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
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
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?
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
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
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
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
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
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
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
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
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
y =7.85+ 0.92xR2 = 0.91***
50
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
y =63.66+1.84xR2 = 0.90***
50
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
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?
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
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.
ACKNOWLEDGMENT
TUBITAK
(The Scientific and Technological Research Council of Turkey)
THANK YOU
FOR
YOUR ATTENTION