phenylalanine and 3 mL of 50 mM borate buffer (pH 8.5). After
incubation of the mixture at 40 C for 1 h, the reaction was stopped
by adding 0.1 mL of 5 mM HCl. PAL activity was measured at room
temperature. PAL activity was calculated from the absorbance of
the assay mixture at 290 nm, based on the production of cinnamic
acid. PAL enzyme activity expressed as mmol of cinnamic acid
mg1 protein h1.
PPO was extracted and assayed using the method of by Nguyen
et al. (2003). One gram of spathe was homogenized in 10 mL of
phosphate buffer (0.1 M, pH 7.8) with 1 g of polyvinylpyrrolidone
(PVP), and the solution was then centrifuged at 20000
g for
15 min at 4 C. The supernatant was collected as a crude PPO
extract. The reaction mixture contained 0.1 M catechol in 0.05 M
phosphate buffer (pH 6.0). Changes in the absorbance at 410 nm
were measured. One unit of PPO activity was defined as a change of
0.01 at 410 nm in the absorbance per min. PPO activity expressed as
mkat per mg 1 protein. Protein content was estimated according to
Bradford (1976) using BSA as a standard.
2.7. Statistical analysis
The experiment was arranged as split plots for time on the basis
of completely randomized design with three replications. Analysis
of variance (ANOVA) was carried out with SPSS software. Differ-
ences between means were assessed by Tukey–Kramer’s multiple
range test with differences being considered significant at P < 0.05.
3. Results
3.1. Chilling injury symptoms and vase life
CI score increased during the whole storage at 4 C and the
increase was delayed by pre and postharvest GABA treatment
(P < 0.01; Figs. 1 and 3). CI symptoms of anthurium cut
flowers cv.
Sirion were visible within 7 days of storage. Treatment with
preharvest GABA at 1 mM and postharvest GABA at 5 mM resulted
in a lower CI score (P < 0.01) as well as browning index (P < 0.05)
(Figs. 1–4), while pre and postharvest treatment with GABA at
20 mM resulted in higher CI scores and browning indices. Thus,
GABA effects on CI of anthurium cut
flowers are concentration
dependent. Based on these results, 1 mM GABA for preharvest and
5 mM GABA for postharvest treatment was chosen for further
analyses. In this study, GABA was applied at pre and postharvest
stage and could significantly reduce postharvest CI in anthurium
cut
flowers (Figs. 1–4). The spathe browning in control anthurium
cut
flowers initiate after 4 days storage at 4 C, which show shortest
vase life, 16 days. But, in anthurium cut
flowers treated with 1 mM
GABA at preharvest and 5 mM GABA at postharvest stage, spathe
browning initiate after 8 and 7 days storage at 4 C, which show
longest vase life, 26 and 24 days, respectively