Showing papers in "Journal of Chemical Ecology in 1985"

cis-Vaccenyl acetate as an aggregation pheromone inDrosophila melanogaster.

Abstract: Pentane extracts of matureDrosophila melanogaster males substantially increased the attractiveness of food odors to both males and females in a wind-tunnel olfactometer. Extracts of females caused no such increase. An active component of the extract was isolated and identified as (Z)-11-octadecenyl acetate (cis-vaccenyl acetate, cVA), and synthetic cVA was active in bioassay. Hydrolysis of the ester linkage or movement of the double bond to the 9 position destroyed the activity. Mature virgin males released cVA into their feeding vials, and amounts of synthetic CVA equal to that released per male caused significant bioassay responses. Females, which were known to receive cVA from males during copulation, were found to emit relatively large amounts of the ester into their feeding vials within 6 hr after mating. cVA had been demonstrated previously to be a close-range pheromone inD. melanogaster, discouraging males from courting other males or recently mated females; it now appears to have a longer-range function as well.

Double-bond location in monounsaturated fatty acids by dimethyl disulfide derivatization and mass spectrometry: Application to analysis of fatty acids in pheromone glands of four lepidoptera.

Abstract: A rapid analytical procedure for the determination of the position of double bonds in mixtures of monounsaturated fatty acid methyl esters has been developed. The method is based on direct capillary GC-MS-EI analysis of dimethyl disulfide adducts. The procedure was applied to mixtures of monounsaturated fatty esters from pheromone gland extracts of three tortricids from theChoristoneura genus,C. fumiferana, C. occidentalis, andC. pinus pinus, and one noctuid from the Plusiinae subfamily,Plusia chalcites. A correlation was found between the known major pheromone components in the four species with the corresponding fatty acids. Some of the additional fatty acids may be precursors to as yet unidentified minor pheromone components, present in extremely small quantities, in these species.

Use of dye-labeled protein as spectrophotometric assay for protein precipitants such as tannin.

Abstract: Bovine serum albumin has been covalently labeled with Remazol brilliant blue R to provide a substrate for a convenient spectrophotometric assay for protein precipitants. The blue protein is especially useful for measuring protein precipitation by vegetable tannins because its absorption maximum is at a wavelength where plant pigments exhibit minimum absorption. Blue BSA has been used to determine, by competition experiments, the relative affinity of various proteins for tannins. A procedure for purifying condensed tannin from commercially available quebracho extract is described.

Synergism between myristicin and xanthotoxin, a naturally cooccurring plant toxicant.

Abstract: Myristicin, a methylenedioxyphenyl (MDP)-containing phenylpropene constituent of the leaves of many plants in the family Umbelliferae, is a highly effective Synergist of the cooccurring furanocoumarin xanthotoxin. As little as 0.10 % in an artificial diet can increase the toxicity of xanthotoxin toHeliothis zea (Lepidotera: Noctuidae) fivefold. In addition to increasing the proportion of caterpillars dying at a given xanthotoxin concentration, myristicin also increases the rate at which they die and increases the time to molt of surviving larvae. That there was no increase in the deterrency of xanthotoxin in the presence of myristicin suggests that the mechanism of synergism is not behaviorial but rather is biochemical, via MDP competitive inhibition of microsomal mixed function oxidases.

Compared behavioral responses of maleDrosophila melanogaster (Canton S) to natural and synthetic aphrodisiacs.

Abstract: Cuticular aphrodisiacs fromD. melanogaster females were further characterized and the male response specificity towards such natural and synthetic unsaturated hydrocarbons was investigated. The behavioral activity seems to be correlated with some chain-length requirement and double-bond position; at least one double bond in position 7 seems necessary. This position is more abundant among natural monoenes, and among dienes which also bear a second double bond in position 11, whatever the chain length. Bioassays of the synthetic (Z,Z)-7,11-heptacosadiene yielded a dose-response curve close to that of the natural mixture of heptacosadienes in which the 7–11 isomer is predominant. This female specific 7,11 heptacosadiene appears to be the most potent aphrodisiac for males of the species. Its threshold is lower than that of both 7,11-nonacosadiene and 7-pentacosene which might also play a role in sex and species recognition.

