In the name of GOD
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The effects of gibberellin4+7 on the
vase life and flower quality of
Alstroemeria cut flowers
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Introduction
growers often encounter an appreciable
loss in quality of cut Alstroemeria flowers
as a result of leaf senescence due to
chlorophyll loss, thereby incurring
significant postharvest
losses.
Obviously, the maintenance of green
colour in the leaves is an important quality
attribute in these economically significant
ornamental plants.
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This problem, which is also known as the‘senescence
syndrome’ is a complex, genetically determined
programmed cell death characterised by a decline in the
concentration of several macromolecules, including total
protein, RNA,Plant Growth
membrane lipids and chloroplast degradation(Weaver et
al. 1998).
Senescence is a normal catabolic process

that enables the plant to salvage and
redistribute its carbon and nitrogen into growing tissues
(Bleecker 1998).
The initiation and progression of leaf

senescence can be influenced by
both internal and external factors such as extremes of
temperatures, moisture, pathogens, radiation
intensity and duration (Smart 1994; Weaver et
al.1998).
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Smart (1994) stated that a decrease in photosynthesis
below a threshold level might als function as a signal to
induce leaf senescence.
However, internal senescence-inducing factors
i.e.ethylene and abscisic acid (ABA) appear to be
hormonally regulated (Thimann 1980; Weaver et al.
1998). In contrast, phytohormones, such as cytokinins
and in some cases gibberellins (GA),
can delay the loss of chlorophyll (Thimann 1980).
Recently, it has been reported that plant growth
regulators containing both benzyladenine (BA) and
GA4+7 in the form of AccelR can reduce leaf
chlorosis in Alstroemeria (Mutui et al. 2001) and Easter
lilies (Han 1997; Ranwala and Miller 1999; Ranwala et
al. 2003).
Although both BA and GA4+7 are effective in preventing leaf yellowing,GA4+7
is much more effective than BA as a spray at lower concentrations (Han 1997;
Mutui et al.
2001; Ranwala et al. 2003). Han (1995) suggests that BA has a synergistic
effect when combined with GA3 in delaying the onset of leaf chlorosis in
Easter lily. The leaf yellowing in Alstroemeria associated with chlorophyll
breakdown can be reduced by treatment with thidiazuron (TDZ) (Ferrante et al.
2002), GAs or cytokinins (Jordi
et al. 1995; Mutui et al. 2003), whereas auxins and polyamines had no effect
(Jordi et al. 1995).
Also, bioactive GAs are perceived by a putative plasma membrane receptor
and may affect both ethylene biosynthesis and response (Sun and Gubler
2004).
While leaf senescence and yellowing is under the control of many hormones
(Zacarias and Reid 1990), premature leaf yellowing seems to be associated
with low concentrations of GAs in the leaves of certain cultivars of
Alstroemeria (Dai and Paull 1991).
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Beevers (1966) also suggested relationship between GA
concentration in the leaves of Tropaeolum majus and the onset of
senescence.
However, dark-incubated leaf discs of Rumex species showed
delayed senescence when exogenous GAs were applied (Whyte
and Luckwill
The present study was performed to investigate the effect of
GA4+7 on vase life, leaf chlorophyll concentration and overall
post-harvest quality of Alstroemeria cut flowers. Alstroemeria
leaves offer a good model system, in which the leaf chlorosis
response is easily detected, and thus can provide insight into the
possible mode of action of GAduring leaf senescence.
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Materials
Plant materials
Cut flowers of Alstroemeria cvs ‘Yellow King’ and
‘Marina’ from 24 month-old-stock plants were obtained from a commercial farm
Chemicals
Treatments and experimental design
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methods
Vase Life parameters
Leaf chlorophyll determination
nitrogen concentration determination
Statistical analysis
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Results
Vase life of Alstroemeria cut flowers Gibberellins
(GA4+7) applications had no significant effect on the
number of days to full opening
of primary florets in Alstroemeria cut flowers, except in
the first experiment when 10 mg l1 GA4+7 delayed full
opening of primary florets by 0.8 days,
which is an 18% delay (Table 1). The cultivar differences
were highly significant (p £ 0.05) with ‘Yellow King’
taking 1.3 and 0.8 more days than
‘Marina’ to open, in the first and second
experiments,respectively (Table 1).
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Chlorophyll concentration
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Leaf nitrogen concentration
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Discussion
The lack of effect by GA4+7 treatment on the opening of
primary florets of Alstroemeria can possibly be attributed
to the low concentrations of GA4+7 (2.5–15.0 mg l1) used
in this study.
Cywinska-Smoter et al. (1978) reported.
the onset of Alstroemeria cut flower senescence, The
GA4+7 treatments used here significantly delayed with
all concentrations having a beneficial effect
via increased flower longevity (Table 1).
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Studies with nasturtium (Tropaeolum majus L.) suggest
a relationship between GA concentration in leaves and
the timing of the onset of senescence (Beevers 1966)
with concentrations of GA declining as senescence
begins.
while the delay in appearance of leaf chlorosis caused
by GA4+7, in the current study, seems to be linked to
increased concentrations of GA4+7 in leaves.
Application of GA4+7 retarded chlorophyll degradation,
even at the lowest doses as evident with maintenance of
leaf nitrogen concentrations in Alstroemeria leaves (Table
2). Though the mechanistic basis of applied GA4+7, on
retarding
leaf senescence, is not clear (van Doorn et al.
1992), our results show that GA4+7 maintained higher leaf
nitrogen concentrations. Applied GA3 is also known to
interfere with the biosynthesis of carotenoids and
anthocyanins when used to retard ripening of tomatoes
(Dostal and Leopold 1967).
Gibberellins have been shown to enhance the regreening of
Valencia oranges, indicating that they act as retardants of
chloroplast degradation and not merely as inhibitors of
senescence(Goldschmidt 1974).
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Taken together, these results suggest that leaf
yellowing in cut stems of Alstroemeria is caused by
chlorophyll and protein degradation. Thus, inclusion
ofGA4+7 in the holding solutions for transport of the
flowers may arrest nitrogen breakdown during
chloroplast degradation, thereby delaying the onset of
leaf senescence and prolonging the vase life of
Alstroemeria cut flowers.
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Thank you for attention!!
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