238 P. BISWAS ET AL.
stimulated or inhibited depending on the species (Watkins and Ekman
2004). For instance, low temperatures induced ethylene production in
apple (Knee et al. 1983; Larrigaudiere et al. 1997) and citrus (Cooper
et al. 1969; McDonald et al. 1985) but inhibited the synthesis of ACC
and ethylene production in plum (Larrigaudiere et al. 2009). Ethylene
production might be stimulated once the chilled fruit were transferred
to a reconditioning temperature (Cheng and Shewfelt 1988; Sanchez-Bel
et al. 2012); the magnitude of the ethylene peak began to decline as the
time of chilling was prolonged (Rugkong et al. 2011). A decrease in ethy-
lene stimulation by a longer chilling period was previously reported in
cucumber (Wang and Adams 1980), possibly as a result of chilling dam-
age to the system that converts ACC to ethylene (Cheng and Shewfelt
1988). In mango, after long-term cool storage (4 weeks), no significant
capacity to convert added ACC to ethylene was observed upon removal
to shelf-life conditions (Lederman et al. 1997). Tomato fruit stored at 3◦C
for 1 week showed increased ethylene production but the production
decreased when fruit were stored for 4 weeks and subsequently trans-
ferred to 20◦C (Rugkong et al. 2011). They found that increased ethy-
lene production in fruit stored for 1 week was associated with either
increased or unchangedACS2,ACS4,andACO1gene expression while
lower ethylene production in fruit stored for 4 weeks was associated
with reducedACS2,ACS4,andACO1gene expression. Results for the
expression of genes involved in ethylene signal transduction showed
different responses to chilling. For instance, expression of thenor(non-
ripening) receptor gene was markedly reduced by chilling that may have
delayed ripening (Tieman et al. 2000) whileLeETR1expression was
induced and the expression of theLeETR4receptor gene was downreg-
ulated by chilling (Rugkong et al. 2011).
It is, however, unclear if the rise or fall in ethylene production from
chilling is caused by or is a consequence of, or may play a role in
alleviating CI (Concellon et al. 2005). A surge in ethylene produc- ́
tion may be a mere response to low temperature stress in chilling-
sensitive species (Sevillano et al. 2009) or it could be related to ripen-
ing, and stress-induced ethylene production can be confounded with
ripening-associated ethylene production after cool storage (Watkins
2002). Importantly, it is unclear whether induced ethylene after sub-
sequent warming in higher temperature acts as a defense mechanism
directly to cope with chilling stress or indirectly helps fruit to advance
in ripening and thus reduces chilling sensitivity.
Although there is no clear-cut interpretation of the significance of
chilling-induced ethylene stimulation, chilling sensitivity of tissues can
be altered by application of exogenous ethylene. Ethylene application