Influence of Pretreatment Stresses on Inhibitory Effects of Ferulic Acid, an Allelopathic Phenolic Acid

Experiments were conducted to determine the potential for acclimation (i.e., increased tolerance) to allelopathic phenolic acids resulting from pretreatment of seedlings with allelochemical (ferulic acid), drought, or nutrient stress. Cucumber seedlings were exposed to pretreatment stresses in a nutrient culture system for nine days, starting with day 3. Seedlings were subsequently treated for 5 hr with 0, 0.25, 0.5, or 0.75 mM ferulic acid. Acclimation (tolerance) was quantified by percentage inhibition of net phosphorus uptake. Seedlings grown with ferulic acid or drought pretreatment stresses were more tolerant to subsequent ferulic acid treatments (i.e., inhibition of net phosphorus uptake by ferulic acid was reduced). Nutrient pretreatment stress eliminated the inhibitory activity of ferulic acid on net phosphorus uptake. The results suggest that a general acclimation response to a variety of pretreatment stresses can confer an increased tolerance of plants to allelopathic phenolic acids such as ferulic acid.     

Inhibition and recovery of cucumber roots given multiple treatments of ferulic acid in nutrient culture

Ferulic acid, a frequently cited allelopathic agent, inhibited photosynthesis, leaf expansion, and root elongation of cucumber seedlings grown in aerated nutrient cultures in a growth chamber. Other effects were a reduction in the proportion of radioactivity fixed by photosynthesis translocated to roots, a stimulation in secondary root initiation, and an increase in root-shoot ratios. Inhibition of leaf expansion and root elongation induced by multiple ferulic acid treatments was rapidly lost once ferulic acid was removed from the root environment. The changes in general root morphology, i.e., average root length and root number, associated with ferulic acid treatments, were partially reversed or not affected when ferulic acid was removed from the root environment.Paper No. 11411 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 the North Carolina Agricultural Research Service of the products named, nor criticism of similar ones not mentioned.     

Effects of ferulic acid,an allelopathic compound,on net P,K, and water uptake by cucumber seedlings in a split-root system

Since distribution of allelopathic compounds in soils is highly variable, injurious effects by such compounds should be related to the frequency of contact with roots. Experiments were conducted to determine how P, K, and water uptake of cucumber seedlings were affected as the fraction of roots in contact with ferulic acid (FA) was increased. Seedlings were grown in Hoagland's nutrient solution for 14 days and then transferred to 0.5 mM CaSO₄ solution for 24 hr before being placed into a split-root culture system. The containers in the system were filled with 0.5 mM concentrations of KH₂PO₄ and CaSO₄ or 0.5 mM concentrations of KH₂PO₄, CaSO₄, and ferulic acid (FA). Net uptake of P by seedlings (milligrams per seedling) decreased in a curvilinear (concave) manner as the fraction of the roots in contact with FA increased. Net uptake of K (milligrams per seedling) and water (milliliters per seedling) by seedlings decreased linearly as the fraction of the roots in contact with FA increased. Net uptake of P, K, and water by seedlings was reduced 57, 75, and 29%, respectively, when the whole root system was exposed to FA. Net P and K uptake of roots (milligrams per gram root fresh weight) not in contact with FA decreased in a linear and curvilinear (convex) manner, respectively, as the fraction of roots in contact with FA increased. Net P and K uptake of roots in contact with ferulic acid increased in a linear and curvilinear (convex) manner, respectively. Net water uptake of roots (milliliters per gram root fresh weight) not in contact with FA increased in a curvilinear (concave) manner as the frequency of the roots in contact with FA increased. Net water uptake of roots in contact with FA did not show a trend. Transpiration (milliliters per square centimeter) was reduced in a linear manner as the fraction of roots in contact with FA increased. A very slight compensation by roots not in contact with FA for roots in contact with FA was observed for net water uptake rates. No compensation for P and K uptake rates was observed.Paper Mo. 12421 of the Journal Series of the North Carolina Agricultural Research Service, Raleigh, North Carolina 27695-7643. The use of trade names in this publication does not imply endorsement by the North Carolina Agricultural Research Service of the products named, nor criticism of similar ones not mentioned.     

