Changes in the contents of four free amino acids in anthers from tulip bulbs cultivar ‘Apeldoorn’, stored at 5 or 17°C, as criteria related to cold treatment

Abstract

Asparagine, aspartic acid, glutamic acid and glutamine were estimated in freeze-dried anthers from tulip bulbs precooled at 5°C for 12 weeks and subsequently at 17°C for 1 week (transport simulation), and from a control batch kept at 17°C. Based on the patterns of changes of these 4 free amino acids, we deduced the following: (1) the asparagine content could be an indicator of cold treatment: it was less than 7 mmol kg −1 for cold-stored bulbs and higher than 15 mmol kg −1 for the control; (2) an aspartic acid content of 3–6 mmol kg −1 could indicate that cold treatment had lasted for at least 11 weeks. These criteria apply to laboratory-scale tests; (3) the contents of glutamine and glutamic acid cannot be used as criteria of cold treatment because they are similar in treated and control bulbs during 1 week of transport simulation.