Leaf production and nitrogen and phosphorus tissue content of Littorella uniflora (L.) Aschers. In relation to nitrogen and phosphorus enrichment of the sediment in oligotrophic Lake Hampen, Denmark

Littoral sediments with a dense population of Littorella uniflora (L.) Ascers. were artificially enriched with nitrogen and phosphorus. Responses to increasing levels of nutrients were recorded as leaf production and tissue nutrient content. Phosphorus enrichment resulted in increasing P concentrations in all plant fractions (leaves, stem and roots), whereas only leaves and roots showed increasing N concentrations when inorganic N was added. Leaf production increased significantly after increasing the sediment P level 2, 3 and 5 times. Nitrogen did not affect leaf production. The tissue content of total N and P in control plants averaged 3.29 and 0.28%, respectively. Thus the critical P level in L. uniflora seems to be about 0.28%, which is higher than previously published values. It was also found that L. uniflora translocates phosphorus from old to younger leaves.