CONSTRUCTION COSTS FOR SOME AQUATIC PLANTS

Abstract Resource allocation reflects a plant's response to its environment and affects its overall growth and performance in a particular habitat. We measured ash, C, N, and caloric content for various parts of Hydrilla verticillata (L.f.) Royle, Potamogeton nodosus Poir., P. gramineus L., and P. pectinatus L. Mean ash content of vegetative propagules ranged from 2.96 to 5.46%, lower than values previously reported for aquatic plant shoots. Potamogeton propagule C and N contents were greater than those of Hydrilla propagules. Mean propagule caloric content ranged from 3753 to 4198 cal g −1 and construction costs from 1.00 to 1.12 g glucose g −1 . They were similar to or slightly greater than those for shoots or leaves. Construction costs for leaves of eight aquatic species averaged 1.02 g glucose g −1 . Vegetative propagules had sink strengths similar to those of shoots. H. verticillata, P. pectinatus , and P. gramineus were grown in a greenhouse with different levels of N in the water column. In this experiment, P. pectinatus and H. verticillata roots had higher construction costs than shoots whereas P. gramineus did not. Only the costs for P. pectinatus shoots and roots were affected by the N level in the water column. Construction costs for aquatic plant vegetative propagules, shoots, and roots were lower than similarly calculated values published for roots, stems and leaves of terrestrial plants, in agreement with expectations based on the structural characteristics of leaves and stems of aquatic plants.