Influence of Phenolic acids on microbial populations in the rhizosphere of cucumber

Experiments were conducted to determine whether changes in soil microbial populations that occur in response to additions of certain allelopathic phenolic acids to bulk soil also occur in the rhizosphere. Cucumber seedlings were transplanted into cups containing a nutrient-enriched mixture of Portsmouth B₁, soil and sand and were watered five times (once every 48 hr) with aqueous solutions of ferulic,p-coumaric, or vanillic acid (each at 0, 0.25, or 0.50ol/g soil material). Nutrient solution was applied on alternate days. Leaf growth was suppressed by up to 42% by phenolic acids, but changes in root growth varied with the compound and concentration in solution. Significant increases (over 600% relative to controls) in populations of fast-growing bacteria in the rhizosphere were detected after two but not after five treatments, and increases (400% relative to controls) in numbers of fungal propagules were detected after five treatments. Such increases suggested that chronic exposure to a phenolic acid might resuit in high populations of rhizosphere microorganisms that could metabolize the compounds and thus alter observable responses by the plant. To test this, plants were watered repeatedly with a low-concentration solution of ferulic acid (chronic treatments; 0.0 or 0.1mol/g soil material in one experiment, 0.000 or 0.025imol/g soil material in a second) and then once with a highconcentration solution (acute treatment; 0.0, 0.5, or 1.0mol/g soil material in the first experiment; 0.000, 0.125, or 0.250mol/g soil material in the second).Paper No. 12385 of the Journal Series of the North Carolina Agricultural Research Service, Raleigh, North Carolina. The use of trade names in this publication does not imply endorsement by the North Carolina Agricultural Research Service or the United States Department of Agriculture of the products named, nor criticism of similar ones not mentioned. Acute treatments and some chronic treatments suppressed leaf growth, but results were inconsistent for root growth. Acute treatments increased numbers of several types of bacteria in the rhizosphere but had inconsistent effects on fungi. Chronic treatments had no effect on numbers of bacteria or fungal propagules in the rhizosphere. Furthermore, chronic treatments did not alter responses of plants or microbial populations to the subsequent acute treatment. Results demonstrated that phenolic acids in soil, which must pass through the rhizosphere before interaction with plant roots can occur, alter the microbial ecology of the rhizosphere. However, microbially mediated acclimation of plants to relatively high concentrations of ferulic acid was not observed.     

Phenolic acids affect photosynthesis and protein synthesis by isolated leaf cells of velvet-leaf

The effects ofp-coumaric, ferulic, chlorogenic, and vanillic acids on photosynthesis and protein synthesis by isolated leaf cells of velvetleaf (Abutilon theophrasti Medik) were investigated. Photosynthesis and protein synthesis were measured in cell suspensions by the incorporation of¹⁴CO₂ and [¹⁴C]leucine, respectively. None of the tested phenolic acids except vanillic reduced photosynthesis by more than 50% at the highest concentration and 30 min of incubation. At 100M concentrations and 60-min incubation periods,p-coumaric, ferulic, chlorogenic, and vanillic acids inhibited photosynthesis by 33, 37, 57, and 65%, respectively. Ferulic acid was the most inhibitory to protein synthesis and reduced the incorporation of [¹⁴C]leucine by 50% at about 1.0M after 60 min of incubation. At the highest concentrations tested in this study, vanillic and ferulic acids were inhibitory to photosynthesis and protein synthesis, respectively, whereas chlorogenic andp-coumaric acids did not inhibit either physiological process. The maximum inhibition of protein synthesis by chlorogenic acid was 19% and by vanillic acid was 28% at 100M concentrations. Chlorogenic, vanillic, andp-cou-maric acids at 0.1M caused increased protein synthesis over the untreated control. Overall, photosynthesis was more sensitive than protein synthesis to the four phenolic acids tested.Florida Agricultural Experiment Station Journal Series No. 9228.     

