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Francesco Loreto - One of the best experts on this subject based on the ideXlab platform.
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Diversification of petal monoterpene profiles during floral development and senescence in wild roses: relationships among geraniol content, petal colour, and floral lifespan
Oecologia, 2020Co-Authors: K. G. Srikanta Dani, Silvia Fineschi, Marco Michelozzi, Alice Trivellini, Susanna Pollastri, Francesco LoretoAbstract:Wild roses store and emit a large array of fragrant Monoterpenes from their petals. Maximisation of fragrance coincides with floral maturation in many angiosperms, which enhances pollination efficiency, reduces floral predation, and improves plant fitness. We hypothesized that petal Monoterpenes serve additional lifelong functions such as limiting metabolic damage from reactive oxygen species (ROS), and altering isoprenoid hormonal abundance to increase floral lifespan. Petal Monoterpenes were quantified at three floral life-stages (unopened bud, open mature, and senescent) in 57 rose species and 16 subspecies originating from Asia, America, and Europe, and relationships among monoterpene richness, petal colour, ROS, hormones, and floral lifespan were analysed within a phylogenetic context. Three distinct types of petal monoterpene profiles, revealing significant developmental and functional differences, were identified: Type A, species where monoterpene abundance peaked in open mature flowers depleting thereafter; Type B, where Monoterpenes peaked in senescing flowers increasing from bud stage, and a rare Type C (8 species) where Monoterpenes depleted from bud stage to senescence. Cyclic Monoterpenes peaked during early floral development, whereas acyclic Monoterpenes (dominated by geraniol and its derivatives, often 100-fold more abundant than other Monoterpenes) peaked during floral maturation in Type A and B roses. Early-diverging roses were geraniol-poor (often Type C) and white-petalled. Lifetime changes in hydrogen peroxide (H_2O_2) revealed a significant negative regression with the levels of petal geraniol at all floral life-stages. Geraniol-poor Type C roses also showed higher cytokinins (in buds) and abscisic acid (in mature petals), and significantly shorter floral lifespan compared with geraniol-rich Type A and B roses. We conclude that geraniol enrichment, intensification of petal colour, and lower potential for H_2O_2-related oxidative damage characterise and likely contribute to longer floral lifespan in monoterpene-rich wild roses.
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Emissions of Monoterpenes linalool and ocimene respond differently to environmental changes due to differences in physico-chemical characteristics
Atmospheric Environment, 2006Co-Authors: Steffen M. Noe, Francesco Loreto, Paolo Ciccioli, Enzo Brancaleoni, Ülo NiinemetsAbstract:Abstract We investigated the 13 C-labeling kinetics of the emission of two major Monoterpenes emitted by needles of Mediterranean conifer Pinus pinea L., monoterpene alcohol linalool and non-oxygenated monoterpene trans - β -ocimene. These data were further used to develop and parameterize a dynamics monoterpene emission model, predicting the emissions of Monoterpenes with contrasting physico-chemical properties to environmental changes. All Monoterpenes emitted were labeled by 13 C in short pulse-labeling experiments. 13 C-labeling experiments further indicated for these two Monoterpenes comprising 77% of total emissions that a major part of the emissions of these two Monoterpenes relied on recently synthesized carbon not on specific storage compartments within the resin ducts. However, labeling kinetics suggested existence of transient storage pools, located within the needle aqueous and lipid phases. For linalool, we found half-lives of 13 min for the aqueous phase storage and 3 h for the lipid phase while trans - β -ocimene exhibit an aqueous phase half-life of 2 and 15 min for the lipid phase, overall indicating that the transient storage due to limited monoterpene volatility can significantly alter the emission dynamics. The key physico-chemical characteristics determining the time constants of the transient storage pools were the Henry's law constant (liquid/gas phase partition coefficient) and the octanol/water (lipid/liquid) phase partition coefficient. As monoterpene Henry's law constants vary over four orders of magnitude and octanol/water partition coefficients over three orders of magnitude, the capacity for non-specific storage, and damping of the effects of rapidly changing environmental conditions is expected to strongly vary among different Monoterpenes. Overall, our study suggests that non-specific storage due to limited volatility is a common phenomenon of common of plant-emitted compounds.
