An Apparent Trade-Off between Direct and Signal-Based Induced Indirect Defence against Herbivores in Willow Trees

Signal-based induced indirect defence refers to herbivore-induced production of plant volatiles that attract carnivorous natural enemies of herbivores. Relationships between direct and indirect defence strategies were studied using tritrophic systems consisting of six sympatric willow species, willow leaf beetles (Plagiodera versicolora), and their natural predators, ladybeetles (Aiolocaria hexaspilota). Relative preferences of ladybeetles for prey-infested willow plant volatiles, indicating levels of signal-based induced indirect defence, were positively correlated with the vulnerability of willow species to leaf beetles, assigned as relative levels of direct defence. This correlation suggested a possible trade-off among the species, in terms of resource limitation between direct defence and signal-based induced indirect defence. However, analyses of volatiles from infested and uninfested plants showed that the specificity of infested volatile blends (an important factor determining the costs of signal-based induced indirect defence) did not affect the attractiveness of infested plant volatiles. Thus, the suggested trade-off in resource limitation was unlikely. Rather, principal coordinates analysis showed that this ‘apparent trade-off’ between direct and signal-based induced indirect defence was partially explained by differential preferences of ladybeetles to infested plant volatiles of the six willow species. We also showed that relative preferences of ladybeetles for prey-infested willow plant volatiles were positively correlated with oviposition preferences of leaf beetles and with the distributions of leaf beetles in the field. These correlations suggest that ladybeetles use the specificity of infested willow plant volatiles to find suitable prey patches.     

Herbivore‐induced poplar cytochrome P450 enzymes of the CYP71 family convert aldoximes to nitriles which repel a generalist caterpillar

Numerous plant species emit volatile nitriles upon herbivory, but the biosynthesis as well as the relevance of these nitrogenous compounds in plant–insect interactions remains unknown. Populus trichocarpa has been shown to produce a complex blend of nitrogenous volatiles, including aldoximes and nitriles, after herbivore attack. The aldoximes were previously reported to be derived from amino acids by the action of cytochrome P450 enzymes of the CYP79 family. Here we show that nitriles are derived from aldoximes by another type of P450 enzyme in P. trichocarpa. First, feeding of deuterium‐labeled phenylacetaldoxime to poplar leaves resulted in incorporation of the label into benzyl cyanide, demonstrating that poplar volatile nitriles are derived from aldoximes. Then two P450 enzymes, CYP71B40v3 and CYP71B41v2, were characterized that produce aliphatic and aromatic nitriles from their respective aldoxime precursors. Both possess typical P450 sequence motifs but do not require added NADPH or cytochrome P450 reductase for catalysis. Since both enzymes are expressed after feeding by gypsy moth caterpillars, they are likely to be involved in herbivore‐induced volatile nitrile emission in P. trichocarpa. Olfactometer experiments showed that these volatile nitriles have a strong repellent activity against gypsy moth caterpillars, suggesting they play a role in induced direct defense against poplar herbivores.     

Greenhouse and field assessment of phytoremediation for petroleum contaminants in a riparian zone

Greenhouse and field studies were conducted to evaluate the feasibility of phytoremediation for clean-up of highly contaminated sediments from Indiana Harbor. In the greenhouse study, plant species evaluated were willow (Salix exigua), poplar (Populus spp.), eastern gamagrass (Tripsacum dactyloides), arrowhead (Sagitaria latifolia), switchgrass (Panicum virgatum), and sedge (Carex stricta). Sediments with sedge, switchgrass, and gamagrass had significantly less residual total petroleum hydrocarbons (TPH) after one year of growth (approximately 70% reduction) than sediments containing willow, poplar, or no plants (approximately 20% reduction). Although not all polycyclic aromatic hydrocarbons (PAH) had concentration differences due to the presence of plants, residual pyrene concentrations in the unvegetated pots were significantly higher than in pots containing sedge, switchgrass, arrowhead, and gamagrass. As evaluated by TPH dissipation in the upper section of the pots, the sedge, switchgrass, and gamagrass treatments had higher TPH degradation than the unvegetated, willow and poplar treatments. These trends were similar for soil at the bottom of the pots, with the exception that in the switchgrass treatment, degradation was not significantly different than in the unvegetated soil. Two target contaminants, pyrene and benzo[b]fluoranthene, showed differences in degradation between planted and unvegetated treatments. In the field study, phytoremediation plant species were eastern gamagrass (T. dactyloides), switchgrass (P. virgatum), and sedge (C. stricta). In addition, rhizosphere characteristics of arrowhead (S. latifolia) and sedge were assessed. Arrowhead- and sedge-impacted soils were found to contain significantly more PAH-degrading bacteria than unvegetated soils. However, over the 12-month field study, no significant differences in contamination were found between the planted and unplanted soils for TPH and PAH concentrations. TPH concentrations near the canal were greater than concentrations further from the canal, indicating that the canal may have served as a continuous source of contamination during the study.     

