Comparison of volatile organic compounds from uninfested and Monochamus alternatus Hope infested Pinus massoniana Lamb.

Monochamus alternatus is a destructive stem‐boring herbivore of Pinus massoniana, and the principal vector of pine wood nematode. To investigate the impacts of boring by M. alternatus larvae on the emission of volatile organic compounds (VOCs) from their host trees, the VOCs from uninfested and M. alternatus larvae infested P. massoniana trees were observed using a gas chromatograph–mass spectrometer. We detected 12, 9, 18 and 14 volatile organic compounds from infested xylem, infested phloem, uninfested xylem and uninfested phloem, respectively. In P. massoniana xylem, the boring of M. alternatus larvae induced cyclosativene, and inhibited 4‐carene, humulene, styrene, α‐phellandrene, β‐myrcene, β‐phellandrene and γ‐terpinene. The relative amounts of camphene, copacamphene, longicyclene, longifolene, tricyclene and α‐longipinene were significantly increased, and the relative amounts of α‐pinene and β‐pinene were significantly decreased by the boring behaviors of M. alternatus larvae. In P. massoniana phloem, the boring of M. alternatus larvae induced 2‐bornanone, copacamphene, longicyclene and α‐longipinene, and inhibited 2‐carene, 4‐carene, styrene, α‐phellandrene, β‐myrcene, β‐phellandrene, β‐pinene, γ‐terpinene and ο‐cymene. The relative amounts of camphene, caryophyllene and longifolene were significantly increased by the boring behaviors of M. alternatus larvae. The results indicate that the boring behaviors of M. alternatus larvae changed both the sorts and contents of the VOCs from P. massoniana trees.     

茉莉酸甲酯对马尾松萜类合成酶活性及其细胞化学定位的影响

马尾松(Pinus massoniana)是我国南方生态建设与造林用材的主要树种,为了揭示马尾松抗虫机理尤其是诱导抗虫性的分子机制,该研究以马尾松幼苗为材料,通过外源喷施茉利酸甲酯(Me JA),分析了处理与对照间植株针叶显微结构、萜类合成酶活性及其细胞化学定位的变化。结果表明:在0.2 mmol·L~(-1)Me JA处理下马尾松植株松针中萜类物质,尤其是单萜、二萜的相对含量增加,马尾松毛虫拒食性明显,诱导抗性增强。显微观测中,针叶叶肉细胞内树脂道分泌物增加,叶绿体数目减少,但叶绿体体积增大,叶绿体片层结构增加。Me JA处理4周后,针叶中萜类合成酶活性增加,通过电镜酶细胞化学观察,膜系统尤其是叶绿体膜上萜类合成酶活性定位明显增强。这说明Me JA诱导的马尾松诱导抗性可能与改变的叶绿体结构及绿色质体萜类合成酶活性密切相关。     

Influences of host volatiles on feeding behaviour of the Japanese pine sawyer, Monochamus alternatus

Abstract: Choice and no‐choice feeding assays on the twigs of three host species demonstrated the following feeding preference sequence by Monochamus alternatus: Pinus massoniana > Cedrus deodara > Pinus thunbergii. There were significant differences in the concentrations of α‐pinene, camphene, d ‐limonene, β‐phellandrene, longifolene and β‐caryophyllene in volatiles emitted by twigs among the three species. We tested the effects of six monoterpenes (α‐pinene, β‐pinene, 3‐carene, myrcene, limonene and β‐caryophyllene) added to an artificial diet consisting of bark from P. thunbergii on consumption rates by M. alternatus. The addition of α‐pinene at all four concentrations 0.4, 1.2, 3.6 and 10.8 μl/ml resulted in increases of a twofold greater consumption rate than the control at a concentration of 3.6 μl/ml. Limonene inhibited diet consumption at concentrations >0.4 μl/ml. The concentration of α‐pinene in volatiles emitted by twigs was significantly higher for P. massoniana than for P. thunbergii, whereas the reverse was true for limonene. There were no differences for any of the other host components, suggesting that α‐pinene and limonene may play an important role in the adult's selection and acceptance of suitable and unsuitable feed host. Mixed compounds promoted the consumption of artificial diet at a concentration of 0.4 μl/ml, whereas consumption was inhibited at a concentration of 10.8 μl/ml. There were significant linear correlations (β‐pinene: r² = 0.930, P < 0.05; myrcene: r² = 0.933, P < 0.05) between the amount of diets consumed and diet concentrations of β‐pinene and myrcene. In conclusion, host volatile terpenes may stimulate or repel M. alternatus depending on terpene concentrations they encounter during initial feeding and then possibly inhibit further feeding activity once concentrations increase to threshold levels.     

