Altitudinal differences in UV absorbance, UV reflectance and related morphological traits of Quercus ilex and Rhododendron ferrugineum in the Mediterranean region

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.
Enllaç
Doi: 10.1023/A:1009826803540

Resum:

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.

Llegeix més

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

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.
Enllaç
Doi: 10.1016/S1146-609X(99)80024-1

Resum:

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.

Llegeix més

Dependence of ozone biomonitoring on meteorological conditions of different sites in Catalonia (N.E. Spain)

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.
Enllaç
Doi: 10.1023/A:1006062613552

Resum:

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.

Llegeix més