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One barrier to predicting biogenic secondary organic aerosol (SOA) formation in a changing climate can be attributed to the complex nature of plant volatile emissions. Plant volatile emissions are dynamic over space and time, and change in response to environmental stressors. This study investigated SOA production from emissions of healthy and aphid-stressed Scots pine saplings via dark ozonolysis and photooxidation chemistry. Laboratory experiments using a batch reaction chamber were used to investigate SOA production from different plant volatile mixtures. The volatile mixture from healthy plants included monoterpenes, aromatics, and a small amount of sesquiterpenes. The biggest change in the volatile mixture for aphid-stressed plants was a large increase (from 1.4 to 7.9 ppb) in sesquiterpenes-particularly acyclic sesquiterpenes, such as the farnesene isomers. Acyclic sesquiterpenes had different effects on SOA production depending on the chemical mechanism. Farnesenes suppressed SOA formation from ozonolysis with a 9.7-14.6% SOA mass yield from healthy plant emissions and a 6.9-10.4% SOA mass yield from aphid-stressed plant emissions. Ozonolysis of volatile mixtures containing more farnesenes promoted fragmentation reactions, which produced higher volatility oxidation products. In contrast, plant volatile mixtures containing more farnesenes did not appreciably change SOA production from photooxidation. SOA mass yields ranged from 10.8 to 23.2% from healthy plant emissions and 17.8-26.8% for aphid-stressed plant emissions. This study highlights the potential importance of acyclic terpene chemistry in a future climate regime with an increased presence of plant stress volatiles.

Our objective was to study how changes in the light spectra affect growth; the concentration of carbohydrate, chlorophyll, carotenoid, terpene, alkaloid, and phenolic compounds; and the emissions of BVOC (biogenic volatile organic compound) of Norway spruce (Picea abies (L.) Karst.) seedlings. This study was conducted during the growth of the third needle generation in plant growth chambers. The plants were exposed to two light spectra with equal photon flux densities but different proportions of blue light (400-500 nm) produced by LED (light-emitting diode) lamps: (i) control (white light +12% blue light) and (ii) increased blue light (+B) (white light + 45% blue light). The +B treatment increased the concentrations of total flavonoids and acetophenones in needles. The major changes in the phenolic profile were an accumulation of astragalin derivatives and the aglycone of picein. The +B treatment also decreased concentrations of the main alkaloid compound, epidihydropinidine, and its precursor, 2-methyl-6-propyl-1,6-piperideine; the emission rates of limonene, myrcene, and total monoterpenes; and the concentrations of a few terpenoid compounds, mainly in stems. Growth as well as the carbohydrates and pigments present in the needles were not affected. The results suggest that supplemental blue light shifts carbon allocation between secondary metabolism routes--from alkaloid and terpenoid synthesis to flavonoid and acetophenone synthesis. The changes may affect herbivory and abiotic stress tolerance of Norway spruce. Key words: blue light, Norway spruce, biogenic volatile organic compounds, phenolic compounds, alkaloids. Notre objectif consistait a etudier de quelle facon les changements dans le spectre lumineux influencent la croissance, la concentration des hydrates de carbone, de la chlorophylle, des carotenoides, des terpenes, des alcaloides et des composes phenoliques, ainsi que les emissions de composes organiques volatiles biogeniques chez des semis d'epicea commun (Picea abies (L.) Karst.). Cette etude a ete effectuee en phytotrons durant la croissance des aiguilles de troisieme generation. Les plants ont ete exposes a deux spectres lumineux avec une densite egale du flux photonique qui se distinguaient principalement par la proportion de lumiere bleue (400-500 nm) produite par des lampes a DEL (diode electroluminescente) : (i) temoin (lumiere blanche + 12 % de lumiere bleue) et (ii) plus forte proportion de lumiere bleue (+B) (lumiere blanche + 45 % de lumiere bleue). Le traitement +B a augmente la concentration totale des flavonoides et des acetophenones dans les aiguilles. L'accumulation de derives de l'astragaline et de l'aglycone de la piceine est le changement majeur observe dans le profil des composes phenoliques. Le traitement +B a aussi reduit la concentration du principal compose alcaloide, l'epidihydropinidine et son precurseur, la 2-methyl-6-propyl-1,6-piperideine, les taux d'emission du limonene, du myrcene et des monoterpenes totaux, ainsi que la concentration de quelques composes terpenoides, principalement dans la tige. La croissance, ainsi que les pigments et les hydrates de carbone presents dans les aiguilles n'ont pas ete modifies. Les resultats indiquent que le supplement de lumiere bleue modifie l'allocation du carbone vers les sentiers metaboliques secondaires, de la synthese des alcaloides et des terpenoides vers la synthese des flavonoides et des acetophenones. Ces changements pourraient avoir un impact sur la tolerance de l'epicea commun aux herbivores et aux stress abiotiques. [Traduit par la Redaction] Mots-cles : lumiere bleue, epicea commun, composes organiques volatiles biogeniques, composes phenoliques, alcaloides., Introduction Quality and quantity of light are primary factors affecting plant germination, morphogenesis, growth, reproduction, and defence. Several photoreceptors participate in perceiving different wavelengths of light, such as phototropins and [...]

