Role of Ecological Variables in the Seasonal Variation of Flavonoid Content of Cistus ladanifer Exudate

The leaves and photosynthetic stems of Cistus ladanifer, a plant that colonizes arid lands, secrete an exudate that shows a large seasonal variation in its flavonoid content. The maximum secretion of flavonoids in the exudate is produced during summer, increasing approximately three-to fourfold with respect to the secretion measured in spring. Summer is the season in which the plant suffers the greatest stress from environmental physical variables such as UV irradiation, high temperatures, and hydric stress. Studies were conducted in plants from several locations, which were selected considering daily UV irradiation (open or shaded areas), annual precipitation, and annual average maximum and minimum temperatures. Additional studies to control UV irradiation, drought, and temperature separately were performed with C. ladanifer plants growing in a glasshouse and in a culture room. The UV irradiation was found to be the major inducer of the enhanced flavonoid secretion during summer, because no significant increase of flavonoid secretion during summer was observed when the C. ladanifer plants in the field were covered with a Plexiglas box (total UV absorption below 380 nm). These results support an ecophysiological role of the flavonoids in the exudate to protect the plant against the damaging effects of UV irradiation. The culture room experiments confirmed this point and also showed that the induction of flavonoid secretion by UV irradiation is synergistically augmented by drought. The glasshouse and culture room experiments showed drought and high temperatures (between 30° and 45°C) to correlate with the summer increase of the more methylated flavonoids (kaempferols and 7-methylated apigenins) in the exudate. Because these more methylated flavonoids have higher hydropathy than the less methylated, these results suggest that the secretion of more methylated flavonoids is part of the defense mechanism of the plant against the hydric stress of summer.     

Inhibition of Mouth Skeletal Muscle Relaxation by Flavonoids of Cistus ladanifer L.: A Plant Defense Mechanism Against Herbivores

Cistus ladanifer exudate is a potent inhibitor of the sarcoplasmic reticulum Ca2+-ATPase (Ca2+-pump) of rabbit skeletal muscle, a well-established model for active transport that plays a leading role in skeletal muscle relaxation. The low concentration of exudate needed to produce 50% of the maximum inhibition of the sarcoplasmic reticulum Ca2+-ATPase activity, 40-60 microg/ml, suggests that eating only a few milligrams of C. ladanifer leaves can impair the relaxation of the mouth skeletal muscle of herbivores, as the exudate reaches up to 140 mg/g of dry leaves in summer season. The flavonoid fraction of the exudate accounts fully for the functional impairment of the sarcoplasmic reticulum produced by the exudate (up to a dose of 250-300 microg/ml). The flavonoids present in this exudate impair the skeletal muscle sarcoplasmic reticulum function at two different levels: (i) by inhibition of the Ca2+-ATPase activity, and (ii) by decreasing the steady state ATP-dependent Ca2+-accumulation. Among the exudate flavonoids, apigenin and 3,7-di-O-methyl kaempferol are the most potent inhibitors of the skeletal muscle sarcoplasmic reticulum. We conclude that the flavonoids of this exudate can elicit an avoidance reaction of the herbivores eating C. ladanifer leaves through impairment of mouth skeletal muscle relaxation.     

Seasonal and population variation in flavonoid and alliarinoside content of Alliaria petiolata

Pieris napi oleracea, an indigenous butterfly in North America, lays eggs on Alliaria petiolata, an invasive weed that was introduced from Europe. However, larval development on plants from different sources varies considerably. A. petiolata is a compulsive biennial, and its foliage is rich in apigenin flavonoids. We compared the chemistry of different vegetative forms from different populations in the vicinity of Ithaca, NY throughout the year. Significant differences occurred in the number of apigenin derivatives in different populations and vegetative forms, and seasonal variations in the amounts of these compounds were found. We have previously isolated two major compounds, alliarinoside [(2Z)-4-(-D-glucopyranosyloxy)-2-butenenitrile] (1) and isovitexin-6-O-D-glucoside (3), which negatively affect development of P. napi oleracea larvae. Comparative analyses of these compounds in two populations throughout the year showed that their concentrations reached maxima twice annually. Foliage is almost devoid of flavonoids in June-July. Thus, variation in the chemistry of the plant may account for observed variation in development rates and survival of the larvae. Several apigenin compounds were isolated and identified by spectral studies.     