Isolation and identification of mosquito repellents in Artemisia vulgaris

Abstract: The mugwortArtemisia vulgaris L. (Compositae: Anthemideae) contains insect repellents which can be released from the plant tissues by combustion. Work was carried out to isolate and identify the repellent compounds. The dried, pulverized whole plants were steam-distilled to give a repellent essential oil which was fractionated by column chromatography. Active fractions were analyzed by capillary GC and by combined GC-MS. A number of compounds, mainly monoterpenoids, were identified. When tested as repellents against the yellow fever mosquitoAedes aegypti L. (Diptera: Culicidae), (±)-linalool, (±)-camphor, (+)-camphor, (−)-camphor, isoborneol, (−)-borneol, terpinen-4-ol, and isobornyl acetate were active at 0.14 mg/cm2 or higher. Nonanone-3, (α+β)-thujone, and bornyl acetate were active at 0.28 mg/cm2 or higher. β-Pinene, myrcene, α-terpinene, (+)− limonene, and cineole were active at 1.4 mg/cm2. Of the repellent compounds identified, terpinen-4-ol was the most active and was as effective as dimethyl phthalate.

Use of predator odors as repellents to reduce feeding damage by herbivores : II. Black-tailed deer (Odocoileus hemionus columbianus).

Abstract: The effectiveness of predator odors (fecal and urine) in suppressing feeding damage by black-tailed deer was investigated in pen bioassays at the University of British Columbia Research Forest, Maple Ridge, British Columbia, Canada. A total of eight bioassay trials tested the effects of these odors on deer consumption of salal leaves and coniferous seedlings. Cougar, coyote,and wolf feces as well as coyote, wolf, fox, wolverine, lynx, and bobcat urines provided the most effective suppression of deer feeding damage. Novel odors of ammonia and human urine did not reduce feeding. Predator fecal odor formulations in direct foliar application, adhesive application, and in plastic vials were all effective in suppressing deer feeding. Of all urines tested, coyote provided the most consistent suppression of deer browsing on salal. Deer consumed significantly more untreated Douglas fir and western red cedar seedlings than those protected by coyote urine odor. The active repellent components of predator odors which suppress deer feeding may be suitable for encapsulation in controlled-release devices which could provide long-term protection for forest and agricultural crops.

Cucurbitacins : Plant-derived defense compounds for diabroticites (Coleoptera: Chrysomelidae).

Abstract: Four species of diabroticites with different host specificities are shown for the first time to sequester cucurbitacins. While all beetles fed on an artificial diet (no cucurbitacins) were readily consumed by Chinese praying mantids, a significant proportion of adultDiabrotica balteata (72%),D. undecimpunctata howardi (46%), andD. virgifera virgifera (24%) fed on squash fruit containing cucurbitacins B and D were rejected. Moreover, even when adults did not feed on cucurbitacins, 21-24% ofAcalymma vittatum were rejected by the mantids which is consistent with larval sequestration of cucurbitacins. The mantids failed to learn to avoid any of the beetle species despite adverse effects associated with ingestion, i.e., uncoordination, regurgitation, etc. A cucurbitacin D metabolite accumulated and was sequestered for extended periods of time in the hemolymph of all four species. In addition, female beetles that had ingested cucurbitacins laid eggs containing substantial amounts of cucurbitacins.

Three European corn borer populations in New York based on sex pheromones and voltinism

Abstract: Pheromone blend analyses of glands from individual female European corn borers,Ostrinia nubilalis (Hubner), from field-collected larvae or pupae associated with bivoltine flights in June and August and a univoltine flight in July have shown that: (1) a site in western New York has a bivoltine biotype utilizing (Z)-11-tetradecenyl acetate as its primary pheromone component (designatedZ), (2) two sites in central New York have mixed populations consisting of a bivoltine biotype utilizing theE pheromone isomer (designatedE) and a univoltine biotype utilizingZ, and (3) one site in central New York was found to have only the univoltineZ biotype. The combinations of voltine biotypes and pheromone strains found in New York support the existence of three European corn borer populations designated bivoltineE, bivoltineZ, and univoltineZ.

