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