Farré-Armengol G., Filella I., Llusia J., Primante C., Peñuelas J. (2015) Enhanced emissions of floral volatiles by Diplotaxis erucoides (L.) in response to folivory and florivory by Pieris brassicae (L.). Biochemical Systematics and Ecology. 63: 51-58.LinkDoi: 10.1016/j.bse.2015.09.022
The main function of floral emissions of volatile organic compounds (VOCs) in entomophilous plants is to attract pollinators. Floral blends, however, can also contain volatile compounds with defensive functions. These defensive volatiles are specifically emitted when plants are attacked by pathogens or herbivores. We characterized the changes in the floral emissions of Diplotaxis erucoides induced by folivory and florivory by Pieris brassicae. Plants were continually subjected to folivory, florivory and folivory + florivory treatments for two days. We measured floral emissions with proton transfer reaction/mass spectroscopy (PTR-MS) at different times during the application of the treatments. The emissions of methanol, ethyl acetate and another compound, likely 3-butenenitrile, increased significantly in response to florivory. Methanol and 3-butenenitrile increased 2.4- and 26-fold, respectively, in response to the florivory treatment. Methanol, 3-butenenitrile and ethyl acetate increased 3-, 100- and 9-fold, respectively, in response to the folivory + florivory treatment. Folivory alone had no detectable effect on floral emissions. All VOC emissions began immediately after attack, with no evidence of delayed induction in any of the treatments. Folivory and florivory had a synergistic effect when applied together, which strengthened the defensive response when the attack was extended to the entire plant. © 2015 Elsevier Ltd.
Llusia J., Roahtyn S., Yakir D., Rotenberg E., Seco R., Guenther A., Peñuelas J. (2015) Photosynthesis, stomatal conductance and terpene emission response to water availability in dry and mesic Mediterranean forests. Trees - Structure and Function. : 1-11.LinkDoi: 10.1007/s00468-015-1317-x
Key message: Warmer summer conditions result in increased terpene emissions except under severe drought, in which case they strongly decrease.Abstract: Water stress results in a reduction of the metabolism of plants and in a reorganization of their use of resources geared to survival. In the Mediterranean region, periods of drought accompanied by high temperatures and high irradiance occur in summer. Plants have developed various mechanisms to survive in these conditions by resisting, tolerating or preventing stress. We used three typical Mediterranean tree species in Israel, Pinus halepensis L., Quercus calliprinos and Quercus ithaburensis Webb, as models for studying some of these adaptive mechanisms. We measured their photosynthetic rates (A), stomatal conductance (gs), and terpene emission rates during spring and summer in a geophysical gradient from extremely dry to mesic from Yatir (south, arid) to Birya (north, moist) with intermediate conditions in Solelim. A and gs of P. halepensis were threefold higher in Birya than in Yatir where they remained very low both seasons. Quercus species presented 2–3-fold higher A and gs but with much more variability between seasons, especially for Q. ithaburensis with A and gs that decreased 10–30-fold from spring to summer. Terpene emission rates for pine were not different regionally in spring but they were 5–8-fold higher in Birya than in Yatir in summer (P < 0.05). Higher emissions were also observed in Solelim for the drought resistant Q. ithaburensis (P < 0.001) but not for Q. calliprinos. α-Pinene followed by limonene and 3-carene were the dominant terpenes. Warmer summer conditions result in increased Terpene emission rates except under severe drought, in which case they strongly decrease. © 2015 Springer-Verlag Berlin Heidelberg
Penuelas J., Bartrons M., Llusia J., Filella I. (2015) Sensing the energetic status of plants and ecosystems. Trends in Plant Science. 20: 528-530.LinkDoi: 10.1016/j.tplants.2015.07.002
The emerging consistency of the relationship between biochemical, optical, and odorous signals emitted by plants and ecosystems offers promising prospects for continuous local and global monitoring of the energetic status of plants and ecosystems, and therefore of their processing of energy and matter. © 2015 Elsevier Ltd.