Feeding deterrency of some pyrrolizidine, indolizidine, and quinolizidine alkaloids towards pea aphid (Acyrthosiphon pisum) and evidence for phloem transport of indolizidine alkaloid swainsonine

Abstract: The feeding deterrency of a series of pyrrolizidine, indolizidine, and quinolizidine alkaloids and selected derivatives was measured against the pea aphid (Acyrthosiphon pisum Harris). The indolizidine alkaloid, castanospermine, was intensely active (ED50, 20 ppm) as were the quinolizidine alkaloids, but only modest feeding deterrency was observed with most of the pyrrolizidine alkaloids tested. The insect survival rate of aphids on a castanospermine-supplemented diet over 24 hr was also very low relative to the controls. Castanospermine does not inhibit aphid trehalase. The indolizidine alkaloid swainsonine occurred in the honeydew of pea aphid feeding on the locoweed,Astragalus lentiginosus. Since the pea aphid is a phloem feeder, swainsonine must be transported in the phloem.

Effect of hypoxanthine-3(N)-oxide and hypoxanthine-1(N)-oxide on central nervous excitation of the black tetraGymnocorymbus ternetzi (Characidae, Ostariophysi, Pisces) indicated by dorsal light response.

Abstract: The change of state in the central nervous system ofGymnocorymbus ternetzi after detection of hypoxanthine-l(N)-oxide, hypoxanthine-3(N)-oxide, and of the alarm substance from conspecifics was measured quantitatively by means of the fishes' equilibrium behavior. The fish swam freely in a tiny cage, illuminated horizontally from one side. The change of the angle of inclination of the dorsoventral axis of the fish was registered by means of a videorecorder. The recordings were later measured on the monitor in single frames at 0.2-sec intervals where the equilibrium position of the fish could be accurately determined ± 1 °. Various substances were presented to the fish, and their effects upon equilibrium position were recorded. An enhanced optical alertness shown by an increase in the fishes' inclination was generally produced with alarm substance. Without any additional stimulation, the factorU, representing quantitatively the degree of the change of central state, varied slightly within the experimental period of 1 min; however, this factor never exceededU= 1.0 ± 0.15 in control fish. The increase ofU usually exceeded considerably the value 1.15 when skin extract from conspecifics or 7–8 μg of hypoxanthine-3(N)-oxide were given. However, when hypoxanthine-l (N)-oxide was presented,U generally did not exceed 1.15. The difference between hypoxanthine-3(N)-oxide and hypoxanthine-l(N)-oxide was highly significant. This result is in accordance with the findings on fish schools ofDanio malabaricus, where hypoxanthine-3(N)-oxide elicited the fright reaction, but hypoxanthine-1(N)-oxide was ineffective. The results support the hypothesis that the alarm substance from the skin ofPhoxinus phoxinus is identical with hypoxanthine-3(N)-oxide. The results with alarm substance or hypoxanthine-3(N)-oxide did not show any adaptation. This was also true in fish that were stimulated repeatedly at intervals of a couple of minutes only. InGymnocorymbus, which has compensated for removal of the otolith of one utriculus, conspecific skin extract triggers the typical postoperative phenomenon, i.e., rotation around the fishes' long axis towards the operated side. Whereas such a decompensation could be elicited by hypoxanthine-3(N)-oxide as well, hypoxanthine-l(N)-oxide had no effect. This finding is interpreted as an effect of the alarm substance and of hypoxanthine-3(N)-oxide on the centers of equilibrium.

Gaster flagging by fire ants (Solenopsis spp.): Functional significance of venom dispersal behavior

Abstract: Behavioral and chemical studies with laboratory colonies indicate that the imported fire antSolenopsis invicta Buren (Myrmicinae) disperses venom through the air by raising and vibrating its gaster (i.e., “gaster flagging”). This mechanism of airborne venom dispersal is unreported for any ant species. Foraging workers utilize this air-dispersed venom (up to 500 ng) to repel heterospecifics encountered in the foraging arena, while brood tenders dispense smaller quantities (∼ 1 ng) to the brood surface, presumably as an antibiotic. Brood tenders removed from the brood cell and tested in heteropspecific encounters in the foraging arena exhibited the complete repertoire of agonistic gaster flagging behavior. These observations suggest that airborne venom dispersal by workers is context specific rather than temporal caste specific and that workers can control the quantity of venom released.