Detection of plant volatiles after leaf wounding and darkening by proton transfer reaction "time-of-flight" mass spectrometry (PTR-TOF)

Proton transfer reaction-time of flight (PTR-TOF) mass spectrometry was used to improve detection of biogenic volatiles organic compounds (BVOCs) induced by leaf wounding and darkening. PTR-TOF measurements unambiguously captured the kinetic of the large emissions of green leaf volatiles (GLVs) and acetaldehyde after wounding and darkening. GLVs emission correlated with the extent of wounding, thus confirming to be an excellent indicator of mechanical damage. Transient emissions of methanol, C5 compounds and isoprene from plant species that do not emit isoprene constitutively were also detected after wounding. In the strong isoprene-emitter Populus alba, light-dependent isoprene emission was sustained and even enhanced for hours after photosynthesis inhibition due to leaf cutting. Thus isoprene emission can uncouple from photosynthesis and may occur even after cutting leaves or branches, e.g., by agricultural practices or because of abiotic and biotic stresses. This observation may have important implications for assessments of isoprene sources and budget in the atmosphere, and consequences for tropospheric chemistry.     

Comparison of volatile leaf compounds and herbivorous insect communities on three willow species

 Plants produce volatile compounds known to influence insect preferences for oviposition and feeding. To examine whether volatile leaf compounds are correlated with the herbivorous insect community, we analyzed volatile compounds in leaves from three co-occurring willow species, Salix serissaefolia, S. eriocarpa, and S. integra, and investigated their associated insect communities in 3 months across different years. The gas chromatographic profiles of volatile compounds were highly specific to each willow species and remained constant in the study months. In a comparison between the chemical composition of the volatile compounds and the taxon composition of the insect communities, dissimilarity patterns in chemical composition among the three willow species were very close to those in herbivorous insect communities. These findings indicate that willow leaves produce specific volatiles that are highly correlated with the community structure of herbivorous insects associated with them. Received: October 10, 2002 / Accepted: March 17, 2003     

Changes in composition of essential oils and volatile emissions of Minthostachys mollis, induced by leaf punctures of Liriomyza huidobrensis

Plant defensive mechanisms against herbivores include chemical changes following damage. Effects of feeding punctures produced by Liriomyza huidobrensis (pea leafminers) adult females on the plant's dominant monoterpenes, pulegone and menthone were assessed by monitoring essential oil composition at 24, 48, and 120 h; emission of volatiles was also measured 24 and 48 h after wounding. We studied such changes in Minthostachys mollis, a Lamiaceae species native to Central Argentina with medicinal and aromatic uses. Leaf puncturing resulted in reduced menthone throughout the experiment and increased pulegone concentration in M. mollis essential oil during the first 48 h. The adjacent undamaged leaves showed similar changes, suggesting a systemic response. Composition of volatiles released from damaged leaves was also altered, most noticeably by increasing pulegone and diminishing menthone emissions. Such herbivore-induced chemical changes in aromatic plants are economically relevant, since the quality of essential oils and volatile emissions are altered.     

Resistant poplar genotypes inhibit pseudogall formation by the wooly poplar aphid,Phloeomyzus passerinii Sign

Key message

Phloeomyzus passerinii can induce a pseudogall within the bark of susceptible poplar genotypes, while in resistant genotypes the induction seems to be impeded by lignification processes.

