Llusià J., Peñuelas J. (1999) Pinus halepensis and Quercus ilex terpene emission as affected by temperature and humidity. Biologia Plantarum. 42: 317-320.EnllaçDoi: 10.1023/A:1002185324152
The short-term relationships of monoterpene emission with temperature and relative humidity were studied in Pinus halepensis L. and Quercus ilex L. seedlings grown in air-conditioned chamber. In P. halepensis terpene emission rate increased with temperature (from 15 to 35 °C) and relative humidity (from 40 - 60 to 65 - 95 %). In Q. ilex, a terpene non-storing species, it increased with temperature only at high relative humidities but not at relative humidities lower than 60 %.
Estiarte M, Peñuelas J, Kimball BA, Hendrix DL, Pinter PA Jr, Wall GW, LaMorte RL, Hunsaker DJ (1999) Free-air CO2 enrichment of wheat: leaf flavonoid concentration throughout the growth cycle. Physiologia Plantarum 105:423-433.
Estiarte M, Peñuelas J (1999) Excess carbon: the relationship with phenotypical plasticity in storage and defense functions of plants. Orsis 14:159-203.
Peñuelas J., Filella I., Terradas J. (1999) Variability of plant nitrogen and water use in a 100-m transect of a subdesertic depression of the Ebro valley (Spain) characterized by leaf δ13C and δ15N. Acta Oecologica. 20: 119-123.EnllaçDoi: 10.1016/S1146-609X(99)80024-1
We studied carbon and nitrogen isotopic composition (δ13C and δ15N) in sunlit leaves of four dominant species (Rosmarinus officinalis L., Stipa parviflora L., Juniperus thurifera L. and Pinus halepensis L.) in a characteristic gradient of water and nitrogen availability produced by relief and micrometeorology in a subdesertic valley of central-NE Spain. Minimum values of δ13C were found at the foothills, and higher values were found both in the valley and oil the top of the hill where water availability was lower. However, different species (functional groups) presented different δ13C values in the same valley. The lowest values of δ15N were found on the top of the hill and the highest ones in the valley, where N losses would thus be higher. In general, when growing together, trees showed 2 ‰ higher values for δ13C as well as for δ15N than shrubs and grasses. The specific responses show that they use different available water and nitrogen resources within small catchments. For this ecosystem type, C and N isotope analyses are sensitive enough to resolve fine spatial and functional patterns even over a very short distance (100 m), where topography generates great gradients in microclimate, hydrology, soil physical conditions, vegetation and biogeochemistry.
Peñuelas J., Inoue Y. (1999) Reflectance indices indicative of changes in water and pigment contents of peanut and wheat leaves. Photosynthetica. 36: 355-360.EnllaçDoi: 10.1023/A:1007033503276
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.
Peñuelas J., Llusià J. (1999) Short-term responses of terpene emission rates to experimental changes of PFD in Pinus halepensis and Quercus ilex in summer field conditions. Environmental and Experimental Botany. 42: 61-68.EnllaçDoi: 10.1016/S0098-8472(99)00018-0
The diurnal relationships of monoterpene emission with PFD and photosynthetic rates were studied in the Mediterranean trees Pinus halepensis, a terpene storing species, and Quercus ilex, a non-storing species, under summer field conditions. At morning, midday and evening, leaves were submitted to different irradiance levels by differentially shading them. Both species emitted large amounts of monoterpenes (about 20 μg g DM-1 h-1). The most emitted terpene by P. halepensis was Δ3-carene followed by β-myrcene, α-pinene and β-pinene. The most emitted terpene by Q. ilex was limonene followed by α-pinene and α-pinene. No clear correlation to temperature was found for Q. ilex emission within the diurnal range of 21-33°C, whereas P. halepensis emissions increased with the temperature. There was no consistent link between terpene emissions and PFD or photosynthetic rates for P. halepensis but there were significant relationships for Q. ilex. However, emissions by Q. ilex became inhibited at highest PFDs and during the course of the day when net photosynthesis decreased under summer drought. The study shows that the emission rates of both species are highly variable and that during a hot Mediterranean summer day (with limited water availability) the diurnal variation of emission is not only driven by the common light and temperature dependencies. Water stress, branch-to-branch variability and other influences must explain great part of the observed variability.
Peñuelas J., Ribas A., Gimeno B.S., Filella I. (1999) Dependence of ozone biomonitoring on meteorological conditions of different sites in Catalonia (N.E. Spain). Environmental Monitoring and Assessment. 56: 221-224.EnllaçDoi: 10.1023/A:1006062613552
Evaluation of visual symptoms of ozone damage was conducted in the network of bioindicater rural stations of Catalonia (NE Spain) every 14 days from May to October. Damage rates of ozone (and consequently, ozone biomonitoring capacity of bioindicators) were found to vary highly in time and space depending on the local environmental and meteorological conditions. Lower ozone damage to foliage was produced when meteorological conditions favour stomata resistance. Modulatory effects of meteorological conditions need to be considered in biomonitoring and when modeling plant ozone doses and damage.
Ribas A, Filella I, Gimeno BS, Peñuelas J (1998) Evaluation of tobacco cultivars as bioindicators and biomonitors of ozone phytotoxical levels in Catalonia. Water, Air and Soil Pollution 107:347-365.
Ribas A, Peñuelas J, Gimeno BS, Filella I (1998) Climate change and plant ozone damage in the mediterranean region. The Earth's Changing Land GCTE-LUCC Open Science Conference on Global Change Abstracts. Institut Cartogràfic de Catalunya, Barcelona, pp. 187.
Filella I, Llusià J, Piñol J, Peñuelas J (1998) Leaf gas exchange and fluorescence of Phillyrea latifolia, Pistacia lentiscus and Quercus ilex saplings in severe drought and high temperature conditions. Environmental and Experimental Botany 39:213-220.
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