Submersed macrophyte growth at low pH : I. CO enrichment effects with fertile sediment.

Vallisneria americana was grown for six weeks in a greenhouse on relatively fertile sediment to test for factors other than nutrient limitation which may slow growth of this submersed macrophyte at pH 5. On the basis of dry mass accumulated, (1) low pH significantly depressed Vallisneria growth at constant free CO levels; (2) free CO enrichment, however, greatly stimulated Vallisneria growth at pH 5, by 2.8-fold and 10-fold at 3.