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Impact of ozone on monoterpene emissions and evidence for an isoprene-like antioxidant action of Monoterpenes emitted by Quercus ilex leaves.
Tree physiology, 2004Co-Authors: Francesco Loreto, Paola Pinelli, Fausto Manes, Hannes KollistAbstract:Quercus ilex (L.) leaves emit Monoterpenes, particularly alpha-pinene, beta-pinene and sabinene. Apart from the monoterpene pools that are stored in specialized structures and have a clear defensive or attractive role, the function of Monoterpenes in Q. ilex leaves is unknown. We tested whether Monoterpenes have an antioxidant role, as has previously been found for isoprene in isoprene-emitting leaves. We exposed Q. ilex leaves to either mild and repeated ozone exposure (Experiment I) or to a single acute ozone exposure (Experiment II) at temperatures ranging between 20 and 32 degrees C. Both ozone treatments rapidly stimulated monoterpene synthesis, but had no effect on photosynthesis and caused no visible damage to leaves maintained at 25, 30 or 32 degrees C. Ozone inhibited both photosynthesis and monoterpene synthesis in leaves maintained at 20 degrees C. To characterize the relationship between Monoterpenes and ozone-induced damage, we fed detached leaves fosmidomycin, a selective inhibitor of isoprene synthesis. Fosmidomycin caused rapid and complete inhibition of monoterpene emissions in leaves maintained at 30 degrees C, confirming that Monoterpenes are synthesized by the same biochemical pathway as isoprene. However, over the experimental period, fosmidomycin did not affect concentrations of compounds that are formed from chloroplastic isoprenoids and that might have conferred antioxidant protection, either directly (carotenoids) or indirectly (chlorophylls, xanthophylls). In leaves whose monoterpene synthesis had been inhibited by fosmidomycin, ozone rapidly and significantly inhibited photosynthesis and increased the production of hydrogen peroxide and malonyldialdehyde. We conclude that Monoterpenes produced by Q. ilex leaves share the same biosynthetic pathway and function as isoprene. Furthermore, all volatile isoprenoids may have similar antioxidant properties and may be stimulated by the same stress-inducing conditions.
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Monoterpene emission and monoterpene synthase activities in the Mediterranean evergreen oak Quercus ilex L. grown at elevated CO2 concentrations
Global Change Biology, 2001Co-Authors: Francesco Loreto, Paolo Ciccioli, Enzo Brancaleoni, Jörg-peter Schnitzler, Robert Fischbach, Carlo Calfapietra, Guenther SeufertAbstract:Monoterpene emissions, monoterpene synthase activities, photosynthesis, fluorescence yield in the dark and drought stress indicators (stomatal conductance and mid-day water potential) were concurrently measured under similar temperature and illumination in current-year leaves of Quercus ilex L. of plants grown in open-top chambers at ambient (350 ppm) and elevated (700 ppm) CO2. The study was undertaken to understand the effect of CO2 on monoterpene biosynthesis, and to predict and parameterize the biogenic emissions at growing CO2 concentrations. The results of the 1998 and 1999 studies show that at elevated CO2, and in the absence of persistent environmental stresses, photosynthesis was stimulated with respect to ambient CO2, but that the emission of the three most abundantly emitted Monoterpenes (a-pinene, sabinene and b-pinene) was inhibited by approximately 68%. The enzyme activities of the monoterpene synthases catalysing the formation of the three Monoterpenes were also inhibited at elevated CO2 and an excellent relationship was found between monoterpene emission and activity of the corresponding enzyme both at ambient and elevated CO2. Interestingly, however, limonene emission was enhanced in conditions of elevated CO2 as it was also the corresponding synthase. The ratio between enzyme activity and emission of the three main Monoterpenes was high (above 20) at ambient CO2 but it was below 10 at elevated CO2 and, for limonene, on both treatments. Our results indicate that the overall emission of Monoterpenes at elevated CO2 will be inhibited because of a concurrent, strong down-regulation of monoterpene synthase activities. When the enzyme activity does not change, as for limonene, the high photosynthetic carbon availability at elevated CO2 conditions may even stimulate emission. The results of the 1997 study show that severe and persistent drought, as commonly occurs in the Mediterranean, may inhibit both photosynthesis and monoterpene (a-pinene) emission, particularly at ambient CO2. Thus, emission is probably limited by photosynthetic carbon availability; the effect of elevated CO2 per se is not apparent if drought, and perhaps other environmental stresses, are also present.
