Quantifying the Influence of Select Plant Growth

Transcription

Quantifying the Influence of Applications of Select
Plant Growth Regulators on Height and Tillering
of Ornamental Grasses
Sonali Padhye and Jude Groninger
Department of Environmental Horticulture, University of Florida,
West Florida Research and Education Center (WFREC)
5988 Highway 90, Bldg 4900, Milton, FL 32583
Introduction
The popularity of ornamental grasses has soared in the recent years, increasing their market demand.
Ornamental grasses are not only used in the landscape, but have become a prominent design element
in mixed containers, a growing segment of the floriculture industry. Ornamental grasses comprise of
grasses and grass-like plants are monocots from several families including Poaceae (grass family),
Cyperaceae (sedge family), Juncaceae (rush family), Restionaceae (restio family) and Typhacea (cattail family).
Regulating the plant height and increasing the number of tillers per plant and are significant to
commercial ornamental grass growers for improving the crop quality. Since grasses are monocots,
applications of plant growth retardants (PGRs) developed for the height control of dicots such as
common bedding plants provide varying degrees of height control and published information on
height control of ornamental grasses is limited. Additionally, to our knowledge, no published
studies have investigated the influence of benzyladenine on increasing branching of ornamental
grasses. The objective of this study was to quantify the influence of applications of select plant
growth regulators on height control and tillering of ornamental grasses.
Materials and Methods
Young propagules of Carex buchananii, Carex comans ‘Frosted Curls’, Carex flagellifera ‘Toffee
Twist’, Cortaderia selloana ‘Rosea’, Miscanthus sinensis ‘Gracillimus’, and Muhlenbergia
capillaries were received from a commercial grower (Figure 1).
Figure 1. Plugs of Carex buchananii (A), Carex comans ‘Frosted Curls’ (B), Carex
flagellifera ‘Toffee Twist’ (C), Cortaderia selloana ‘Rosea’ (D), Miscanthus sinensis
‘Gracillimus’ (E), and Muhlenbegia capillaris (F) at the initiation of the experiment.
A
B
C
D
E
F
Height Control and Branching of Ornamental Grasses
©Padhye and Groninger, University of Florida 2008
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Plants were transplanted in a peat-based medium (Fafard 3B) and grown in a polycarbonate
greenhouse at WFREC, Milton under a 16-hour photoperiod provided as a day-extension from 5 pm
to 12 am using high-pressure sodium lamps. Plants received two foliar sprays of PGRs (volume of 2
quarts/100 ft2, with Capsil as a surfactant). The treatments are outlined in the table below:
Plant Growth Regulator
Application Rate
Benzyladenine [(BA) Configure; Fine Americas]
500 or 1000 ppm (mg·L−1)
Concise (Uniconazole; Fine Americas)
20 or 40 ppm
Trinexapac-ethyl (turf PGR for comparison; Primo; Syngenta)
220 ppm (label rate)
The first PGR application was made after the plants were established
in containers and the roots of plants were visible around the containers
(Figure 2).
The experimental schedule is below:
Date
Activity
6/24/2008
Plug receipt and transplant
7/15/2008
Spray 1
7/22/2008
Spray 1
7/31/2008
Spray 2
7/29/2008
2-week data
8/6/2008
2-week data
8/12/2008
4-week data
8/19/2008
4-week data
9/8/2008
8-week data
9/17/2008
8-week data
Figure 2. Timing of the
first PGR application.
Species
Carex, Cortaderia, Miscanthus, Muhlenbergia
Carex
Cortaderia, Miscanthus, Muhlenbergia
Carex, Cortaderia, Miscanthus, Muhlenbergia
Carex
Carex
Carex
A non-sprayed control was maintained. Ten plants were subjected to each treatment combination.
The fertility and pest management was as per standard protocols developed at WFREC. The plant
height (from surface of the medium to the tallest point of grass) and the number of tillers per plant
were recorded at weeks 2, 4 and 8 weeks after the first PGR application.