Host Foraging Behavior of <Emphasis Type="Italic">Dastarcus helophoroides</Emphasis> (Coleoptera: Bothrideridae) Adults,a Coleopteran Parasitoid of <Emphasis Type="Italic">Monochamus alternatus</Emphasis> (Coleoptera: Cerambycidae)

Dastarcus helophoroides adults, a coleopteran parasitoid of Monochamus alternatus, were reared in the laboratory. The objectives of this paper are to investigate the host foraging behavior of D. helophoroides, and the evidence for learning in such behaviors. Choice and no-choice experiments were carried out. The choice experiments show that the number of D. helophoroides adults choosing the Pinus massoniana log infested with M. alternatus larvae was significantly higher than that choosing the blank (a flavorless simulative log made of brown kraftpaper), and the number of D. helophoroides adults choosing the uninfested P. massoniana log was also significantly higher than that choosing the blank. The no-choice experiment shows no significant difference between the number of D. helophoroides adults that chose the infested log and that chose the uninfested log, despite previous experience with uninfested log, infested log, or neither of them. No evidence of learning in host foraging behavior in D. helophoroides adults was found. The results indicate that the volatile chemicals emitted by uninfested P. massoniana logs and infested logs with M. alternatus larvae are equally attractive to D. helophoroides.     

New method for rapidly estimating population densities of the concealed wood‐borer Monochamus alternatus (Coleoptera: Cerambycidae) in the field

To rapidly estimate pine sawyer, Monochamus alternatus Hope, population densities in forests, the vertical distributions of M. alternatus oviposition sites and larvae on infested Masson pines (Pinus massoniana Lamb.) were studied. Results showed that the number of oviposition sites on sections of trunks between 0 and 2 m above ground was significantly greater than on sections of trunk above 2 m, and the vertical distribution had a significant logarithmic relationship with trunk height. The larval number of M. alternatus on dead infested trees had a significant difference among heights of trunks. Sections on trunks at 2–4 m usually contained the largest number of M. alternatus larvae, while the number of larvae on trunks above 10 m declined significantly, as well as in the 1 m section of trunk at the base. The vertical distribution of M. alternatus larvae on dead infested pines showed a distinct parabolic relationship with trunk height. The number of oviposition sites of M. alternatus on infested Masson pine trunks revealed a significant exponential relationship with the diameter at breast height (DBH) of trees. A significant positive linear relationship also was observed between M. alternatus larval number and DBH on the host pine trees, as well as between the numbers of larvae and oviposition sites on an individual tree. The total number of larvae in an infested tree could be calculated easily using an established equation, through counting the number of oviposition sites at 3–4 m of trunk aboveground. This study developed a practical method for rapid estimation of M. alternatus populations.     

