Castells E., Peñuelas J., Valentine D.W. (2005) Effects of plant leachates from four boreal understorey species on soil N mineralization, and white spruce (Picea glauca) germination and seedling growth. Annals of Botany. 95: 1247-1252.EnllaçDoi: 10.1093/aob/mci139
• Background and Aims: Natural regeneration of white spruce (Picea glauca) after disturbance has been reported to be very poor. Here a study was made to determine whether C compounds released from understorey species growing together with white spruce could be involved in this regeneration failure, either by (1) changing soil nutrient dynamics, (2) inhibiting germination, and/or (3) delaying seedling growth. • Methods: Foliage leachates were obtained from two shrubs (Ledum palustre and Empetrum hermaphroditum) and one bryophyte (Sphagnum sp.) with high phenolic compound concentrations that have been reported to depress growth of conifers in boreal forests, and, as a comparison, one bryophyte (Hylocomium splendens) with negligible phenolic compounds. Mineral soil from a white spruce forest was amended with plant leachates to examine the effect of each species on net N mineralization. Additionally, white spruce seeds and seedlings were watered with plant leachates to determine their effects on germination and growth. • Key Results: Leachates from the shrubs L. palustre and E. hermaphroditum contained high phenolic compound concentrations and dissolved organic carbon (DOC), while no detectable levels of C compounds were released from the bryophytes Sphagnum sp. or H. splendens. A decrease in net N mineralization was determined in soils amended with L. palustre or E. hermaphroditum leachates, and this effect was inversely proportional to the phenolic concentrations, DOC and leachate C/N ratio. The total percentage of white spruce germination and the growth of white spruce seedlings were similar among treatments. • Conclusions: These results suggest that the shrubs L. palustre and E. hermaphroditum could negatively affect the performance of white spruce due to a decrease in soil N availability, but not by direct effects on plant physiology. © The Author 2005. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved.
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., Ribas A. (2005) Using plant biomonitors and flux modelling to develop O 3 dose-response relationships in Catalonia. Environmental Pollution. 134: 145-151.EnllaçDoi: 10.1016/j.envpol.2004.07.007
We used tobacco Bel-W3 biomonitoring data and ozone flux modelling (WINDEP model) with the aim of developing the absorbed dose-response relationship, and comparing this approach with the most commonly used AOT40 (the sum of hourly ozone concentrations above a cut-off of 40 ppb during daylight hours, when global radiation exceeds 50 W m -2) in the estimation of exposure-damage curves. Leaf damage values were more related to OAD 15 days, potential (potential ozone absorbed dose calculated over 15 consecutive days) than to AOT40 in all the studied stations. An OAD 15 days, potential of 180 mg m -2 was found to be the threshold for damage to the most sensitive species in this region under well watered conditions. The results show the applicability of the flux approach for risk assessment at the local scale, the improvement of the ozone damage estimation when the potential absorbed dose is modelled and used instead of just the ozone exposure, and finally, the possibilities opened by the use of biomonitoring networks. Modelling of biomonitors ozone absorbed dose improves damage estimation in comparison with exposure indices such as AOT40. © 2004 Elsevier Ltd. All rights reserved.
Lloret F, Peñuelas J, Estiarte M (2005) Effect of vegetation canopy and climate on seedling establishment in a Mediterranean shrubland. Journal of Vegetation Science 16: 67-76.
Lloret F, Peñuelas J, Estiarte M, Ogaya R (2005) Patterns of plant population dieback and recvery alter drought episodes in Mediterranean forests and shrublands. Climate Change-Forest Ecosystems & Landscape Zvolen (Slovakia). Forest Research Institute Zvolen and the European Forest Institute.
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).
Sardans J, Peñuelas J (2005) Drought decreases soil enzyme activity in a Mediterranean Quercus ilex L. forest. Soil Biology & Biochemistry 37: 455–461.
Sardans J, Peñuelas J (2005) Disponibilidad y uso del fósforo en los ecosistemas terrestres mediterráneos. La inspiración de Margalef. Ecosistemas 1: 1-11.
Gimeno BS, Bermejo V, Peñuelas J, Porcuna JL, Santamaría J, Sanz MJ (2005) Ozone effects on Spanish crops and vegetation. An overview. 18th Task Force Meeting of the UN/ECE ICP Vegetation. Almería, 1-4 Febrero.
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