ROLE OF ETHYLENE ON SPROUTING OF ONION BULBS (ALLIUM CEPA L.)

Ethylene is a volatile hormone that has received considerable interest as a regulator of plant growth and is involved in numerous aspects of plant life. It has long been recognized as a crucial factor in the storage of horticultural products, and was employed in various cultural and postharvest practices long before it was identified as the causative agent (Abeles et al., 1992). It has been shown that sprouting of onion bulbs is controlled by some hormones which inhibit (abscissic acid) or promote (cytokinins) growth, and ethylene may also inhibit or promote bud growth by regulating these factors. However, its role in breaking dormancy and promoting sprouting of onion bulbs remains unclear (Woltering & Sterling, 1986; Abeles et al., 1992). Exogenous ethylene (ethephon) has been used to overcome the dormancy of both Gladiolus (Halevy et al., 1970) and Liatris (Keren-Paz et al., 1989) corms. In addition to promoting sprouting of gladiolus, ethephon increases the effectiveness of fungicides, apparently by increasing their penetration into corm tissues (Simchon et al., 1972). In this investigation, we have studied the role of ethylene (ethephon) and silver thiosulfate (STS), a patent inhibitor of ethylene action, on the sprouting of onion bulbs during storage.