Posters Part 1

Schima superba and Pinus massoniana distributed over large areas in southern China both are dominant species at Dinghushan Biosphere Reserve. In the present study, the changes of chlorophyll fluorescence and xanthophyll cycle in the leaves of S. superba and P. massoniana exposed to simulated acid rain (SAR) were measured. When exposed to high light, the PSII photochemistry efficiency (F _v/F _m), efficiency of energy conversion in PSII (ΦPSII) and photochemical quenching (qP) of both S. superba and P. massoniana all decreased when acidity of SAR increased. Regarding non-photochemical quenching (qN), S. superba exposed to SAR had higher value than control plants, but there was no significant difference between the respective seedlings of P. massoniana. As for xanthophyll cycle of the two plant species, the leaves of S. superba exposed to SAR showed a higher content of carotenoids and a higher ability to convert violaxanthin to zeaxanthin than leaves of P. massoniana, which was consistent with S. superba exhibiting a stronger resistance to high light than P. massoniana. Although both species were susceptible to acid rain as shown by our results, P. massoniana was more susceptible compared to S. superba. These results provide an insight into how to protect the forest ecosystem at Dinghushan Biosphere Reserve.     

Methyl jasmonate induces traumatic resin ducts,terpenoid resin biosynthesis,and terpenoid accumulation in developing xylem of Norway spruce stems

Norway spruce (Picea abies L. Karst) produces an oleoresin characterized by a diverse array of terpenoids, monoterpenoids, sesquiterpenoids, and diterpene resin acids that can protect conifers against potential herbivores and pathogens. Oleoresin accumulates constitutively in resin ducts in the cortex and phloem (bark) of Norway spruce stems. De novo formation of traumatic resin ducts (TDs) is observed in the developing secondary xylem (wood) after insect attack, fungal elicitation, and mechanical wounding. Here, we characterize the methyl jasmonate-induced formation of TDs in Norway spruce by microscopy, chemical analyses of resin composition, and assays of terpenoid biosynthetic enzymes. The response involves tissue-specific differentiation of TDs, terpenoid accumulation, and induction of enzyme activities of both prenyltransferases and terpene synthases in the developing xylem, a tissue that constitutively lacks axial resin ducts in spruce. The induction of a complex defense response in Norway spruce by methyl jasmonate application provides new avenues to evaluate the role of resin defenses for protection of conifers against destructive pests such as white pine weevils (Pissodes strobi), bark beetles (Coleoptera, Scolytidae), and insect-associated tree pathogens.     

生态恢复对马尾松叶片化学计量及氮磷转移的影响

为了解生态恢复对侵蚀红壤恢复的马尾松林叶片碳氮磷化学计量及氮磷养分转移的影响,在福建省长汀县河田镇典型侵蚀红壤区选取恢复13、30、33a的马尾松林为研究对象,并以未治理侵蚀地(CK1)和次生林(CK2)分别作为恢复前和恢复后的对照,通过测定马尾松叶片的碳、氮、磷含量,计算其计量比,内稳性指数和氮磷转移率,分析了侵蚀红壤生长的马尾松养分限制与养分转移的关系。结果表明:在侵蚀红壤恢复过程中,马尾松1年龄叶片C、N、P含量及1年龄叶片C∶N、C∶P、N∶P变化较小,这与马尾松较高的内稳性有关(N和P内稳性指数分别为7.57和3.89)。所有实验地马尾松1年龄叶片N∶P处于11.0—13.4之间,表明马尾松的生长受N、P共同限制,其中马尾松叶片N转移率显著低于P转移率,这与生态恢复过程中马尾松养分利用效率、生长需求以及土壤养分供应状况有关。1年龄叶片C∶N、C∶P分别与马尾松N、P转移率成负相关关系,当马尾松叶片C∶N、C∶P较低时,表明N、P利用效率较低,叶片衰老时更多的N和P被转移利用;反之,则N、P利用效率较高,转移率低。同时,C∶N、C∶P分别与树高、胸径成显著负相关关系,即马尾松生长对N、P的需求同样会影响化学计量比的变化,从而影响养分转移。虽然侵蚀地生态恢复过程中土壤N、P含量增加,但仍较贫瘠,不足以满足马尾松的生长,马尾松养分转移率较高,因此,为了提高侵蚀地恢复的马尾松林的生产力,建议下一步恢复措施中适当施加N肥和P肥。该研究将侵蚀红壤不同生态恢复年限的马尾松叶片C、N、P化学计量及养分转移结合,有助于全面、系统地揭示生态恢复过程马尾松林的养分循环,对指导侵蚀红壤恢复和提高马尾松生产力具有重要意义。     

