5. Conclusions
Premature fruit drop is often associated with abiotic stresses. During
the early development, apple fruit are exposed to abnormal cold
conditions following temperature fluctuations. Our results indicate that
apple trees having early developing fruit produce signals for abscission
induction in response to cold. Once the initial elevation of ABA
biosynthesis in the pedicel spreads to adjacent organs, increased ABA
signalling orchestrates cold response. AZ development is coordinated
with the signals for cell wall modification produced in the branch and
inhibition of negative hormones in the fruit. Based on these findings,
we suggest that ABA-dependent responses to cold contribute to abscission
induction signalling in early developing apple.