Antifungal polyoxygenated fatty acids fromAeollanthus parvifolius

Two polyoxygenated fatty acids with antifungal activity have been isolated from aerial parts ofAeollanthus parvifolius (Labiatae) using bioassay-guided isolation procedures. Spectroscopic analysis was used to identify the compounds as (Z)-4,9-diacetoxy-6,7-epoxy-5-hydroxy-8-oxododeca-2-enoic acid and (Z)-4,6,7,9-tetraacetoxy-5-hydroxy-8-oxododeca-2-enoic acid. Both of these compounds inhibited spore germination ofCladosporium cucumerinum. Minimum inhibitory doses were 1 µg and 5 µg, respectively, but only the former inhibited germination ofAspergillus niger at a dose of 5 µg. Neither compound exhibited antibacterial activity. (Z)-4,9-Diacetoxy-6,7-epoxy-5-hydroxy-8-oxododeca-2-enoic acid reduced the hyphal growth ofPythium ultimum. The mode of action was not resolved but did not involve either the disruption of the cell wall membrane or the inhibition of extracellular enzymes. Application of (Z)-4,6,7,9-tetraacetoxy-5-hydroxy-8-oxododeca-2-enoic acid to seedling plants did not give any protection against fungal attack, and indeed the compound appeared to be phytotoxic.     

Linamarin and histamine in the defense of adultZygaena filipendulae

We determined the protective values of histamine and linamarin to an aposematic moth,Zygaena filipendulae. Using ion-exchange resin techniques, we found that the mean histamine concentrations in the wings were 0.061 ± 0.047 g/mg and 0.013 ± 0.0051 in the moths' bodies (totals: 0.586 g and 2.921 g, respectively, all wet weights). Average HCN evolution (mainly from the bitter cyanogen linamarin) from the wings was 0.049 ± 0.41 g/mg (0.426 g/ml of linamarin could produce this amount of HCN) and 0.029 ± 0.0026 g/mg HCN (0.281 g/mg linamarin) evolved from the bodies (total linamarin 4.09 g and 61.258 g, respectively, all wet weights). Therefore, higher concentrations of toxicants were found in the part of the body most liable to initial attack. We found, in offering various toxic solutions to 10 common quails, that 0.1% linamarin (mean linamarin consumed equal to about 70% of the average total wing content) but 1.0% histamine (mean histamine consumed equal to that found in about 8.9 average wing sets) solutions significantly lowered drinking rates. However, combination solutions were still effectively aversive at 0.001% histamine plus 0.028% linamarin. This synergism would allow a moth under local abiotic or dietary stress to elaborate substantially less of one or both compounds than that normally synthesized. The implications to kin selection are discussed.     

Effects of soil nitrogen level on ferulic acid inhibition of cucumber leaf expansion

It has been suggested that the allelopathic activity of phenolic acids should be primarily important in soils of low fertility. If this is true, then plant growth inhibition by phenolic acids may be unimportant in managed agricultural soils. The objective of this study was to determine how soil nitrogen (N) level might modify phenolic acid inhibition of growth. Cucumber seedlings (Cucumis sativus cv Early Green Cluster) grown in containers in growth chambers under varying N levels (5, 10, 15, 20, and 25 g N/g soil) in Portsmouth B,-horizon soil material were treated with ferulic acid (0 or 10 g/g soil). Nitrogen and ferulic acid (FA) were applied every other day to the soil surface. The amount of FA in the soil solution declined with depth in the containers. A more rapid disappearance of FA from the soil solution was observed for the last FA treatment (0% recovered after 10 hr on day 23) than the first treatment (44% recovered after 10 hr on day 13). Both low N (5 g N/g soil) and FA treatments reduced shoot dry weight, the mean absolute (AGR) and the mean relative (RGR) rates of leaf expansion, and increased the root-shoot ratio. High N treatments reduced shoot dry weight and the AGR. Ferulic acid inhibited cucumber seedling growth over a range of N concentrations, suggesting that the allelopathic activity of phenolic acids may be important in both nutrient limiting and nonlimiting soils for some species.Paper No. 12219 of the journal series of the North Carolina Agricultural Research Service, Raleigh, North Carolina 27695-7601. The use of tradenames in this publication does not imply endorsement by the North Carolina Agricultural Research Service of products named, nor criticism of similar ones not mentioned.     

