Sampedro L., Moreira X., Llusia J., Peñuelas J., Zas R. (2010) Genetics, phosphorus availability, and herbivore-derived induction as sources of phenotypic variation of leaf volatile terpenes in a pine species. Journal of Experimental Botany. 61: 4437-4447.EnllaçDoi: 10.1093/jxb/erq246
Oleoresin produced and stored in pine tree leaves provides direct resistance to herbivores, while leaf volatile terpenes (LVT) in the resin are also powerful airborne infochemicals. Resin concentration and profile show considerable spatial and temporal phenotypic variation within and among pine populations. LVT biochemistry is known to be under genetic control, and although LVT should be plastic to diverse abiotic and biotic environmental factors such as nutrient availability and herbivore attack, little is known about their relative contributions and interactive effects. The aim of this paper was to clarify whether reduced phosphorus availability could increase the LVT concentration and affect the expression of herbivore-derived induced defences, and how plasticity would contribute to the phenotypic variation of LVT. The constitutive and methyl-jasmonate (MeJa) induced LVT concentration and profile were analysed in 17 half-sib Pinus pinaster families growing under two levels of P-availability (complete and P-limited fertilization). Individual terpene concentrations showed large additive genetic variation, which was more pronounced in the control than in MeJa-induced pines. MeJa application did not affect the LVT concentration, but significantly modified the LVT profile by depleting the α-pinene content and reducing the sesquiterpene fraction. Low P-availability strongly reduced plant growth and foliar nutrient concentrations, but did not affect LVT concentration and profile, and did not interact with MeJa-induction. Results indicate a strong homeostasis of LVT concentration to P-availability, and minor changes in the LVT profile due to MeJa-induction. Genetic variation appears to be the main source of phenotypic variation affecting the LVT concentration in this pine species. © 2010 The Author.
Sardans J., Llusià J., Niinemets U., Owen S., Peñuelas J. (2010) Foliar Mono- and Sesquiterpene Contents in Relation to Leaf Economic Spectrum in Native and Alien Species in Oahu (Hawai'i). Journal of Chemical Ecology. 36: 210-226.EnllaçDoi: 10.1007/s10886-010-9744-z
Capacity for terpene production may confer advantage in protection against abiotic stresses such as heat and drought, and also against herbivore and pathogen attack. Plant invasive success has been intense in the Hawaiian islands, but little is known about terpene content in native and alien plant species on these islands. We conducted a screening of leaf terpene concentrations in 35 native and 38 alien dominant plant species on Oahu island. Ten (29%) of the 35 native species and 15 (39%) of the 38 alien species contained terpenes in the leaves. This is the first report of terpene content for the ten native species, and for 10 of the 15 alien species. A total of 156 different terpenes (54 monoterpenes and 102 sesquiterpenes) were detected. Terpene content had no phylogenetic significance among the studied species. Alien species contained significantly more terpenes in leaves (average ± SE = 1965 ± 367 μg g-1) than native species (830 ± 227 μg g-1). Alien species showed significantly higher photosynthetic capacity, N content, and lower Leaf Mass Area (LMA) than native species, and showed higher total terpene leaf content per N and P leaf content. Alien species, thus, did not follow the expected pattern of "excess carbon" in comparison with native species. Instead, patterns were consistent with the "nutrient driven synthesis" hypothesis. Comparing alien and native species, the results also support the modified Evolution of Increased Competitive Ability (EICA) hypothesis that suggests that alien success may be favored by a defense system based on an increase in concentrations of less costly defenses (terpenes) against generalist herbivores. © 2010 Springer Science+Business Media, LLC.