Use of predator odors as repellents to reduce feeding damage by herbivores : I. Snowshoe hares (Lepus americanus).

Abstract: The effectiveness of predator odors (fecal, urine, and anal scent gland) in suppressing feeding damage by snowshoe hares was investigated in pen bioassays at the University of British Columbia Research Forest, Maple Ridge, British Columbia, Canada. A total of 28 bioassay trials tested the effects of these odors on hare consumption of willow browse and coniferous seedlings. Lynx and bobcat feces, weasel anal gland secretion, and lynx, bobcat, wolf, coyote, fox, and wolverine urines resulted in the most effective suppression of hare feeding damage. Novel odors of domestic dog urine and 2-methylbutyric acid did not reduce feeding. A field bioassay with lodgepole pine seedlings and weasel scent provided significant results comparable to the pen bioassays. The short-term (up to seven days) effectiveness of these treatments was more likely due to evaporative loss of the active repellent components of a given odor than habituation of hares to the stimulus. Predator odors as repellents have a biological basis compared with the anthropomorphic origins of commercial repellents. When encapsulated in weather-proof controlled-release devices, these odors could provide long-term protection for forestry plantations and agricultural crops which experience hare/rabbit feeding damage.

Stimulatory effects of tannins and cholic acid on tryptic hydrolysis of proteins: Ecological implications.

Abstract: The biochemical basis for considering tannins as digestion inhibitors has been reexamined. Both stimulatory and inhibitory effects of tannins on tryptic hydrolysis are reported. We show how stimulation may result from tannin-induced structural changes in the substrate protein, effectively denaturing it. The surfactant and bile constituent cholic acid also produced similar stimulatory effects. These results have considerable implications for normal digestive physiology as well as for the impact of tannins on argicultural and natural herbivore populations.

Insect antifeedant activity of clerodane diterpenoids against larvae ofSpodoptera Littoralis (Boisd.) (Lepidoptera).

Abstract: Antifeedant activities of nine clerodane diterpenoids, isolated in this laboratory from different species ofAjuga plants, have been studied against larvae of Egyptian cotton leafwormSpodoptera littoralis (Boisd.) (Lepidoptera) by application of the leaf disk method. Evaluation of activity was carried out by calculating, at different time intervals, the feeding ratio (FR) from the relationship between the consumed areas of treated disks (CTD) and control disks (CCD); for comparison purposes a FR50 defined as the FR at a CCD of 50% was established. Some compounds exhibited activity at a 0.01 μg/cm2 dose (0.3 ppm). Structure-activity relationships are discussed

Effects of surfactants, pH, and certain cations on precipitation of proteins by tannins.

Abstract: Tannic acid and pin oak tannins precipitate large amounts of the abundant leaf protein, ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPC), over a wide pH range (6.15-9.30) in the presence of sodium, potassium, magnesium, and calcium ions at concentrations comparable to those reported in the gut fluids of lepidopteran herbivores. The presence of lysolecithin, a surfactant known to be present in the gut fluids of some insects, significantly reduces the amount of RuBPC precipitated under these conditions. We conclude that high detergency is far more effective than high alkalinity in countering the potential protein-precipitating properties of tannins. We further conclude that tannins do not deserve the status they were once accorded as general, all-purpose, dose-dependent, antidigestive defensive chemicals. We also describe the application of the Schaffner-Weissman protein assay for studying the protein-precipitating capacity of plant extracts. This method is far superior to the one we have used in our earlier studies.

Kairomones for the egg parasiteTrichogramma evanescens Westwood

Abstract: In a four-armed airflow olfactometerTrichogramma evanescens Westwood females were attracted by a volatile substance(s) released by virgin females of the great cabbage white butterfly,Pieris brassicae L. Males or recently mated females did not cause attraction. Furthermore,T. evanescens was also attracted by volatiles released by calling virgin cabbage moths,Mamestra brassicae L. However, the parasites did not respond to (Z)-11-hex-adecenylacetate (the main component of the sex pheromone ofM. brassicae), a crude hexane extract of the sex pheromone gland, or to males or recently mated females.

Inhibition of barnacle settlement and behavior by natural products from whip corals,Leptogorgia virgulata (Lamarck, 1815).

