Agriculture Reference
In-Depth Information
before harvest. Wang et al. (2011) studied that ethanol vapor treatment
(250 or 500 mL/L for 3 hr) alone or in combination with hot air treatment
(48ºC for 3 hr) in Chinese bayberries significantly lower decay incidence
caused by
Verticicladiella abietina, Penicillium citrinum
or
Trichoderma
viridae
compared to control. Ethanol acts as a precursor of natural aroma
compounds. Ethanol is converted to acetaldehyde by enzyme alcohol de-
hydrogenase. Acetaldehyde is the precursor for the acetate esters. Thus
Berger and Drawert (1984) reported that storage of 'Red Delicious' apples
for 24 hr in an atmosphere containing ethanol vapors resulted in more than
three-fold increase in the ethyl ester formation. The effect of ethylene on
a range of climacteric fruit has been shown to enhance or inhibit ripening
depending on the type of fruit. Another application is to enhance the an-
thocyanin content in fruit tissues as reported in bayberry fruit when treated
with 1000 mL/L ethanol (Zhang et al., 2007). Spraying Cabernet Sauvi-
gnon grapes with 5% ethanol at veraison stage also enhances anthocyanin
accumulation (Kereamy et al., 2002). Postharvest application of ethanol
vapor in 'Amas' bananas and in persimmon removes the astringency (Es-
guerra et al., 1992; Khademi et al., 2010). Ethanol reacts with soluble
tannins to form an insoluble gel, which is nonastringent. Ethanol vapor
exposure of fruits also has insecticidal activity as reported by Dentener et
al. (2000) in apples against
E. postvittana
. Application of ethanol vapors
was also effective in reducing farnesene and conjugated trienes, involved
in the development of scald in 'Granny Smith' apples (Ghahamani et al.,
1999). Thus exogenous application of ethanol can be beneficially applied
to many fruits for improving their aroma, controlling decay, delaying rip-
ening and ethylene production and reduction of chilling injury symptoms.
16.6 POLYAMINES
Polyamines (PAs) are low molecular weight small aliphatic amines that
are ubiquitous in living organisms and have been implicated in a wide
range of biological processes, including plant growth, development and
response to stress (Smith, 1985). In plants, they have been implicated in
a wide range of biological processes, including growth, development and
abiotic stress responses. The most common polyamines are Putrescine
(PUT), Spermidine (SPD) and Spermine (SPM) found in every plant cell
in titers ranging from approximately micromolar to millimolar, together
