(2015) The application of ecological stoichiometry to plant-microbial-soil organic matter transformations. . : -.EnllaçDoi: 10.1890/14-0777.1
(2015) Survival vs. growth trade-off in early recruitment challenges global warming impacts on Mediterranean mountain trees. . : -.EnllaçDoi: https://doi.org/10.1016/j.ppees.2015.06.004
Achotegui-Castells A., Danti R., Llusia J., Rocca G.D., Barberini S., Penuelas J. (2015) Strong Induction of Minor Terpenes in Italian Cypress, Cupressus sempervirens, in Response to Infection by the Fungus Seiridium cardinale. Journal of Chemical Ecology. : 0-0.EnllaçDoi: 10.1007/s10886-015-0554-1
Seiridium cardinale, the main fungal pathogen responsible for cypress bark canker, is the largest threat to cypresses worldwide. The terpene response of canker-resistant clones of Italian cypress, Cupressus sempervirens, to two differently aggressive isolates of S. cardinale was studied. Phloem terpene concentrations, foliar terpene concentrations, as well as foliar terpene emission rates were analyzed 1, 10, 30, and 90 days after artificial inoculation with fungal isolates. The phloem surrounding the inoculation point exhibited de novo production of four oxygenated monoterpenes and two unidentified terpenes. The concentrations of several constitutive mono- and diterpenes increased strongly (especially α-thujene, sabinene, terpinolene, terpinen-4-ol, oxygenated monoterpenes, manool, and two unidentified diterpenes) as the infection progressed. The proportion of minor terpenes in the infected cypresses increased markedly from the first day after inoculation (from 10 % in the control to 30–50 % in the infected treatments). Foliar concentrations showed no clear trend, but emission rates peaked at day 10 in infected trees, with higher δ-3-carene (15-fold) and total monoterpene (10-fold) emissions than the control. No substantial differences were found among cypresses infected by the two fungal isolates. These results suggest that cypresses activate several direct and indirect chemical defense mechanisms after infection by S. cardinale. © 2015 Springer Science+Business Media New York
Bernal M., Verdaguer D., Badosa J., Abadia A., Llusia J., Penuelas J., Nunez-Olivera E., Llorens L. (2015) Effects of enhanced UV radiation and water availability on performance, biomass production and photoprotective mechanisms of Laurus nobilis seedlings. Environmental and Experimental Botany. 109: 264-275.EnllaçDoi: 10.1016/j.envexpbot.2014.06.016
Climate models predict an increase in ultraviolet (UV) radiation and a reduction in precipitation in the Mediterranean region in the coming decades. High levels of UV radiation and water shortage can both cause photo-oxidative stress in plants. The aim of this study was to investigate the effects of enhanced UV radiation and its interaction with low water availability on seedling performance, biomass production, and photoprotective mechanisms of the sclerophyllous evergreen species Laurus nobilis L. (laurel). To achieve this goal, one-year-old seedlings of L. nobilis were grown outdoors under three UV conditions (ambient UV, enhanced UV-A, and enhanced UV-A. +. UV-B) and under two watering regimes (watered to field capacity and reduced water supply). The results show that plants produced more biomass when exposed to above ambient levels of UV-A or UV-A. +. UV-B radiation, especially under low water availability. This was probably related to a UV-induced increase in leaf relative water content and in leaf water use efficiency under water shortage. Even though our results suggest that UV-A supplementation may play an important role in the stimulation of biomass production, plants grown under enhanced UV-A plots showed higher levels of energy dissipation as heat (measured as NPQ) and a higher de-epoxidation state of the violaxanthin cycle. This suggests a greater excess of light energy under UV-A supplementation, in accordance with the observed reduction in the foliar content of light-absorbing pigments in these plants. Strikingly, the addition of UV-B radiation mitigated these effects. In conclusion, UV enhancement might benefit water status and growth of L. nobilis seedlings, especially under low water availability. The results also indicate the activation of different plant response mechanisms to UV-A and UV-B radiation, which would interact to produce the overall plant response. © 2014 Elsevier B.V.