Ferulic Acid and P-Coumaric Acid Synergistically Attenuate Non-Alcoholic Fatty Liver Disease through HDAC1/PPARG-Mediated Free Fatty Acid Uptake

Non-alcoholic fatty liver disease (NAFLD) is the most common liver disease and has become a growing public health concern worldwide. Polyphenols may improve high-fat diet (HFD)-related NAFLD. Our previous study found that ferulic acid (FA) and p-coumaric acid (p-CA) were the polyphenols with the highest content in foxtail millet. In this study, we investigated the mechanism underlying the impact of ferulic acid and p-coumaric acid (FA/p-CA) on non-alcoholic fatty liver (NAFLD). The association of FA and p-CA with fatty liver was first analyzed by network pharmacology. Synergistic ameliorating of NAFLD by FA and p-CA was verified in oleic acid (OA) and palmitic acid (PA) (FFA)-treated hepatocytes. Meanwhile, FA/p-CA suppressed final body weight and TG content and improved liver dysfunction in HFD-induced NAFLD mice. Mechanistically, our data indicated that FA and p-CA bind to histone deacetylase 1 (HDAC1) to inhibit its expression. The results showed that peroxisome proliferator activated receptor gamma (PPARG), which is positively related to HDAC1, was inhibited by FA/p-CA, and further suppressed fatty acid binding protein (FABP) and fatty acid translocase (CD36). It suggests that FA/p-CA ameliorate NAFLD by inhibiting free fatty acid uptake via the HDAC1/PPARG axis, which may provide potential dietary supplements and drugs for prevention of NAFLD.     

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.     

Effects of mixtures of phenolic acids on phosphorus uptake by cucumber seedlings

To determine how individual phenolic acids in a mixture might affect phosphorus (P) uptake, 15-day-old cucumber seedlings grown in solution culture were treated with ferulic, vanillic,p-coumaric, or equimolar mixtures of these phenolic acids. Phenolic acid and P uptake were determined by solution depletion. The joint action of the mixtures of these phenolic acids on P uptake was primarily additive. Thus, as the number of phenolic acids increased in the mixture, the concentrations of the individual phenolic acids in the mixture required to bring about a given response declined. Seedling uptake of individual phenolic acids from solution mixtures of phenolic acids was reduced when compared to the uptake of phenolic acids from single phenolic acid solutions. The magnitude of the reduction varied with phenolic acid and concentration. The dose required for 50% inhibition of P uptake was approximately two to three times higher for vanillic acid (6.73 mM) than for ferulic (2.27 mM) andp-coumaric acids (3.00 mM) when dose was based on the initial treatment concentrations. The dose required for 50% inhibition of P uptake was not significantly different for the three phenolic acids (42 ± 5 mol/g root fresh weight) when dose was based on phenolic acid uptake. Potential reasons for these differences are discussed.Paper No. 12527 of the Journal Series of the North Carolina Agricultural Research Service, Raleigh, North Carolina 27695-7643. 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. This research was partially supported by the US-Spain Joint Committee for Scientific and Technological Cooperation project CCA-8309/166.     

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

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.Paper No. 9256 of the Journal Series of the North Carolina Agricultural Research Service, Raleigh, North Carolina. Mention of a trademark or proprietary product does not constitute a guarantee or warranty of the product by the Agricultural Research Service and does not imply its approval to the exclusion of other products that may be suitable.     

Simultaneous effects of ferulic andp-coumaric acids on cucumber leaf expansion in split-root experiments

Experiments were conducted to determine how plant responses to mixtures of allelochemicals may change as the proportion of roots in contact with allelochemicals is modified. Thirteen-day-old cucumber seedlings were treated with ferulic and/orp-coumaric acid in a split-root nutrient culture system. Leaf areas were determined just prior to treatment and at harvest, 24 hr after treatment. Ferulic acid was more inhibitory to cucumber leaf expansion thanp-coumaric acid. The effects of ferulic andp-coumaric acids on leaf expansion were additive. For individual acids, mixtures of ferulic andp-coumaric acids in the same container and combinations of ferulic andp-coumaric acids in separate containers, the inhibition of leaf expansion was directly related to the product of the concentration of the acid(s) and the proportion of roots treated with the acid(s). Pretreatment with 0.2 or 0.4 mM ferulic acid and subsequent treatment with 0.5 mM ferulic acid failed to show evidence of acclimation by cucumber seedlings.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.     

Inhibition of cucumber leaf expansion by ferulic acid in split-root experiments

Experiments were conducted to determine how the proportion of a root system in contact with an allelopathic compound may affect seedling responses. Cucumber seedlings grown in a split-root nutrient culture system were given either single (1 mM) or multiple applications (0.5 mM) of ferulic acid. Seedlings receiving single applications were left in the treatment solutions for two days and then harvested, while seedlings receiving multiple applications had their solutions changed every other day for a total of three changes. Leaf areas were determined daily starting with the initial ferulic acid treatment. Mean absolute and mean relative rates of leaf expansion were inversely related to the proportion of the root system in ferulic acid solution. Leaf expansion was inhibited primarily during the first 24 hr after each treatment. A partial recovery of growth occurred during the second 24-hr period following each treatment. Root length was reduced by ferulic acid. These results suggest that information on root and allelochemical distribution in soils is important when assessing the potential of allelopathic interactions between plants.Paper No. 11940 of the Journal Series of the North Carolina Agricultural Research Service, Raleigh, North Carolina 27695-7643. 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.     

