Search Results - (Author, Cooperation:J. Penuelas)

2015-09-30

Nature Publishing Group (NPG)

0028-0836

1476-4687

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

Cold Temperature ; Europe ; *Global Warming ; Models, Biological ; Photoperiod ; Plant Leaves/*growth & development ; *Seasons ; Time Factors ; Trees/*growth & development

2015-12-25

Nature Publishing Group (NPG)

0028-0836

1476-4687

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

Forests ; Internationality ; Models, Biological ; *Phenotype ; Plant Leaves/physiology ; Trees/*anatomy & histology/growth & development/*physiology ; Wood/analysis

2013-09-06

Nature Publishing Group (NPG)

0028-0836

1476-4687

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

Carbon/metabolism ; Carbon Cycle ; Carbon Dioxide/metabolism ; Cell Respiration ; Circadian Rhythm ; *Darkness ; Ecosystem ; *Geography ; *Global Warming ; Photosynthesis/radiation effects ; Plants/*metabolism/radiation effects ; Sunlight ; Temperature

1365-3040

Blackwell Publishing Journal Backfiles 1879-2005

Biology

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.

Electronic Resource

1365-3040

Blackwell Publishing Journal Backfiles 1879-2005

Biology

Δ13C were determined for herbarium specimens of 12 C3 plants (trees, shrubs and herbs) collected during the last 240 years in Catalonia, an area with a Mediterranean climate. Values were 19.91 (S.E. = 0.32, n= 21) for 1750–1760, 19–86 (S.E. = 0.21, n= 49) for 1850–1890 and 19.95 (S.E. = 0.29, n= 25) for 1925–1950, and decreased significantly to 18.87 (S.E. = 0.31, n= 29) for 1982–1988. More irregular temporal changes were found in Δ13C of two C4 species, but they also suggest a decrease in discrimination in recent decades. These results suggest that either carbon assimilation rates have increased or stomatal conductance has decreased, and therefore, that there has been an increase in water use efficiency over the last few decades.

Electronic Resource

1365-2486

Blackwell Publishing Journal Backfiles 1879-2005

Biology

Energy, Environment Protection, Nuclear Power Engineering

Geography

We studied carbon-based secondary and structural compounds (CBSSCs) in Myrtus communis, Erica arborea, and Juniperus communis co-occurring in a natural CO2 spring site and in a nearby control site in a Mediterranean environment. Leaf concentrations of phenolics and CBSSCs, such as lignin, cellulose, and hemicellulose, total nonstructural carbohydrates (TNCs), and lipids were measured monthly (phenolics) and every two months (the other compounds) throughout a year. There was a slight seasonal trend towards maximum concentrations of most of these CBSSCs during autumn–winter and minimum values during the spring season, particularly in Myrtus communis. For most of the CBSSCs and species, there were no consistent or significant patterns in response to the elevated [CO2] (c. 700 μmol mol−1) of the spring site. These results were not due to a dilution effect by increased structural or nonstructural carbon. Therefore, in contrast to many experimental studies of CO2 enrichment, mainly conducted for short periods, there were no greater concentrations of phenolics, and, as in many of these studies, there were neither greater concentrations of the other CBSSCs. These results do not agree with the predictions of the carbon source-sink hypotheses. Possible causes of this disagreement are discussed. These causes include the complex heterogeneous environmental conditions and the variability of resource availabilities in the field, photosynthetic down-regulation, and/or the homeostatic and evolutionary nature of organisms. These results suggest evolutionary adaptive responses to changes in CO2. They also suggest caution in attributing increased CBSSC concentrations to elevated [CO2] at long-term scale in natural conditions, and therefore in their implications for plant–herbivore interactions and for decomposition.

Electronic Resource

0098-8472

Chlorophyll ; Nitrogen ; Respiration ; Sitka spruce ; Water potential

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Biology

Electronic Resource

1432-1939

Key words Atmospheric CO2 concentration ; δ15N ; δ13C ; Herbarium specimens ; Nitrogen

Springer Online Journal Archives 1860-2000

Biology

Abstract  Atmospheric CO2 concentration has increased by 25% over the preindustrial level. A parallel increase in C concentration and decreases in N concentration and δ13C of plants grown throughout this century have been observed in plant specimens stored in herbaria. We tested our previous results in a study of 12 more species collected in the western Mediterranean throughout this century (1920–1930, 1945–1955, and 1985–1990) and tree rings of Quercus pubescens from the same area. These changes were accompanied by apparent increases in condensed tannin concentration. A decreasing trend in δ15N both in herbarium material and tree rings was also found, indicating that ecosystems might cope with higher plant N demand by decreasing N losses and increasing N fixation and mineralization. These results may contribute to a better understanding of the effects of global change on carbon and nitrogen cycling.