Results and Discussion
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Figure 3. The influence of PGR sprays on the height of ornamental grasses.
Control
90
Carex buchananii
Benzyladenine
Carex buchananii
A
Uniconazole
Carex buchananii
B
Trinexapac-ethyl
C
Carex buchananii
D
G
Carex comans
H
K
Carex flagellifera
L
O
Cortaderia selloana
P
S
Miscanthus sinensis
T
W
Muhlenbergia capillaris
X
8
0
8
80
70
60
-1
-1
500 mg·L
-1
1000 mg·L
20 mg·L
-1
40 mg·L
50
Carex comans
Carex comans
E
Carex comans
F
45
40
35
-1
-1
500 mg·L
-1
1000 mg·L
30
90
Carex flagellifera
80
Carex flagellifera
J
-1
-1
500 mg·L
-1
1000 mg·L
70
Height (cm)
Carex flagellifera
I
20 mg·L
-1
40 mg·L
20 mg·L
-1
40 mg·L
60
50
Cortaderia selloana
175
M
Cortaderia selloana
-1
-1
500 mg·L
-1
1000 mg·L
150
Cortaderia selloana
N
20 mg·L
-1
40 mg·L
125
100
75
Miscanthus sinensis
140
Q
Miscanthus sinensis
Miscanthus sinensis
R
120
100
80
60
120
-1
-1
500 mg·L
-1
1000 mg·L
U
105
20 mg·L
-1
40 mg·L
V
-1
-1
500 mg·L
-1
1000 mg·L
20 mg·L
-1
40 mg·L
90
75
60
0
2
4
6
8
0
2
4
6
8
0
2
4
Time (weeks)
6
2
4
6
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Figure 4. The influence of PGR sprays on the tiller number of ornamental grasses.
Control
Carex buchananii
Benzyladenine
Carex buchananii
A
Uniconazole
Carex buchananii
B
Trinexapac-ethyl
C
Carex buchananii
D
G
Carex comans
H
K
Carex flagellifera
L
O
Cortaderia selloana
P
S
Miscanthus sinensis
T
W
X
8
0
8
80
-1
-1
500 mg·L
-1
1000 mg·L
60
20 mg·L
-1
40 mg·L
40
20
Carex comans
Carex comans
E
200
-1
-1
500 mg·L
-1
1000 mg·L
150
Carex comans
F
20 mg·L
-1
40 mg·L
100
50
0
Carex flagellifera
140
Carex flagellifera
I
-1
Tillers (no.)
-1
500 mg·L
-1
1000 mg·L
105
Carex flagellifera
J
20 mg·L
-1
40 mg·L
70
35
Cortaderia selloana
12
M
Cortaderia selloana
-1
-1
500 mg·L
-1
1000 mg·L
9
Cortaderia selloana
N
20 mg·L
-1
40 mg·L
6
3
0
Miscanthus sinensis
100
Q
Miscanthus sinensis
-1
-1
500 mg·L
-1
1000 mg·L
80
Miscanthus sinensis
R
20 mg·L
-1
40 mg·L
60
40
160
U
V
-1
-1
500 mg·L
-1
1000 mg·L
120
20 mg·L
-1
40 mg·L
80
40
0
2
4
6
8
0
2
4
6
8
0
2
Time (weeks)
4
6
2
4
6
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Table 1. Increase in the average plant height between two measurements ± standard error (SE) of 10
replicates for six ornamental grass species.
Weekz of
preceding
measurement
Week of
succeeding
measurement
0
2
4
2
4
8
Increase in the average plant height between two measurements (cm) ± SE
C.
C.
comans
flagellifera
C.
C.