Seasonal variation in laboratory response to behavioral chemicals of the southern pine beetle

The response ofDendroctonus frontalis to an attractant mixture (frontalin,trans-verbenol, and loblolly pine turpentine) was measured in the laboratory over a four-year period. Beetle response was highest in late winter and early spring, and lowest in midsummer and early fall. Males consistently responded higher than females. Female beetles displayed significantly higher responses in early morning and late afternoon than in the middle of the day. Analysis of beetle pronotal width and fat content revealed a high degree of correlation between these two parameters in female beetles, but there was no correlation of response with either fat content or pronotal width for either sex. There was no evident relationship between mean monthly beetle response and total amounts of frontalin andtrans-veibenol found in hindgut extracts. Daily temperature in months both during which beetles were bioassayed and immediately prior to bioassay was highly correlated to response to the attractant.Texas Agricultural Experiment Station Paper Number 16652. This research was supported by McIntire-Stennis Project 1525, and the U.S. Department of Agriculture-sponsored program entitled The Expanded Southern Pine Beetle Research and Applications Program through TAES-SEA-CR Grant 904-15-4. The findings, opinions, and recommendations expressed herein are those of the authors and not necessarily those of the U.S. Department of Agriculture. All programs and information of the Texas Agricultural Experiment Station are available to everyone without regard to race, color, religion, sex, age, or national origin.     

Seasonal variation of three ketones in the interdigital gland secretion of reindeer (Rangifer tarandus L.)

The seasonal variation of the three ketones, 6-methyl-2-heptanone, 7-methyl-3-octanone, and 7-methyl-1-octen-3-one, in the interdigital gland secretion of reindeer (Rangifer tarandus L.) has been investigated. A group of four adult animals, three females and one male, was used as a test group during a period of two years. Even though the three compounds are monitored in only a small number of test animals, it is evident that the ratios of the secretion's components vary over time. The variations are cyclic and are repeated from year to year.     

Fatty acid variation of runner peanut (Arachis hypogaea L.) among geographic localities from Córdoba (Argentina)

Fatty acid compositions of runner peanuts were determined among fifteen geographic localities from Córdoba, Argentina. Significant differences were found within these fatty acid profiles. Samples from the Reducción zone had the best oleic-to-linoleic ratio and iodine value.     

Repellency of oral exudate to eastern and western spruce budworm larvae (Lepidoptera: Tortricidae)

A two-choice feeding bioassay was used to investigate the intra-specific repellency of the larval oral exudate of eastern and western spruce budworms,Choristoneura fumiferana (Clem.) andC. occidentalis Free., respectively. Results of the bioassay indicated that feeding behavior on artificial diet-drop feeding stations was modified in the presence of exudate, with feeding stations treated with conspecific exudate being avoided when an untreated station was available 3 cm away. Feeding was suppressed when a single, exudate-treated station was provided, or when the treated and untreated stations were separated by only 1 cm. The repellent effect functioned both inter- and intraspecifically. When induced to produce exudate,C. occidentalis larvae were not immediately repelled by either their own or other individuals' exudate. However, 24 hr after induction, test larvae were repelled by exudate from either source. In both species, larval oral exudate probably functions to repel conspecific competitors.     