Abstract: Laboratory-reared barnacle larvae were used to study natural products from whip corals. Biological assays used barnacle responses in behavioral assays and in larval settlement assays. Whip corals contained substances that were active in both assays. Substances inhibiting swimming and reversible attachment of barnacle larvae were found in an aqueous extract of whip corals. Low-molecular-weight substances inhibiting barnacle settlement were found in a methylene chloride extract of material soluble in aqueous methanol. Antisettlement activity was associated with substances with specific mobilities in several chromatography systems. Partially purified material was effective in preventing settlement at concentrations of less than 0.2 μ/ml. Settlement inhibition involves adsorption of the natural product to surfaces.

Differences and similarities in cardenolide contents of queen and monarch butterflies in florida and their ecological and evolutionary implications.

Abstract: Florida queen butterflies are highly variable in cardenolide content and, in three populations studied, contained less cardenolide than did a sample of sympatric Florida monarchs. The possibility that queens stored a more potent set of cardenolides from their host plants (and therefore were as well protected as monarchs, even at lower concentrations) is refuted by Chromatographic analysis of wild butterflies, as well as controlled laboratory rearings. It therefore appears that, with respect to cardenolides, monarchs are better defended than are queens. Consequently, cardenolides are unlikely to explain the apparent shift in Florida viceroy mimicry away from resemblance of the monarch, toward mimicry of the queen. Other hypotheses to explain this mimetic phenomenon are suggested. Adult monarchs exhibit significant negative correlations between the concentration of cardenolide stored in their tissues and both body size and weight, whereas queens show no such correlations. The implications of these results for the study of “metabolic costs” of allelochemic storage are discussed. Chromatographic evidence is provided that monarchs do breed in south Florida during the winter months and that the likely host plant employed by the population studied wasAsclepias curassavica. This represents the first practical application of cardenolide “fingerprinting” to identify the larval host plants of wild danaid butterflies.

Use ofLemna minor L. as a bioassay in allelopathy.

Abstract: Investigations in allelopathy often require the use of a bioassay for evaluating limited quantities of potentially active growth regulators. A bioassay procedure was developed usingL. minor grown in 1.5-ml aliquots of nutrient medium with and without allelochemicals in wells of 24-well tissue culture cluster dishes with loose-fitting lids. Tests using six replications per treatment with several flavonoid compounds and derivatives of coumarin, benzoic acid, and cinnamic acid demonstrated that the bioassay was capable of measuring inhibition at levels of compound ranging from 50 to 1000 μmol. Strongly inhibitory treatments were visible after 1 or 2 days. After 7 days of growth, frond number, growth rate, and dry weight were used to evaluate effects. The bioassay system is relatively simple, very sensitive, reproducible, and can be used for testing small amounts and dilute concentrations of unknowns which have been separated by chromatography.

Determination of chirality of alcohol or latent alcohol semiochemicals in individual insects.

Abstract: A method is described for determining the enantiomeric composition of chiral alcohols, lactones, and hydroxy acids in quantities ranging from 25 ng to 10 μg. Derivatization of the substance with chirally pure acetyl lactate, followed by splitless capillary gas chromatography, enables enantiomeric determinations to be made within 1–3% of the actual value. This technique was applied in the determination of semiochemical inIps pini (Say),Apis mellifera (L.), andCryptolestes ferrugineus (Stephens). The results indicate that considerable variability exists within populations of some insects in the composition of their chiral semiochemicals, whereas others produce substances of constant composition.

Chemical detection of sex and condition in the crayfishOrconectes virilis.

Abstract: Individual crayfish (Orconectes virilis) were tested for responses to water containing conspecific individuals of several sex-status categories. Isolated males did not react to “self” water but did show aggressive postures while isolated, nonself male water was introduced. Males' responses to female water was different from responses to male water. Water from aggressing males elicited fewer agonistic postures and more “neutral” postures. Females showed little difference in response to waters from different categories of conspecifics.

Disturbance pheromones in the crayfishOrconectes virilis.