‘Frosted
‘Toffee
selloana
M. sinensis
M.
buchananii
Curls’
Twist’
‘Rosea’
‘Gracillimus’
capillaris
Control
5.3 ± 1.4
1.3 ± 0.5
2.6 ± 0.7
41.8 ± 2.6
23.3 ± 2.6
8.4 ± 1.9
3.7 ± 1.0
3.6 ± 0.8
7.1 ± 1.2
32.9 ± 1.5
15.5 ± 1.1
7.9 ± 1.6
6.7 ± 2.3
3.6 ± 0.9
17.8 ± 1.3
19.5 ± 1.5
14.7 ± 2.2
22.2 ± 3.0
2
4
8
1.0 ± 0.5
0.8 ± 0.3
0.4 ± 0.3
500 mg·L−1 Benzyladenine
1.7 ± 1.0
30.9 ± 2.4
3.1 ± 0.7
31.5 ± 1.5
18.2 ± 1.4
14.3 ± 1.7
26.8 ± 1.6
17.3 ± 1.6
14.6 ± 1.8
6.9 ± 2.6
0.8 ± 0.5
19.4 ± 3.2
0.9 ± 0.5
0.7 ± 0.2
0.2 ± 0.1
3.3 ± 1.2
28.5 ± 5.1
1.8 ± 0.5
30.6 ± 1.5
12.4 ± 1.9
14.9 ± 2.4
30.9 ± 1.9
15.5 ± 2.7
12.9 ± 2.1
5.1 ± 1.5
0.4 ± 0.2
18.0 ± 2.9
0.7 ± 0.3
0.2 ± 0.1
0.1 ± 0.1
20 mg·L−1 Uniconazole
2.5 ± 1.0
20.4 ± 3.9
0.8 ± 0.3
22.8 ± 1.8
6.2 ± 2.0
7.7 ± 3.0
23.7 ± 2.6
16.2 ± 1.4
11.2 ± 1.4
9.5 ± 2.5
5.2 ± 1.6
20.7 ± 2.2
0.5 ± 0.2
0.0 ±0.0
0.0 ±0.0
1.5 ± 0.4
12.9 ± 4.1
0.2 ± 0.1
21.0 ± 2.3
4.4 ± 1.8
5.8 ± 2.3
23.0 ± 2.7
15.2 ± 2.8
23.3 ± 2.4
6.9 ± 2.5
3.4 ± 1.4
27.9 ± 1.7
1.4 ± 1.0
0.5 ± 0.2
0.0 ±0.0
220 mg·L−1 Trinexapac-ethyl
0.5 ± 0.3
8.5 ± 1.8
0.5 ± 0.2
15.1 ± 1.5
6.1 ± 1.6
4.0 ± 1.2
11.9 ± 2.0
2.2 ± 0.3
14.9 ± 3.1
3.3 ± 0.8
0.1 ± 0.1
0.2 ± 0.1
0
2
4
0
2
4
0
2
4
0
2
4
0
2
4
2
4
8
2
4
8
2
4
8
2
4
8
6.2 ± 2.1
2.5 ± 0.7
11.6 ± 2.5
2.8 ± 1.0
3.3 ± 0.8
10.6 ± 1.9
2.6 ± 1.0
0.8 ± 0.3
2.2 ± 1.1
5.6 ± 2.1
0.4 ± 0.3
1.0 ± 0.6
1.7 ± 0.4
0.5 ± 0.3
10.2 ± 2.8
z
week of the first PGR application was considered as week 0.
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Table 2. Increase in the average tiller number between two measurements for six ornamental grass
species.
Weekz of
preceding
measurement
Week of
succeeding
measurement
0
2
4
2
4
8
Increase in the average tiller number between two measurements (no.)
C.
C. comans
flagellifera
C.
C.
‘Frosted
‘Toffee
selloana
M. sinensis
M.