Sorgoleone from root exudate inhibits mitochondrial functions

The aim of this investigation was to determine if sorgoleone (SGL), a hydrophobic compound inSorghum bicolor (L.) Moench root exudate, interferes with mitochondrial functions. Tests were conducted on mitochondria isolated from etiolated soybean [Glycine max (L.) Merr.] and corn (Zea mays L.) seedlings. The data show SGL is a potent inhibitor of state 3 and state 4 respiration rates in both soybean and corn. Using either NADH, succinate, or malate as substrate, the I₅₀ was about 0.5M SGL for state 3 and 5.0M for state 4 based on 0.3–0.5 mg mitochondrial protein. Absorption spectra indicate SGL blocks electron transport at theb-c ₁ complex. These data show that disruption of mitochondrial function may be a mechanism of SGL-mediated growth inhibition previously reported and demonstrate a probable role of SGL inSorghum allelopathy.This study was supported in part by National Science Foundation grant RII-8902066 (South Dakota EPSCOR).     

Repellent of root-knot nematodes from exudate of host roots

A chemotaxis assay was developed to measure attraction or repulsion of infective juveniles of the root-knot nematodeMeloidogyne incognita to exudates of host roots. The assay was sufficiently sensitive to measure the repellent activity of a 25-l sample of 7 mM NaCl. In tests of root exudate collected in a variety of ways from a variety of plants, avoidance responses were usually found but attraction was not. Extraction of the exudate from tomato with various organic solvents revealed that the repellent activity was highly polar. On Sephadex G-15 chromatography this exudate separated into two clearly defined peaks with apparent molecular weights of about 500 and 1000 daltons. The faster running peak (larger apparent size) contained much more activity than the other peak. Subsequent analysis of material from the larger peak via HPLC on a C18 column revealed a single peak of repellent activity. None of the chemical fractionations uncovered reproducible attractant activity.     

Seasonal and regional variation in triglyceride composition of French butterfat

In the present study, high-performance liquid chromatography analysis of butterfat allowed separation of 46 peaks at 32°C. Knowing the theoretical carbon number value of each triglyceride (TG), 32 peaks of the butterfat chromatogram were identified. These TGs were determined by extrapolation of their capacity factor values, and their identifications were confirmed with some standard TGs. Analysis of winter and summer butterfat from five different French areas showed significant seasonal and regional variation in the TG composition. However, the most important contribution to this variation was provided by TG groups represented by only four peaks. To approximately select the predominant TGs in these four peaks, a random distribution hypothesis was used to predict the amount of each TG. This hypothesis allowed the prediction of the TG components that seem to provide the most important contribution to both seasonal and regional variation.     

Seasonal variation in phytotoxicity of bracken (Pteridium aquilinum L. Kuhn)

Laboratory bioassays were used to test for the phytotoxicity of volatile compounds, fresh plant material as a seed bed, and water extracts from bracken [Pteridium aquilinum (L.) Kuhn] pinnules to germination and seedling growth of aspen (Populus tremula L.) and Scots pine (Pinus sylvestris L.). Fronds were sampled from two bracken populations, one in the south and one in the north of Sweden. All three bioassays showed inhibitory effects, and these varied seasonally with the most inhibitory effects occurring in May, June, and September. The peak of inhibition in May and June coincides with the start of the growing season when bracken still is immature and vulnerable to interference from other species. The increase in inhibitory effects in September appears to be due to transformation of natural products or an accumulation of inhibitory compounds that are released during decomposition following frond death. Addition of activated carbon did not remove the inhibitory effects.     

Analysis of trichome exudate from mite-resistant geraniums

Trichome exudate from mite-resistant geraniums (Pelargonium horlorum) was analyzed, principally by mass spectrometry and NMR spectroscopy. The exudate was found to consist of two anacardic acid derivatives,o-pentadecenylsalicylic acid ando-heptadecenylsalicylic acid. Bioassays established a moderate toxicity of these compounds to the two-spotted spider mite,Tetranychus urticae. The production of these compounds in geraniums was correlated with the two complementary dominant genes previously reported for host resistance to spider mites.     