Electronic Resource

1432-1939

Chlorophyll fluorescence ; Photosynthesis ; Remote sensing ; Sunflower (Helianthus annuus) ; Xanthophyll cycle

Springer Online Journal Archives 1860-2000

Biology

Summary Sudden illumination of sunflower (Helianthus annuus L. cv. CGL 208) leaves and canopies led to excess absorbed PFD and induced apparent reflectance changes in the green, red and near-infrared detectable with a remote spectroradiometer. The green shift, centered near 531 nm, was caused by reflectance changes associated with the de-epoxidation of violaxanthin to zeaxanthin via antheraxanthin and with the chloroplast thylakoid pH gradient. The red (685 nm) and near-infrared (738 nm) signals were due to quenching of chlorophyll fluorescence. Remote sensing of shifts in these spectral regions provides non-destructive information on in situ photosynthetic performance and could lead to improved techniques for remote sensing of canopy photosynthesis.

Electronic Resource

1432-1939

Nitrogen ; Water ; Phenolics ; Peppers ; Herbivorous insect

Springer Online Journal Archives 1860-2000

Biology

Abstract Pepper plants were grown under different water and nitrogen availabilities that produced severe nitrogen limitations and mild water stress. Nitrogen limitation produced lower leaf N content, higher C:N, and higher leaf content of phenolic compounds, in consonance with the carbon/nutrient balance hypothesis. Nitrogen limitation also produced lower nutritional quality of leaves, with lower relative growth rates and lower efficiency of conversion of ingested biomass on the polyphagous herbivoreHelicoverpa armigera. The biomass gained per gram nitrogen ingested also tended to be lower in those insects feeding on nitrogen-limited plants, in parallel with their higher phenolic content. However, larvae fed on nitrogen-limited plants did not increase the ingestion of food to compensate for the N deficiency of leaves. The mild water stress, which only slightly tended to increase the phenolic content of pepper leaves, had no significant effect on nutritional indices.

Electronic Resource

1573-2932

Springer Online Journal Archives 1860-2000

Energy, Environment Protection, Nuclear Power Engineering

Abstract High ozone (O3) levels have been recorded in eastern Spain. A project was developed to identify the areas of elevated O3 and determine if these levels were above critical concentrations for plant damage. Thus, a network of bioindicators was established in two Autonomous Communities of Spain: Catalunya (31.930 km2) and Valencia (23.305 km2) to assess O3 phytotoxicity. Three tobacco cultivars, (Bel-W3, Bel-C and Bel-B) were used during the 1994 growing season in both Regions. In Catalunya the highest O3 phytotoxicity was recorded in coastal areas, while the phytotoxicity decreased as plants were grown further in-land. A lower O3 phytotoxicity was observed in coastal sites of the Valencia Autonomous Community, compared to Catalunya, although the O3 injury was observed downwind from Valencia city in the most resistant cultivar Bel-B. The results in the Valencian Community were difficult to interpret, since plant viruses were widely distributed, not only in indicator plants, but also in commercial crops grown in the area. The analysis of O3 concentrations, meteorological parameters and visible injury at the Catalan sites showed that high relative humidity levels could favour O3 phytotoxicity. Therefore, the interactions between O3 exposure and environmental conditions on plant response should be further studied for the establishment of sound critical levels.

Electronic Resource

1573-9058

biomass ; Nutrients

Springer Online Journal Archives 1860-2000

Biology

Abstract From literature sources we compiled the data on carbon-based-secondary compounds CBSC (phenolics and terpenoids) and biomass of 17 plant species grown at different CO2 concentrations under low and high nutrient availabilities. With a low nutrient availability a possible inverse correlation was found between the biomass and CBSC changes. On the contrary, under a high nutrient availability, both the CBSC and biomass increased with elevated CO2. The wide variation in the CBSC production among species and compounds (larger responses in phenolics than in terpenoids) indicates that the allocation to CBSC may not completely be governed by changes in CO2 and nutrient availabilities per se. Yet the comparison shows that elevated CO2 generally loads the carbon into CBSC [their leaf concentration increased an overall average of 14 % at 700 umol(CO2) mol-r] which may improve our understanding of the carbon storage and cycling in ecosystems under the “global change” of climate.