Abstract: The reactions of individual crayfish to the introduction of waters from tanks containing other individuals were recorded to test for the release of chemicals by stressed crayfish. FemaleOrconectes virilis and maleO. rusticus did not show responses to stressed crayfish. MaleO. virilis responded differently to undisturbed and disturbed male crayfish (conspecific and heterospecific). Responses to waters from tanks which contained disturbed individuals were similar whether the source of disturbance was aggressive, predatory, or thermal. Chemical(s) involved appear to persist for at least one hour at room temperature.

Effect of some floral scents on host finding by thrips (Insecta: Thysanoptera)

Abstract: The role of floral scents in host location by flower-dwelling thrips is investigated by experiment in the field. The scent of anisaldehyde significantly increased the catches of seven species of flower-dwelling thripid, but had no significant effect on three species of cereal thripid and one species of flower-dwelling aeolothripid. The catches of white (without UV) traps were increased by a factor of 3.3 to 8.3 in the presence of the scent.

Disposition and fate of cucurbitacin B in five species of diabroticites

Abstract: Five species of diabroticites with different host-plant preferences produced an essentially identical array of metabolites when fed radiolabeled cucurbitacin B synthesized in vivo and purified fromCucurbita maxima Duchesne seedlings. All species excreted the bulk of the cucurbitacin (67,17-94.59% total dpm), permanently sequestered a small proportion of a cucurbitacin conjugate in the hemolymph (0.98–2.76%), and apportioned the remainder between the gut, the body, and the eggs (when present). Markedly different ratios between the excretory metabolites (i.e., polar vs. unmetabolized cuc) suggest thatDibrotica virgifera virgifera, a grass specialist, andAcalymma vittatum, a cucurbit specialist, have lower rates of metabolic alteration than the polyphagousD. undecimpunctata howardi, D. balteata, andD. cristata, which is associated with relict prairies. Mean life-spans ofD. balteata and D. v. virgifera and maleA. vittatum decreased significantly with continuous feeding onCucurbita fruit containing cucurbitacins (vs. fruit devoid of cucs). The longevity of femaleA. vittatum, however, was unaffected by the presence of cucurbitacins.

Effects of various mixtures of ferulic acid and some of its microbial metabolic products on cucumber leaf expansion and dry matter in nutrient culture.

Abstract: Cucumber seedlings (Cucumis sativus cv. ‘Early Green Cluster’) ranging from 6 to 16 days of age were treated with various concentrations (0– 1 mM) of caffeic, ferulic,p-coumaric,p-hydroxybenzoic, protocatechuic, sinapic, syringic, and vanillic acids and mixtures of ferulic acid and one or two of the other phenolic acids. Seedlings were grown in full-strength Hoagland's solution which was changed every other day. Phenolic acid treatments were given with each nutrient solution change starting at day 6 or given once when seedlings were 13 or 14 days old. Leaf area, mean relative rates of leaf expansion, transpiration rates, water utilization, and the concentrations of the phenolic acids in nutrient solution were determined at one- or two-day intervals. Seedling dry weight was determined at final harvest. Seedling leaf area and dry weight were linearly related. Since leaf areas can be easily obtained without destructive sampling and leaf area expansion responds rapidly to phenolic acid treatments, it was utilized as the primary indicator of plant response. The resulting data suggested that a number of ferulic acid microbial metabolic products, as well as two other phenolic acids observed in soils (p-coumaric and syringic acid), can reduce seedling dry weight, leaf expansion, and water utilization of cucumber seedlings in a similar manner. The magnitude of impact of each of the phenolic acids, however, varied with phenolic acid and concentration. It appears that the inhibitory activity of these phenolic acids involved water relations of cucumber seedlings, since the phenolic acid treatments resulted in closure of stomata which then remained closed for several days after treatment. The data also demonstrated that the effects of mixtures of phenolic acids on cucumber seedlings may be synergistic, additive, or antagonistic. The type of response observed appeared to be related to the factor measured, the compounds in the nmixture, and the magnitued of inhibition associated with each compounds. The data also indicated that the effects of the various phenolic acids were reversible, since seedling leaf area increased rapidly once phenolic acids were removed from the root environment. Mean relative rates of leaf expansion recovered even in the presence of the various phenolic acids.

Effects of ferulic acid, an allelopathic compound, on leaf expansion of cucumber seedlings grown in nutrient culture.