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fumigation with exogenous Monoterpenes of a non isoprenoid emitting oak quercus suber monoterpene acquisition translocation and effect on the photosynthetic properties at high temperatures
New Phytologist, 2000Co-Authors: Sebastiano Delfine, Guenther Seufert, Olav Csiky, Francesco LoretoAbstract:We tested if fumigation with exogenous Monoterpenes might induce thermotolerance in leaves of an oak species (Quercus suber) which does not form and emit isoprenoids. To understand if exogenous monoterpene fumigation results in internal accumulation of Monoterpenes, a physical method of monoterpene extraction was used. The internal content of Monoterpenes increased in concert with increasing fumigation doses. This unambiguously demonstrated acquisition of exogenous Monoterpenes. We exposed fumigated Q. suber leaves to two cycles of increasing temperatures from 35 to 55°C at 5°C steps. When leaves were exposed to a low dose of exogenous Monoterpenes, yielding an internal content similar to that endogenously formed in the leaves of the monoterpene-emitter Q. ilex, no clear improvement in thermotolerance was found. When leaves were exposed to a high dose of exogenous Monoterpenes, yielding an internal content of about five fold the endogenous pool of Q. ilex, but comparable with the expected content following stress-induced stomatal closure, photosynthesis inhibition at high temperatures was attenuated. This effect was observed only at temperatures < 45°C during the first cycle, but at all temperatures between 35 and 55°C when plants were exposed to two cycles of high temperatures. Monoterpenes were still found in the leaves of Q. suber 12 h after ending the fumigation. Monoterpenes were also found in non-fumigated leaves distant up to 45 cm from the fumigated leaves. If Monoterpenes make the photosynthetic apparatus more resistant to high temperatures, the effect might not be limited to the fumigated leaves and might be persistent after fumigation.
Joerg Bohlmann - One of the best experts on this subject based on the ideXlab platform.
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toxicity of pine Monoterpenes to mountain pine beetle
Scientific Reports, 2017Co-Authors: Christine C Chiu, Christopher I Keeling, Joerg BohlmannAbstract:The mountain pine beetle (Dendroctonus ponderosae; MPB) is an eruptive bark beetle species affecting pine forests of western North America. MPB are exposed to volatile Monoterpenes, which are important host defense chemicals. We assessed the toxicity of the ten most abundant Monoterpenes of lodgepole pine (Pinus contorta), a major host in the current MPB epidemic, against adult MPB from two locations in British Columbia, Canada. Monoterpenes were tested as individual volatiles and included (−)-β-phellandrene, (+)-3-carene, myrcene, terpinolene, and both enantiomers of α-pinene, β-pinene and limonene. Dose-mortality experiments identified (−)-limonene as the most toxic (LC50: 32 μL/L), and (−)-α-pinene (LC50: 290 μL/L) and terpinolene (LC50: >500 μL/L) as the least toxic. MPB body weight had a significant positive effect on the ability to survive most monoterpene volatiles, while sex did not have a significant effect with most Monoterpenes. This study helps to quantitatively define the effects of individual Monoterpenes towards MPB mortality, which is critical when assessing the variable monoterpene chemical defense profiles of its host species.
