Amino-acid Pools In Nutrient Limited Cyanidium-caldarium and Responses To Resupply

Amino acid pools in Cyanidium caldarium (Tilden) Geitler, growing under conditions of sufficiency of nutrients (sufficient cells), or under conditions of nitrogen, potassium or phosphorus limitation (N-, K- or P-limited cells), and responses upon nutrient resupply were investigated. Glutamate was the dominant amino acid in sufficient cells [11.2-mu-mol ml-1 packed cell volume (pcv)], in N-limited cells (7.71-mu-mol ml-1 pcv) and in P-limited cells (7.46-mu-mol ml-1 pcv), whereas in K-limited cells the dominant amino acid was alanine (8.83-mu-mol ml-1 pcv). Other amino acids detected occurring at significantly high concentrations were: citrulline, alanine, aspartate, glutamine and delta-aminolevulinic acid in sufficient cells, alanine in N-limited cells; alanine, citrulline, serine, arginine and asparagine in P-limited cells; glutamate, arginine, glutamine, citrulline, asparagine, serine, aspartate and putrescine in K-limited cells. On adding NH4+ to N-limited cells the level of glutamate decreased and then increased to the starting value; there occurred an increase in the level of glutamine, aspartate, citrulline, arginine, alanine, serine, as well as of delta-ALA and putrescine. Resupply of Pi to P-limited cells caused a significant decrease of glutamate and a concomitant increase of alanine, but was without effect on the concentration of other amino acids. On adding K+ to K-limited cells there was an increase of glutamate and citrulline, and a decrease of putrescine, whereas arginine and alanine remained unvaried at the very high level occurring before addition.