Blanch J.S., Peñuelas J., Llusià J., Sardans J., Owen S.M. (2015) Differences in photosynthesis and terpene content in leaves and roots of wild-type and transgenic Arabidopsis thaliana plants. Russian Journal of Plant Physiology. 62: 823-829.EnllaçDoi: 10.1134/S1021443715060035
We investigated the hypotheses that two different varieties of Arabidopsis thaliana show differences in physiology and terpene production. The two varieties of A. thaliana used in this study were wild-type (WT) and transgenic line (CoxIV-FaNES I) genetically modified to emit nerolidol with linalool/nerolidol synthase (COX). Photosynthetic rate, electron transport rate, fluorescence, leaf volatile terpene contents and root volatile terpene contents were analyzed. For both types, we found co-eluting α-pinene+β-ocimene, limonene, and humulene in leaves; and in the roots we found co-eluting α-pinene+β-ocimene, sabinene+β-pinene, β-myrcene, limonene, and humulene. At the end of the growing cycle, COX plants tended to have lower pools of terpene compounds in their leaves, with 78.6% lower photosynthesis rates and 30.8% lower electron transport rates, compared with WT plants at that time. The maximal photochemical efficiency Fv/Fm was also significantly lower (25.5%) in COX plants, indicating that these varieties were more stressed than WT plants. However, COX plants had higher (239%) root terpene contents compared to WT plants. COX plants appear to favor root production of volatile terpenes rather than leaf production. Thus we conclude that there were significant differences between COX and WT plants in terms of terpenoid pools, stress status and physiology. © 2015, Pleiades Publishing, Ltd.
Calfapietra C., Penuelas J., Niinemets T. (2015) Urban plant physiology: Adaptation-mitigation strategies under permanent stress. Trends in Plant Science. 20: 72-75.EnllaçDoi: 10.1016/j.tplants.2014.11.001
Urban environments that are stressful for plant function and growth will become increasingly widespread in future. In this opinion article, we define the concept of 'urban plant physiology', which focuses on plant responses and long term adaptations to urban conditions and on the capacity of urban vegetation to mitigate environmental hazards in urbanized settings such as air and soil pollution. Use of appropriate control treatments would allow for studies in urban environments to be comparable to expensive manipulative experiments. In this opinion article, we propose to couple two approaches, based either on environmental gradients or manipulated gradients, to develop the concept of urban plant physiology for assessing how single or multiple environmental factors affect the key environmental services provided by urban forests. © 2014 Elsevier Ltd.
Campioli M., Vicca S., Luyssaert S., Bilcke J., Ceschia E., Chapin Iii F.S., Ciais P., Fernández-Martínez M., Malhi Y., Obersteiner M., Olefeldt D., Papale D., Piao S.L., Peñuelas J., Sullivan P.F., Wang X., Zenone T., Janssens I.A. (2015) Biomass production efficiency controlled by management in temperate and boreal ecosystems. Nature Geoscience. 8: 843-846.EnllaçDoi: 10.1038/ngeo2553
Plants acquire carbon through photosynthesis to sustain biomass production, autotrophic respiration and production of non-structural compounds for multiple purposes. The fraction of photosynthetic production used for biomass production, the biomass production efficiency, is a key determinant of the conversion of solar energy to biomass. In forest ecosystems, biomass production efficiency was suggested to be related to site fertility. Here we present a database of biomass production efficiency from 131 sites compiled from individual studies using harvest, biometric, eddy covariance, or process-based model estimates of production. The database is global, but dominated by data from Europe and North America. We show that instead of site fertility, ecosystem management is the key factor that controls biomass production efficiency in terrestrial ecosystems. In addition, in natural forests, grasslands, tundra, boreal peatlands and marshes, biomass production efficiency is independent of vegetation, environmental and climatic drivers. This similarity of biomass production efficiency across natural ecosystem types suggests that the ratio of biomass production to gross primary productivity is constant across natural ecosystems. We suggest that plant adaptation results in similar growth efficiency in high- and low-fertility natural systems, but that nutrient influxes under managed conditions favour a shift to carbon investment from the belowground flux of non-structural compounds to aboveground biomass. © 2015 Macmillan Publishers Limited.
