Inhaltszusammenfassung

To assess the effects of excess nitrogen (N) and drought stress on the foliar concentrations of allelochemicals, two-year-old pedunculate (Quercus robur L.) and sessile oaks (Q. petraea [Matt.] Liebl.) were grown in the open during the growing season and provided with two treatments of N, 2 g m -2 ('normal N' treatment, Nn) or 24 g m -2('excess N', Ne). The trees were adequately watered except for four specimens of both species and N treatments which were subjected to drought stress for two m...To assess the effects of excess nitrogen (N) and drought stress on the foliar concentrations of allelochemicals, two-year-old pedunculate (Quercus robur L.) and sessile oaks (Q. petraea [Matt.] Liebl.) were grown in the open during the growing season and provided with two treatments of N, 2 g m -2 ('normal N' treatment, Nn) or 24 g m -2('excess N', Ne). The trees were adequately watered except for four specimens of both species and N treatments which were subjected to drought stress for two months. In September, leaves were harvested for analysis of nutrient concentrations. In selected leaf samples with distinctly contrasting N concentrations (normal N concentrations in samples from the Nn treatment, and high N concentrations in those from the Ne treatment), we measured the concentrations of total phenolics and condensed tannins as well as the protein precipitation capacity. In general, only weak correlations were found between the foliar concentrations of N and allelochemicals. The strongest effect was exerted by the combination of excess N and drought stress which led to a steep decline in tannin concentration and protein precipitation capacity in the pedunculate, but not in the sessile oak. The foliar concentrations of allelochemicals in sessile oak proved to be less susceptible to drought stress and excess N as compared to the pedunculate oak. It is hypothesized that, in pedunculate oaks with high foliar N concentrations, drought stress will increase the risk of severe insect defoliation.» weiterlesen» einklappen

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DDC Sachgruppe:
Biowissenschaften, Biologie