Abstract

Phloeomyzus passerinii is a major pest of poplar stands in Europe, North Africa and the Near East. This aphid feeds in the cortical parenchyma of different poplar species and hybrids, and can affect their growth and survival through unknown mechanisms. In some genotypes, however, resistance prevents either the settlement or the development of aphid colonies. For a better understanding of tree reactions to aphid probing, we compared the anatomical and biochemical modifications undergone within the bark of stem cuttings, after different delays of either aphid colonization or mechanical wounding. To assess how resistance may modulate tree reactions, the comparison was performed using three poplar genotypes exhibiting different resistance levels. In these three genotypes, mechanical wounding induced a similar, localized, wound periderm. In contrast, aphid colonization triggered more extended reactions, which differed among genotypes. In the susceptible genotype, aphids induced a reaction tissue, characterized after a month by thin-walled hypertrophied cells and a depletion of soluble phenolic compounds and starch. Anatomical features of this reaction tissue suggest that the aphid initiates a pseudogall in the cortical tissues of its susceptible host. In the resistant genotypes, however, the differentiation of the reaction tissue was totally or partially inhibited, probably because of extended lignification processes. The implications of a pseudogall induction on susceptible hosts’ physiology, and the impact of lignification on aphid development and behavior, are discussed.     

Can herbivore‐induced plant volatiles inform predatory insect about the most suitable stage of its prey?

The leaf beetle Plagiodera versicolora (Coleoptera: Chrysomelidae) is a specialist herbivore, all of whose mobile stages feed on the leaves of salicaceous plants. Both the larval and adult stages of the ladybird Aiolocaria hexaspilota (Coleoptera: Coccinellidae) are dominant natural enemies of the larvae of the leaf beetle. To clarify the role of plant volatiles in prey‐finding behaviour of A. hexaspilota, the olfactory responses of the ladybird in a Y‐tube olfactometer are studied. The ladybird adults show no preference for willow plants Salix eriocarpa that are infested by leaf beetle adults (nonprey) over that for intact plants but move more to the willow plants infested by leaf beetle larvae (prey) than to intact plants. Moreover, ladybird larvae show no preference for willow plants infested by leaf beetle larvae or adults over intact plants. Using gas chromatography‐mass spectrometry, six volatile compounds are released in larger amounts in the headspace of willow plants infested by leaf beetle larvae than in the headspace of willow plants infested by leaf beetle adults. In addition, the total amount of volatiles emitted from willow plants that are either intact or infested by leaf beetle adults is much smaller than that from willow plants infested by leaf beetle larvae. These results indicate that volatiles from S. eriocarpa infested by P. versicolora inform A. hexaspilota adults about the presence of the most suitable stage of their prey, whereas A. hexaspilota larvae do not use such information.     

北京地区侧柏和垂柳释放有益挥发性有机物组分日动态变化特征

以侧柏(Platycladus orientalis)和垂柳(Salix babylonica)为研究对象,采用动态顶空套袋采集法和自动热脱附-气相色谱/质谱联用技术来分析这些植物释放的挥发性有机物(VOCs)的组成和释放模式。选择不同的时间和天气条件下的样本进行采集,并记录相关信息。通过对原始数据的分析,确定有益挥发性有机物(BVOCs)的成分和相对百分含量。研究结果显示,侧柏和垂柳在不同季节释放的BVOCs成分主要包括醇类、醛类、烯烃类等其他类化合物,这些有益BVOCs在植物的生理和生态功能中扮演着重要的角色,对于深入了解植物与环境之间的相互作用具有重要意义。侧柏和垂柳释放BVOCs成分在不同季节会有所变化。其次,研究分析了侧柏和垂柳在不同季节中有益BVOCs成分的含量和变动趋势。侧柏在不同季节的释放模式呈现出明显的差异。春季的释放模式呈现出“单峰单谷”曲线,夏季的释放模式呈现出“单峰”曲线,而秋季的释放模式呈现出“双峰单谷”曲线。这表明侧柏在不同季节中的挥发物释放存在明显的季节性变化。相比之下,垂柳的释放模式在不同季节中相对稳定,呈现出一致的“单峰型”曲线。这说明垂柳的挥发物释放...     

Factors affecting songbird communities using new short rotation coppice habitats in spring

The aim of this study was to describe the songbird communities occupying willow and poplar short rotation coppice (SRC) crops during the breeding season, and to identify the features of existing plantations that affect their abundance. Songbird point-counts were undertaken at 66 different plots of SRC at 29 sites throughout Britain and Ireland during spring 1993. Measures of vegetation and coppice management in each plot were also taken. The songbird species using the SRC survey plots were similar to those reported from traditional coppice habitats. Willow SRC contained more resident and migrant songbird species than poplar SRC. Warbler species and buntings in particular were rarely recorded from poplar plots. Finches, tits and thrushes were recorded equally from both willow and poplar. More migrant species were recorded from year 2 willow coppice (i.e. in its third growth season since winter cutting) than in either year 1 or year 3. Most resident species selected older willow or poplar coppice growth up to year 3 or 4, the oldest age classes in the sample. These 4-year trends for migrant and resident songbirds are similar to those observed in traditional coppice woodland over a 10- or 12-year rotation. Skylark and Meadow Pipit were recorded from recently cut SRC plots (year 0). In a regression analysis, the number of songbird species and individuals, particularly migrants, were found to be positively related to the increased structural density or complexity of the coppice vegetation.     