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.     

阿魏酸和川芎嗪在超临界CO2中溶解度的测定

采用动态法分别测定了阿魏酸和川芎嗪在超临界CO2中的溶解度.实验结果表明在压力10～35MPa和温度308.15～338.15K范围内,阿魏酸在超临界CO2中的溶解度(摩尔分数)为6.936×10(7～26.527×10(7;在压力10～30MPa和温度318.15～338.15K范围内,川芎嗪在超临界CO2中的溶解度(摩尔分数)为0.010～0.131.阿魏酸在超临界CO2中的溶解度随着压力的增加而增大;温度对阿魏酸溶解度的影响较为复杂,出现了交迭压力行为.而川芎嗪在超临界CO2中的溶解度在实验范围内没有出现交迭压力行为.采用Chrastil方程分别对阿魏酸和川芎嗪在超临界CO2中的溶解度数据进行了关联,其AARD值分别为12.92%和4.23%.     

Effects of Temperature and Photoperiod on Phytotoxic Root Exudates of Cucumber (Cucumis sativus) in Hydroponic Culture

In order to elucidate the effects of temperature and photoperiod on the quality and quantity of plant root exudates, a Japanese cucumber (Cucumis sativus, cv. Shougoin-Aonaga-Fushinari) was grown hydroponically in growth chambers under controlled temperature and photoperiod conditions with or without the addition of activated charcoal (AC) to the nutrient solutions. Fresh AC was used to trap the organic compounds exuded from cucumber roots every two weeks. Cucumber plants without AC were severely retarded in root growth and in the accumulation of dry matter, especially at high temperature and long photoperiod, compared to those with AC. The growth inhibitors, adsorbed on the AC or accumulated in the nutrient solution without AC, were extracted by organic solvents and analyzed by GC-MS. Benzoic acid and its derivatives, cinnamic acid derivatives, and fatty acids were identified. The rate of root exudation in vegetative and reproductive stages for some of these organic acids increased with the elevation of temperature and the elongation of photoperiod, and the mean rate was two or more times higher than the minimum exudation at low temperature with short photoperiod. Some of the identified compounds significantly inhibited the germination and/or root growth of lettuce and cucumber.     

The Allelochemical Sorgoleone Inhibits Root H+-ATPase and Water Uptake

Sorghum plants inhibit the growth of some adjacent species. Root exudates from grain sorghum (Sorghum bicolor), consisting primarily of the quinone sorgoleone, are phytotoxic to several plant species, yet the mechanisms of growth inhibition remain to be fully explained. Disruption of electron transport functions in isolated mitochondria and chloroplasts has been reported as one explanation for growth inhibition. In the studies reported here, however, soybean seedlings grown in nutrient solution with 10, 50, or 100 microM sorgoleone showed no disruption of photosynthesis, as measured by leaf fluorescence and oxygen evolution, yet their mean leaf surface area was less when grown in 100 microM sorgoleone. Furthermore, in the presence of these same concentrations of sorgoleone, decreased nutrient solution use by soybean seedlings and decreased H+-ATPase activity in corn root microsomal membranes were observed. This suggests that impairment of essential plant processes, such as solute and water uptake, driven by proton-pumping across the root cell plasmalemma should also be considered as a mechanism contributing to observed plant growth inhibition by sorgoleone.     

Solution volume and seed number: Often overlooked factors in allelopathic bioassays

Cucumber seeds were germinated under various combinations of solution volume and seed number with a range of ferulic acid concentrations. At each concentration, radicle growth decreased as the relative amount of ferulic acid available per seed increased from (25 seeds/5 ml) to 5 (5 seeds/5 ml) to 19 (25 seeds/95 ml). With 2.0 mM ferulic acid in buffered solution, radicle lengths after 48 hr ranged from 71 to 47% of control. The amount of ferulic acid remaining in 2.0 mM solution after 48 hr was directly proportional to the amount initially available per seed, and ranged from 9 to 91%. Solution volume and seed number also significantly affected inhibition by vanillic acid, caffeic acid, and juglone. With 0.1 mM juglone, radicle lengths after 48 hr were 88% of control with 25 seeds/5 ml, 68% with 5 seeds/5 ml, and 56% with 25 seeds/90 ml. The data demonstrated that lower phytotoxin concentrations can produce equivalent or greater inhibitory effects than higher concentrations when the amount available per seed for uptake is greater. Equivalent inhibition of radicle growth was observed with 1.0 mM (5 seeds/5 ml) and 2.0 mM (25 seeds/5 ml) ferulic acid. Available literature on herbicides indicates that similar effects occur in greenhouse and field studies.     

