Copolovici L.O., Filella I., Llusià J., Niinemets Ü., Peñuelas J. (2005) The capacity for thermal protection of photosynthetic electron transport varies for different monoterpenes in Quercus ilex. Plant Physiology. 139: 485-496.EnllaçDoi: 10.1104/pp.105.065995
Heat stress resistance of foliar photosynthetic apparatus was investigated in the Mediterranean monoterpene-emitting ever green sclerophyll species Quercus ilex. Leaf feeding with fosmidomycin, which is a specific inhibitor of the chloroplastic isoprenoid synthesis pathway, essentially stopped monoterpene emission and resulted in the decrease of the optimum temperature of photosynthetic electron transport from approximately 38°C to approximately 30°C. The heat stress resistance was partly restored by fumigation with 4 to 5 nmol mol1 air concentrations of monoterpene α-pinene but not with fumigations with monoterpene alcohol α-terpineol. Analyses of monoterpene physicochemical characteristics demonstrated that α-pinene was primarily distributed to leaf gas and lipid phases, while α-terpineol was primarily distributed to leaf aqueous phase. Thus, for a common monoterpene uptake rate, α-terpineol is less efficient in stabilizing membrane liquid-crystalline structure and as an antioxidant in plant membranes. Furthermore, α-terpineol uptake rate (U) strongly decreased with increasing temperature, while the uptake rates of α-pinene increased with increasing temperature, providing a further explanation of the lower efficiency of thermal protection by α-terpineol. The temperature-dependent decrease of α-terpineol uptake was both due to decreases in stomatal conductance,gw, and increased volatility of α-terpineol at higher temperature that decreased the monoterpene diffusion gradient between the ambient air (FA) and leaf (FI; U = gW[F A - FI]). Model analyses suggested that α-pinene reacted within the leaf at higher temperatures, possibly within the lipid phase, thereby avoiding the decrease in diffusion gradient, FA - F I. Thus, these data contribute to the hypothesis of the antioxidative protection of leaf membranes during heat stress by monoterpenes. These data further suggest that fumigation with the relatively low atmospheric concentrations of monoterpenes that are occasionally observed during warm windless days in the Mediterranean canopies may significantLy improve the heat tolerance of nonemitting vegetation that grows intermixed with emitting species. © 2005 American Society of Plant Biologists.
Filella I, Peñuelas J, Llusià J (2005) Application of jasmonic acid enhances the emissions of monoterpenes and methyl salicylate and decreases the uptake of formaldehyde by Quercus ilex. Geophysical Research Abstracts Vol. 7, 05456 (p).
Llorens L, Llusià J, Beerling D, Peñuelas J (2005) Terpene emissions of "living fossil" conifers under elevated CO2 and a polar light regime. Plant Frontier Meeting, Sheffield 21-23 March 2005. Pàgina 18 (p).
Peñuelas J, Filella I, Stefanescu C, Llusià J (2005) Caterpillar-feeding induces large increases in foliar emissions of methanol, LOX volatiles and monoterpenes by Succisa pratensis. Geophysical Research Abstracts, Vol. 7, 05404 (p).
Llusià J., Peñuelas J., Asensio D., Munné-Bosch S. (2005) Airborne limonene confers limited thermotolerance to Quercus ilex. Physiologia Plantarum. 123: 40-48.EnllaçDoi: 10.1111/j.1399-3054.2004.00426.x
The purpose of the study was to test the possible and controversial thermotolerance role of monoterpene production and emission and the related responses of antioxidants. Quercus ilex seedlings were exposed to a ramp of temperatures of 5°C steps from 25 to 50°C growing with and without limonene fumigation (7.5 μll-1). Net photosynthetic rates, maximal photochemical efficiency of PSII (Fv/Fm), oxidation state of ascorbic acid, and lipid peroxidation estimated by malondialdehyde concentrations of limonene-fumigated (LF) plants did not significantly differ from control (C) plants. No consistent changes in emissions of the other monoterpenes, α-pinene, β-phellandrene, β-pinene or β-myrcene were found. However, slight differences were found in the concentration of antioxidants. The amounts of α-tocopherol did not change or even tended to decrease at high temperatures in LF plants whereas they tended to increase by approximately 60% at 45 and 50°C relative to 25°C in C plants. Ascorbic acid reached its maximum concentration only at 45°C in LF plants whereas it reached its maximum at 35°C in C plants. β-Carotene did not decrease at high temperatures in LF plants whereas it decreased by approximately 15% at 45-50°C in C plants. Brown pigment index (BPI), an optical indicator of tissue oxidative processes, was lower in LF plants than in C plants. The photochemical reflectance index (PRI), an optical indicator of photosynthetic light use efficiency, was higher for LF plants than for C plants at elevated temperatures. Visual leaf damage (browning) tended to be less in LF plants than in C plans although not significantly (26.5 ± 8.5 versus 16.2 ± 4.8%). These results show that limonene does not confer clear and strong thermotolerance but might have some minor role. These results are in agreement with previous indications of weaker thermotolerance effect of monoterpenes than of isoprene.