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Low-density Ceratocystis polonica inoculation of Norway spruce (Picea abies) triggers accumulation of Monoterpenes with antifungal properties
European Journal of Forest Research, 2014Co-Authors: Metka Novak, Joerg Bohlmann, Andreja Urbanek Krajnc, Ljerka Lah, Neja Zupanec, Nada Kraševec, Mitja Križman, Radovan KomelAbstract:Among the most devastating pests of Norway spruce ( Picea abies ) are the European spruce bark beetle ( Ips typographus ) and the associated pathogenic blue-stain fungus Ceratocystis polonica. Following attack and colonization, the beetle and the fungus must cope with induced host chemical defenses, such as Monoterpenes that are generally thought to be toxic to both symbionts. The goal of this study was to better understand the response of Norway spruce following C. polonica inoculation at low density that does not overwhelm the tree and to identify Monoterpenes mobilized toward the fungus. We inoculated healthy mature trees and monitored monoterpene profiles 2, 3, and 5 months post-inoculation. We also exposed three different C. polonica strains to the most abundant or significantly up-regulated Monoterpenes to determine differences in monoterpene toxicity and resistance among strains. Total monoterpene levels, including limonene, were increased at 2 and 3 months after inoculation and had dropped after 5 months. In in vitro assays, all Monoterpenes were inhibitory to C. polonica . Limonene and β-pinene were the most potent inhibitors of fungal growth. The extent of inhibition varied between the three strains tested. These results showed a defense response of Norway spruce to C. polonica , in which limonene may play a critical role in inhibiting the spread of the fungus. We also showed that differences between strains of C. polonica must be taken into account when assessing the role of the fungus in this bark beetle–symbiont system.
Rodney Croteau - One of the best experts on this subject based on the ideXlab platform.
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Biosynthesis of marine natural products: isolation and characterization of a myrcene synthase from cultured tissues of the marine red alga Ochtodes secundiramea.
Archives of Biochemistry and Biophysics, 2002Co-Authors: Mitchell L Wise, Jason J. Polzin, Gregory L Rorrer, Rodney CroteauAbstract:Abstract The acyclic monoterpene myrcene is the likely progenitor of the unusual cytotoxic halogenated Monoterpenes that are found in marine algae and that function as feeding deterrents to herbivores. Myrcene synthase was isolated from suspension cultures of the marine red alga Ochtodes secundiramea, representing the first enzyme of this type from a marine organism. The algal myrcene synthase produces exclusively myrcene from the natural substrate geranyl diphosphate (GDP), utilizes Mg +2 as the required divalent metal ion cofactor, has a molecular mass of about 69 kDa, and exhibits a pH optimum near 7.2. These features are similar to those of monoterpene synthases from terrestrial organisms. When incubated with neryl diphosphate (the cis -isomer of GDP), the O. secundiramea myrcene synthase produces the cyclic monoterpene limonene, whereas incubation with (±)linalyl diphosphate (the tertiary allylic isomer of geranyl diphosphate) yields both acyclic and cyclic Monoterpenes. These results suggest that the enzyme is incapable of isomerizing geranyl diphosphate to linalyl diphosphate, a feature common to all monoterpene cyclases from terrestrial sources. The limited catalytic capability of the myrcene synthase may reflect the ancient evolutionary origin of the producing organism. The ability to assay this enzyme in cultured algae, grown under strictly defined conditions, provides an unparalleled opportunity to delineate factors eliciting the biosynthesis of this class of secondary metabolites, to investigate the metabolic pathway leading to the halogenated Monoterpenes, and to determine their role in the chemical ecology of marine algae.
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Strategies for transgenic manipulation of monoterpene biosynthesis in plants.
Trends in plant science, 2002Co-Authors: Soheil S. Mahmoud, Rodney CroteauAbstract:Monoterpenes, the C(10) isoprenoids, are a large family of natural products that are best known as constituents of the essential oils and defensive oleoresins of aromatic plants. In addition to ecological roles in pollinator attraction, allelopathy and plant defense, Monoterpenes are used extensively in the food, cosmetic and pharmaceutical industries. The importance of these plant products has prompted the definition of many monoterpene biosynthetic pathways, the cloning of the relevant genes and the development of genetic transformation techniques for agronomically significant monoterpene-producing plants. Metabolic engineering of monoterpene biosynthesis in the model plant peppermint has resulted in yield increase and compositional improvement of the essential oil, and also provided strategies for manipulating flavor and fragrance production, and plant defense.