buchananii
Curls’
Twist’
‘Rosea’
‘Gracillimus’
capillaris
Control
4.4 ± 0.6
16.3 ± 1.1
9.1 ± 1.1
0.1 ± 0.1
16.8 ± 2.8
2.6 ± 0.6
13.5 ± 0.9
62.2 ± 3.4
37.4 ± 2.2
3.0 ± 0.7
53.6 ± 4.2
53.7 ± 2.6
25.9 ± 4.1
123.4 ± 15.7
48.6 ± 2.3
2.9 ± 0.3
28.8 ± 4.4
77.1 ± 4.4
2
4
8
2.7 ± 0.8
16.7 ± 2.3
2.7 ± 3.4
12.5 ± 1.9
72.9 ± 7.9
116.2 ± 16.0
14.8 ± 1.5
0.2 ± 0.1
43.1 ± 2.0
3.8 ± 0.4
46.3 ± 2.9
3.9 ± 0.5
7.5 ± 1.5
53.3 ± 4.8
30.3 ± 2.9
4.5 ± 1.1
47.4 ± 1.9
95.0 ± 4.0
3.0 ± 0.6
16.2 ± 1.6
22.7 ± 2.7
19.3 ± 3.2
15.2 ± 2.2
0.0 ± 0.0
60.7 ± 5.5
42.0 ± 1.6
3.4 ± 0.5
138.1 ± 16.6
50.0 ± 1.3
4.7 ± 0.9
8.8 ± 1.9
47.0 ± 3.7
25.4 ± 4.2
4.3 ± 1.3
53.8 ± 3.0
84.3 ± 6.4
12.4 ± 2.5
39.1 ± 2.5
108.3 ± 15.0
9.3 ± 1.4
0.3 ± 0.2
41.3 ± 1.9
4.2 ± 0.6
88.4 ± 8.4
5.3 ± 0.8
8.0 ± 2.2
56.9 ± 3.7
29.8 ± 2.9
3.7 ± 1.1
47.1 ± 2.0
86.2 ± 3.0
10.7 ± 2.2
47.1 ± 2.7
65.2 ± 10.9
7.8 ± 1.0
0.1 ± 0.1
37.8 ± 2.6
4.4 ± 0.6
56.2 ± 3.0
5.5 ± 1.0
5.9 ± 1.2
50.1 ± 3.2
22.0 ± 1.7
6.7 ± 1.0
44.2 ± 2.5
73.1 ± 3.1
7.0 ± 1.6
52.5 ± 3.6
28.3 ± 3.6
7.8 ± 1.8
34.4 ± 1.5
51.3 ± 4.1
0
2
4
0
2
4
0
2
4
0
2
4
0
2
4
2
4
8
2
4
8
2
4
8
2
4
8
2.8 ± 0.9
12.7 ± 3.0
36.5 ± 6.5
2.7 ± 0.5
11.1 ± 1.5
39.9 ± 3.8
4.2 ± 0.7
9.2 ± 1.7
21.5 ± 2.4
220 mg·L−1 Trinexapac-ethyl
13.1 ± 1.9
5.5 ± 1.1
0.6 ± 0.2
47.9 ± 4.3
46.8 ± 2.0
3.2 ± 0.5
312.6 ± 10.3
39.8 ± 3.3
6.5 ± 0.6
z
week of the first PGR application was considered as week 0.
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Carex buchananii
Figure 6. The influence of PGR applications on height and tiller number of Carex buchananii.
Height Control
 Overall, at the concentrations tested, BA did not influence the average plant height compared
with the average height of controls (Figure 3A and B, Table 1).
 Uniconazole suppressed the increase in height by 52 to 89% between measurements compared
with the height increase of controls (Figure 3A and C). Forty ppm uniconazole suppressed the
increase in height at weeks 4 and 8 more compared with the height suppression by the 20 ppm
uniconazole treatment.
 Trinexapac-ethyl strongly suppressed the height for 4 weeks after the first application (Figure 3
A and D). However, after 8 weeks, the effect of trinexapac-ethyl wore off and the average height
after 8 weeks was higher than the heights of controls.
Tiller Number
 At the rates tested, BA, uniconazole, and trinexapac-ethyl application did not consistently
influence tiller production compared with the tiller production of controls (Figure 4A to D, Table
2).
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Carex comans ‘Frosted Curls’
Figure 7. The influence of PGR applications on height and tiller number of Carex comans
‘Frosted Curls’.