Farre-Armengol G., Filella I., Llusia J., Niinemets U., Penuelas J. (2014) Changes in floral bouquets from compound-specific responses to increasing temperatures. Global Change Biology. : 0-0.LinkDoi: 10.1111/gcb.12628
We addressed the potential effects of changes in ambient temperature on the profiles of volatile emissions from flowers and tested whether warming could induce significant quantitative and qualitative changes in floral emissions, which would potentially interfere with plant-pollinator chemical communication. We measured the temperature responses of floral emissions of various common species of Mediterranean plants using dynamic headspace sampling and used GC-MS to identify and quantify the emitted terpenes. Floral emissions increased with temperature to an optimum and thereafter decreased. The responses to temperature modeled here predicted increases in the rates of floral terpene emission of 0.03-1.4-fold, depending on the species, in response to an increase of 1 °C in the mean global ambient temperature. Under the warmest projections that predict a maximum increase of 5 °C in the mean temperature of Mediterranean climates in the Northern Hemisphere by the end of the century, our models predicted increases in the rates of floral terpene emissions of 0.34-9.1-fold, depending on the species. The species with the lowest emission rates had the highest relative increases in floral terpene emissions with temperature increases of 1-5 °C. The response of floral emissions to temperature differed among species and among different compounds within the species. Warming not only increased the rates of total emissions, but also changed the ratios among compounds that constituted the floral scents, i.e. increased the signal for pollinators, but also importantly altered the signal fidelity and probability of identification by pollinators, especially for specialists with a strong reliance on species-specific floral blends. © 2014 John Wiley & Sons Ltd.
Greenberg J.P., Penuelas J., Guenther A., Seco R., Turnipseed A., Jiang X., Filella I., Estiarte M., Sardans J., Ogaya R., Llusia J., Rapparini F. (2014) A tethered-balloon PTRMS sampling approach for surveying of landscape-scale biogenic VOC fluxes. Atmospheric Measurement Techniques. 7: 2263-2271.LinkDoi: 10.5194/amt-7-2263-2014
Landscape-scale fluxes of biogenic gases were surveyed by deploying a 100 m Teflon tube attached to a tethered balloon as a sampling inlet for a fast-response proton-transfer-reaction mass spectrometer (PTRMS). Along with meteorological instruments deployed on the tethered balloon and a 3 m tripod and outputs from a regional weather model, these observations were used to estimate landscape-scale biogenic volatile organic compound fluxes with two micrometeorological techniques: mixed layer variance and surface layer gradients. This highly mobile sampling system was deployed at four field sites near Barcelona to estimate landscape-scale biogenic volatile organic compound (BVOC) emission factors in a relatively short period (3 weeks). The two micrometeorological techniques were compared with emissions predicted with a biogenic emission model using site-specific emission factors and land-cover characteristics for all four sites. The methods agreed within the uncertainty of the techniques in most cases, even though the locations had considerable heterogeneity in species distribution and complex terrain. Considering the wide range in reported BVOC emission factors for individual vegetation species (more than an order of magnitude), this temporally short and inexpensive flux estimation technique may be useful for constraining BVOC emission factors used as model inputs. © 2014 Author(s).
Llusia J., Bermejo-Bermejo V., Calvete-Sogo H., Penuelas J. (2014) Decreased rates of terpene emissions in Ornithopus compressus L. and Trifolium striatum L. by ozone exposure and nitrogen fertilization. Environmental Pollution. 194: 69-77.LinkDoi: 10.1016/j.envpol.2014.06.038
Increasing tropospheric ozone (O3) and nitrogen soil availability (N) are two of the main drivers of global change. They both may affect gas exchange, including plant emission of volatiles such as terpenes. We conducted an experiment using open-top chambers to analyze these possible effects on two leguminous species of Mediterranean pastures that are known to have different O3 sensitivity, Ornithopus compressus and Trifolium striatum. O3 exposure and N fertilization did not affect the photosynthetic rates of O. compressus and T. striatum, although O3 tended to induce an increase in the stomatal conductance of both species, especially T. striatum, the most sensitive species. O3 and N soil availability reduced the emission of terpenes in O. compressus and T. striatum. If these responses are confirmed as a general pattern, O3 could affect the competitiveness of these species. © 2014 Elsevier Ltd. All rights reserved.
Llusia J., Sardans J., Niinemets U., Owen S.M., Penuelas J. (2014) A screening study of leaf terpene emissions of 43 rainforest species in Danum Valley Conservation Area (Borneo) and their relationships with chemical and morphological leaf traits. Plant Biosystems. 148: 307-317.LinkDoi: 10.1080/11263504.2013.770803
We have conducted a screening study of leaf terpene emissions for 43 rainforest woody species of Borneo. To the best of our knowledge, this study reports for first time the terpene emission capacity of 43 species belonging to 22 genera of rainforest woody plant species. We have used a general lineal model with phylogenetic control by the phylogenetic distance matrix when necessary. The proportion of the species that emitted terpenes in this set of Borneo woody species was 95% and the species average total terpene emissions of emitting species were 0.04-11.6 μg g-1 h-1, which is in the range of the reported emissions in similar screening studies conducted in other biomes. Altogether, 85 terpene compounds were detected, and 11 common monoterpenes and sesquiterpenes were identified and quantified. Only two of the terpenes, ocimene and γ-terpinene, of the 11 determined compounds showed a phylogenetic signal. No significant relationships were found between the terpene emissions and the physiological, chemical and morphological foliar traits and the data also showed a lock of constant applicability of the "excess carbon" hypothesis for this set of species. This evidence suggests multiple and diverse factors and conditions driving plant chemistry in the tropical forests. © 2013 © 2013 Società Botanica Italiana.