Seasonal variability in response ofIps pini (Coleoptera: Scolytidae) to ipsdienol in New York

In May,Ips pini in New York did not respond in the field to 50–98.5% (R)-(–)-ipsdienol (synthetic). In September, beetles responded strongly to 50–60% (R)-(–)-ipsdienol (synthetic). In May and June, New York beetles showed marked preference for their own males over Arizona males, which produce an average of 94.1% (R)-(–)-ipsdienol. This suggested that ipsdienol stereochemistry alone does not ensure activity and that an additional compound is necessary for attraction in May. In the second year of field tests, attraction to synthetic ipsdienol and male beetles was tested in the spring, summer, and fall. There was response only to males in the spring and mid-summer and to both males and synthetic ipsdienol in the late summer and fall, causing a significant treatment x sampling period (date) interaction. Laboratory-reared beetles were not significantly more attracted to ipsdienol than to a blank airstream in laboratory assays, while male volatiles were significantly more attractive than ipsdienol and the blank. These data demonstrate that there is one or more unknown semiochemicals necessary for pheromonal response and that the behavioral activity of synthetic ipsdienol varies seasonally.Deceased.     

Fatty acid variation among U.S. Runner-type peanut cultivars

Fatty acid composition was determined among seven U.S. runner-type peanut (Arachis hypogaea L.) cultivars: Florunner, Sunrunner, GK-7, Southern Runner, Sunbelt Runner, Okrun, and Langley. Significant year and cultivar differences were found within these fatty acid profiles. Southern Runner had the best oleic to linoleic ratio and iodine values; whereas Florunner, Sunrunner, and Langley were the highest in unsaturated and lowest in saturated and long-chain fatty acids. For the future, breeding programs need to continue developing peanut cultivars with improved oil quality.     

Biochemical investigations of antibiosis material in leaf exudate of wildNicotiana species and interspecific hybrids

A model system involving severalNicotiana species containing novel nicotine alkaloids was used to study heritability and expression of alkaloid production in leaf trichomes. The three species that comprise the section Repandae (N. repanda, N. stocktonii, andN. nesophila) were hybridized with eitherN. tabacum orN. sylvestris (neither of which producesN-acylnornicotine). The progeny of the hybrid with sylvestris produced theN-acylnornicotines at a level found in the Repandae parent.Nicotiana repanda was crossed toN. tabacum, and the F₂ progeny produced the alkaloid at the same level as the original Repandae parent. Inheritance of the ability to acylate nornicotine in Repandae species is inherited in hybrids in a dominant manner These and other data obtained suggest that theN-acyltransferase that acylates nornicotine in Repandae species inherited in hybrids is in a dominant manner and that the regulatory sequence(s) for the gene is expressed in leaf trichomes when the gene is in a foreignNicotiana background.     

Inhibition of seedling growth of crop species by recirculating root exudates ofBidens pilosa L.

The allelopathic effects of root exudates ofBidens pilosa L. on seedling growth ofLactuca sativa L.,Phaseolus vulgaris L.,Zea mays L., andSorghum bicolor (L.) Moench were studied using a root exudate recirculating system that allows continuous exposure of crop plants to allelopathic chemicals. This system maintains an undisturbed rhizosphere and eliminates competition and physical contact between the donor and acceptor plants. Comparison of responses to hydrophobic and hydrophilic root exudates is made possible by removal of hydrophobic compounds using XAD-4. Treatments consisted ofB. pilosa, B. pilosa with an Amberlite XAD-4 resin column attached to the donor pot to remove hydrophobic allelochemicals, and a donor pot without weeds.B. pilosa significantly inhibited seedling growth of all crop species tested. The crop species varied in response to the root exudates, withL. sativa being most sensitive. Larger and olderB. pilosa plants caused greater inhibition of seedling growth ofL. sativa andP. vulgaris than did smaller (younger)B. pilosa plants.B. pilosa with XAD-4 caused significantly less inhibition to all crop species, exceptZ. mays, thanB. pilosa without XAD-4, indicating that the hydrophobic exudates played an important role in the allelopathic growth inhibition. Variability in species response toB. pilosa with and without XAD-4 was probably due to differences in sensitivity to hydophobic and hydrophilic allelochemicals.Supported by a grant under USDA Agreement No. 83-CRSR-2-2293. Journal Series No. 2887 of the Hawaii Institute of Tropical Agriculture and Human Resources.     