Estiarte M., Penuelas J. (2015) Alteration of the phenology of leaf senescence and fall in winter deciduous species by climate change: Efects on nutrient proficiency. Global Change Biology. 21: 1005-1017.EnllaçDoi: 10.1111/gcb.12804
Leaf senescence in winter deciduous species signals the transition from the active to the dormant stage. The purpose of leaf senescence is the recovery of nutrients before the leaves fall. Photoperiod and temperature are the main cues controlling leaf senescence in winter deciduous species, with water stress imposing an additional influence. Photoperiod exerts a strict control on leaf senescence at latitudes where winters are severe and temperature gains importance in the regulation as winters become less severe. On average, climatic warming will delay and drought will advance leaf senescence, but at varying degrees depending on the species. Warming and drought thus have opposite effects on the phenology of leaf senescence, and the impact of climate change will therefore depend on the relative importance of each factor in specific regions. Warming is not expected to have a strong impact on nutrient proficiency although a slower speed of leaf senescence induced by warming could facilitate a more efficient nutrient resorption. Nutrient resorption is less efficient when the leaves senesce prematurely as a consequence of water stress. The overall effects of climate change on nutrient resorption will depend on the contrasting effects of warming and drought. Changes in nutrient resorption and proficiency will impact production in the following year, at least in early spring, because the construction of new foliage relies almost exclusively on nutrients resorbed from foliage during the preceding leaf fall. Changes in the phenology of leaf senescence will thus impact carbon uptake, but also ecosystem nutrient cycling, especially if the changes are consequence of water stress. © 2014 John Wiley & Sons Ltd.
Farre-Armengol G., Filella I., Llusia J., Niinemets U., Penuelas J. (2015) Optimum temperature for floral terpene emissions tracks the mean temperature of the flowering season. Functional Plant Biology. 42: 851-857.EnllaçDoi: 10.1071/FP14279
Emissions of volatiles from leaves exhibit temperature dependence on maximums, but the optimum temperatures for the release of floral volatiles and the mechanism(s) of optimising these emissions have not been determined. We hypothesised that flowers have an optimum temperature for the emission of volatiles and, because the period of flowering varies highly among species, that this optimum is adapted to the temperatures prevailing during flowering. To test these hypotheses, we characterised the temperature responses of floral terpene emissions of diverse widespread Mediterranean plant species flowering in different seasons by using dynamic headspace sampling and analysis with GC-MS. The floral emissions of terpenes across species exhibited maximums at the temperatures corresponding to the season of flowering, with the lowest optimal temperatures observed in winter-flowering and the highest in summer-flowering species. These trends were valid for emissions of both total terpenes and the various terpene compounds. The results show that the optimum temperature of floral volatile emissions scales with temperature at flowering, and suggest that this scaling is the outcome of physiological adaptations of the biosynthetic or emission mechanisms of flowers. © CSIRO 2015.
Farre-Armengol G., Filella I., Llusia J., Penuelas J. (2015) Relationships among floral VOC emissions, floral rewards and visits of pollinators in five plant species of a Mediterranean shrubland. Plant Ecology and Evolution. 148: 90-99.EnllaçDoi: 10.5091/plecevo.2015.963
Background and aims–In plant-pollinator communities seasonal changes in the abundance of pollinators lead to seasonal changes in competition among flowering plants for their services. Here we address the following question: Do flowers of a given species produce more olfactory signals (emissions of volatile compounds) and rewards (nectar and pollen) during the phase(s) of the flowering period within which they have to maximally compete with the signals and rewards of other co-flowering species in the community, compared to the amount of signals and rewards produced during the period(s) with less floral competition? Methods–We analysed the floral emission rates of biogenic volatile organic compounds by gas chromatography and proton transfer reaction mass spectrometry, the visitation rates of pollinators, and the availability of nectar and pollen during the flowering periods of five species to test whether floral rewards and signals would decrease with an increase in pollinator visitation rates during late spring and early summer, i.e. coinciding with decreasing competitive pressure for the services of pollinators. Key results–The results indicate that phenological patterns in the production of rewards are only present at the species level in those species with long flowering periods or with matching periods of changes in pollinator populations. The capacity of emitting isoprenoids and oxidised volatile organic compounds, however, did not present significant patterns during the flowering period in any of the five species studied. Conclusions–The results support the hypothesis of a decreasing competitive pressure for the attraction of pollinators that may drive a decrease in floral investment in rewards but not an accompanying decrease of the capacity of emitting volatile olfactory signals in a species with long flowering period. However, the negative correlation between nectar production and visitation rates may be reinforced by the opposite responses of these variables to climatic conditions. This fact makes difficult to discern possible evolutionary forces tending to decrease rewards from plastic responses to changing environmental conditions in that part of the flowering period in which pollinator visitation rates are higher. © 2015 Botanic Garden Meise and Royal Botanical Society of Belgium.
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