Content of protein-amino acids in the buds and effect of trunk injection treatment of asparagine, arginine, and abscisic acid on development of spur buds and flower bud differentiation in apple trees

The effect of amino acids as nitrogen source on flower bud differentiation was studied in order to clarify one of the internal factors influencing the flower bud differentiation in apple trees. Amino acids content of spur bud, terminal bud and lateral bud of shoot was analyzed and amino acids were injected into branches in order to investigate the effect on the spur development and flower bud differentiation as compared with abscisic acid treatment in Fuji and Spur EarliBlaze cultivars. Among protein-amino acids contained in spur bud, terminal bud and lateral bud of shoot in Fuji and Spur EarliBlaze cultivar, aspartic acid was highest and followed by glutamic acid, threonine, and serine, in this order. Content of total protein-amino acids was highest in spur bud of Fuji and terminal bud of shoot of Spur EarliBlaze, but percent of amino acids was higher in lateral bud than in spur bud and terminal bud of shoot in both cultivars. Effect of amino acid injection on the development of spur buds showed a little increase in spur bud size in the treatment of 1.0 and 2.0% concentration of asparagine and 0.1, 1.0% of arginine, but there was no significant increase. High concentration of 200 and 300 ppm of abscisic acid reduced considerably the size of spur bud and number of bud scales. Rate of flower differentiated spur buds was increased by injection of low concentration of asparagine and arginine and the rate of burst buds was not different with control. However, higher concentration above 0.5% of asparagine and above 5.0% of arginine reduced significantly flower bud differentiation and increased significantly burst buds. Low concentration up to 100 ppm of ABA increased the rate of flower differentiated spur buds and reduced the rate of burst buds, but high concentration of 200 and 300 ppm reduced significantly the rate of flower-differentiated buds and increased drastically inhibited buds to open