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regulation of monoterpene accumulation in leaves of peppermint
Plant Physiology, 2000Co-Authors: Jonathan Gershenzon, Marie E Mcconkey, Rodney CroteauAbstract:Plants synthesize numerous classes of natural products that accumulate during development and are thought to function as constitutive defenses against herbivores and pathogens. However, little information is available about how the levels of such defenses are regulated. We measured the accumulation of Monoterpenes, a model group of constitutive defenses, in peppermint ( Mentha × piperita L.) leaves and investigated several physiological processes that could regulate their accumulation: the rate of biosynthesis, the rate of metabolic loss, and the rate of volatilization. Monoterpene accumulation was found to be restricted to leaves of 12 to 20 d of age, the period of maximal leaf expansion. The rate of monoterpene biosynthesis determined by 14 CO 2 incorporation was closely correlated with monoterpene accumulation, as determined by gas chromatographic analysis, and appeared to be the principal factor controlling the monoterpene level of peppermint leaves. No significant catabolic losses of Monoterpenes were detected throughout leaf development, and monoterpene volatilization was found to occur at a very low rate, which, on a monthly basis, represented less than 1% of the total pool of stored Monoterpenes. The composition of volatilized Monoterpenes differed significantly from that of the total plant monoterpene pool, suggesting that these volatilized products may arise from a separate secretory system. With the demonstration that the rate of biosynthesis is the chief process that determines monoterpene accumulation in peppermint, efforts to improve production in this species can now focus on the genes, enzymes, and cell differentiation processes that regulate monoterpene biosynthesis.
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Monoterpene synthases of loblolly pine (Pinus taeda) produce pinene isomers and enantiomers.
Archives of Biochemistry and Biophysics, 1999Co-Authors: Michael A Phillips, Thomas J Savage, Rodney CroteauAbstract:Abstract The turpentine fraction of conifer oleoresin is a complex mixture of monoterpene olefins and plays important roles in defense and in the mediation of chemical communication between conifer hosts and insect predators. The stereochemistry of the turpentine Monoterpenes is critical in these interactions, influencing host recognition, toxicity, and potency of derived pheromones, and the stereochemical composition of these compounds lends insight into their biogenetic origin, with implications for the numbers and types of enzymes responsible and their corresponding genes. Analysis of the oleoresin from several tissues of loblolly pine (Pinus taeda) showed the derived turpentine to consist mainly of (+)-(3R:5R)-α-pinene and (−)-(3S:5S)-β-pinene. Cell-free extracts from xylem tissue yielded three monoterpene synthases which together account for the monoterpene isomer and enantiomer content of the turpentine of this tissue. The major products of these enzymes, produced from the universal precursor of Monoterpenes, geranyl diphosphate, were shown to be (+)-α-pinene, (−)-α-pinene, and (−)-β-pinene, respectively. In most properties (molecular mass of ∼60 kDa, Km for geranyl diphosphate of 3 μM, requirement for monovalent and divalent cations), these enzymes resemble other monoterpene synthases from conifer species.
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Metabolism of Monoterpenes in mint (mentha) species.
Planta Medica, 1991Co-Authors: Rodney CroteauAbstract:Commercial mint (Mentha) species produce either C3-oxygenated or C6-oxygenated p-menthane monoterpene as the major essential oil components. The biosynthetic origin of both of these monoterpene families from the common precursor (-)-limonene is described. The metabolic turnover of Monoterpenes occurs during late stages of plant development, and the pathway for the transport and catabolism of (-)-menthone in peppermint is reviewed as a model for this general process. The developmental regulation of monoterpene metabolism is briefly outlined
Josep Peñuelas - One of the best experts on this subject based on the ideXlab platform.
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human absorption of Monoterpenes after a 2 hs forest exposure a field experiment in a mediterranean holm oak forest
Journal of Pharmaceutical and Biomedical Analysis, 2021Co-Authors: Albert Bach, Joan Llusià, Josep Peñuelas, Roser Maneja, Quim Zaldoaubanell, Teresa Romanillos, Alba Eustaquio, Oscar PalaciosAbstract:Abstract The current body of literature points Monoterpenes as one of the determinant factors of the interaction between forests and human health. The present study aims at analyzing the monoterpene absorption by humans during a 2 -hs forest exposure in a Mediterranean holm oak forest focusing on the four most abundant monoterpene compounds: alpha-pinene, beta-pinene, alpha-phellandrene and limonene. Participants’ blood samples were collected before and after exposure to forest or urban environment (control). We conducted air and blood sampling using cartridges and head space method and determined the monoterpene compounds through CG-MS. We identified the four compounds in forest air during the experimental study being alpha-pinene the monoterpene with the greatest concentration. Results show no significant changes in monoterpene blood concentrations for the forest and control group. However, a negative significant relationship between absorption and baseline blood concentration of the most abundant forest air Monoterpenes, alpha-pinene and beta-pinene, was found in individuals visiting the forest, i.e. higher absorption was found the lower the baseline blood concentration was. Although no significant lineal correlation could be spotted between the vital variables and the monoterpene absorption, we found significant correlations between the absorption of the monoterpene compounds. This attempt, first in a Mediterranean holm oak forest, can serve as a starting point and constitute a valuable contribution for further research in regard to experimental design and laboratory analysis.
