β-Ala4 at the corner position of the turn; it is the first observation of a type II β-turn enlargement due to the insertion of an extra methylene group of the β-alanine residue. The rest of the molecule participates in a newly characterized C12-ring structure, which incorporates a β-Ala residue at position i of the turn. © 1996 John Wiley & Sons, Inc. 相似文献
63.
64.
Gary C. du Moulin Zorina Pitkin Yuan-Jin Shen Evelyn Conti Jean Ko Stewart Carla Charles Dylan Hamilton 《Cytotechnology》1994,15(1-3):365-372
Somatic cell and gene therapy involve the application of biological technologies to an individual patient through the use of living cells which provide a therapeutic benefit (Aliski, 1991). Various forms of cellular and gene therapies are being developed and evaluated in an increasing number of clinical trials for congential and acquired disorders. The potential and progress of these therapeutic applications have resulted in an increasing effort by the Food and Drug Administration (FDA) to develop the regulatory framework under which these therapeutic approaches would insure safety and efficacy, the primary mandate of the FDA.Over five years ago Cellcor began to define the parameters, specifications, and conditions relevant to a Quality Assurance/Quality Control (QA/QC) program that has evolved to insure safety and maximize the efficacy of applications of the company'sex vivo technology, autolymphocyte therapy. Autolymphocyte therapy is an outpatient form of somatic cell immunotherapy based upon the infusion of T cells that have been activatedex vivo using a combination of previously generated autologous cytokines and an anti-CD3 monoclonal antibody.We have been able to demonstrate the feasibility for the safe, controlled, and consistent preparation and delivery of a cellular therapy by application of relevant GMP regulations. This presentation reviews aspects of this program and chronicles our experience which at present amounts to over 4400 infusions for over 700 patients. This program provides a high degree of assurance that a cellular therapy program can be carried out in a multisite mode involving hundreds of patients through the strict adherence to cGMP as set forth in existing regulations. It would be prudent that developers of cellular andex vivo gene therapies establish a similar cell processing and QA/QC infrastructure at an early developmental stage to optimize safety and reproducibility and facilitate regulatory review. 相似文献
65.
L. M. Mansur K. G. Lark H. Kross A. Oliveira 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1993,86(8):907-913
Quantitative trait loci (QTL) were mapped in segregating progeny from a cross between two soybean (Glycine max (L.) Merr.) cultivars: Minsoy (PI 27.890) and Noir 1 (PI 290.136). The 15 traits analyzed included reproductive, morphological, and seed traits, seed yield and carbon isotope discrimination ratios (13C/12C). Genetic variation was detected for all of the traits, and transgressive segregation was a common phenomenon. One hundred and thirty-two linked genetic markers and 24 additional unlinked markers were used to locate QTL by interval mapping and one-way analysis of variance, respectively. Quantitative trait loci controlling 11 of the 15 traits studied were localized to intervals in 6 linkage groups. Quantitative trait loci for developmental and morphological traits (R1, R5, R8, plant height, canopy height, leaf area, etc.) tended to be clustered in three intervals, two of which were also associated with seed yield. Quantitative trait loci for seed oil were separated from all the other QTL. Major QTL for maturity and plant height were linked to RFLP markers R79 (31% variation) and G173 (53% variation). Quantitative trait loci associated with unlinked markers included possible loci for seed protein and weight. Linkage between QTL is discussed in relation to the heritability and genetic correlation of the traits. 相似文献
66.
Luigi R. Ceci Adolfo Saiardi Luisa Siculella Carla Quagliariello 《Plant molecular biology》1993,23(4):727-736
A tRNAVal (GAC) gene is located in opposite orientation 552 nucleotides (nt) down-stream of the cytochrome oxidase subunit III (coxIII) gene in sunflower mitochondria. The comparison with the homologous chloroplast DNA revealed that the tRNAVal gene is part of a 417 nucleotides DNA insertion of chloroplast origin in the mitochondrial genome. No tRNAVal is encoded in monocot mitochondrial DNA (mtDNA), whereas two tRNAVal species are coded for by potato mtDNA. The mitochondrial genomes of different plant species thus seem to encode unique sets of tRNAs and must thus be competent in importing the missing differing sets of tRNAs. 相似文献
67.