Sardans J., Montes F., Peñuelas J. (2010) Determination of As, Cd, Cu, Hg and Pb in biological samples by modern electrothermal atomic absorption spectrometry. Spectrochimica Acta - Part B Atomic Spectroscopy. 65: 97-112.EnllaçDoi: 10.1016/j.sab.2009.11.009
Pollution from heavy metals has increased in recent decades and has become an important concern for environmental agencies. Arsenic, cadmium, copper, mercury and lead are among the trace elements that have the greatest impact and carry the highest risk to human health. Electrothermal atomic absorption spectrometry (ETAAS) has long been used for trace element analyses and over the past few years, the main constraints of atomic absorption spectrometry (AAS) methods, namely matrix interferences that provoked high background absorption and interferences, have been reduced. The use of new, more efficient modifiers and in situ trapping methods for stabilization and pre-concentration of these analytes, progress in control of atomization temperatures, new designs of atomizers and advances in methods to correct background spectral interferences have permitted an improvement in sensitivity, an increase in detection power, reduction in sample manipulation, and increase in the reproducibility of the results. These advances have enhanced the utility of Electrothermal atomic absorption spectrometry (ETAAS) for trace element determination at μg L -1 levels, especially in difficult matrices, giving rise to greater reproducibility, lower economic cost and ease of sample pre-treatment compared to other methods. Moreover, the recent introduction of high resolution continuum source Electrothermal atomic absorption spectrometry (HR-CS-ETAAS) has facilitated direct solid sampling, reducing background noise and opening the possibility of achieving even more rapid quantitation of some elements. The incorporation of flow injection analysis (FIA) systems for automation of sample pre-treatment, as well as chemical vapor generation renders (ETAAS) into a feasible option for detection of As and Hg in environmental and food control studies wherein large numbers of samples can be rapidly analyzed. A relatively inexpensive approach with low sample consumption provide additional advantages of this technique that reaches figures of merit equivalent to Inductively coupled plasma mass spectrometry (ICP-MS). Herein is presented an overview of recent advances and applications of (ETAAS) for the determination of As, Cd, Cu, Hg and Pb in biological samples drawn from studies over the last decade. © 2009 Elsevier B.V. All rights reserved.
Sardans J., Peñuelas J. (2010) Soil enzyme activity in a mediterranean forest after six years of drought. Soil Science Society of America Journal. 74: 838-851.EnllaçDoi: 10.2136/sssaj2009.0225
A 6-yr experiment in drought manipulation was conducted in a Quercus ilex L. Mediterranean forest to simulate the drought conditions projected for the coming decades. We investigated the effects of those drought conditions on soil urease, protease, and β-glucosidase activities and the changes in C and N stocks in soil, leaves, and leaf litter. Elimination of runoff and rainfall resulted in lower soil water content than in control soils in autumn, winter, and spring (27, 61, and 53%, respectively). In soils subjected to runoff plus partial rainfall elimination, urease activities were reduced by 25% in autumn, winter, and spring; soil protease activities by 33% in winter and spring; and β-ghicosidase by 25 to 30% in summer and spring. Drought reduced the C/N ratio of the leaf litter of the dominant species, Q. ilex, by 11%, indicating a decrease in N remobilization before leaf fall. We therefore did not observe an increase in the C/N concentration ratio in litter and soil as we had expected. Drought decreased N availability in spring, the growing season, by reducing soil NO3- concentration. The reduction in enzyme activities in the droughtaffected soils was mainly due to the prolonged decrease in water availability and, to a lesser extent, to current soil water availability, mainly in summer, and to changes in the nutritional quality of the enzyme substrate. The observed drop in soil enzyme activity can contribute to a decrease in the amount of N liberated and consequendy to a decline in the plant N capture, which was observed in some community species such as Arbutus unedo L. © Soil Science Society ot America, 5585 Guilford Rd., Madison WI 53711 USA. All rights reserved.
Sardans J., Peñuelas J., Lope-Piedrafita S. (2010) Changes in water content and distribution in Quercus ilex leaves during progressive drought assessed by in vivo 1H magnetic resonance imaging. BMC Plant Biology. 10: 0-0.EnllaçDoi: 10.1186/1471-2229-10-188
Background: Drought is a common stressor in many regions of the world and current climatic global circulation models predict further increases in warming and drought in the coming decades in several of these regions, such as the Mediterranean basin. The changes in leaf water content, distribution and dynamics in plant tissues under different soil water availabilities are not well known. In order to fill this gap, in the present report we describe our study withholding the irrigation of the seedlings of Quercus ilex, the dominant tree species in the evergreen forests of many areas of the Mediterranean Basin. We have monitored the gradual changes in water content in the different leaf areas, in vivo and non-invasively, by 1H magnetic resonance imaging (MRI) using proton density weighted (ρ w) images and spin-spin relaxation time (T 2) maps.Results: ρ wimages showed that the distal leaf area lost water faster than the basal area and that after four weeks of similar losses, the water reduction was greater in leaf veins than in leaf parenchyma areas and also in distal than in basal leaf area. There was a similar tendency in all different areas and tissues, of increasing T 2values during the drought period. This indicates an increase in the dynamics of free water, suggesting a decrease of cell membranes permeability.Conclusions: The results indicate a non homogeneous leaf response to stress with a differentiated capacity to mobilize water between its different parts and tissues. This study shows that the MRI technique can be a useful tool to follow non-intrusively the in vivo water content changes in the different parts of the leaves during drought stress. It opens up new possibilities to better characterize the associated physiological changes and provides important information about the different responses of the different leaf areas what should be taken into account when conducting physiological and metabolic drought stress studies in different parts of the leaves during drought stress. © 2010 Sardans et al; licensee BioMed Central Ltd.
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