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linking photorespiration Monoterpenes and thermotolerance in quercus
New Phytologist, 2002Co-Authors: Josep Peñuelas, Joan LlusiàAbstract:Summary • The functions of two important plant processes, photorespiration and monoterpene production remain controversial. Here, we investigated one possible function, that of protection of plants from photodamage at high temperatures. • Fluorescence, reflectance, monoterpene concentrations and visual leaf damage were measured in Quercus ilex seedlings exposed to temperature increases from 25 to 50°C (in 5°C steps) under photorespiratory (21% O 2 ) or nonphotorespiratory (2% O 2 ) atmospheres, and under control or terpene fumigation conditions. • Lower variable to maximum fluorescence ratio (Fv : Fm: potential photochemical efficiency of photosystem II, PSII) and electron transport rate (ETR) were found in nonphotorespiratory conditions at temperatures greater than 35°C. Monoterpene concentrations were also lower, and leaf damage greater, in the low O 2 atmospheres. Monoterpene fumigation, which increased the foliar terpene concentrations by two- to four-fold, increased the photochemical efficiency between 35°C and 50°C, and decreased leaf damage, only under the nonphotorespiratory conditions. • These results provide evidence that: photorespiration decreases photodamage, especially at high temperatures; photorespiration increases monoterpene production; plants are able to acquire exogenous Monoterpenes and the acquisition response to temperature follows the stomatal conductance response; and Monoterpenes can replace photorespiration in protection from photodamage at high temperatures, possibly by scavenging oxygen-reactive species, but they do not provide additional thermotolerance.
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linking photorespiration Monoterpenes and thermotolerance in quercus
New Phytologist, 2002Co-Authors: Josep Peñuelas, Joan LlusiàAbstract:Summary • The functions of two important plant processes, photorespiration and monoterpene production remain controversial. Here, we investigated one possible function, that of protection of plants from photodamage at high temperatures. • Fluorescence, reflectance, monoterpene concentrations and visual leaf damage were measured in Quercus ilex seedlings exposed to temperature increases from 25 to 50°C (in 5°C steps) under photorespiratory (21% O 2 ) or nonphotorespiratory (2% O 2 ) atmospheres, and under control or terpene fumigation conditions. • Lower variable to maximum fluorescence ratio (Fv : Fm: potential photochemical efficiency of photosystem II, PSII) and electron transport rate (ETR) were found in nonphotorespiratory conditions at temperatures greater than 35°C. Monoterpene concentrations were also lower, and leaf damage greater, in the low O 2 atmospheres. Monoterpene fumigation, which increased the foliar terpene concentrations by two- to four-fold, increased the photochemical efficiency between 35°C and 50°C, and decreased leaf damage, only under the nonphotorespiratory conditions. • These results provide evidence that: photorespiration decreases photodamage, especially at high temperatures; photorespiration increases monoterpene production; plants are able to acquire exogenous Monoterpenes and the acquisition response to temperature follows the stomatal conductance response; and Monoterpenes can replace photorespiration in protection from photodamage at high temperatures, possibly by scavenging oxygen-reactive species, but they do not provide additional thermotolerance.
Joan Llusià - One of the best experts on this subject based on the ideXlab platform.
