Filella I., Peñuelas J., Seco R. (2009) Short-chained oxygenated VOC emissions in Pinus halepensis in response to changes in water availability. Acta Physiologiae Plantarum. 31: 311-318.LinkDoi: 10.1007/s11738-008-0235-6
Short-chained oxygenated VOC (oxVOCs) emissions from Pinus halepensis saplings were monitored in response to changes in water availability. Online measurements were made with a proton transfer reaction-mass spectrometer under controlled conditions, together with CO2 and H2O exchange measurements. Masses corresponding to methanol and acetone were the most emitted oxVOCs. All the oxVOC exchanges, except that of acetone (M59), were significantly related to stomatal conductance and transpiration. Acetaldehyde (M45) emission showed, moreover, a strong dependence on the concentration of acetaldehyde in the ambient: stomatal opening (stomatal conductance above 75 mmol m-2 s-1) only allowed increased emissions when external concentration were below 6 ppb. Acetone (M59) presented an important peak of emission following light and stomatal opening in the morning when plants were water stressed. Thus, the alterations in oxVOC emissions in P. halepensis caused by the water deficit seem to be mainly driven by water stress effect on stomatal closure and oxVOC air concentrations. © 2008 Franciszek Górski Institute of Plant Physiology, Polish Academy of Sciences, Kraków.
Filella I., Porcar-Castell A., Munné-Bosch S., Bäck J., Garbulsky M.F., Peñuelas J. (2009) PRI assessment of long-term changes in carotenoids/chlorophyll ratio and short-term changes in de-epoxidation state of the xanthophyll cycle. International Journal of Remote Sensing. 30: 4443-4455.LinkDoi: 10.1080/01431160802575661
The Photochemical Reflectance Index (PRI), an index based on leaf reflectance at 531 nm, has been found suitable for tracking variations in photosynthetic activity from leaf to ecosystem levels. This suitability has been attributed to PRI correlation with xanthophyll interconversion and photosynthetic radiation-use efficiency. However, other pigments and factors may be involved in such relationships. We studied the relationship between PRI and xanthophylls and other carotenoids in saplings of two widely distributed evergreen species (Scots pine and Holm oak) submitted to experimentally changing light conditions in a field experiment. PRI was strongly correlated with the de-epoxidation state of xanthophylls (DEPS, an expression of the relative concentration of the three xanthophyll cycle pigments), but also with carotenoids/chlorophyll ratio and β-carotene/chlorophyll ratio in both species. However, following momentary decreases in light due to clouds, PRI changed following the DEPS changes, while the carotenoids/chlorophyll ratio remained constant. The results show that PRI was able to reveal short-term changes in de-epoxidation state, i.e. the signal of xanthophyll interconversion, but it also tracked long-term changes in carotenoids/chlorophyll. Carotenoids other than xanthophylls, e.g. β-carotene, are also related to photoprotective processes, thus also making PRI effective as a measure of changes in photosynthetic light-use efficiency in response to stress on a long-term level. © 2009 Taylor & Francis.
Peñuelas J., Filella I., Seco R., Llusià J. (2009) Increase in isoprene and monoterpene emissions after re-watering of droughted Quercus ilex seedlings. Biologia Plantarum. 53: 351-354.LinkDoi: 10.1007/s10535-009-0065-4
We followed the diurnal cycles of isoprenoid emissions from Quercus ilex seedlings under drought and after re-watering. We found that Quercus ilex, generally considered a non-isoprene emitter, also emitted isoprene although at low rates. The emission rates of isoprene reached 0.37 ± 0.02 nmol m-2 s-1 in controls, 0.15 ± 0.03 nmol m-2 s-1 under drought and 0.35 ± 0.04 nmol m-2 s-1 after re-watering, while emission rates of monoterpenes reached 11.0 ± 3.0, 7.0 ± 1.0 and 23.0 ± 5.0 nmol m-2 s-1, respectively. Emission rates recovered faster after re-watering than photosynthetic rate and followed diurnal changes in irradiance in controls and under drought, but in leaf temperature after re-watering. © 2009 Springer Science+Business Media B.V.
Stefanescu C., Peñuelas J., Filella I. (2009) Rapid changes in butterfly communities following the abandonment of grasslands: A case study. Insect Conservation and Diversity. 2: 261-269.LinkDoi: 10.1111/j.1752-4598.2009.00063.x
1. Abandonment of grasslands is a major threat for the conservation of biodiversity in Europe. The response of butterflies towards secondary succession has been studied in northern temperate grasslands, but always by comparing sites at different stages. 2. Here, we present a trajectory study based on the monitoring of butterflies from a series of abandoned grasslands in northeast Spain. One additional meadow was traditionally managed for the whole 8-year sampling period and provided a useful control. Both general changes at the community level and species population trends were documented through standardised transect counts. 3. The increase in turf height was neither accompanied by an increase in butterfly diversity nor by consistent trends in body size, dispersal ability and host-plant specialization. However, there was a significant decrease in habitat specialization, consistent with the hypothesis that richness in generalist herbivores is more dependent on biomass production than on plant richness. The number of generations decreased, in line with the hypothesis that species living in habitats subjected to greater disturbance need higher reproductive rates. 4. Butterfly communities underwent substantial changes, as indicated by composition similarity and species population trends. Grassland specialists were forced to disperse from the abandoned meadows and search for refugial habitats, allowing the establishment of new populations in the contiguous managed meadow. 5. Our study shows that grassland abandonment had immediate strong effects on butterflies, acting as an excellent indicator of habitat change. It also points out to the substitution of grassland specialists by common butterflies, less important for conservation purposes. © 2009 The Royal Entomological Society.
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