Electronic Resource

1573-9058

biomass ; Capsicum annuum ; carbon and nitrogen contents ; cytochrome pathway ; Phaseolus vulgaris ; salicylhydroxamic acid ; water stress

Springer Online Journal Archives 1860-2000

Biology

Abstract We analyzed the combined effects of mild drought stress and severe nitrogen (N) deprivation on respiration of acclimated mature leaves of beans (Phaseolus vulgaris L. cv. Garrofal) and peppers (Capsicum annuum L., pure line B6). Rates of oxygen uptake were measured polarographically, and inhibitors were added to the closed cuvette to compare the effects of environmental stress on the cytochrome (cyt) and alternative pathways of mitochondrial respiration. Dark oxygen uptake was decreased by the water deficit treatment in both plants, and in the case of N limitation leaf respiration rates (RD) of peppers were also reduced. RD of leaves of beans and peppers grown under N-limiting conditions did not follow the decrease in leaf N concentration, since RD expressed per unit of tissue N was considerably higher in the N-stressed leaves. Values obtained with specific inhibitors of the two terminal oxidases of mitochondrial respirations suggested that the cyt pathway of respiration was affected by mild drought and severe N stress. When plants were exposed to both environmental stresses, leaf respiration response was similar to that under N limitation, in this case the most severe stress.

Electronic Resource

1573-9058

Arachis ; leaf desiccation ; normalized difference vegetation index ; relative water content ; structural independent pigment index ; Triticum ; water index

Springer Online Journal Archives 1860-2000

Biology

Abstract Measurements of reflectance in visible and near-infrared spectral regions were made on detached leaves of two crop species of different leaf morphology, structure, and water content (peanut and wheat) throughout progressive desiccation. Relative water content (RWC) was well correlated with water index (WI) but even better with the ratio of WI and normalized difference vegetation index. RWC was also significantly correlated with structural independent pigment index indicative of carotenoids/chlorophyll ratio. New indication is thus provided to assess leaf water content and apply simple and fast radiometric techniques for plant water stress management.

Electronic Resource

1573-9058

carbon based secondary compounds (CBSC) ; isoorientin ; leaf age ; litter ; phenolics ; tricin ; Triticum aestivum

Springer Online Journal Archives 1860-2000

Biology

Abstract We compared flavonoids in green, mature, and senescing flag leaves of wheat grown under ambient (AC - 370 μmol mol-1) and elevated (EC - 550 μmol mol-1) concentrations of CO2 in a FACE (Free Air CO2 Enrichment) system. The concentrations of flag leaf flavonoids (e.g., isoorientin and tricin) decreased to one third in mature leaves, and the majoritary isoorientin almost disappeared in senescing leaves. Flavonoid concentrations increased in green well-developed flag leaves under EC (46 % isoorientin and 55 % tricin), whereas the differences disappeared in mature and senescing flag leaves. Predictions of changes in litter phenolic concentrations and their effects on decomposition rates under EC based on changes in green leaves need to be revised.

Electronic Resource

1573-2932

Bel-B ; Bel-C ; Bel-W3 ; Catalonia ; colorimetry ; ozone ; phytotoxicity ; tobacco cultivars

Springer Online Journal Archives 1860-2000

Energy, Environment Protection, Nuclear Power Engineering

Abstract A field study was conducted from May to October 1995 to assess ozone (O3) phytotoxicity in Catalonia (NE Spain) by determining a percentage value of leaf area injured by ozone on three tobacco cultivars, Bel-W3, Bel-C and Bel-B as bioindicators. Colorimetric parameters were also determined in an effort to have an objective assessment of ozone injury. The study was conducted simultaneously on eight sites where ozone levels and several meteorological parameters were continuosly monitored. Two sets of plants were used at each site. The first one was composed of six plants of each cultivar which were changed every two weeks while the second one involved two plants of each cultivar which were kept in the plots throughout the whole experimental period. Open Top Chambers were also used to test the response of the three cultivars to ozone under controlled conditions. The ozone levels correlated well with ozone injury on the Bel-W3 cultivar but not as well on the other two cultivars. The ozone levels did not fully account for all the observed injury. The response of tobacco plants to ozone concentrations and therefore its biomonitoring capacity depended also on different environmental conditions linked to stomatal behaviour such as temperature, humidity, wind or altitude. These environmental conditions had some effects on the intensity of Ozone injury. Ozone concentrations accumulated over a threshold of 60 ppb (AOT60) when VPD was below 1 KPa. Correlated well with the ozone injury and best explained the intensity tobacco injury symptoms. For large plants growing throughout the whole period of study, Bel-C was the best indicator cultivar for AOT60 over the 3 days prior to the last ozone injury assessment. The colorimetric parameters were indicators of seasonal changes but they were not good ozone damage indicators. It is concluded that tobacco cultivars were good bioindicators but meteorological and other environmental factors need to be considered in there use as biomonitors.

