Agriculture Reference
In-Depth Information
with the enzymes regulating their metabolism and depend greatly on envi-
ronmental conditions, especially stress.
Polyamines can be isolated commercially from plant as well as micro-
bial sources. Among plant sources they can be isolated from leaves and
stems of corn (
Zea mays
L.), cucumber (
Cucumis sativus
L.), oat (
Avena
sativa
L.) and radish (
Raphanus sativus
L.). They can also be isolated
from
Saccharomyces cerevisiae
and
Candida utilis
.
16.6.1 POLYAMINES IN POSTHARVEST MANAGEMENT OF
FRUITS
Polyamines have been proposed to be a new category of plant growth reg-
ulator and are proposed to be involved in large spectrum of physiological
and biological processes of fruits. Polyamines in their free forms have
been reported as antisenescent agent, from both endogenous and exoge-
nous applications (Valero et al., 1998). The main effects of PAs in post har-
vest management of fruits are- inhibit biosynthesis of ethylene, increase
fruit firmness, reduce respiration rate, reduce chilling injury, retard color
changes and reduce mechanical damage.
To investigate the role of putrescine in ethylene biosynthesis in plum,
Khan et al. (2007) treated the fruits by dipping in aqueous solution contain-
ing different concentrations of putrescine (1 mM, 2 mM) and Tween-20
(0.01%) as a surfactant. Following PUT treatment fruits were stored at 0 ±
1 °C and 90 ± 5% RH for 6 weeks. Results found that PUT treatment re-
duced ethylene production during storage in 'Angelino' plum fruits. There
was an inverse relationship between concentration of PUT and ethylene
production rate. The reduction in ethylene production with PUT treatment
attributed to competitive biosynthesis mechanism between ethylene and
polyamine.
The effect of polyamine on maintaining fruit firmness can be attributed
to their cross-linkage to the carboxyl group of the pectic substances in the
cell wall, resulting in rigidification thus blocks the access of degrading
enzymes and reducing rate of softening (Valero et al.
,
2002). Post harvest
treatment of fruits with polyamine found effective on increasing fruit firm-
ness in apple, plum mango, apricot, lemon, etc., however, the efficiency
was generally greater for those molecules with higher number of available
cations, that is SPM
+4
>SPD
+3
>PUT
+2
.