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human absorption of Monoterpenes after a 2 hs forest exposure a field experiment in a mediterranean holm oak forest
Journal of Pharmaceutical and Biomedical Analysis, 2021Co-Authors: Albert Bach, Joan Llusià, Josep Peñuelas, Roser Maneja, Quim Zaldoaubanell, Teresa Romanillos, Alba Eustaquio, Oscar PalaciosAbstract:Abstract The current body of literature points Monoterpenes as one of the determinant factors of the interaction between forests and human health. The present study aims at analyzing the monoterpene absorption by humans during a 2 -hs forest exposure in a Mediterranean holm oak forest focusing on the four most abundant monoterpene compounds: alpha-pinene, beta-pinene, alpha-phellandrene and limonene. Participants’ blood samples were collected before and after exposure to forest or urban environment (control). We conducted air and blood sampling using cartridges and head space method and determined the monoterpene compounds through CG-MS. We identified the four compounds in forest air during the experimental study being alpha-pinene the monoterpene with the greatest concentration. Results show no significant changes in monoterpene blood concentrations for the forest and control group. However, a negative significant relationship between absorption and baseline blood concentration of the most abundant forest air Monoterpenes, alpha-pinene and beta-pinene, was found in individuals visiting the forest, i.e. higher absorption was found the lower the baseline blood concentration was. Although no significant lineal correlation could be spotted between the vital variables and the monoterpene absorption, we found significant correlations between the absorption of the monoterpene compounds. This attempt, first in a Mediterranean holm oak forest, can serve as a starting point and constitute a valuable contribution for further research in regard to experimental design and laboratory analysis.
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linking photorespiration Monoterpenes and thermotolerance in quercus
New Phytologist, 2002Co-Authors: Josep Peñuelas, Joan LlusiàAbstract:Summary • The functions of two important plant processes, photorespiration and monoterpene production remain controversial. Here, we investigated one possible function, that of protection of plants from photodamage at high temperatures. • Fluorescence, reflectance, monoterpene concentrations and visual leaf damage were measured in Quercus ilex seedlings exposed to temperature increases from 25 to 50°C (in 5°C steps) under photorespiratory (21% O 2 ) or nonphotorespiratory (2% O 2 ) atmospheres, and under control or terpene fumigation conditions. • Lower variable to maximum fluorescence ratio (Fv : Fm: potential photochemical efficiency of photosystem II, PSII) and electron transport rate (ETR) were found in nonphotorespiratory conditions at temperatures greater than 35°C. Monoterpene concentrations were also lower, and leaf damage greater, in the low O 2 atmospheres. Monoterpene fumigation, which increased the foliar terpene concentrations by two- to four-fold, increased the photochemical efficiency between 35°C and 50°C, and decreased leaf damage, only under the nonphotorespiratory conditions. • These results provide evidence that: photorespiration decreases photodamage, especially at high temperatures; photorespiration increases monoterpene production; plants are able to acquire exogenous Monoterpenes and the acquisition response to temperature follows the stomatal conductance response; and Monoterpenes can replace photorespiration in protection from photodamage at high temperatures, possibly by scavenging oxygen-reactive species, but they do not provide additional thermotolerance.
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linking photorespiration Monoterpenes and thermotolerance in quercus
New Phytologist, 2002Co-Authors: Josep Peñuelas, Joan LlusiàAbstract:Summary • The functions of two important plant processes, photorespiration and monoterpene production remain controversial. Here, we investigated one possible function, that of protection of plants from photodamage at high temperatures. • Fluorescence, reflectance, monoterpene concentrations and visual leaf damage were measured in Quercus ilex seedlings exposed to temperature increases from 25 to 50°C (in 5°C steps) under photorespiratory (21% O 2 ) or nonphotorespiratory (2% O 2 ) atmospheres, and under control or terpene fumigation conditions. • Lower variable to maximum fluorescence ratio (Fv : Fm: potential photochemical efficiency of photosystem II, PSII) and electron transport rate (ETR) were found in nonphotorespiratory conditions at temperatures greater than 35°C. Monoterpene concentrations were also lower, and leaf damage greater, in the low O 2 atmospheres. Monoterpene fumigation, which increased the foliar terpene concentrations by two- to four-fold, increased the photochemical efficiency between 35°C and 50°C, and decreased leaf damage, only under the nonphotorespiratory conditions. • These results provide evidence that: photorespiration decreases photodamage, especially at high temperatures; photorespiration increases monoterpene production; plants are able to acquire exogenous Monoterpenes and the acquisition response to temperature follows the stomatal conductance response; and Monoterpenes can replace photorespiration in protection from photodamage at high temperatures, possibly by scavenging oxygen-reactive species, but they do not provide additional thermotolerance.