NITROGEN AND CARBON CONCENTRATIONS, SOLUBLE-PROTEINS AND FREE AMINO-ACIDS IN SUBTERRANEAN TURIONS OF HYDRILLA DURING OVERWINTERING

The forms of nitrogen in subterranean turions of both biotypes of hydrilla found in the U. S. were quantified monthly from December 1989 to April 1990. Mean concentrations of free amino acids in subterranean turions ranged from 33.5 to 83.7 and 42.3 to 58.4 nmoles (mg dry weight)(-1) for the monoecious and dioecious biotypes, respectively. Concentrations of soluble proteins in subterranean turions ranged from 19.9 to 28.3 and 15.7 to 22.7 mu g (mg dry weight)(-1) for turions of the monoecious and dioecious biotype, respectively. There were no significant linear time-dependent changes in the concentrations of free amino acids or soluble proteins during the overwintering period. Asparagine, alanine and arginine were major free amino acids in turions of both biotypes in October and April. Carbon concentrations decreased from 42 to 39% between December and April for turions of either biotype, while nitrogen concentrations fell from 1.41% to 1.21% for monoecious turions, with an approximately equivalent change in nitrogen composition for dioecious turions.