Synergism of Polygodial and trans-Cinnamic Acid on Inhibition of Root Elongation in Lettuce Seedling Growth Bioassays

A bicyclic sesquiterpene dialdehyde, polygodial did not inhibit root elongation up to a concentration of 12.5 g/ml in a lettuce seedling assay: trans-Cinnamic acid inhibited the elongation by 50% at 1.2 g/ml (8.1 M). The inhibitory activity of trans-cinnamic acid was enhanced 17-fold when used in combination with 6.25 g/ml (26.5 M) of polygodial. A decrease in the pH of the medium was observed during normal seedling growth, indicating transport of protons from the cells by a plasma membrane H⁺-ATPase. The inhibitory effect of trans-cinnamic acid on the elongation was reduced to some extent in 2 mM phosphate buffer (pH 7.0) during seedling growth. Although polygodial did not inhibit the activity of H⁺-ATPase in the plasma membrane fraction of roots in normally growing seedlings, a decrease in activity was found in the fraction obtained from seedlings incubated with 20 g/ml of polygodial. These results suggest that polygodial functions synergistically with trans-cinnamic acid in the inhibition of root elongation via restriction of proton transport from the cytoplasm of germinated cells.     

Dihydromatricariate-based triglycerides,glyceride ethers,and waxes in the australian soldier beetle,Chauliognathus lugubris (Coleoptera: Cantharidae)

The soldier beetleChauliognathus lugubris is shown to contain triglycerides and glyceride ethers of 8-dihydromatricaria acid, and waxes of the C₁₂ homolog, of this acid, as well as the previously reported free acid. The triglycerides contain one, two, or three dihydromatricariate moieties, with any remaining positions esterified with normal fatty acids. The glyceride ethers were monostearyl ethers of glycerol esterified with dihydromatricaria acid and oleic or linoleic acid. The waxes, which also include a dihydromatricaria chromophore in the alcohol moiety, occur only in the females and are present in paired accessory glands in the abdomen. The ethers are restricted to females and appear to be associated with developing eggs. The triglycerides are much more abundant in females than males. Triglycerides, glyceride ethers, and waxes represent about 95% of the dihydromatricariate moiety (average, ca. 590 g) in females with free acid the remainder; in males free acid is present to over 50% (ca. 22 g) and the remainder is triglyceride (ca. 15 g). Larvae contain mainly tridihydromatricariate-substituted triglyceride and a smaller quantity of the free acid.     

Aphid deterrence by glucose esters in glandular trichome exudate of the wild tomato,Lycopersicon pennellii

Settling of the potato aphid,Macrosiphum euphorbiae, on feeding membranes was deterred by methanolic leaf rinses ofLycopersicon pennellii, or of its F₁ with tomato,L. esculentum. The active compounds in theL. pennellii rinsates were identified as 2,3,4-tri-O-acylglucoses bearing short to medium chain length fatty acids. These compounds are localized in the glandular exudate of the type IV trichomes and may accumulate to levels in excess of 400 g/cm². In choice assays, purified glucose esters fromL. pennellii reduced aphid settling at concentrations as low as 25 g/cm²; at concentrations of 150 g/cm² or more, all aphids avoided treated areas. Glucose esters were also active in deterring aphid settling in no-choice assays. At 100 g/ cm², these esters resulted in increased levels of mortality after 48 hr.     

Phytotoxicity of Vulpia Residues: II. Separation, Identification, and Quantitation of Allelochemicals from Vulpia myuros

Phytotoxicity-based extraction and fractionation were employed to separate and purify the allelochemicals from an aqueous extract of vulpia (Vulpia myuros) residues. Further analyses, identification, and quantitation of these allelochemicals were conducted by gas chromatography–mass spectrometry on the most toxic fraction. Twenty-one compounds were identified in the ether fraction from the vulpia residue aqueous extract. They were catechol, hydroquinone, 3,4-dimethoxyphenol, pyrogallol, coniferyl alcohol, and benzoic, succinic, hydrocinnamic, salicylic, protocatechuic, vanillic, gentisic, syringic, p-hydroxybenzoic, -hydroxybenzenepropanoic, p-hydroxyphenylacetic, p-hydroxybenzenepropanoic, hydroferulic, p-coumaric, hydrocaffeic, and ferulic acids. A chromatographic internal standard method with multiple-point calibration graphs was used to quantify the identified compounds. Quantities in the vulpia residues ranged from 1.36 to 81.0 g/g dry residue, in total accounting for 0.05% of the dry weight residue. The combined syringic and hydroferulic acids were present in the largest amount, 140.11 g/g residue. Vanillic, succinic, p-hydroxybenzenepropanoic, and salicylic acids were next in amount, ranging from 37.24 to 81.24 g/g residue. Catechol, hydrocinnamic acid, and hydroquinone were present in the smallest quantities, ranging from 1.36 to 1.82 g/g residue. The remainder of the compounds were intermediate in amount, ranging from 2.33 to 18.1 g/g residue.     