Precursor limitations in methyl jasmonate-induced Catharanthus roseus cell cultures

Jasmonates enhance the expression of various genes involved in terpenoid indole alkaloid (TIA) biosynthesis in Catharanthus roseus. We applied precursor feeding to our C. roseus suspensions to determine how methyl jasmonate (MJ) alters the precursor availability for TIA biosynthesis. C. roseus suspensions were induced with MJ (100 μM) on day 6 and fed loganin (0.30 mM), tryptamine (0.15 mM), loganin plus tryptamine, or geraniol (0.1–1.0 mM) on day 7. While MJ increased ajmalicine production by 3-fold, induced cultures were still limited by terpenoid precursors. However, both induced and non-induced cultures became tryptamine-limited with excess loganin. Geraniol feeding also increased ajmalicine production in non-induced cultures. But MJ appeared to increase geraniol availability in induced cultures, due presumably to the increased expression of Dxs with MJ addition.     

林龄对重庆武陵山区马尾松天然次生林C、N、P生态化学计量特征的影响

在国家碳达峰和碳中和背景下，为准确评估区域植被固碳增汇功能和科学指导其经营管理，以重庆武陵山区14、25、38、45、62年生马尾松天然次生林为研究对象，对马尾松各器官（叶、枝、干、根和皮）、凋落物以及土壤C、N、P含量及其生态化学计量特征进行研究。结果表明：（1）马尾松针叶C、N、P含量分别变化在444.48-518.03 g/kg、12.31-16.15 g/kg、1.75-2.21 g/kg之间，总体呈"C适中、N缺乏及P充足"的养分格局，且马尾松生长主要受N限制。（2）马尾松各器官C、N、P生态化学计量受林龄影响及其变化规律各有不同，但不同器官差异显著（P<0.05），其中C含量以皮最大，N、P含量则以针叶最大。（3）林龄对马尾松凋落物C、N、P生态化学计量影响不显著（P>0.05）；马尾松林土壤P含量低（变化在0.09-0.41 g/kg之间），但各土层生态化学计量比却普遍较高，且受林龄影响各不相同。（4） C、N、P生态化学计量在马尾松各器官-凋落物-土壤之间总体呈显著相关性（P<0.05），其中，针叶C、N含量均与土壤N含量呈显著正相关，但针叶P含量与土壤N含量呈显著负相关。因此，对于该区域的马尾松天然次生林，应采取适当增施氮肥或林下补植固氮树种的营林措施，以提升马尾松天然次生林的固碳增汇能力。     

Ethylene in induced conifer defense: cDNA cloning, protein expression, and cellular and subcellular localization of 1-aminocyclopropane-1-carboxylate oxidase in resin duct and phenolic parenchyma cells

Members of the Pinaceae family have complex chemical defense strategies. Conifer defenses associated with specialized cell types of the bark involve constitutive and inducible accumulation of phenolic compounds in polyphenolic phloem parenchyma cells and oleoresin terpenoids in resin ducts. These defenses can protect trees against insect herbivory and fungal colonization. The phytohormone ethylene has been shown to induce the same anatomical and cellular defense responses that occur following insect feeding, mechanical wounding, or fungal inoculation in Douglas fir (Pseudotsuga menziesii) stems (Hudgins and Franceschi in Plant Physiol 135:2134–2149, 2004). However, very little is known about the genes involved in ethylene formation in conifer defense or about the temporal and spatial patterns of their protein expression. The enzyme 1-aminocyclopropane-1-carboxylate oxidase (ACO) catalyzes the final step in ethylene biosynthesis. We cloned full-length and near full-length ACO cDNAs from three conifer species, Sitka spruce (Picea sitchensis), white spruce (P. glauca), and Douglas fir, each with high similarity to Arabidopsis thaliana ACO proteins. Using an Arabidopsis anti-ACO antibody we determined that ACO is constitutively expressed in Douglas fir stem tissues and is up-regulated by mechanical wounding, consistent with the wound-induced increase of ethylene levels. Immunolocalization showed cytosolic ACO is predominantly present in specialized cell types of the wound-induced bark, specifically in epithelial cells of terpenoid-producing cortical resin ducts, in polyphenolic phloem parenchyma cells, and in ray parenchyma cells.J.W. Hudgins and Steven G. Ralph contributed equally to this work.     