Carla Tatone Christina Grietje Van Eekelen Rosella Colonna 《Molecular reproduction and development》1994,38(2):200-208
The ability of parthenogenetically activated mouse eggs to establish a plasma membrane (PM) block to sperm penetration was studied. Zona-free eggs preloaded with Hoechst 33342 were activated by exposure to ethanol or OAG (1-oleoyl-2-acetyl-sn-glycerol) and inseminated after different periods. Eggs challenged with sperm at 30- or 60-min postactivation displayed a fertilization frequency significantly lower than that of control eggs. Conversely, when insemination was carried out at 120-min postactivation, the proportion of fertilized eggs was equivalent to that observed in the control group. Moreover, we report that when the eggs were induced to resume meiosis without any notable loss of CGs (egg exposure to OAG at 100 μM external Ca2+ or to heat shock), a normal ability to be penetrated was recorded at 30-min postactivation. Similar behaviour was exhibited by eggs that underwent a CG exocytosis close to that triggered by sperm in absence of nuclear activation (microinjection of inositol 1,4,5-trisphosphate into the egg at 1 μM cytosolic concentration). Present data support the conclusion that parthenogenetically activated mouse eggs are capable of a transitory PM block response that requires both CG exocytosis and meiosis resumption to occur. © 1994 Wiley-Liss, Inc. 相似文献
68.
The Effects of Aluminum on the Influx of Calcium,Potassium, Ammonium,Nitrate, and Phosphate in an Aluminum-Sensitive Cultivar of Barley (Hordeum vulgare L.) 总被引:6,自引:4,他引:2 下载免费PDF全文
The mechanism by which aluminum interferes with ion influx is not known. In this study, the effects of aluminum on the influx of the cations calcium, potassium, and ammonium and the anions nitrate and phosphate were measured in an aluminum-sensitive cultivar of barley (Hordeum vulgare L.). Aluminum (100 [mu]M) was found to inhibit the influx of the cations calcium (69%), ammonium (40%), and potassium (13%) and enhancing the influx of the anions nitrate (44%) and phosphate (17%). Aluminum interfered with the binding of the cations in the cell wall by the same order of magnitude as their respective influxes, whereas phosphate binding was strongly enhanced. The results are consistent with a mechanism whereby aluminum binds to the plasma membrane phospholipids, forming a positively charged layer that influences ion movement to the binding sites of the transport proteins. A positive charge layer would retard the movement of cations and increase the movement of anions to the plasma membrane in proportion to the charges carried by these ions. 相似文献
69.
Carla Caruso Carlo Caporale Elia Poerio Angelo Facchiano Vincenzo Buonocore 《Journal of Protein Chemistry》1993,12(4):379-386
The amino acid sequence of wheatwin1, a monomeric protein of 125 residues isolated from wheat kernel (variety S. Pastore), is reported. Wheatwin1 is highly homologous (95%) to barwin, a protein from barley seed, which was shown to be related to the C-terminal domain of two proteins encoded by the wound-induced geneswin1 andwin2 in potato and to a protein encoded by the same domain of the hevein gene (hev1) in rubber tree. Similarly to barwin, wheatwin1 contains six cysteine residues all linked in disulfide bridges and the N-terminal residue is pyroglutamate. Moreover, structural studies performed on wheatwin1 andwin1 protein by predictive methods demonstrated that these proteins and barwin are closely related in the secondary structure also. The high level of homology found with the product ofwin1,win2, andhev1 genes strongly suggests that barwin and wheatwin1 play a common role in the mechanism of plant defence. 相似文献
70.
Carlos Rafael Borges Mendes Raul Rodrigo Costa Afonso Ferreira Bruno Jesus Virginia Maria Tavano Tiago Segabinazzi Dotto Miguel Costa Leal Rodrigo Kerr Carolina Antuarte Islabão Andréa de Oliveira da Rocha Franco Mauricio M. Mata Carlos Alberto Eiras Garcia Eduardo Resende Secchi 《Global Change Biology》2023,29(7):1791-1808
The western Antarctic Peninsula (WAP) is a climatically sensitive region where foundational changes at the basis of the food web have been recorded; cryptophytes are gradually outgrowing diatoms together with a decreased size spectrum of the phytoplankton community. Based on a 11-year (2008–2018) in-situ dataset, we demonstrate a strong coupling between biomass accumulation of cryptophytes, summer upper ocean stability, and the mixed layer depth. Our results shed light on the environmental conditions favoring the cryptophyte success in coastal regions of the WAP, especially during situations of shallower mixed layers associated with lower diatom biomass, which evidences a clear competition or niche segregation between diatoms and cryptophytes. We also unravel the cryptophyte photo-physiological niche by exploring its capacity to thrive under high light stress normally found in confined stratified upper layers. Such conditions are becoming more frequent in the Antarctic coastal waters and will likely have significant future implications at various levels of the marine food web. The competitive advantage of cryptophytes in environments with significant light level fluctuations was supported by laboratory experiments that revealed a high flexibility of cryptophytes to grow in different light conditions driven by a fast photo-regulating response. All tested physiological parameters support the hypothesis that cryptophytes are highly flexible regarding their growing light conditions and extremely efficient in rapidly photo-regulating changes to environmental light levels. This plasticity would give them a competitive advantage in exploiting an ecological niche where light levels fluctuate quickly. These findings provide new insights on niche separation between diatoms and cryptophytes, which is vital for a thorough understanding of the WAP marine ecosystem. 相似文献