Changes of ABA Content during Bulbing and Dormancy and in vitro Bulbing in Onion Plant

Abstract

Correlation between growth and dormancy, and changes in abscisic acid (ABA) levels was studied in onion (Allium cepa L. cv. Awaji Chukodaka). ABA in the growing tip, leaf, bulb and root tissues was identified by ECD gas chromatography. ABA was detected in all tissues and their levels varied depending on the developmental stages of onion. Higher concentration of ABA was observed in the growing tip and was about twice that in other tissues. An increase in endogenous ABA level commenced at the onset of bulbing and attained the highest level at the time of lodging. Although a high level was observed during the dormant stage, the level gradually decreased during storage period. It was at its lowest at the end of dormancy, one month after storage. Upon sprouting, ABA level increased again in sprouted leaves.
In vitro bulbing of plantlets from apices was induced by the exogenous application of NAA or BA, but it was neither promoted nor inhibited by ABA or GA treatments.