Terpenoids are transported in the xylem sap of Norway spruce

Norway spruce is a conifer storing large amounts of terpenoids in resin ducts of various tissues. Parts of the terpenoids stored in needles can be emitted together with de novo synthesized terpenoids. Since previous studies provided hints on xylem transported terpenoids as a third emission source, we tested if terpenoids are transported in xylem sap of Norway spruce. We further aimed at understanding if they might contribute to terpenoid emission from needles. We determined terpenoid content and composition in xylem sap, needles, bark, wood and roots of field grown trees, as well as terpenoid emissions from needles. We found considerable amounts of terpenoids—mainly oxygenated compounds—in xylem sap. The terpenoid concentration in xylem sap was relatively low compared with the content in other tissues, where terpenoids are stored in resin ducts. Importantly, the terpenoid composition in the xylem sap greatly differed from the composition in wood, bark or roots, suggesting that an internal transport of terpenoids takes place at the sites of xylem loading. Four terpenoids were identified in xylem sap and emissions, but not within needle tissue, suggesting that these compounds are likely derived from xylem sap. Our work gives hints that plant internal transport of terpenoids exists within conifers; studies on their functions should be a focus of future research.     

Effects of forest types on leaf functional traits and their interrelationships of Pinus massoniana coniferous and broad‐leaved mixed forests in the subtropical mountain,Southeastern China

Leaf functional traits are widely used to detect and explain adaptations that enable plants to live under various environmental conditions. This study aims to determine the difference in leaf functional traits among four forest types of Pinus massoniana coniferous and broad‐leaved mixed forests by leaf morphological, nutrients, and stoichiometric traits in the subtropical mountain, Southeastern China. Our study indicated that the evergreen conifer species of P. massoniana had higher leaf dry matter content (LDMC), leaf C content, C/N and C/P ratios, while the three deciduous broad‐leaved species of L. formosana, Q. tissima, and P. strobilacea had higher specific leaf area (SLA), leaf N, leaf P nutrient contents, and N/P ratio in the three mixed forest types. The results showed that the species of P. massoniana has adapted to the nutrient‐poor environment by increasing their leaf dry matter for higher construction costs thereby reducing water loss and reflects a resource conservation strategy. In contrast, the three species of L. formosana, Q. tissima, and P. strobilacea exhibited an optimized resource acquisition strategy rather than resource conservation strategy in the subtropical mountain of southeastern China. Regarding the four forest types, the three mixed forest types displayed increased plant leaf nutrient contents when compared to the pure P. massoniana forest, especially the P. massoniana–L. formosana mixed forest type (PLM). Overall, variation in leaf functional traits among different forest types may play an adaptive role in the successful survival of plants under diverse environments because leaf functional traits can lead to significant effects on leaf function, especially for their acquisition of nutrients and use of light. The results of this study are beneficial to reveal the changes in plant leaf functional traits at the regional scale, which will provide a foundation for predicting changes in leaf traits and adaptation in the future environment.     

