Interspecific Responses of Marigold to Manganese as Influenced by Nitrogen Source

Responses of two hydroponically grown marigold species, Tagetes erects L. `pumpkin Crush' and T. patula L. `Janie Yellow', to Mn concentrations of 0.5 mg·liter-1 or 10 mg·liter-1 with KNO3 and Ca(NO3)2 (NO3 source) or NH4N O3 as the N source were investigated. In both species, Mn uptake was enhanced with the NO3 source while reduced with NH4NO3. With Mn supplied at 0.5 mg·liter-1 and NO3 as the N source, T. erects absorbed twice the Mn per gram of dry matter as T. patula. T. erecta accumulated higher concentration of Mn in the shoot than in the root irrespective of the N source. T. patula accumulated higher concentration of Mn in the roots with the NO3 source while NH4NO3 shifted the Mn accumulation to the shoot. Growth of both species was suppressed with 10 mg Mn/liter and the suppression was greater with the NO3 source than with the NH4NO3. These results indicate an interspecific response to Mn concentration as well as an N source influence on the uptake of Mn in marigold grown under hydroponic conditions.

Vocal Mimicry and Interspecific Aggression in Songbirds: Experiments Using White-Crowned Sparrow Imitation of Song Sparrow Song

A series of playback experiments was carried out to determine whether territorial male song sparrows could discriminate between their own species song, and the same song produced by a white-crowned sparrow. In two out of three measures of response, the males did not discriminate between model and mimic song. In constrast, most males showed no response to control white-crowned sparrow song, although two individuals showed a strong interspecific response. Other examples of interspecific aggression were also detected during the experiments. The results are discussed in relation to recent studies on interspecific song learning and the competition hypothesis of vocal mimicry in songbirds.