Anti-Oxidation and Anti-Inflammatory Potency Evaluation of Ferulic Acid Derivatives Obtained through Virtual Screening

Various factors such as ultraviolet rays can cause a continuous threat to our skin, resulting in inflammation or oxidation problems. Ferulic acid (FA), with certain antioxidant and anti-inflammatory properties, is widely used in many cosmetics, even used to treat various diseases in the clinic. In this study, the FA structural skeleton was used to search for FA derivatives. Then, molecular docking, the rule of five, and Veber rules were performed to virtually screen compounds that can bind to proteins with a good drug likeness. DPPH and ABTS were used to evaluate their antioxidant potency and an MTT assay was employed to investigate the toxicities of the compounds, while Griess Reaction System and ELISA were used to judge the concentration variations of NO and different inflammatory factors (TNF-α, IL-1β, and IL-6). Western blotting featured nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) protein expression levels. The trend of the intracellular changes of reactive oxygen species (ROS) was detected by the DCFH-DA method and fluorescence staining. As a result, we found that the ferulic acid derivative S-52372 not only had certain scavenging effects on free radicals in biochemical experiments, but also prevented inflammation and oxidative stress in LPS-stimulated RAW264.7 cells in the cellular environment; intracellular ROS and inflammatory mediators, including iNOS, COX-2, TNF-α, and IL-6, were also suppressed. In a computer prediction, S-52372 owned better water solubility and lower toxicity than FA. This compound deserves further research to find an ideal FA derivative.     

Effects of mixtures of four phenolic acids on leaf area expansion of cucumber seedlings grown in Portsmouth B1 soil materials

Cucumber seedlings growing in a 12 mixture of soil (Portsmouth B₁) and sand adjusted to pH 5.2 were treated every other day five times with 0, 0.0625, 0.125, 0.25, or 0.5 mol/g soil of ferulic, caffeic,p-coumaric,p-hydroxybenzoic, protocatechuic, sinapic, syringic, or vanillic acids. Treatments began when seedlings were 8 days old. The effects on mean absolute rates of leaf expansion were used to estimate the relative potencies of these phenolic acids to ferulic acid. Based on the results of this experiment, ferulic,p-coumaric,p-hydroxybenzoic, and vanillic acids were chosen for further study. Materials and procedures were identical in the second study, but treatments consisted of mixtures of the four phenolic acids at concentration combinations designed to achieve 40 % or 60 % inhibition of absolute rates of leaf expansion. Using joint action analysis, a model describing the action of the phenolic acid mixtures was developed. A model involving only two factor terms was sufficient to describe the observed responses of cucumber leaf area to the phenolic acid mixtures. The action ofp-hydroxybenzoic acid on absolute rates of leaf expansion was inhibited by the presence of the other three phenolic acids. No other antagonisms or synergisms existed among the four compounds.This research was partially supported by the North Carolina Agricultural Research Service, Raleigh, North Carolina 27695-7643 and by the US-Spain Joint Committee for Scientific and Technological Cooperation project CCA-8309/166.     

Effects of Microbial Utilization of Phenolic Acids and their Phenolic Acid Breakdown Products on Allelopathic Interactions

Reversible sorption of phenolic acids by soils may provide some protection to phenolic acids from microbial degradation. In the absence of microbes, reversible sorption 35 days after addition of 0.5–3 mol/g of ferulic acid or p-coumaric acid was 8–14% in Cecil A_p horizon and 31–38% in Cecil B_t, horizon soil materials. The reversibly sorbed/solution ratios (r/s) for ferulic acid or p-coumaric acid ranged from 0.12 to 0.25 in A_p and 0.65 to 0.85 in B_t horizon soil materials. When microbes were introduced, the r/s ratio for both the A_p and B_t horizon soil materials increased over time up to 5 and 2, respectively, thereby indicating a more rapid utilization of solution phenolic acids over reversibly sorbed phenolic acids. The increase in r/s ratio and the overall microbial utilization of ferulic acid and/or p-coumaric acid were much more rapid in A_p than in B_t horizon soil materials. Reversible sorption, however, provided protection of phenolic acids from microbial utilization for only very short periods of time. Differential soil fixation, microbial production of benzoic acids (e.g., vanillic acid and p-hydroxybenzoic acid) from cinnamic acids (e.g., ferulic acid and p-coumaric acid, respectively), and the subsequent differential utilization of cinnamic and benzoic acids by soil microbes indicated that these processes can substantially influence the magnitude and duration of the phytoxicity of individual phenolic acids.     