Llusià J., Peñuelas J., Munné-Bosch S. (2005) Sustained accumulation of methyl salicylate alters antioxidant protection and reduces tolerance of holm oak to heat stress. Physiologia Plantarum. 124: 353-361.EnllaçDoi: 10.1111/j.1399-3054.2005.00519.x
Methyl salicylate (MeSA) is thought to have a major role in biotic and abiotic stresses by acting as a signal to trigger the oxidative burst, which is needed to activate gene expression in plant stress responses. To assess the potential effects of sustained foliar accumulation of MeSA on plant stress tolerance, the extent of photo- and antioxidant protection, lipid peroxidation and visual leaf area damage were evaluated in MeSA-treated (c. 60 nl l -1 in air) and control holm oak (Quercus ilex L.) plants exposed to heat stress. Control plants showed an increase in foliar MeSA levels up to 1.8 nmol [gDW]-1 as temperature increased and they displayed tolerance to temperatures as high as 45°C, which might be attributed, at least in part, to enhanced xanthophyll de-epoxidation and increases in ascorbate and α-tocopherol. MeSA-treated plants showed a sustained foliar accumulation of this compound, with values ranging from 10 to 23 nmol [gDW]-1 throughout the experiment. These plants showed lower ascorbate and tocopherol levels and higher oxidative damage at 50°C than controls, as indicated by enhanced malondialdehyde levels and leaf area damage and lower maximum efficiency of PSII photochemistry (Fv/Fm ratio). These results demonstrate that a sustained foliar accumulation of MeSA is detrimental to plant function and that it can reduce thermotolerance in holm oak by altering antioxidant defences. Copyright © Physiologia Plantarum 2005.
Peñuelas J., Filella I., Stefanescu C., Llusià J. (2005) Caterpillars of Euphydryas aurinia (Lepidoptera: Nymphalidae) feeding on Succisa pratensis leaves induce large foliar emissions of methanol. New Phytologist. 167: 851-857.EnllaçDoi: 10.1111/j.1469-8137.2005.01459.x
• A major new discovery made in the last decade is that plants commonly emit large amounts and varieties of volatiles after damage inflicted by herbivores, and not merely from the site of injury. However, analytical methods for measuring herbivore-induced volatiles do not usually monitor the whole range of these compounds and are complicated by the transient nature of their formation and by their chemical instability. • Here we present the results of using a fast and highly sensitive proton transfer reaction-mass spectrometry (PTR-MS) technique that allows simultaneous on-line monitoring of leaf volatiles in the pptv (pmol mol-1) range. • The resulting on-line mass scans revealed that Euphydryas aurinia caterpillars feeding on Succisa pratensis leaves induced emissions of huge amounts of methanol - a biogeochemically active compound and a significant component of the volatile organic carbon found in the atmosphere - and other immediate, late and systemic volatile blends (including monoterpenes, sesquiterpenes and lipoxygenase-derived volatile compounds). • In addition to influencing neighboring plants, as well as herbivores and their predators and parasitoids, these large emissions might affect atmospheric chemistry and physics if they are found to be generalized in other plant species. © New Phytologist (2005).
Peñuelas J., Llusià J., Asensio D., Munné-Bosch S. (2005) Linking isoprene with plant thermotolerance, antioxidants and monoterpene emissions. Plant, Cell and Environment. 28: 278-286.EnllaçDoi: 10.1111/j.1365-3040.2004.01250.x
The purpose of the present study was to test the possible plant thermotolerance role of isoprene and to study its relationship with non-enzymatic antioxidants and terpene emissions. The gas exchange, chlorophyll fluorescence, extent of photo- and oxidative stress, leaf damage, mechanisms of photo- and antioxidant protection, and terpene emission were measured in leaves of Quercus ilex seedlings exposed to a ramp of temperatures of 5°C steps from 25 to 50°C growing with and without isoprene (10 μL L-1) fumigation. The results showed that isoprene actually conferred thermotolerance (shifted the decrease of net photosynthetic rates from 35 to 45°C, increased Fv/Fm at 50°C from 0.38 to 0.65, and decreased the leaf area damaged from 27 to 15%), that it precluded or delayed the enhancement of the antioxidant non-enzymatic defence conferred by α-tocopherol, ascorbic acid or β-carotene consumption in response to increasing temperatures, and that it decreased by approximately 70% the emissions of monoterpenes at the highest temperatures. This suggests that there are inducible mechanisms triggered by the initial stages of thermal damage that up-regulate these antioxidant compounds at high temperatures and that these mechanisms are somehow suppressed in the presence of exogenous isoprene, which seems to already exert an antioxidant-like behaviour. © 2004 Blackwell Publishing Ltd.
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