In
lettuce seeds, the maturation temperature influences seed
germination by affecting ET production [50]. The intervention
of ET during the maintenance of seed dormancy and during the
transition from dormancy to germination constitutes parts of a
puzzle with many pieces still missing. Opinions vary
concerning the developmental stage during which ET regulates
dormancy; some suggest that ET acts minimally during
dormancy inception and that its major action is during
imbibition to terminate dormancy and/or initiate germination
[39]. However, the inhibitory effect on germination by ABA
may be partially reversed by the addition of ACC