Distribución de la superficie arbolada en relación con la protección legal del suelo y su pendiente en el espacio natural de las Guilleries-Savassona (Barcelona).

Margall M, Burriel JA (2001) Distribución de la superficie arbolada en relación con la protección legal del suelo y su pendiente en el espacio natural de las Guilleries-Savassona (Barcelona). In Actas del Congreso de Ordenación y Gestión Sostenible de Montes. Tomo I: 259-266.

Emission of volatile organic compounds by apple trees under spider mite attack and attraction of predatory mites

Llusià J., Peñuelas J. (2001) Emission of volatile organic compounds by apple trees under spider mite attack and attraction of predatory mites. Experimental and Applied Acarology. 25: 65-77.
Enllaç
Doi: 10.1023/A:1010659826193

Resum:

Emission rates of volatile organic compounds (VOCs) from Pirus malus L. subsp. mitis (Wallr.) var. Golden Delicious and var. Starking attacked by the phytophagous mite Panonychus ulmi Koch, and their attractiveness to the predatory mites Amblyseius andersoni Chant and Amblyseius californicus McGregor, were studied during three years. A large variability was found in the emission of individual VOCs depending on the infestation, the apple tree variety and the date. There were larger total VOC emission rates and larger total VOC leaf concentrations in apple trees attacked by phytophagous mites, especially in the var. Starking. In infested trees of this variety, there were also more predatory mites. An olfactometer assay showed that predatory mites preferentially chose branches infested by Panonychus ulmi (85% went to infested branches vs 15% to uninfested control branches) indicating that volatiles may be used as cues to find their prey.

Llegeix més

Fine-root longevity of Quercus ilex

López B., Sabaté S., Gracia C.A. (2001) Fine-root longevity of Quercus ilex. New Phytologist. 151: 437-441.
Enllaç
Doi: 10.1046/j.0028-646X.2001.00189.x

Resum:

Fine-root longevity and phenology were studied in a Quercus ilex (holm oak) forest in Prades (NE Spain). Differences were investigated among roots that had appeared in different seasons and at different depth intervals, differentiating between white and brown roots. Using minirhizotrons installed in March 1994, 1211 roots were monitored every 3 wk from June 1994 to March 1997. Mean and median fine-root longevity were 125 ± 4 d and 67 d, respectively. Longevity of summer and winter roots was greater than that of spring and autumn roots. Although roots appeared and disappeared throughout the year, the rate of appearance was greatest in spring. Maximum longevity occurred at a soil depth of 20-30 cm. Differences among 10-cm depth intervals were due to the number of days that roots were brown, since roots remained white for a similar number of days, independent of soil depth. Temperate soil temperatures and lignotubers permitted the appearance of roots throughout the year. Holm oak fine roots might be more efficient during the first 50 d of their life before the white roots become less efficient brown roots. © New Phytologist (2001).

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Annual and seasonal changes in fine root biomass of a Quercus ilex L. forest

López B., Sabaté S., Gracia C.A. (2001) Annual and seasonal changes in fine root biomass of a Quercus ilex L. forest. Plant and Soil. 230: 125-134.
Enllaç
Doi: 10.1023/A:1004824719377

Resum:

The biomass, production and mortality of fine roots (roots with diameter <2.5 mm) were studied in a typical Mediterranean holm oak (Quercus ilex L.) forest in NE Spain using the minirhizotron methodology, A total of 1212 roots were monitored between June of 1994 and March of 1997. Mean annual fine root biomass in the holm oak forest of Prades was 71 ±8 g m-2 yr-1. Mean annual production for the period analysed was 260+11 g m-2 yr-1. Mortality was similar to production, with a mean value of 253±3 g m-2 yr-1. Seasonal fine root biomass presented a cyclic behaviour, with higher values in autumn and winter and lower in spring and summer. Production was highest in winter, and mortality in spring. In summer, production and mortality values were the lowest for the year. Production values in autumn and spring were very similar. The vertical distribution of fine root biomass decreased with increasing depth except for the top 10-20 cm, where values were lower than immediately below. Production and mortality values were similar between 10 and 50 cm depth. In the 0-10 cm and the 50-60 cm depth intervals, both production and mortality were lower.

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RAPD differentiation between Borderea pyrenaica and B. chouardii (Dioscoreaceae), two relict endangered taxa.

Mayol M, Rosselló JA (2001) RAPD differentiation between Borderea pyrenaica and B. chouardii (Dioscoreaceae), two relict endangered taxa. Israel Journal of Plant Sciences 49:259-268.

Seed isozyme variation in Petrocoptis A. Braun (Caryophyllaceae).

Mayol M, Rosselló JA (2001) Seed isozyme variation in Petrocoptis A. Braun (Caryophyllaceae). Biochemical Systematics and Ecology 29:379-392.

Why nuclear ribosomal DNA spacers (ITS) tell different stories in Quercus.

Mayol M, Rosselló JA (2001) Why nuclear ribosomal DNA spacers (ITS) tell different stories in Quercus. Molecular Phylogenetics and Evolution 19:167-176.

Why nuclear ribosomal DNA spacers (ITS) tell different stories in Quercus

Mayol M., Rosselló J.A. (2001) Why nuclear ribosomal DNA spacers (ITS) tell different stories in Quercus. Molecular Phylogenetics and Evolution. 19: 167-176.
Enllaç
Doi: 10.1006/mpev.2001.0934

Resum:

The molecular systematics of Quercus (Fagaceae) was recently assessed by two teams using independently generated ITS sequences. Although the results disagreed in several remarkable features, the phylogenetic trees for either hypothesis were highly supported by bootstrap resampling. We have reanalyzed the ITS sequences used by both teams (eight taxa) to reveal the underlying patterns of this divergence. Within species, conspicuous length and G + C% divergence were evident in most sequence comparisons. In addition, a high rate of substitutions and deletions involving highly conserved motifs in both ITS spacers were present in a set of sequences. This was coupled with a less thermodynamic stability in the RNA structure, lacking conserved hairpins that are putatively involved in the processing of the RNA transcripts. Compelling evidence suggests that the divergent ITS alleles reported by one team are pseudogenes, i.e., nonfunctional paralogous loci. The hypothesis that the contrasting phylogenetic histories drawn from Quercus using ITS data are not strictly related to technical differences between laboratories, but that they have rather been generated from the analysis of paralogous sequences, best reconciles the available data. The risk of incorporating ITS paralogues in plant evolutionary studies which can distortion the phylogenetic signal should caution molecular systematists. Without a detailed inspection of some basic features of the sequence, including the integrity of the conserved motifs and the thermodynamic stability of the secondary structures of the RNA transcripts, errors in evolutionary inferences could be easily overlooked. © 2001 Academic Press.

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Gene flow and local adaptation in two endemic plant species.

Petit C, Fréville H, Mignot A, Colas B, Riba M, Imbert E, Hurtrez-Boussès S, Virevaire M, Olivieri I (2001) Gene flow and local adaptation in two endemic plant species. Biological Conservation 100:21-34.

Diagnostic de la situation de Centaurea corymbosa (Asteraceae), endémique du massif de la Clape (Aude, France).

Riba M, Colas B, Fréville H, Henry J-P, Mignot A, Petit C, Ronce O, Olivieri I (2001) Diagnostic de la situation de Centaurea corymbosa (Asteraceae), endémique du massif de la Clape (Aude, France). Bocconea 13:173-179.

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