The Effects of Competition with Agropyron repens and of Nitrogen-and Water Supply on the Nitrogen Content of Impatiens parviflora

The nitrogen contents of plants of Impatiens parviflora grown in pots with and without root competition from Agropyron repens, and with two levels of nitrogenand water-supply, were determined. The nitrogen percentage and the nitrogen content were depressed by competition and increased by nitrogen application. Watering increased nitrogen content and percentage in plants growing with competition; the increased growth associated with such watering was approximately equivalent to the nitrogen increase. These effects were chieftly due to responses in the nitrogen absorption rate per unit root dry-weight. Root dry-weight/total dry-weight ratio changes were generally in the opposite direction, but were relatively small. When Net Assimilation Rate was calculated on a leaf nitrogen basis, the effect of competition was relatively less than when it was calculated on a leaf area basis, but the depression caused by high nitrogen status was much larger. When Net Assimilation Rate calculated on a leaf area basis was compared with nitrogen per unit leaf area there was evidence of a single relationship for all treatments. It appeared that most of the variation in Net assimilation Rate between treatments was caused by differences in nitrogen status.