Seasonal variation in the hepatoproteome of the dehydration and freeze-tolerant wood frog, Rana sylvatica

Winter’s advent invokes physiological adjustments that permit temperate ectotherms to cope with stresses such as food shortage, water deprivation, hypoxia, and hypothermia. We used liquid chromatography (LC) in combination with tandem mass spectrometry (MS/MS) quantitative isobaric (iTRAQ™) peptide mapping to assess variation in the abundance of hepatic proteins in summer- and winter-acclimatized wood frogs (Rana sylvatica), a northerly-distributed species that tolerates extreme dehydration and tissue freezing during hibernation. Thirty-three unique proteins exhibited strong seasonal lability. Livers of winter frogs had relatively high levels of proteins involved in cytoprotection, including heat-shock proteins and an antioxidant, and a reduced abundance of proteins involved in cell proliferation, protein synthesis, and mitochondrial function. They also exhibited altered levels of certain metabolic enzymes that participate in the biochemical reorganization associated with aphagia and reliance on energy reserves, as well as the freezing mobilization and post-thaw recovery of glucose, an important cryoprotective solute in freezing adaptation.     

Seasonal patterns of juglone in soil beneathJuglans nigra (black walnut) and influence ofJ. nigra on understory vegetation

The allelopathic nature ofJ. nigra L. was investigated in several planted mixed hardwood stands located near Syracuse, New York. Concentrations of chloroform-extracted juglone from soil collected beneathJ. nigra was determined by thin-layer chromatography (TLC) and high-pressure liquid chromatography (HPLC). Soil juglone concentrations were corrected based on recovery of synthetic juglone added to soil. Soil juglone levels were high in the spring, decreased during the summer, and were high again in the fall. The quantification of juglone from soil by HPLC was found to be more accurate than by TLC. Regression analysis indicated that individual tree variation in soil juglone levels could not be explained by differences in soil moisture, pH, organic matter content, and texture. The results of juglone recovery experiments suggest that chloroform-extractable juglone does not persist in soil. Juglone degradation by microorganisms could only explain a portion of the juglone decline. Ordinations revealed that the herbaceous and woody vegetation beneathJ. nigra, in comparison to vegetation beneathAcer saccharum andQuercus rubra, is distinct in only one of the four stands studied. This vegetational difference did not appear to be a consequence of any strong allelopathic influences ofJ. nigra (Scheffe's method of contrast, chi-square analysis). The allelopathic nature of juglone under these field conditions is questionable.     

C10-polyacetylenes as allelopathic substances in dominants in early stages of secondary succession

cis-Dehydromatricaria ester (cis-DME) inSolidago altissima, andcis-matricaria ester (cis-ME),trans-matricaria ester (trans-ME), andcis-lachnophyllum ester (cis-LE) inErigeron spp. show strong growth inhibitory effects on other plants. Thecis- andtrans-DMEs were found in soil at the border ofS. altissima communities in concentrations that were inhibitory to test plants. Among four species ofErigeron, the most dominant plant,E floribundus, showed the highest concentrations of the esters. From the results of our experiments, we conclude that these polyacetylenes are probably allelopathic substances with ecological importance.     

生活垃圾填埋场中恶臭气体的季节变化特点

通过对生活垃圾填埋场中恶臭气体（硫化氢、氨、氮氧化物、甲烷等）,在不同季节（春、夏、冬季）的监测,分析其随季节的变化特点。得出夏季垃圾填埋场恶臭气体的浓度高于冬季,和恶臭气体并不是由单个恶臭气体浓度简单加和而成,而是有明显的协同作用两个结论。从而为生活垃圾填埋场的恶臭污染控制提供参考依据。