Phenolic metabolites in forest trees play a key role in the defence against biotic and abiotic stressors, yet we lack information about the effects of combined abiotic factors on phenolic compounds in conifers. We studied the effects of combined abiotic factors (ozone x temperature, ozone x nitrogen, temperature x nitrogen, and ozone x temperature x nitrogen) on phenolic concentrations in stems of Scots pine (Pinus sylvestris L.) seedlings in a 3-year-long field experiment in central Finland. In current-year stems, elevated ozone increased the concentrations of total phenolics, soluble proanthocyanidins, and total proanthocyanidins, while warming reduced the concentrations of piceatannol glucoside, pinosylvin, isorhamnetin + kaempferol-3-rhamnoside, and monocoumaroyl isoquercitrin 1. Complex interaction effects on current-year stems showed that nitrogen addition increased the concentrations of some flavonoids in ambient ozone and temperature levels. In the stems from the previous years, ozone decreased the concentrations of total phenolics, total proanthocyanidins, and several flavonoids in ambient temperature, while warming increased their concentrations in combination with elevated ozone. Our results suggest that phenolic defence responses in Scots pine seedlings are affected by all three factors, but that the level of phenolics in the stems from previous years may increase under the combined exposure to elevated temperature and ozone--an expected climate trend in the Northern Hemisphere. Key words: ozone, temperature, nitrogen addition, phenolics, Pinus sylvestris. Les metabolites phenoliques dans les arbres forestiers jouent un role cle dans la defense contre les stress biotiques et abiotiques, mais nous manquons d'information au sujet des effets des facteurs abiotiques combines sur les composes phenoliques chez les coniferes. Nous avons etudie les effets de differentes combinaisons de facteurs abiotiques (ozone x temperature, ozone x azote, temperature x azote et ozone x temperature x azote) sur la concentration des phenols dans la tige de semis de pin sylvestre (Pinus sylvestris L.) dans le cadre d'une experience au champ d'une duree de 3 ans etablie dans le centre de la Finlande. Dans les tiges de l'annee, une quantite elevee d'ozone a cause une augmentation de la concentration totale des phenols, des proanthocyanidines solubles et des proanthocyanidines totales tandis qu'un rechauffement a reduit la concentration du glycoside du piceatannol, de la pinosylvine, de l'isorhamnetine + kaempferol-3-rhamnoside et du mono coumaroyl isoquercitrine 1. Des effets d'interaction complexe dans les tiges de l'annee en cours ont montre que l'apport d'azote a cause une augmentation de la concentration de certains flavonoides en presence d'un niveau ambiant d'ozone et de temperature. Dans les tiges des annees anterieures, la presence d'ozone a cause une diminution de la concentration totale des phenols, des proanthocyanidines totales et de plusieurs flavonoides a la temperature ambiante tandis qu'un rechauffement combine a une quantite elevee d'ozone a augmente leurs concentrations. Nos resultats indiquent que la reaction de defense a base de phenols chez les semis de pin sylvestre est influencee par les trois facteurs mais que la concentration des composes phenoliques dans les tiges des annees anterieures peut augmenter en presence de niveaux eleves de temperature et d'ozone, ce qui correspond a une tendance climatique anticipee dans l'hemisphere nord. [Traduit par la Redaction] Mots-cles : ozone, temperature, apport d'azote, composes phenoliques, Pinus sylvestris., Introduction Climate change caused by anthropogenic greenhouse gas emissions have had a widespread impact on Earth's forests in the recent years (Intergovernmental Panel on Climate Change (IPCC) 2014). Northern Europe [...]