Four terpene synthases produce major compounds of the gypsy moth feeding-induced volatile blend of Populus trichocarpa

After herbivore damage, many plants increase their emission of volatile compounds, with terpenes usually comprising the major group of induced volatiles. Populus trichocarpa is the first woody species with a fully sequenced genome, enabling rapid molecular approaches towards characterization of volatile terpene biosynthesis in this and other poplar species. We identified and characterized four terpene synthases (PtTPS1-4) from P. trichocarpa which form major terpene compounds of the volatile blend induced by gypsy moth (Lymantria dispar) feeding. The enzymes were heterologously expressed and assayed with potential prenyl diphosphate substrates. PtTPS1 and PtTPS2 accepted only farnesyl diphosphate and produced (−)-germacrene D and (E,E)-α-farnesene as their major products, respectively. In contrast, PtTPS3 and PtTPS4 showed both mono- and sesquiterpene synthase activity. They produce the acyclic terpene alcohols linalool and nerolidol but exhibited opposite stereospecificity. qRT-PCR analysis revealed that the expression of the respective terpene synthase genes was induced after feeding of gypsy moth caterpillars. The TPS enzyme products may play important roles in indirect defense of poplar to herbivores and in mediating intra- and inter-plant signaling.     

不同季节黑杨萎蔫叶片挥发物的化学成分分析

采用水蒸气蒸馏法和气相色谱-质谱联用技术,分析黑杨不同季节的叶片,即嫩叶、成熟叶和衰老叶萎蔫后释放的气味物质成分.结果表明,嫩叶挥发物主要成分为顺-3-己烯醇、-甲基-1-戊醇和邻羟基苯甲醛,其相对含量分别为44.81%、21.85%和15.19%;成熟叶挥发物主要组分也是顺-3-己烯醇,相对含量28.71%,其次为邻羟基苯甲醛,相对含量10.35%.邻羟基苯甲醛为衰老叶挥发物的主要组分为,其相对含量为28.81%,其次是苯甲醇,相对含量15.06%;随着叶龄增长,挥发物中顺-3-己烯醇含量显著减少,而具有芳香性化合物种类及其含量显著增加.     

Volatile Semiochemicals Released from Undamaged Cotton Leaves (A Systemic Response of Living Plants to Caterpillar Damage)

Cotton plants (Gossypium hirsutum L.), attacked by herbivorous insects release volatile semiochemicals (chemical signals) that attract natural enemies of the herbivores to the damaged plants. We found chemical evidence that volatiles are released not only at the damaged site but from the entire cotton plant. The release of volatiles was detected from upper, undamaged leaves after 2 to 3 d of continuous larval damage on lower leaves of the same plant. Compounds released systemically were (Z)-3-hexenyl acetate, (E)-[beta]-ocimene, linalool, (E)-4,8-dimethyl-1,3,7-nonatriene, (E)-[beta]-farnesene, (E,E)-[alpha]-farnesene, and (E,E)-4,8,12-trimethyl-1,3,7,11-tridecatetraene. All systemically released compounds are known to be induced by caterpillar damage and are not released in significant amounts by undamaged plants. Other compounds, specifically indole, isomeric hexenyl butyrates, and 2-methylbutyrates, known to be released by cotton in response to caterpillar damage, were not released systemically. However, when upper, undamaged leaves of a caterpillar-damaged plant were damaged with a razor blade, they released isomeric hexenyl butyrates, 2-methylbutyrates, and large amounts of constitutive compounds in addition to the previously detected induced compounds. Control plants, damaged with a razor blade in the same way, did not release isomeric hexenyl butyrates or 2-methylbutyrates and released significantly smaller amounts of constitutive compounds. Indole was not released systemically, even after artificial damage.     

Are Vegetative Reproduction Capacities the Cause of Widespread Invasion of Eurasian Salicaceae in Patagonian River Landscapes?

