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ABSTRACT Transmission electron microscopy was used to study the penetration and infection of pansy roots by Thielaviopsis basicola. Events observed in 7- to 10-day-old roots produced on moist filter paper differed slightly from those in roots from 4-week-old plants washed free of potting media prior to inoculation. By 3 h postinoculation (PI), epidermal cells of roots produced on filter paper exhibited aggregated cytoplasm and papilla formation in response to germ tube tips. The presence of callose in papillae was demonstrated using immunogold labeling. Papilla formation was not effective in preventing host cell penetration. A slender infection hypha emerged from a germ tube tip and grew through a papilla. Its tip then expanded to form a globose infection vesicle. By 6 h PI, infection hyphae emerged from infection vesicles, and invaded host cells showed signs of necrosis. By 8 h PI, infection hyphae had grown into cortical cells in spite of papilla formation in these cells. By 24 h PI, distinctive intracellular hyphae were present in necrotic cortical cells. In washed roots, most epidermal cells failed to respond to invasion. Hyphae simply grew through these cells and contacted cortical cells that exhibited aggregated cytoplasm and papillae formation. Infection structures similar to those produced in epidermal cells from roots grown on filter paper then formed in cortical cells of washed roots. The fact that T. basicola formed infection structures only in cells that responded to invasion suggests that T. basicola has a more complex relationship with its host than would be expected in a nectrotrophic pathogen. We believe that T. basicola is best described as a necrotrophic hemibiotroph. 相似文献
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Mozaina K Cantrell CL Mims AB Lax AR Tellez MR Osbrink WL 《Journal of agricultural and food chemistry》2008,56(11):4021-4026
A large number of naturally occurring and synthetic benzoquinones were evaluated for activity against the Formosan subterranean termite, Coptotermes formosanus, with potential use in termite control. Among these bioactive naturally occurring benzoquinones are 2-methyl-5-isopropyl-1,4-benzoquinone, 2-methoxy-6-pentyl-1,4-benzoquinone, 2,3-dimethoxy-5-methyl-6-(3-methyl-2-butenyl)-1,4-benzoquinone, 2,3-dimethoxy-5,6-dimethyl-1,4-benzoquinone, and 2,3-dichloro-5,6-dimethyl-1,4-benzoquinone. All five of these compounds demonstrated 100% mortality against C. formosanus by day 11 at a concentration of 1% (wt/wt) or less. In general, benzoquinones with one or two hydrophobic groups on the 5 and/or 6 positions of the quinone ring along with one or two group(s) on the opposite side of the ring, at the 2 and/or 3 position, led to high rates of mortality against C. formosanus. Quantitative structure-activity relationship (QSAR) studies showed no correlation between lipophilicity (calculated log P) and mortality for the entire group of nonhalogenated benzoquinones. A correlation was observed between C-6 chain length and day 3 percent mortality for 2,3-dimethoxy-5-methyl-6-substituted aliphatic benzoquinones where short chain lengths resulted in higher mortality. 相似文献
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Edible films have been used for decades on fresh produce to create a semipermeable membrane on the surface to suppress respiration, control moisture loss, and more recently to provide a delivery mechanism for the inclusion of functional components. Scientists at the Southern Regional Research Center (SRRC) have previously demonstrated that a thin biodegradable film can be produced from soapstock, an underused byproduct from the vegetable oil industry. After physical and chemical treatments, a thin film was produced from various soapstocks (cottonseed and safflower). Different hydration ratios were tested since the initial soapstock solutions were rather viscous. To examine the potential use of an oilseed-derived lipid film for the extension of shelf life, different types of the oilseed-derived soapstocks were utilized to produce lipid films with different hydration ratios, and containing 0, 5, and 10% of paraffin wax for application on ‘Camelot’ bell peppers. Control bell peppers lost almost 25% weight per unit surface area (SA) in 78 h when stored under ambient conditions. Cottonseed film-coated peppers, hydrated at 1:4, lost only about 5% moisture per unit SA after 78 h and minimized weight loss by up to 79% compared to the control. However, since a 1:4 hydration ratio remained rather viscous, 1:8 was preferred and these cottonseed films reduced weight loss per unit SA by up to 48% during storage. Safflower-derived soapstock film resulted in the least effective water retention of the films and ratios tested, with roughly 21–25% reduction in weight loss per SA compared to controls. Safflower-derived soapstock was higher in unsaturated fatty acids, which are less efficient to control moisture migration because they are more polar than saturated lipid materials, as contained in cottonseed-derived materials. Addition of wax to the cottonseed-derived films decreased water loss slightly, similar to previous reports in the literature. An ANOVA supported the conclusion that the oilseed-derived lipid films significantly reduced moisture loss across the produce epidermis. To avoid potential allergenicity concerns in cottonseed soapstock, additional cleanup steps and tests with commonly used edible coating additives would be required before attaining food grade status. 相似文献
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Mims MC, Olden JD, Shattuck ZR, Poff NL. Life history trait diversity of native freshwater fishes in North America. Ecology of Freshwater Fish 2010: 19: 390–400. © 2010 John Wiley & Sons A/S Abstract – Freshwater fish diversity is shaped by phylogenetic constraints acting on related taxa and biogeographic constraints operating on regional species pools. In the present study, we use a trait‐based approach to examine taxonomic and biogeographic patterns of life history diversity of freshwater fishes in North America (exclusive of Mexico). Multivariate analysis revealed strong support for a tri‐lateral continuum model with three end‐point strategies defining the equilibrium (low fecundity, high juvenile survivorship), opportunistic (early maturation, low juvenile survivorship), and periodic (late maturation, high fecundity, low juvenile survivorship) life histories. Trait composition and diversity varied greatly between and within major families. Finally, we used occurrence data for large watersheds (n = 350) throughout the United States and Canada to examine geographic patterns of life history variation. Distinct patterns of life history strategies were discernible and deemed congruent with biogeographic processes and selection pressures acting on life history strategies of freshwater fishes throughout North America. 相似文献
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O. Linhart J. Cosson S.D. Mims M. Rodina D. Gela W.L. Shelton 《Fish physiology and biochemistry》2003,28(1-4):203-205
In the present study was summarize the factors activating and/or inhibiting the motility of intact and/or demembranated spermatozoa of common carp and paddlefish as teleostean and chondrostean models using methods of sperm demembranation. The movement of spermatozoa of cyprinids species, common carp, is influenced by osmotic pressure or high concentration of ions. The movements of spermatozoa of chrondrostean species, paddlefish, are under reciprocal control by the concentration of K+ and Ca2+. 相似文献
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