Acclimation of conifer needle anatomy to climate change is poorly understood. We studied needle anatomy, shoot gas exchange, current-year shoot length, and stem diameter growth in Norway spruce (Picea abies (L.) Karst.) and Scots pine (Pinus sylvestris L.) seedlings exposed to elevated ozone (1.35x to 1.5x ambient concentration) and elevated temperature (0.9-1.3[degrees]C + ambient temperature) alone and in combination for two exposure seasons in two separate open-field experiments in central Finland. Pines grew also at two soil nitrogen levels. In spruce, warming increased mesophyll intercellular space and reduced gas exchange and shoot growth and made needles narrower and the epidermis and hypodermis thinner. In pine, warming made needles bigger, increased shoot and stem growth, stomatal row number, and proportions of vascular cylinder, phloem, and xylem and reduced the proportion of mesophyll. These responses indicate that pine benefited and spruce suffered from moderate warming. Ozone caused a thickening of epi- and hypo-dermis and a lower stomatal conductance in both species, reduced stomatal density in spruce, and increased proportions of phloem, xylem, and sclerenchyma and reduced growth in pine. Ozone responses suggest increased oxidative stress defense. Stomatal responses were affected by interactions of elevated temperature and ozone in both species. Nitrogen availability modified ozone and temperature responses, particularly in the vascular tissues in pine. Key words: [O.sub.3], elevated temperature, global change, conifer, microscopy. Resume: L'acclimatement de l'anatomie des aiguilles de conifere au changement climatique est mal compris. Nous avons etudie l'anatomie des aiguilles, les echanges gazeux des pousses de l'annee et la croissance en diametre de la tige de semis d'epicea commun (Picea abies (L.) Karst.) et de pin sylvestre (Pinus sylvestris L.) exposes a une concentration elevee d'ozone (1,35-1,5 fois la concentration ambiante) et a une temperature elevee (0,9-1,3[degrees]C au-dessus de la temperature ambiante). Les traitements ont ete appliques separement et conjointement durant deux saisons dans deux experiences a ciel ouvert distinctes dans le centre de la Finlande. Les pins ont aussi ete soumis a deux niveaux d'azote dans le sol. Chez l'epicea, le rechauffement a augmente l'espace intercellulaire dans le mesophylle, reduit les echanges gazeux et la croissance des pousses, retreci les aiguilles et aminci l'epiderme et l'hypoderme. Chez le pin, le rechauffement a rendu les aiguilles plus grosses, augmente la croissance des pousses et de la tige, augmente le nombre de rangees de stomates ainsi que la proportion de cylindre vasculaire, de phloeme et de xyleme et reduit la proportion de mesophylle. Ces reactions indiquent que le pin a beneficie alors que l'epicea a souffert des effets d'un rechauffement modere. L'ozone a cause un epaississement de l'epiderme et de l'hypoderme et reduit la conductance stomatique chez les deux especes, reduit la densite des stomates chez l'epicea et augmente la proportion de phloeme, de xyleme et de sclerenchyme et reduit la croissance chez le pin. Les reactions a l'ozone correspondent a une reaction de defense a un stress oxydant accru. La reaction des stomates etait influencee par les interactions entre la temperature elevee et la plus grande concentration d'ozone chez les deux especes. La disponibilite de l'azote a modifie les reactions a l'ozone et a la temperature particulierement dans les tissus vasculaires chez le pin. [Traduit par la Redaction] Mots-cles: [O.sub.3], augmentation de la temperature, changement mondial, conifere, microscopie., Introduction Ongoing climate change is affecting boreal forests. In the boreal zone, air temperature is projected to increase by 1-2[degrees]C from the 1986-2005 level to 2016-2035 (Kirtman et al. 2013), [...]