Further studies on the use of free amino acids in anthers from tulip bulbs cultivar ‘Apeldoorn’ as indicators about cold treatment at 5°C

Abstract

Twenty-one free amino acids were estimated in freeze-dried anthers from tulip bulbs cooled at 5°C for 12 weeks and subsequently kept at 17°C for 1 week (transport simulation (TS)), and from a control batch kept at 17°C. By comparing the patterns of changes of these amino acids in controlled laboratory trials with the contents in anthers from nine batches of special precooled (12 weeks at 5°C) bulbs from different regions of The Netherlands (“practical samples”), we deduced the following. (1) Arginine, asparagine, glycine, histidine, lysine and tryptophan contents lower than 108, 6, 3, 4, 5 and 3 mmol kg −1, respectively, indicated bulbs that had been precooled. (2) An aspartic acid content lower than 7 mmol kg −1 indicated that cold treatment had lasted for at least 10 weeks. (3) Only aspartic acid constitutes a criterion for duration of treatment.