Effects of excess nitrogen and drought on the foliar concentrations ofalleloehemicals in young oaks (Quercus robur L-and Q-petraea [Matt.]Liebl.)

摘要

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.