Morfopoulos C., Sperlich D., Penuelas J., Filella I., Llusia J., Medlyn B.E., Niinemets U., Possell M., Sun Z., Prentice I.C. (2014) A model of plant isoprene emission based on available reducing power captures responses to atmospheric CO2. New Phytologist. 203: 125-139.LinkDoi: 10.1111/nph.12770
Summary: We present a unifying model for isoprene emission by photosynthesizing leaves based on the hypothesis that isoprene biosynthesis depends on a balance between the supply of photosynthetic reducing power and the demands of carbon fixation. We compared the predictions from our model, as well as from two other widely used models, with measurements of isoprene emission from leaves of Populus nigra and hybrid aspen (Populus tremula × P. tremuloides) in response to changes in leaf internal CO2 concentration (Ci) and photosynthetic photon flux density (PPFD) under diverse ambient CO2 concentrations (Ca). Our model reproduces the observed changes in isoprene emissions with Ci and PPFD, and also reproduces the tendency for the fraction of fixed carbon allocated to isoprene to increase with increasing PPFD. It also provides a simple mechanism for the previously unexplained decrease in the quantum efficiency of isoprene emission with increasing Ca. Experimental and modelled results support our hypothesis. Our model can reproduce the key features of the observations and has the potential to improve process-based modelling of isoprene emissions by land vegetation at the ecosystem and global scales. © 2014 New Phytologist Trust.
Nogues I., Llusia J., Ogaya R., Munne-Bosch S., Sardans J., Penuelas J., Loreto F. (2014) Physiological and antioxidant responses of Quercus ilex to drought in two different seasons. Plant Biosystems. 148: 268-278.LinkDoi: 10.1080/11263504.2013.768557
Climate change projections forecast a warming and an associated change in the distribution and intensity of rainfalls. In the case of the Mediterranean area, this will be reflected in more frequent and severe drought periods in the future. Within a long-term (9 years) manipulation experiment, we aimed to study the effect of the soil drought projected for the coming decades (an average of 10% soil moisture reduction) onto photosynthetic rates and water relations, and onto the antioxidant and anti-stress defense capacity of Quercus ilex, a dominant species in Mediterranean forests, in two different seasons, spring and summer. Results showed that photosynthesis was limited by stomatal closure in summer. However, a decrease in photosynthesis as a consequence of drought was observed only during spring, possibly due to a low pigment concentration and to an insufficient antioxidant protection. In summer, the increased resistance to CO2 entry reduced photosynthesis in control and drought-treated leaves, though the higher pigment content and antioxidant levels in summer leaves prevented a further decrease in photosynthesis as a consequence of drought. Also total monoterpene emission rates were higher in summer than in spring, though they did not change with drought, as happened with photosynthetic pigments. On the other hand, the antioxidant defense system was induced by drought in both studied seasons, indicating an efficient activation of defense responses aiming at scavenging reactive oxygen species produced in Q. ilex leaves under drought. © 2013 © 2013 Società Botanica Italiana.
Ogaya R., Llusia J., Barbeta A., Asensio D., Liu D., Alessio G.A., Penuelas J. (2014) Foliar CO2 in a holm oak forest subjected to 15 years of climate change simulation. Plant Science. 226: 101-107.LinkDoi: 10.1016/j.plantsci.2014.06.010
A long-term experimental drought to simulate future expected climatic conditions for Mediterranean forests, a 15% decrease in soil moisture for the following decades, was conducted in a holm oak forest since 1999. Net photosynthetic rate, stomatal conductance and leaf water potential were measured from 1999 to 2013 in Quercus ilex and Phillyrea latifolia, two co-dominant species of this forest. These measurements were performed in four plots, two of them received the drought treatment and the two other plots were control plots. The three studied variables decreased with increases in VPD and decreases in soil moisture in both species, but the decrease of leaf water potential during summer drought was larger in P. latifolia, whereas Q. ilex reached higher net photosynthetic rates and stomatal conductance values during rainy periods than P. latifolia. The drought treatment decreased ca. 8% the net photosynthetic rates during the overall studied period in both Q. ilex and P. latifolia, whereas there were just non-significant trends toward a decrease in leaf water potential and stomatal conductance induced by drought treatment. Future drier climate may lead to a decrease in the carbon balance of Mediterranean species, and some shrub species well resistant to drought could gain competitive advantage relative to Q. ilex, currently the dominant species of this forest. © 2014 Elsevier Ireland Ltd.
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