In recent decades, invasive willows and poplars (Salicaceae) have built dense floodplain forests along most of the rivers in Patagonia, Argentina. These invasion processes may affect Salix humboldtiana as the only native floodplain tree species in this region. It is assumed, that the property to reproduce vegetatively can play an important role in the establishment of invasive species in their new range. Thus, in order to contribute to a better understanding of willow and poplar invasions in riparian systems and to assess the potential impacts on S. humboldtiana the vegetative reproduction capacities of native and invasive Salicaceae were analysed. In a greenhouse experiment, we studied cutting survival and growth performance of the three most dominant invasive Salicaceae of the Patagonian Río Negro region (two Salix hybrids and Populus spec.), as well as S. humboldtiana, taking into account three different moisture and two different soil conditions. In a subsequent experiment, the shoot and root biomass of cuttings from the former experiment were removed and the bare cuttings were replanted to test their ability to re-sprout. The two invasive willow hybrids performed much better than S. humboldtiana and Populus spec. under all treatment combinations and tended to re-sprout more successfully after repeated biomass loss. Taking into account the ecology of vegetative and generative recruits of floodplain willows, the results indicate that the more vigorous vegetative reproduction capacity can be a crucial property for the success of invasive willow hybrids in Patagonia being a potential threat for S. humboldtiana.     

Post hibernation dispersal of three leaf-eating beetles (Coleoptera: Chrysomelidae) colonising cultivated willows and poplars

1 We studied the spring dispersal of three common chrysomelids, from overwintering habitats into cultivated willow and poplar coppices at four sites in southern England over 2 years. 2 Adult Galerucella lineola, Phratora vulgatissima and P. vitellinae overwintered under the bark of mature trees or in other niches that simulated this habitat, within a few hundred metres of the coppice plantation. Relatively few beetles remained in the coppice fields during the winter. 3 Phratora vitellinae at the poplar sites emerged several weeks later than G. lineola and P. vulgatissima at the willow sites, reflecting the later leafing of poplar compared to willow. For all species, dispersal was by flight, with most activity during warm periods. Dispersal continued for several weeks for the willow- feeding species but was shorter for P. vitellinae. 4 All three species initially colonized the edge of the coppice field. Typically, 80% or more of the beetles colonising a plantation were within 8 m of the edge. Both Phratora spp. accumulated in the plantation edge zone for several weeks before leaving this area and colonising the crop interior. 5 The patterns of dispersal and colonization identified by this study may facilitate chrysomelid management practices in infested short rotation coppice that avoid the need for insecticide applications over the entire plantation. Keywords Chrysomelidae, Galerucella lineola, Phratora vitellinae, Phratora vulgatissima, poplar, short rotation coppice, willow, winter dispersal.     

Clonal variation in survival and growth of hybrid poplar and willow in an in situ trial on soils heavily contaminated with petroleum hydrocarbons

Species and hybrids between species belonging to the genera Populus (poplar) and Salix (willow) have been used successfully for phytoremediation of contaminated soils. Our objectives were to: 1) evaluate the potential for establishing genotypes of poplar and willow on soils heavily contaminated with petroleum hydrocarbons and 2) identify promising genotypes for potential use in future systems. We evaluated height, diameter, and volume after first year budset by testing 20 poplar clones and two willow clones. Unrooted cuttings, 20 cm long, were planted in randomized complete blocks at 0.91- x 0.91-m spacing at Gary, IN, USA (41.5 degrees N, 87.3 degrees W). Four commercial poplar clones (NM6, DN5, DN34, and DN182) were planted as 20- and 60-cm cuttings. Sixty-cm cuttings exhibited greater height and diameter than 20-cm cuttings; however, we recommend continued use and testing of different combinations of genotype and cutting length. We identified promising genotypes for potential use in future systems and we recommend allocating the majority of resources into commercial poplar clones, given their generalist growth performance. However, further utilization and selection of experimental clones is needed. Specific clones rather than genomic groups should be selected based on the geographic location and soil conditions of the site.     

