Experiments were designed to test the hypothesis that interference with chlorophyll metabolism may be one mechanism of inhibition of plant growth in allelopathic interactions. Effects of ferulic,p-coumaric, and vanillic acids on soybean and grain sorghum growth and chlorophyll content were quantified and compared after seedlings were treated with these compounds in a nutrient culture. Following a 6-day treatment cycle, dry weights of soybean seedlings were reduced by both 10–3 M and 5 × 10–4 M treatments of ferulic,p-coumaric and vanillic acids. Soybean weight reductions in each case were paralleled by a significant reduction in the concentration (g Chl/mg dry wt) of chlorophylls a and b and total chlorophyll in the unifoliate leaves. Sorghum seedling growth was also reduced by each of the compounds at the 5 × 10–4 M level, but leaf chlorophyll concentration was not below that of control plants. 相似文献
The role of ozone was studied for two different configurations combining non-thermal plasma (NTP) and heterogeneous catalysis, namely the use of a gas phase plasma with subsequent exposure of the effluent to a catalyst in a packed-bed reactor (post-plasma treatment) and the placement of the catalyst directly in the discharge zone (in-plasma catalysis). Non-porous and porous alumina and silica were deployed as model catalysts. The oxidation of immobilised hydrocarbons, toluene as a volatile organic compound and CO as an inorganic pollutant were studied in both operational modes.
While conversion and selectivity of hydrocarbon oxidation in the case of catalytic post-plasma treatment can be fully explained by the catalytic decomposition of O3 on γ-Al2O3, the conversion processes for in-plasma catalysis are more complex and significant oxidation was also measured for the other three materials (-Al2O3, quartz and silica gel). It became obvious that additional synergetic effects can be utilised in the case of in-plasma catalysis due to short-lived species formed in the NTP.
The capability of porous alumina for ozone decomposition was found to be correlated with its activity for oxidation of carbon-containing agents. It could be clearly shown that the reaction product CO2 poisons the catalytic sites at the γ-Al2O3 surface. The catalytic activity for O3 decomposition can be partially re-established by NTP treatment. However, for practical purposes the additional reaction pathways provided by in-plasma catalytic processes are essential for satisfactory conversion and selectivity. 相似文献
Epoxy resin was modified by a silane monomer, γ-aminopropyltrimethoxy silane (γ-APS), and was used as the protective coatings for LY12 aluminum alloys. The aim of the modification is to reduce the water uptake of polymeric coatings. The water absorption of coatings was measured by coating capacitance method in 3.5 wt.% NaCl aqueous solution. The result indicates that water uptake of epoxy coatings modified with 1.0 wt.% γ-APS decreases compared with pure epoxy coatings, whereas larger amounts of sliane result in the deterioration in performance against water permeation, due to the excessive consumption of epoxide group in epoxy resin by amino-group in silane agent, thus reduce the cross-linking of epxoy coating as a result of presence of excessive curing agent (polyamide). Tg of silane-modified coatings increases slightly after immersion, extremely contrasting with that of pure epoxy coating, which was observed to decrease significantly after water permeation. The formation of Si–O–Si structure resulting from the hydrolysis and condensation of silane components during the immersion in aqueous media may be a reasonable explanation for the abnormal change in Tg of silane-modified coatings. In addition, all silane-modified coatings display better protection performance, which is characterized by higher charge transfer resistances (Rct) and lower double layer capacitance (Cdl) at substrate/electrolyte interface. 相似文献
Conium maculatum, a Eurasian weed naturalized in North America, contains high concentrations of piperidine alkaloids that act as chemical defenses against herbivores. C. maculatum was largely free from herbivory in the United States, until approximately 30 yr ago, when it was reassociated via accidental introduction with a monophagous European herbivore, the oecophorid caterpillar Agonopterix alstroemeriana. At present, A. alstroemeriana is found in a continuum of reassociation time and intensities with C. maculatum across the continent; in the Pacific Northwest, A. alstroemeriana can cause severe damage, resulting in some cases in complete defoliation. Studies in biological control and invasion biology have yet to determine whether plants reassociated with a significant herbivore from the area of indigeneity increase their chemical defense investment in areas of introduction. In this study, we compared three locations in the United States (New York, Washington, and Illinois) where C. maculatum experiences different levels of herbivory by A. alstroemeriana to determine the association between the intensity of the interaction, as measured by damage, and chemical defense production. Total alkaloid production in C. maculatum was positively correlated with A. alstroemeriana herbivory levels: plants from New York and Washington, with higher herbivory levels, invested two and four times more N to alkaloid synthesis than did plants from Illinois. Individual plants with lower concentrations of alkaloids from a single location in Illinois experienced more damage by A. alstroemeriana, indicative of a preference on the part of the insect for plants with less chemical defense. These results suggest that A. alstroemeriana may act either as a selective agent or inducing agent for C. maculatum and increase its toxicity in its introduced range. 相似文献