Abstract of a publication based on research funded in part by the Australian Flora Foundation

The interaction of water flow and nutrients on aquatic plant growth
Mark N. Crossley1, William C. Dennison2, Richard R. Williams1 & Alan H. Wearing1
1School of Agriculture and Horticulture, University of Queensland, Gatton, Qld 4343, Australia
Tel: +07-54601183. Fax: +07-54601455. E-mail: mark.crossley@mailbox.uq.edu.au
2Marine Botany Group, Department of Botany, University of Queensland, Brisbane, Qld 4072, Australia Hydrobiologia 489: 63–70, 2002.

Key words: Aponogeton, elongatus, flowing water, nutrition interaction

A long-term experiment was conducted to compare the effects of flowing and still water on growth, and the relationship between water flow and nutrients, in Aponogeton elongatus, a submerged aquatic macrophyte. A. elongatus plants were grown for 23 weeks with three levels of nutrition (0, 0.5 and 1g Osmocote Plus fertiliser pot-1) in aquaria containing stirred or unstirred water. Fertilized plants grew much better than non-fertilized. The highest fertilizer level produced 29% wider leaves and 58% higher total dry weight in stirred water. Stirred water increased leaf area by 40% and tuber size by 81%, but only with the highest level of nutrition. These results suggest that this plant depends on its roots for mineral uptake, rather than from the open water, and the major limitation to growth in still water is the supply of dissolved inorganic carbon. It was the combined effects of nutrient availability and stirring that produced the strongest response in plant growth, morphology and composition. This study provides some explanation for the observations of others that these plants grow best in creeks or river systems with permanently flowing water.