Variations in the content of free and bound amino acids during dormancy and the first cell cycle in Helianthus tuberosus tuber explants

Abstract

Abstract Qualitative and quantitative analysis of free and bound amino acids and amides during dormancy and the most important phases of the first cell cycle was carried out in tubers of Helianthus tuberosus. In the dormant tuber arginine was confirmed to be the most abundant amino acid. A high amount of asparagine was also present; on the contrary glutamine was found in very low concentrations. During the progression of dormancy, all the free amino acids and amides declined while aspartic and glutamic acid increased. During the G1 phase of the first cell cycle induced by 2,4-D, all the free amino acids and amides decreased with the exception of glutamic acid. At 18, 20, 24 h of activation with 2,4-D, corresponding to the S phase and the beginning of mitosis, bound amino acids were also determined. In these phases of the cell cycle they increased reaching a maximum at 20 h; on the other hand the free amino acid and amide content, especially aspartic acid, asparagine and arginine, decreased with the exception of glutamic acid, alanine and phenylalanine.