Free amino acids and ammonia in the Azolla-Anabaena association grown with N2, NH4+, and NO3

The level and localization of free amino acids and ammonia in the Azolla-Anabaena association grown with N 2 , NH 4 + , and NO 3 ¯ were compared. In the leaves, the levels of ammonia and most of the amino acids except for aspartic acid and glutamic acid decreased in the dark and increased in the light. In the roots, ammonia was most abundant and its level varied in parallel with the level of ammonia in the leaves. When the plants were grown on media containing NH 4 + , the level of total amino acids plus ammonia in both the leaves and the roots increased markedly, whereas it decreased when the plants were grown on media containing NO 3 ¯. Glutamine in the leaves and ammonia in the roots were the major components responsible for the variation induced by the addition of NH 4 + and NO 3 ¯. The level of total amino acids plus ammonia in Anahaena-free Azolla was comparable to that in Anabaena-containing Azolla when they were fed with NH 4 + . However, when fed with NO 3 ¯, the level of total amino acids plus ammonia in Anabaena-free Azolla was lower than that of diazo-trophic Azolla. The endophytes from stem apices contained a higher level of total amino acids plus ammonia than those from mature leaves. Ammonia was the major constituent of the two types of endophytes followed by glutamic acid, and phenylalanine was hardly observed. Glutamine was much less prevalent in the endophytes from mature leaves than in those from stem apices and in the intact leaf tissues. Arginine occurred only in the plants experiencing some degree of crowding and was predominantly localized in the endophytes, especially in the mature leaves.