ABSTRACT

An investigation was made of the amino acids in nine species of aquatic plants, on a seasonal basis, in two eutrophic-alkalitrophic lakes in central Minnesota. By determining the general quantity of, as well as amount of seasonal variation in, the plant amino acids, the following relative relationships of the amino acids in their natural environments were established: (1) fairly stable and abundant: alanine; (2) fairly stable and moderately abundant: cystine, valine, and glutamic acid; (3) moderately stable and abundant: leucine and glycine; (4) moderately stable and moderately abundant: arginine and aspartic acid; (5) moderately stable but not abundant: threonine; (6) fairly unstable but moderately abundant: lysine, serine, and histidine; (7) fairly unstable and not abundant: phenyla anine and tyrosine; (8) very unstable and sporadic in occurrence: proline and methionine? Ammonia-nitrogen comprises a significant part of the organic nitrogen in the plant specimens studied.

The limnology of the lakes is described and the relationship between the plant amino acids and those in the associated lake sediments is discussed.