Differential anatomical response of Norway spruce stem tissues to sterile and fungus infected inoculations

The anatomical defense responses in stems of Norway spruce (Picea abies) clones of different resistance to pathogenic fungi were characterized over time and distance from small mechanical wounds or wounds inoculated with the root rot fungus Heterobasidion annosum. Common responses for both treatments included division of ray parenchyma and other cells in the cambial zone, accumulation of phenolic inclusions in ray parenchyma cells, activation of phloem parenchyma (PP) cells, and formation of traumatic resin ducts (TDs) in the xylem. TD formation occurred synchronously from a tangential layer of cells, or symplasmic domain, within the zone of xylem mother cells. TD induction is triggered by a signal, which propagates a developmental wave in the axial direction at about 2.5 cm per day. TDs are formed at least 30 cm above single inoculations within 16–36 days after inoculation. The size and number of TDs is attenuated further away from the inoculation site, indicating a dose-dependent activity leading to TD development. Compared to sterile wounding, fungal inoculation gave rise to more and larger TDs in all clones, and multiple rows of TDs in weak clones. Fungal inoculation also induced the formation of more new PP cells, increasing the number of PP cells in the phloem in the year of inoculation up to 100%. TD and PP cell formation was greater in susceptible compared to resistant clones and after fungal versus sterile inoculation. Potential mechanisms responsible for this variable response are discussed.     

抚育择伐对马尾松林主要树种空间分布格局及其关联性的短期影响

探讨不同抚育择伐方式下森林群落物种空间分布格局和关联性,对科学优化森林结构和促进森林稳定发展具有重要意义。以三峡库区马尾松飞播林为研究对象,采用未择伐、伐除优势马尾松、伐除非马尾松、除灌等处理方式建立固定监测样地,利用Ripley′s L函数的空间点格局方法,分析抚育择伐3年后马尾松林的群落组成、空间分布格局、种间关联性的变化特征。结果表明:1)不同抚育择伐措施均在一定程度上改变了物种组成以及部分树种的优势程度,降低了各样地乔木层物种多样性。2)未择伐主要树种空间分布格局以随机分布为主,伐除优势马尾松样地优势树种主要呈现聚集分布,伐除非马尾松改变了香椿和盐肤木等树种的分布格局,呈聚集分布,其他优势树种空间分布格局与对照样地相似;除灌进一步加剧林下更新树种的随机分布。3)未择伐样地主要树种空间关联性表现为正相关或不相关,伐除优势马尾松增加了主要树种间的负相关性,伐除非马尾松和除灌措施则增加了种间的不相关性。短期人为择伐干扰明显改变了林分空间结构和稳定性,择伐对象不同对林分结构产生的影响也不同。单纯调整某个树种或单个层次的结构来开展森林经营,不利于林分空间结构的整体优化,必须要综合考虑择伐强度和择伐对象的选择,将有助于实现森林结构优化和功能提升。     

重庆酸雨区马尾松纯林改造对土壤酸化特征及团聚体稳定性的影响

马尾松对酸沉降危害极其敏感,生产实践中往往通过林分改造来应对酸沉降危害。为掌握酸雨区马尾松纯林改造对土壤酸化环境的影响及科学指导经营管理,采用空间代替时间的方法,对重庆铁山坪林场的马尾松纯林及其阔叶化改造后的香樟林、木荷林、马尾松×香樟混交林和马尾松×木荷混交林土壤养分、酸化特征及团聚体稳定性进行研究。结果表明：（1）除木荷混交林的腐殖质层土壤有机碳和全氮含量显著增加外,其他森林类型总体均减少（P<0.05）;香樟林及其混交林的各层土壤全磷和全钾含量均增加,但木荷林及其混交林均减少（P<0.05）。（2）改造为香樟林及其混交林能显著提高土壤pH值、交换性盐基离子含量和盐基饱和度,降低交换性Al³⁺含量,但改造为木荷林及其混交林则总体对土壤酸化特征影响不明显（P>0.05）。（3）木荷林及其混交林淀积层的水稳性大团聚体含量增加,香樟林及其混交林则是微团聚体含量增加（P<0.05）。（4）改造对各森林类型腐殖质层和木荷林淋溶层及淀积层的土壤团聚体稳定性均无显著影响,但能增强马尾松混交林和香樟林淋溶层或淀积层的土壤团聚体稳定性（P<0.05）。综合来看,改造能改变土壤酸化环境,但各森林类型的影响不同,改造为香樟林或其混交林的改善效果总体好于木荷林或其混交林。因而对酸雨区马尾松纯林改造,还应根据改造树种特性及林分特征,科学确定相应的改造方法,尤其应注重改造林分的全过程抚育经营,以营造良好的林下环境。     

