Filella I., Peñuelas J. (1999) Altitudinal differences in UV absorbance, UV reflectance and related morphological traits of Quercus ilex and Rhododendron ferrugineum in the Mediterranean region. Plant Ecology. 145: 157-165.EnllaçDoi: 10.1023/A:1009826803540
We studied the variations in different physiological parameters associated with UV-B radiation defense: UV-B radiation absorbance, UV-visible spectral reflectance, carotenoids concentration, leaf thickness, SLW (specific leaf weigth) and trichome density in Quercus ilex growing at 200 and 1200 m and Rhododendron ferrugineum growing at 2200 m. We examined the role of these parameters as protection mechanisms in an altitudinal gradient of increasing UV radiation in northern Catalonia and in sun and shade leaves. The concentration of UV-B radiation absorbing pigments was 15% higher in sun leaves of Q. ilex at 1200 m than in those from 200 m altitude. Sun leaves of R. ferrugineum presented concentrations three times higher than those of Q. ilex. Reflectance ranged between 5% (in the region 300-400 nm) and 12% (in the region 280-300 nm). The variation of reflectance with altitude followed an inverse trend respect to absorbance in the 280-300 nm region, with higher values the lower the altitude, but in the 300-400 nm region, reflectance of the lower site was the lowest. In both species and altitudes sun leaves presented higher concentrations of UV-B radiation absorbing pigments and UV reflectance than shade leaves. Quercus ilex trees of the higher location presented higher NDPI (Normalized Difference Pigment Reflectance Index) values, indicating higher carotenoids/chlorophyll a ratio. Actual measurements of carotenoid/chlorophyll a ratio confirmed this pattern. The photochemical reflectance index (PRI) presented higher values the higher the location indicating lower photosynthetic radiation-use efficiency. Specific leaf weight (SLW) and leaf thickness were larger in Q. ilex trees of higher location than in those of lower location. In both sites, sun leaves also presented larger SLW values than shade leaves. Adaxial leaf hair density in sun leaves was significantly higher in the lower location. UV absorption and linked morphological traits (SLW, leaf thickness measured in Q. ilex) presented the larger differences among studied plants at different altitudes and seem to be the dominant UV protecting mechanisms.
Lloret F, Casanovas C, Peñuelas J (1999) Seedling survival of Mediterranean shrubland species in relation to root:shoot ratio, seed size and water and nitrogen use. Functional Ecology 13:210-216.
Inclán R., Ribas A., Peñuelas J., Gimeno B.S. (1999) The relative sensitivity of different Mediterranean plant species to ozone exposure. Water, Air, and Soil Pollution. 116: 273-277.EnllaçDoi: 10.1023/A:1005214005416
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.
Peñuelas J (1999) Biologia d'organismes al 1998. Anuari Ciència, Tecnologia i Medi Ambient, Enciclopèdia Catalana.
Wessman CA, Cramer W, Gurney RJ, Martin PH, Mauser W, Nemani R, Paruelo JM, Peñuelas J, Prince SD, Running SW, Waring RH (1999) Group report: remote sensing perspectives and insights for study of complex landscapes. In Tenhunen JD, Kabat P (eds) Integrating hydrology, ecosystem dynamics and biogeochemistry in complex landscapes. Wiley, pp. 89-103.
Oliveira G, Peñuelas J (1999) Respostas fotoquímicas e fenológicas de uma espécie perenifólia e de uma semi-decídua durante o inverno mediterrânico. Revista de Biologia 17:249-259.
Del Pino F, Paruelo JM, Lauenroth WK, Oesterheld MO, Loreti J, Peñuelas J (1999) Variación de atributos estructurales y funcionales de gramíneas dominantes en pastizales áridos a subhúmedos. Congreso de la Asociación Argentina de Ecología, pp. 35-43.
Inoue Y, Peñuelas J, Nouvellon Y, Moran MS (1999) Estimating water and nitrogen conditions of crop plants based on hyperspectral measurements. Spectral Sensing Research 7:251-257.
Avila A, Peñuelas J (1999) Increasing frequency of Saharan rains over northeastern Spain and its ecological consequences. The Science of the Total Environment 228:153-156.
Peñuelas J, Llusià J (1999) Seasonal emission of monoterpenes by the Mediterranean tree Quercus ilex in field conditions: Relations with photosynthetic rates, temperature and volatility. Physiologia Plantarum 105:641-647.
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