Hydration treatment improves the performance of low vigour ...€¦ · Ageing reduced by hydration...
Transcript of Hydration treatment improves the performance of low vigour ...€¦ · Ageing reduced by hydration...
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Hydration treatment improves the
performance of low vigour seed lots of
pepper through metabolic repair
I. Demir, K. Mavi, B. B. Kenanoglu and T. Celikkol
University of Ankara, Turkey
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Peppers in Turkey
1990 2007
AREA 45.000 Ha 89.000 Ha
PRODUCTION 0.9 m tons 1.7 m tons
• 50% open pollinated cvs (50 t seed)
• Demre most popular cv (16% of seed)
• Produced from transplants under glass
• Some lots – poor seedling emergence, uniformity
• Worse in stress conditions e.g. low temperature
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Slow germination (high MGT)
Smaller (more variable transplants) Older seed (low CD)
MGT = Mean Germination Time = Mean lag period
(start of imbibition to radicle protrusion)
* Demir, Ermis, Mavi and Matthews (2008)
Recent research* on transplants
Longer lag period in aged seeds – needed for metabolic repair?
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Objective:
• To provide evidence that metabolic repair explains
differences in rates of germination (MGT / mean lag
period)
Evidence from experiments on:
• Hydration / dehydration
• Effect of temperature
• Need for O2 - in progress
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Hydration: 25⁰C, 24 h,
top of the paper, dark
Drying to initial mc: 20⁰C, silica gel
Germination: 25⁰C ,
21 day MGT based on
daily counts
CD: 45⁰C, 22% mc.,24h (Normal and totalgermination counts)
Emergence: 22⁰C, 20 days MET based on daily counts
Hydration / dehydration experiments17 commercial lots of cv Demre
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0
20
40
60
80
100
120
140
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
MG
T(h
)
Lots
Datenr
eihen2HydratedSlow
25°C MGT
Hydration for 24 h at 25oC followed by drying back increases
germination rate (lower MGT – shorter lag period)
Possible repair of ageing damage during hydration
Control
Fast
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Hydration increases normal germination after
Controlled Deterioration (i.e. vigour) in 15 out of 17 lots
Possible repair of ageing damage during hydration
20
40
60
80
100
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
CD
No
rmal
Ger
min
atio
n(%
)
Lots
Datenreihen2
Datenreihen3
Control
Hydrated
Aged
Less
AgedCD Germination
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Lots 4, 5 and 17 show marked improvement (lower MET) after hydration
Hydration increases rate of transplant emergence
(lower MET) in 11 out of 15 lots
150
200
250
300
350
400
450
1 2 3 4 5 6 7 8 11 12 13 14 15 16 17
ME
T (
h)
Lots
unhumid
humid
Control
Hydrated
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Effect of hydration on seedling fresh weight (mg/seedling) in
pepper seed lots
Lots 4, 5 and 17 show marked increase – same as for MET
20
40
60
80
100
120
1 2 3 4 5 6 7 8 11 12 13 14 15 16 17
See
dli
ng
fre
sh w
eig
ht
(mg
/pla
nt)
Lots
unhumid
humid
Control
Hydrated
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Emergence of very low vigour (aged) control lots increased
markedly after hydration treatment
Differences due to ageing lost after hydration treatment
R² = 0.36
R² = 0.02
0
20
40
60
80
100
150 200 250 300
See
dli
ng
em
erg
ence
(%
)
MGT (h)
Datenre
ihen1
Control
Hydrated
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Ageing reduced by hydration (increased CD germination) resulting
in increased emergence
Hydration repairs ageing damage and improves emergence
R² = 0.48
R² = 0.10
0
20
40
60
80
100
0 20 40 60 80 100
See
dli
ng
em
erg
ence
(%
)
CD germination (Control, Hydrated)
Datenreihe
n1Hydrated
Control
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215.6
145.3
83.5 82.5
108.6
0
50
100
150
200
250
15oC 20oC 25oC 30oC 35oC
Mea
n g
erm
inat
ion t
ime
(MG
T/
h)
Temperature ( oC )
15 oC 20 oC 25 oC 30 oC 35 oC
Effect of temperature on rate of germination*Average MGT of 17 lots at 5 temperatures
Slowest, longest lag period
Most rapid,
Shortest lag
period
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y =7.85+ 0.92xR2 = 0.91***
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100
150
200
50 100 150 200
25⁰
C M
GT
30⁰C MGT
y = 62.41+1.00xR2 = 0.82***
50
100
150
200
50 100 150 200
20⁰C
MG
T30⁰C MGT
Relative germination rates (MGT) the same at all temperatures
•Seed age determines the relative rates of germination at all temperatures
•At 20 and 25°C (near 30°C optimum), slope of regression close to 1.0
25°C 20°C
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y =63.66+1.84xR2 = 0.90***
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100
150
200
250
300
50 100 150 200 250 300
15⁰
C M
GT
30⁰C MGT
y = 38.84+1.79xR2 = 0.90***
50
100
150
200
250
300
50 100 150 200 250 300
35⁰
C M
GT
30⁰C MGT
Relative germination rates (MGT) the same at all temperatures
•At 15 and 35 °C (above and below optimum) slope of regression > 1.0
•At non-optimum (stress) temperatures, less metabolic repair possible
•Greater impact in aged seeds
15oC 35oC
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Control
Hydrated,
16h, 25oC,
in air+
dehydration
Hydrated,
16h, 25oC,
in nitrogen+
dehydration
Germination and MGT: 25oC Germination (normals) after CD (22% MC, 24h, 45oC)
4 Lots of Pepper Compared
Need for oxygen?
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70
80
90
100
1 2 3 4
No
rmal
ger
min
atio
naf
ter
CD
(%
)
LOTS
Datenreihen2
Datenreihen1
Control
Air
N2
CD germination is affected by hydration in air or nitrogen
Only lots 1 and 3 show a possibility of more repair in air
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Concluding Summary
• Hydration/dehydration increased-
– Rate of germination (decreased lag period to radicle protrusion)
– Seedling emergence and seedling size
– CD germination – possible repair during hydration
• Rate of germination of aged lots most affected by stress
temperatures (15, 35ºC) compared to optimum (30ºC)
– Effect of temperature on metabolic activity and repair?
• No evidence, so far, for need for O2 for repair.
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ACKNOWLEDGMENT
TUBITAK
(The Scientific and Technological Research Council of Turkey)
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THANK YOU
FOR
YOUR ATTENTION