Height Control
 Compared with the controls, all PGRs tested provided height control for 8 weeks after the first
spray with an exception of trinexapac-ethyl after 2 weeks (Figure 3E to H, Table 1). This
suppression of height increased ranged between 20 to 100% depending on the PGR treatment
and timing of data recording.
 The low and high rates of BA and uniconazole elicited similar height responses.
 When produced in 1-gallon containers, Carex comans ‘Frosted Curls’ may not need height
control.
Tiller Number
 At the rates tested, BA and Trinexapac-ethyl did not influence the tiller number compared with
the controls (Figure 4E, F and H, Table 2).
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
Four and 8 weeks after the first spray, plants treated with uniconazole had fewer tillers compared
with the controls (Figure 4E and G).
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Carex flagellifera ‘Toffee Twist’
Figure 8. The influence of PGR applications on height and tiller number of Carex flagellifera
‘Toffee Twist’.
Height Control
 Although BA application provided some height control for up to 8 weeks from the first
application, this response was somewhat inconsistent between the rates used and timing of data
collection (Figure 3I to J and Table 1).
 The average height increase of plants treated with uniconazole was suppressed for 8 weeks from
the first spray compared with that of the controls (Figure 3I and K). Four weeks from the first
spray, the percent suppression of height increase with 20 and 40 ppm uniconazole-treated plants
was 89 and 97% compared with the height increase of the controls, respectively.
 Trinexapac-ethyl suppressed the increase in height by 83, 93, and 67% after 2, 4, and 8 weeks
compared to that of controls (Figure 3I and L).
Tiller Number
 The tiller number of BA-treated plants increased by over 60% compared with the tiller increase
of the controls 2 weeks after the first spray application (Figure 4I and J, Table 2). However after
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
4 and 8 weeks there was minimal to no increase in the number of tillers produced compared with
the controls.
With an exception of an 80% increase in tiller production of 20 ppm uniconazole treated plants
between week 4 and 8 after the first PGR application, the tillers of uniconazole and trinexapacethyl treated plants did not increase considerably (Figure 4I, K and L).
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Cortaderia selloana ‘Rosea’
Figure 9. The influence of PGR applications on height and tiller number of Cortaderia
selloana ‘Rosea’.
Height Control
 All PGRs provided some height control (Figure 3M to P, Table 1). Both concentrations of BA
provided similar height suppression and at week 2 and 8 from the first spray, the suppression of
height increase was over 20% compared with the height increase in the controls. At week 4 from
the first application, the suppression of height increase was minimal (less than 10%) compared
with the height increase of the controls.
 The suppression in height increase by uniconazole was dose-dependent with height increase in
40 ppm uniconazole-treated plants being suppressed more than that of the 20 ppm uniconazole
treatment. At weeks 2, 4, and 8 from the first sprays, the height increase of 40 ppm uniconazoletreated plants was suppressed by 69, 36, and 70%, respectively compared with the height
increase of the controls.
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
Trinexapac-ethyl suppressed the height increase the strongest compared with BA and
uniconazole. At weeks 2, 4, and 8 from the first sprays, the height increase of 40 ppm
uniconazole-treated plants was suppressed by 80, 54, and 80%, respectively compared with the
height increase of the controls.
Tiller Number
 On average, Cortaderia selloana ‘Rosea’ plants had 3 to 10 tillers for up to 8 weeks (Figure 4M
to P). Although the average increase in tillers for PGR-treated plants and controls somewhat
varied, due to low tiller numbers, no conclusions can be drawn regarding the influence be PGRs
on the increase in tillers compared with that of the controls (Table 2).
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Miscanthus sinensis ‘Gracillimus’
Figure 10. The influence of PGR applications on height and tiller number of Miscanthus
sinensis ‘Gracillimus’.
Height Control
 BA provided minimal to no height control of Miscanthus sinensis ‘Gracillimus’ (Figure 3Q and
R, Table 1).
 Twenty and 40 ppm uniconazole provided 19 and 22% suppression of height increase 2 weeks
after the first spray however, after 4 and 8 weeks this height increase suppression was either
negligible or inconsistent (Figure 3Q and S).