Isolation and Identification of Primary Metabolite Feeding Stimulants for Adult Western Corn Rootworm, Diabrotica virgifera virgifera Leconte, from Host Pollens

Consumption of pollens from several host plants was quantified for adult western corn rootworm, Diabrotica virgifera virgifera, with significantly more sweet corn and winter squash pollen consumed than that of common sunflower and Canada goldenrod. Sequential solvent extraction and chromatographic fractionation of host pollens, guided by a feeding bioassay of respective fractions, isolated dominant phagostimulatory activity in pools of free amino acids. Amino acid profiles were determined by TLC and HPLC analysis. For sweet corn pollen, proline was predominant, accounting for 70% of a total 95.3 mol free amino acid/g pollen; serine, alanine, -aminobutyric acid (GABA), and asparagine occurred in decreasing order of concentration. In squash pollen, -alanine predominated (30% of 111 mol amino acid/g pollen), followed by asparagine, alanine, proline, and GABA. Histidine (42% of 83.8 mol amino acid/g pollen), proline, aspartic acid, asparagine, and alanine were dominant for sunflower pollen; and for goldenrod, proline (51% of 50.6 mol amino acid/g pollen), trans-hydroxyproline, serine, histidine, and alanine predominated. The five dominant amino acids from each pollen accounted for 80–90% of total amino acid content. Simple mixtures of some dominant amino acids, approximating levels found in sweet corn and squash pollen, gave phagostimulation similar to that of the crude extracts.     

Behavioral response of male white peach scale to the sex pheromone, (R,Z)-3,9,-dimethyl-6-isopropenyl-3,9-decadien-1-ol propionate and corresponding alcohol

Males of the white peach scale,Pseudaulacaspis pentagona (Tar-gioni-Tozzetti), in Florida differ from this scale in France in their responses to putative pheromonal chemicals presented in a laboratory bioassay. Males from Florida were attracted to, and exhibited sexual (coputatory) behaviors at, the locus of evaporation of (R,Z)-3,9-dimethyl-6-isopropenyl-3,9-deca-dien-1-ol propionate (P) (previously identified from effluvia of Florida females). Addition of the corresponding primary alcohol (A) to the propionate did not alter the attraction of Florida males to the synthetic P and did not alter their sexual responses from those exhibited by males exposed to P alone. In contrast, the effluvia from French scales has been reported to contain P and A, and the alcohol has been reported in laboratory studies to be required to release sexual behavior in French males. This suggests that the conspecific status of the scale in Florida and France should be reexamined. Field trap baits with 2.5 g of a 1 1 mixture of P and A captured significantly fewer Florida males than traps baited with 1.25 g of P alone, but traps similarly baited with 0.125 g of each material captured the same number of insects as traps baited with 0.125 g of P alone.Mention of a commerical or proprietary product in this paper does not constitute an endorsement of that product by the USDA.     

Role of the isoflavonoid coumestrol in the constitutive antixenosic properties of “Davis” soybeans against an oligophagous insect,the mexican bean beetle

The antixenosic properties of the isoflavonoid, coumestrol, were tested in dual-choice leaf disk bioassays with the Mexican bean beetle (Epilachna varivestis Mulsant).E. varivestis preferred the methanol-r,reated (solvent-control) disk when the coumestrol concentration was 1.8 or 0.9/leaf disk. No preference was observed between the coumestrol-treated and the solvent-control disks when the coumestrol concentration was higher, at 3.6, or lower, at 0.45g/leaf disk. Coumestrol alone clearly is not responsible for the significant constitutive antixenosic properties of Davis soybeans,Glycine max (L.) Merrill, because the amount of coumestrol in these plants is significantly less than the minimum concentration which was antixenosic in this study. However, it might contribute to a constitutive antixenosis in Davis involving a profile of allelochemicals. A computer-aided densitometer, adapted to measure the leaf disk area, increased the resolution of the leaf area 250 (X)-fold as compared to the standard LI-COR leaf area meter.     