Scanning electron microscopic analysis of intramyocellular lipid droplets in an animal model of type 2 diabetes

Objective: To evaluate the accumulation pattern of intramyocellular lipids (IMCLs) in striated muscle during the development and progression of diabetes, using a novel scanning electron microscopic method. Methods and Procedures: Hyperglycemia was induced by feeding diabetes‐prone (DP) Psammomys obesus a high‐energy (HE) diet. Lipid accumulation within gastrocnemius muscle fibers was assessed in formalin‐fixed muscle samples during the development of hyperglycemia using high resolution imaging in a scanning electron microscope. We evaluated the temporal relationship between changes in IMCL quantity and morphology and the altered glucose metabolism and assessed the effect of reversal of hyperglycemia on IMCL level and morphology. Diabetes‐resistant (DR) P. obesus served as controls. Results: Lipid accumulation in the muscle fibers of DP animals was increased with the development of hyperglycemia. This was characterized by increased lipid density as well as by an abundance of large lipid droplets. Reversal of the phenotype resulted in the disappearance of large lipid droplets. The IMCL level and the distribution of lipid droplet size were similar in muscles of both the normoglycemic DR and DP animals, with an abundance of small lipid droplets. This profile was changed following a HE diet only in the DP animals. Discussion: Lipid accumulation in the muscle of P. obesus during the development of hyperglycemia is characterized by increased quantity and accumulation of large lipid droplets. These changes were reversible upon normalization of blood glucose. The evaluated methodology is a useful tool for the study of the dynamics of lipid accumulation in different metabolic conditions.     

Will chemical defenses become more effective against specialist herbivores under elevated CO2?

Elevated atmospheric CO₂ is known to affect plant–insect herbivore interactions. Elevated CO₂ causes leaf nitrogen to decrease, the ostensible cause of herbivore compensatory feeding. CO₂ may also affect herbivore consumption by altering chemical defenses via changes in plant hormones. We considered the effects of elevated CO₂, in conjunction with soil fertility and damage (simulated herbivory), on glucosinolate concentrations of mustard (Brassica nigra) and collard (B. oleracea var. acephala) and the effects of leaf nitrogen and glucosinolate groups on specialist Pieris rapae consumption. Elevated CO₂ affected B. oleracea but not B. nigra glucosinolates; responses to soil fertility and damage were also species‐specific. Soil fertility and damage also affected B. oleracea glucosinolates differently under elevated CO₂. Glucosinolates did not affect P. rapae consumption at either CO₂ concentration in B. nigra, but had CO₂‐specific effects on consumption in B. oleracea. At ambient CO₂, leaf nitrogen had strong effects on glucosinolate concentrations and P. rapae consumption but only gluconasturtiin was a feeding stimulant. At elevated CO₂, direct effects of leaf nitrogen were weaker, but glucosinolates had stronger effects on consumption. Gluconasturtiin and aliphatic glucosinolates were feeding stimulants and indole glucosinolates were feeding deterrents. These results do not support the compensatory feeding hypothesis as the sole driver of changes in P. rapae consumption under elevated CO₂. Support for hormone‐mediated CO₂ response (HMCR) was mixed; it explained few treatment effects on constitutive or induced glucosinolates, but did explain patterns in SEMs. Further, the novel feeding deterrent effect of indole glucosinolates under elevated CO₂ in B. oleracae underscores the importance of defensive chemistry in CO₂ response. We speculate that P. rapae indole glucosinolate detoxification mechanisms may have been overwhelmed under elevated CO₂ forcing slowed consumption. Specialists may have to contend with hosts with poorer nutritional quality and more effective chemical defenses under elevated CO₂.