 Trinexapac-ethyl provided the most suppression of height increase compared with that provided
by BA and uniconazole treatments (Figure 3Q to T). Two, 4, and 8 weeks after the first
application, the height increase of plants treated with trinexapac-ethyl was suppressed by 59, 86,
and 0%, respectively compared with that of the controls.
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Tiller Number
 No PGR application elicited a greater percent increase in tillers compared with that of controls
(Figure 4Q to R, Table 2).
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Figure 11. The influence of PGR applications on height and tiller number of Muhlenbergia
capillaris.
Height Control
 The increase in height of BA-treated plants was suppressed by 17 to 96% compared with that of
the controls in up to 8 weeks from the first BA application (Figure 3U and V, Table 1). The
highest height increase suppression was recorded at week 4 and was 90 and 96% for 500 and
1000 ppm BA treatments, respectively.
 The height control provided by uniconazole was somewhat inconsistent (Figure 3U and W). The
maximum (57%) suppression of height increase was recorded by 40 ppm uniconazole treatment
at 4 week from the first spray.
 Trinexapac-ethyl elicited the strongest height suppression compared with the other PGR
treatments (Figure 3U to X). Two, 4, and 8 weeks after the first application, the height increase
of plants treated with trinexapac-ethyl was suppressed by 61, 99, and 99%, respectively
compared with that of the controls.
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Tiller Number
 Tillers of all PGR-treated plants increased more between week 0 and 2 compared with that of the
controls however, since this increase in tiller number ranged between 4 to 8 additional tillers
only (Figure 4U to X). This increase in tiller numbers was diminished or inconsistent after 4 and
8 weeks from the first spray.
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Conclusions
Benzyladenine (BA)
 BA applications suppressed height increase of Carex comans ‘Frosted Curls’, Cortaderia
selloana ‘Rosea’, and Muhlenbergia capillaris by 20 to 96, 4 to 32, and 13 to 96% compared
with that of the controls, respectively, depending on the application rate and timing of data
collection. Although some BA treatments suppressed the height increase of Carex flagellifera
‘Toffee Twist’ compared with that of controls, this suppression was inconsistent with BA rates
and timing of data reporting. BA either did not suppress the height increase or suppressed it
inconsistently for Carex buchananii and Miscanthus sinensis ‘Gracillimus’.

BA application enhanced the increase in tiller number by more than 60% after 2 weeks from the
first application compared with that of controls for Carex flagellifera ‘Toffee Twist’ and
Muhlenbergia capillaris. Conversely, after 4 and 8 weeks, this enhancement was either
diminished or inconsistent. BA did not enhance the tiller production in Carex buchananii, Carex
comans ‘Frosted Curls’, and Miscanthus sinensis ‘Gracillimus’. However, due to the low overall
tiller numbers, the enhancement in tiller production of Cortaderia selloana ‘Rosea’ was
inconclusive.
Uniconazole
 Overall, uniconazole provided stronger height suppression than that with controls in the three
Carex species tested which belong to the sedge family. However, Trinexapac-ethyl suppressed
the height more strongly compared with the uniconazole in the three remaining ornamental
grasses from the grass family. Typically, the suppression in height increase elicited by 40 ppm
uniconazole treatment was not considerably higher than the 20 ppm treatment. Uniconazole
treatment did not suppress the height increase of Miscanthus sinensis ‘Gracillimus’ and
Muhlenbergia capillaris while the height increase in the remaining species was successfully
suppressed by uniconazole.

Uniconazole did not influence the increase in tiller number.
Trinexapac-ethyl
 Trinexapac-ethyl provided a strong height control of Cortaderia selloana ‘Rosea’, Miscanthus
sinensis ‘Gracillimus’, and Muhlenbergia capillaris. Overall, this PGR also controlled the
heights of the three Carex species, although typically uniconazole elicited a stronger height
control.

Trinexapac-ethyl did not enhance tiller production compared with the controls.
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Quantifying the Influence of Select Plant Growth

Transcription

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