Interactions between pheromone traps with different strength lures for the pine beauty moth,Panolis flammea (Lepidoptera: Noctuidae)

Catches of malePanolis flammea in traps baited with lures containing 25 g of sex attractant are enhanced when in the proximity of traps baited with 125-g lures. The degree of enhancement is increased as the intertrap distance is decreased, and when the low-dose trap is upwind of the high-dose one. The patterns of alteration in trap catch suggest that moths initially attracted by one lure may divert into other traps, which may be either upwind of the original trap (overshooting), or downwind (undershooting). Overshooting can result in up to fivefold increases in catch and may provide a useful method for estimating the attractant zone of particular lure/trap combinations.     

Effects of mixtures of phenolic acids on leaf area expansion of cucumber seedlings grown in different pH portsmouth A1 soil materials

Cucumber seedlings growing in A₁horizon Portsmouth soil material adjusted to pH 5.2, 6.0, or 6.9 were treated with 0, 0.25 or 0.5, mol/ g soil ferulic acid,p-coumaric acid, vanillic acid, or an equal mixture (0.5 mol/g total) of two acids every other day. A total of five treatments was given starting with day 7 from seeding. Absolute rates of leaf expansion were determined for seedlings. The experiment was terminated when seedlings were 17 days old. All three phenolic acids inhibited leaf expansion. The dose required for 50% inhibition of absolute rates of leaf expansion increased as pH of the soil systems increased. The order of toxicity based on 50% dose and relative potency were as follows: ferulic acid > vanillic acid =p-coumaric acid. Effects of mixtures of phenolic acids on absolute rates of leaf expansion, when compared to the effects of individual phenolic acids, were found to be antagonistic for the ferulic-vanillic acid mixture and the ferulic-p-coumaric acid mixture in the pH 5.2 soil systems. Several phenolic acid treatments were required before antagonistic effects of mixtures were evident. In all other instances, when treatment effects were significant, the effects of individual phenolic acids were additive.Paper No. 11875 of the Journal Series of the North Carolina Agricultural Research Service, Raleigh, North Carolina 27695-7601. The use of trade names in this publication does not imply endorsement by North Carolina Agricultural Research Service of the product named, nor criticism of similar products not mentioned. This research was partially supported by US-Spain Joint Committee for Scientific and Technological Corporation project CCA-8309/166.     

Caste-dependent pheromones in the head of the antTetramorium caespitum

The heads of maleT. caespitum contain 4-methyl-3-hexanol (1.7 g, only the erythro isomer(s) detected) and 4-methyl-3-hexanone (0.8 g). The heads of alate females contain 0.1 g of each compound, whereas only the alcohol (0.1 g) was found in the heads of workers. Both compounds act as attractants for the workers and their possible functions are discussed.'Chargé de Recherche du F.N.R.S.Chercheur qualifié du F.N.R.S.     

Distribution of the carcinogenic terpene ptaquiloside in bracken fronds,rhizomes (Pteridium aquilinum), and litter in Denmark

The distribution of ptaquiloside (PTA) was studied in four Danish bracken populations in order to evaluate the transfer of PTA from ferns to soil. Populations showed statistically significant differences in PTA contents of fronds and rhizomes despite large in-site variations. The highest concentrations were encountered in fronds with concentrations ranging between 213 and 2145 g/g, while rhizomes had concentrations between 11 and 902 g/g. PTA was present in soil materials in amounts of 0.22–8.49 g/g but apparently with no correlation with PTA contents of fronds or rhizomes. Laboratory tests showed that water could leach PTA from bracken fronds, which is in support of the high soil contents observed at sites exposed to heavy showers just before sampling. The observed soil contents correspond to estimated soil solution concentrations of 200–8500 g/liter, demonstrating a substantial risk of PTA contamination of surface water and groundwater.     

Defensive secretions of three species ofAcilius (Coleoptera: Dytiscidae) and their seasonal variations as determined by high-pressure liquid chromatography

A rapid, sensitive, stable, and quantitative high-pressure liquid chromatographic technique was developed for the analysis of defensive secretions obtained from the pygidial and prothoracic glands of dytiscids. Methods were developed for both normal phase (Porasil) and reverse phase (Bondapak C₁₈) columns. The applicability of this technique was demonstrated when defensive compounds ofAcilius semiculcatus, A. sylvanus andA. mediatus were isolated, identified, and quantitated. No major differences were found in the composition of the defensive secretions between the three species. The seasonal defensive titer ofA. semisulcatus was determined from June through October 1977. The pygidial defensive agents (benzoic acid,p-hydroxybenzaldehyde, and methylp-hydroxybenzoate varied from 9.0 to 67.8 g and exhibited a maximum in July, and a steroid from the prothoracic gland varied from 7.1 to 33.2 g and was maximum in October.     