Effects of exogenously applied ferulic acid,a potential allelopathic compound,on leaf growth,water utilization,and endogenous abscisic acid levels of tomato,cucumber, and bean

To determine the relative sensitivities of tomato, cucumber, and bean to exogenously applied concentrations of ferulic acid (FA) and to determine whether FA-induced stress responses increase endogenous levels of abscisic acid (ABA), wild-type andFlacca (ABA-deficient mutant) tomato (Lycopersicon esculentum Mill. cv. Ailsa Craig), cucumber, (Cucumis sativus L. cv. Early Green Cluster), and bean (Phaseolus vulgaris L. cv. Oregon 91) were treated with FA (0.0, 0.2, 0.4, 0.8 mM) in nutrient solution every other day for a total of two or three treatments. FA inhibited leaf growth and water utilization of wild-type tomato,Flacca tomato, and cucumber, but not of bean. Acclimation to FA was observed following the first FA treatment and increased endogenous ABA levels were found in wild-type tomato,Flacca tomato, and cucumber following multiple FA treatments. Induction of ABA biosynthesis occurred in wild-type tomato within 8 hr of FA treatment and maximum ABA levels were observed 24 hr after treatment. At that time, ABA levels of tomato treated with 0.4 and 0.8 mM FA were 13.7 times and 2.6 times higher than control levels, respectively. A second FA (0.4 or 0.8 mM) treatment, 48 hr after the first, did not appear to affect ABA levels. Ninety-six hours after the first treatment, ABA levels of tomato treated with 0.4 mM FA approached control levels; ABA levels of plants treated with 0.8 mM FA were 1.9 times higher than control levels. Control ABA levels increased gradually with time. The data showed that plant sensitivity and ability of subsequent acclimation to phenolic acids, such as FA, were taxa dependent.The use of trade names in this publication does not imply endorsement by North Carolina Agricultural Research Service of the products named, nor criticism of similar ones not mentioned.     

Role of cucurbitacin C in resistance to spider mite (Tetranychus urticae) in cucumber (Cucumis sativus L.)

Cucurbitacins are bitter triterpenoid compounds that are toxic to most organisms and occur widely in wild and cultivated Cucurbitaceae. The only cucurbitacin identified in Cucumis sativus is cucurbitacin C. The bitter taste of cucumber has been correlated with resistance to the spider mite Tetranychus urticae, but a quantitative relationship has not been established. We determined the spider mite resistance and cucurbitacin C content in the dihaploid progeny derived from the F₁ generation of a cross between a bitter, spider-mite-resistant cucumber line and a bitter-free, spider-mite-susceptible line. The ratio of the number of bitter to bitter-free dihaploids conformed to the expected 1:1 ratio, based on a monogenic segregation pattern. Genetic analysis ascribed 69% of the variance of the difference in spider mite survival rate to the bitterness locus. Within the group of bitter dihaploids, cucurbitacin C content was significantly correlated with spider mite resistance. Thus, a quantitative relationship between cucurbitacin C content and spider mite resistance could be established.     

Allelochemical inhibition of recruitment in a sedimentary assemblage

Chemical signals affect recruitment of organisms in many habitats. Most of the described biogenic chemical moieties in marine environments elicit specific positive responses, for example, of predators to prey or of conspecific larvae to suitable habitats. However, organisms also release noxious chemicals that may elicit negative responses from neighboring members of the assemblage. Herein we measured the effect on recruitment of the release of such compounds (halogenated aromatics) into sediments. The common, sediment-dwelling, terebellid polychaeteThelepus crispus contains brominated aromatic metabolites and contaminates the sediments surrounding its tube with these compounds. Sediments so contaminated are actively rejected by recruitingNereis vexillosa (Nereidae: Polychaeta). Interestingly, many of these noxious biogenic compounds have low solubility in water and, therefore, potentially long residence times in sedimentary environments. The negative response of larvae to sediment contaminated with them is a novel, potentially common, and very important mechanism in which sediment-dwelling organisms release haloaromatic compounds and thus impose a recruitment filter on their community.