Electronic Resource

1573-2932

Mediterranean ; woody species ; ozone ; critical levels

Springer Online Journal Archives 1860-2000

Energy, Environment Protection, Nuclear Power Engineering

Abstract An experimental study was performed in open-top chambers to assess the relative O3-sensitivity of the following Mediterranean woody plants: Quercus ilex ssp. ilex, Quercus ilex ssp. ballota, Olea europaea ssp. sylvestris, Ceratonia siliqua and Arbutus unedo. Assessment of O3 ‘sensitivity’ was based on the development of O3-induced visible injury and the extent of the reduction in relative growth rate induced by O3. Two-year-old seedlings were exposed in open-top chambers to charcoal filtered air (CFA), Non-filtered air (NFA) or Non-filtered air supplied with 40 ppb O3 from 09:00 to 18:00 hours (NFA+40). No clear relationships were found between the development of visible injury and effects on plant growth or accumulated biomass. Olea europea ssp. sylvestris and Quercus ilex ssp. ballota appeared to be the most O3-sensitive tree species screened; a ten month exposure to ambient O3 levels (AOT40 = 12.4 ppm.h) caused reductions in height and/or stem growth. Further research is needed to characterise the physiological, biochemical and anatomical characteristics that may underlie the ‘sensitivity’ of certain Mediterranean species to O3

Electronic Resource

1573-2932

AOT40 ; beans ; ethylene diurea (EDU) ; ozone

Springer Online Journal Archives 1860-2000

Energy, Environment Protection, Nuclear Power Engineering

Abstract A study to evaluate the effects of ethylene diurea (EDU) as a protective antiozonant for beans (Phaseolus vulgaris) submitted to different ambient ozone concentrations was performed in three stations of the rural Network for Air Quality Monitoring (Catalonia, NE Spain). The highest ozone concentrations were accompanied by significant reductions in fruit yield, number of fruits and shoot biomass. These reductions were lower in plants treated with EDU. The results showed toxic ozone effects on sensitive species such as beans and a protective antiozonant effect of EDU. The intensity of the EDU protective effect differed among the different stations characterised by different meteorological conditions and O3 concentrations.

Electronic Resource

1573-8264

damaged trees ; stable isotopes ; water stress ; climate change ; lithologies ; water use efficiency ; nitrogen availability and use

Springer Online Journal Archives 1860-2000

Biology

Abstract A severe drought that took place in Spain and other Mediterranean countries in 1994 produced a dieback of Quercus ilex trees on south-facing conglomerates but only minor defoliations in trees on north-facing schists. The foliar Δ13C of damaged trees continued to decrease in the next two wet years probably indicating increasing water use efficiency, and their δ15N continued to increase indicating progressive ecosystem N saturation and/or N losses whereas there were no significant changes in undamaged trees. Pre-drought Δ13C values were reached in the third year after the drought, but δ15N values did not yet recover. Another co-occurring small tree, Phyllyrea latifolia, did not show any damage and gained dominance in the most affected stands.

Electronic Resource

1573-8264

allelopathy ; α-pinene ; autopathy ; camphene ; volatile organic compounds

Springer Online Journal Archives 1860-2000

Biology

Abstract Seedlings of two common Mediterranean trees, Pinus halepensis L. and Quercus ilex L., were grown alone and together with seedlings of the same or of the other species in the same pot during one year to test the effects of intra- and inter-specific interference on terpene emission. Light, nutrients and water were amply supplied. There were higher emission rates in P. halepensis than in Q. ilex. The emission increased when the neighbour was a pine and decreased when the neighbour was a holm oak. Volatile organic compound and terpene emission rates followed inverse trends to foliar biomass or growth, which decreased when the neighbour was a pine.

Electronic Resource