A peroxisomal β-oxidative pathway contributes to the formation of C6–C1 aromatic volatiles in poplar

Benzenoids (C₆–C₁ aromatic compounds) play important roles in plant defense and are often produced upon herbivory. Black cottonwood (Populus trichocarpa) produces a variety of volatile and nonvolatile benzenoids involved in various defense responses. However, their biosynthesis in poplar is mainly unresolved. We showed feeding of the poplar leaf beetle (Chrysomela populi) on P. trichocarpa leaves led to increased emission of the benzenoid volatiles benzaldehyde, benzylalcohol, and benzyl benzoate. The accumulation of salicinoids, a group of nonvolatile phenolic defense glycosides composed in part of benzenoid units, was hardly affected by beetle herbivory. In planta labeling experiments revealed that volatile and nonvolatile poplar benzenoids are produced from cinnamic acid (C₆–C₃). The biosynthesis of C₆–C₁ aromatic compounds from cinnamic acid has been described in petunia (Petunia hybrida) flowers where the pathway includes a peroxisomal-localized chain shortening sequence, involving cinnamate-CoA ligase (CNL), cinnamoyl-CoA hydratase/dehydrogenase (CHD), and 3-ketoacyl-CoA thiolase (KAT). Sequence and phylogenetic analysis enabled the identification of small CNL, CHD, and KAT gene families in P. trichocarpa. Heterologous expression of the candidate genes in Escherichia coli and characterization of purified proteins in vitro revealed enzymatic activities similar to those described in petunia flowers. RNA interference-mediated knockdown of the CNL subfamily in gray poplar (Populus x canescens) resulted in decreased emission of C₆–C₁ aromatic volatiles upon herbivory, while constitutively accumulating salicinoids were not affected. This indicates the peroxisomal β-oxidative pathway participates in the formation of volatile benzenoids. The chain shortening steps for salicinoids, however, likely employ an alternative pathway.

A three-step peroxisomal β-oxidative pathway mediates the shortening of the propyl side chain of cinnamic acid and contributes to herbivore-induced aromatic volatile formation in poplar.     

Metabolism of poplar salicinoids by the generalist herbivore Lymantria dispar (Lepidoptera)

The survival of insect herbivores on chemically defended plants may often depend on their ability to metabolize these defense compounds. However, only little knowledge is available on how insects actually process most plant defense compounds. We investigated the metabolism of salicinoids, a major group of phenolic glycosides in poplar and willow species, by a generalist herbivore, the gypsy moth (Lymantria dispar). Seven salicinoid metabolites identified in gypsy moth caterpillar feces were mostly conjugates with glucose, cysteine or glycine. Two of the glucosides were phosphorylated, a feature not previously reported for insect metabolites of plant defense compounds. The origins of these metabolites were traced to specific moieties of three major poplar salicinoids ingested, salicin, salicortin and tremulacin. Based on the observed metabolite patterns we were able to deduce the initial steps of salicinoid breakdown in L. dispar guts, which involves cleavage of ester bonds. The conjugated molecules were effectively eliminated within 24 h after ingestion. Some of the initial breakdown products (salicin and catechol) demonstrated negative effects on insect growth and survival in bioassays on artificial diets. Gypsy moth caterpillars with prior feeding experience on salicinoid-containing poplar foliage converted salicinoids to the identified metabolites more efficiently than caterpillars pre-fed an artificial diet. The majority of the metabolites we identified were also produced by other common poplar-feeding insects. The conversion of plant defenses like salicinoids to a variety of water-soluble sugar, phosphate and amino acid conjugates and their subsequent excretion fits the general detoxification strategy found in insect herbivores and other animals.     

Aldehyde volatiles emitted in succession from mechanically damaged leaves of poplar cuttings

Plant aldehydes are volatiles necessary to defenses against environmental stress. To explore their emissions in response to wounding, we performed gas chromatography-mass spectrometry (GC-MS) on cuttings from poplar (Populus simonii×P. pyramidalis ‘Opera 8277’) that were mechanically damaged to mimic herbivore attack. We detected 16 aldehydes, including 11 linear saturated aldehydes, 3 linear unsaturated aldehydes, and 2 non-linear aldehydes. Emissions of these aldehydes were clearly enhanced by such treatment, and exhibited a similar pattern of change, i.e., increasing in the first 2 h, then sharply decreasing before rising again at about 12 h. Two release peaks for these aldehydes were observed. Therefore, we propose two pathways for the mediation of aldehyde emissions following damage. The first peak may represent emissions from plant storage pools, whereas the second release peak might result from greater formationde novo through an activated synthesis pathway.     

Phenotypic plasticity in host plant preference of the willow leaf beetle Phratora vulgatissima: the impact of experience made by adults

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