Abstract: Cucumber seeds and seedlings at various ages (7–19 days old) were treated with a single treatment or multiple treatments (at 2-day intervals) of ferulic acid in nutrient culture. Ferulic acid treatments of cucumber seeds during stages of germination and radicle growth did not significantly reduce subsequent seedling growth. Ferulic acid treatments to seedlings reduced leaf area, leaf expansion, and dry weight of cucumber seedlings. Pretreatment of seeds and seedlings with 0.1 or 0.2 mM ferulic acid did not modify the effects of a single 1 mM ferulic acid treatment on leaf expansion when a single treatment was given at various times to seedlings ranging from 7 to 19 days of age. Treatments of 1mM or greater induced rapid wilting of leaves, but visible recovery occurred within 24–48 hr and subsequent treatments did not cause wilting. Once seedlings were removed from ferulic acid treatments, leaf expansion resumed. The magnitude of recovery depended on the concentration of ferulic acid, frequency of ferulic acid application and age of the seedling. Mean relative rates of leaf expansion recovered rapidly even in the presence of ferulic acid. Recovery of leaf expansion after ferulic acid treatments was faster for seedlings grown in an adequate nutrient environment than for seedlings grown in a limited nutrient environment. Ferulic acid disappeared from nutrient solutions with time, and two microbial metabolic products of ferulic acid (i.e., vanillic and protocatechuic acid) were identified in nutrient solutions.

A multichemical defense mechanism of bitter oliveOlea europaea (oleaceae) : Is oleuropein a phytoalexin precursor?

Abstract: Olea europaea (Oleaceae) is resistant in nature to insect and microbe attack. Two types of chemical protection were found in the foliage. One type is the bitterseco-iridoid glycosides oleuropein (1) and ligstroside (2); The other is a physical barrier of crystalline oleanolic acid (4) that coats the leaf surface. Theseco-iridoid glycosides were isolated using two different countercurrent chromatographies: rotation locular countercurrent chromatography (RLCC) and droplet countercurrent chromatography (DCCC). The dimethyl ester (III) was shown to be an artifact. This is the first isolation of ligstroside fromO. europaea. In an antimicrobial test by the paper disk method againstBacillus subtilis, Saccharomyces cerevisiae, andEscherichia coli, compounds I, II, and III inhibited a growth ofB. subtilis at pH 7. Similar tests under the influence of β-glucosidase suggest an aglycone of oleuropein, either the hemiacetal (i) or the possible enal-aldehyde (ii), could be the active intermediate. This intermediate could be produced rapidly in response to microorganism invasion. Oleuropein producing such a postinfection active intermediate could be referred to as a phytoalexin precursor.

Chemical regulation of polyethism during foraging in the neotropical termiteNasutitermes costalis.

Abstract: The soldiers ofNasutitermes costalis communicate information about the presence and location of food by laying chemical trails of sternal gland secretion. These trails first recruit additional soldiers, and as the number of soldiers contacting food and returning to the nest increases, trail pheromone concentration increases, and workers are recruited. This polyethic pattern of recruitment does not appear to depend on qualitative (caste-specific) properties of soldier and worker sternal gland secretions, but rather on quantitative differences in pheromone production between castes. Large third-instar workers have significantly greater sternal gland volumes than soldiers, and glands of approximately equivalent size have approximately equivalent recruitment effects. The recruitment and orientation effects of artificial trails prepared from worker sternal glands can be mimicked by increasing the concentration of soldier sternal gland pheromone.

Role of olfaction in host finding by aphid parasitoidAphidius nigripes (Hymenoptera: Aphidiidae).

Abstract: The olfactory responses of the parasitoidAphidius nigripes Ashmead were investigated with a four-field airflow olfactometer. Female and male parasitoids did not respond to potato plants, the food plant of their host. However, females were strongly attracted by odors from a preferred host,Macrosiphum euphorbiae (Thomas), and also from less preferred hosts such asMyzus persicae (Sulzer) andAphis nasturtii Kalt. Moreover,A. nigripes females responded positively to odors from a nonhost aphid,Rhopalosiphum maidis Fitch. The honeydew produced by these four aphid species was also very attractive to females. Males did not respond to aphids or honeydew but were highly attracted by odors from conspecific female parasitoids.