Attraction of 3-Methyl-1-Butanol and Ammonia Identified from Enterobacter agglomerans to Anastrepha suspensa

Tests demonstrated that volatile chemicals emitted from Enterobacter agglomerans, a bacterium that has been isolated from adults as well as fruit infested with larvae of the Caribbean fruit fly, Anastrepha suspensa (Loew) and other pest fruit flies, are attractive to female A. suspensa in laboratory bioassays. 3-Methyl-1-butanol and ammonia were identified as the two primary volatile chemicals released from active cultures of E. agglomerans. No 3-methyl-1-butanol and little ammonia (16.0 g/hr) are released from sterile tryptic soy agar plates. E. agglomerans-inoculated tryptic soy agar plates, however, released an average of 1.5 ± 0.53 g/hr 3-methyl-1-butanol and 332.9 ± 239.16 g/hr ammonia after 24 hr of growth. 3-Methyl-1-butanol lures were formulated in a membrane-based system to provide a constant release rate of synthetic chemical. Release rates ranged from 0.046 ± 0.007 to 12.16 ± 2.76 g/hr. In laboratory tests, equal numbers of females were captured in response to ammonium carbonate lures that released ammonia at the rate of 100 g/hr and to 3-methyl-1-butanol lures that released 12.16 ± 2.756 g/hr of synthetic material. The combination of the two lures was more attractive than ammonia alone. Availability of lures formulated for a range of 3-methyl-1-butanol release rates will facilitate field tests of this putative microbial attractant and may lead to a better understanding of the role of bacteria in the ecology of pest fruit flies.     

Modification of allelopathic effects ofp-coumaric acid on morning-glory seedling biomass by glucose,methionine, and nitrate

Studies of allelopathy have emphasized primarily the identification and quantification of phytotoxins in soils, with only limited attention directed toward how organic (carbon) and inorganic constituents (nutrients) in the soil may modify the action of such phytotoxins. In the present study, increasing carbon (C) levels (up to 108g C/g soil) supplied as glucose, phenylalanine, orp-hydroxybenzoic acid did not alter morning-glory biomass, but similar C levels supplied as leucine, methionine, orp-coumaric acid were inversely related to morning-glory biomass. Similar joint action and multiplicative analyses were used to describe morning-glory biomass response to various C sources and to generate dose isolines for combinations ofp-coumaric acid and methionine at two NO₃-N levels and for combinations ofp-coumaric acid and glucose at one NO₃-N level. Methionine, glucose, and NO₃-N treatments influenced the inhibitory action ofp-coumaric acid on biomass production of morning-glory seedlings. For example, results from the multiplicative analysis indicated that a 10% inhibition of morning-glory biomass required 7.5gp-coumaric acid/g soil, while the presence of 3.68g methionine/g soil thep-coumaric acid concentration required for 10% inhibition was only 3.75g/ g soil. Similar response trends were obtained forp-coumaric acid and glucose. The higher NO₃-N (14 vs. 3.5g/g) treatments lowered the methionine and increased thep-coumaric acid concentrations required for 10% inhibition of morning-glory biomass. These results suggested that allelopathic interactions in soil environments can be a function of interacting neutral substances (e.g., glucose), promoters (e.g., NO₃-N), and/or inhibitors (e.g., methionine andp-coumaric acid) of plant growth.The use of trade names in this publication does not imply endorsement by the North Carolina Agricultural Research Service of products named, nor criticism of similar ones not mentioned.     

Fabrication of Micro-Reactors Using Tape-Casting Methods

We have developed a simple, rapid, and inexpensive method for the fabrication of micro-channel reactors using tape-casting methods. Rectangular channels, with self-contained heaters, were fabricated with cross-sectional dimensions of 500 m×800 m and 1000 m×800 m. The conduits were loaded with Pd and Pd/alumina catalysts using a syringe. To demonstrate the capabilities of this methodology, n-butane oxidation rates were measured between 300 and 700 K. Because free-radical reactions are suppressed by the small channel size, it was possible to measure catalytic rates within the flammability limits. Based on the results, it appears that micro-reactors formed using tape-casting methods may be useful for initial catalyst screening.