Studies on the Growth Effects of the Canaline-Urea Cycle Amino Acids with Lemna minor L

The aquatic microphyte, Lemna minor L., was utilized to assess the relative toxicity and general growth effects of canavanine, canaline, ureidohomoserine (UHS), and canavaninosuccinate (CSA). These amino acids are constituents of the canaline-urea cycle and structural analogues of the ornithine-urea cycle amino acids.Comparative growth studies with L. minor revealed that the canaline-urea cycle amino acids are potent antimetabolites. With the exception of CSA, they are extremely toxic at a concentration of 5 mum. Over a concentration range of 1 to 4 mum, canavanine is the most growth-inhibiting of the canaline-urea cycle amino acids. At or above 5 mum, canavanine and canaline possess comparable toxicity. UHS is less growth-inhibiting than canavanine or canaline, and CSA is the least toxic of the canaline-urea cycle intermediates.