effect of priming on seed longevity and water sorption ... · effect of priming on seed longevity...

Effect of priming on seed

longevity and water sorption

isotherms

Ian P. Wood, Fiona R. Hay

Seed Conservation Department, Royal Botanic Gardens Kew, UK

Presentation at the ISTA Seed Symposium

June 2010

Presentation outline

• Background to the study

• Experimental: Rhododendron griersonianum

Priming

Seed ageing

Moisture sorption and desorption isotherms

• Conclusions

Can we improve seed longevity?

60 % RH @ 45 ºC

Powell et al., 2000

Priming and seed longevity

• Seed longevity?

Low-vigour cauliflower seeds

High-vigour cauliflower seeds

Immature or aged foxglove seeds

Non-aged foxglove seeds

collected at storage maturity

Butler et al., 2009

Experimental – M&M• Rhododendron griersonianum seeds

harvested 6 Jan, 3 Feb, 2 Mar 2004

• Stored at 15 % RH, 15 °C

• Samples primed: -1.5 MPa PEG for

3 d, dark, 20 °C

• Experimental storage of non-primed

(“control”) and primed seeds: 60 %

RH, 45 °C

• Samples tested for germination at

regular intervals

• Moisture content determination

Experimental – Results

σi

pKv

Primed

Control

NEDs:

σ

100% i

pKv

Percentage:

Ellis and Roberts (1980)

Experimental – Results

Primed

Control

σ

100% iv

pKCv

Percentage:

Control Primed

• Initial germination

• Cv significant (0.89)

• Ki from 0.4-1.3 to 3.8 NED

• σ from 2.2 to 3.1 days

• p50 4- to 15-fold

Experimental – Results

TreatmentCollection date Storage WC

(g g-1 d. wt)

Control

6 January 0.079 [± 0.0006]

3 February 0.075 [± 0.0011]

2 March 0.073 [± 0.0020]

Primed

6 January 0.053

3 February 0.056 [± 0.0005]

2 March 0.054 [± 0.0012]

• Primed seeds had a lower water content in experimental storage

Sun et al., 1997

Priming, seed longevity, and seed

moisture

• Effect of priming on mung bean seeds

Seed longevity

Weakly bound water

Stongly bound and multimolecular water

• Effect of priming on lettuce seeds

Sensitivity to moisture content during

controlled deterioration

Hill et al., 2007

Experimental – M&M

• For seeds harvested 6 January and

2 March

• Automated water sorption and

desorption isotherm determination at

45 °C

• Fitting of the D‟Arcy-Watt equation

www.hidenisochema.com

Dry-seed

O

O

O

O

O

k

kkc

K

KK

/1

/'/

/1

/'WC

Experimental – Results

Control

Primed

Experimental – Results

Effect of priming:

number of strong water

binding sites

Experimental – Results

Effect of priming:

number of weak water

binding sites

Experimental – Results

Effect of priming:

number of

multimolecular water

binding sites

Experimental – Results

Priming...

weakly bound

water = longevity

( σ)Control

Primed

Conclusions• Priming seeds of Rhododendron griersonianum

Repair resulted in higher initial germination and

a „rejuvenation‟ of the competent seeds (increase

in Ki)

Changes in moisture sorption properties, in

particular a decrease in the amount of weakly

bound water, resulted in a slowing in the rate of

viability loss (increase in σ)

Effects of harvest date on seed longevity not

evident after priming

Thanks to …

Colleagues of the Millennium Seed Bank Partnership

Experimental – Further work

• Target seed-lots of

other Ericaceae

species expected

to be short-lived

Species p50 (days)

C P0 P14 P0,

1

4

Arbutus andrachne 24.3 - 15.1 18.3

Erica quadrangularis 7.9 7.0 - -

Harrimanella

stelleriana

9.0 - 8.1 -

Kalmia latifolia 37.4 20.5 27.8 14.1

Lyonia mariana 35.2 44.3 40.6 42.1

Rhododendron

groenlandicum

8.6 11.8 9.1 11.7

Can we improve

seed longevity?

Species % change in p50

in response to

priming

Amaranthus caudatus -26

Campanula rapunculoides +9

Crassula clavata 0

Damasonium alisma +21

Dasylirion lucidum 0

Epilobium ciliatum +64

Ficus exasperata 0

Filipendula vulgaris 0

Gallium mollugo +23

Geranium lucidum -53

Hyptis suavelolens 0

Nicotiana glutinosa 0

Nicotiana tabacum +70

Oenothera cf. fallax 0

Oxychloris scariosa +66

Portulaca oleracea -45

Primula cortusoides +28

Pycnostachus deflexifolia -18

Rumex crispus +60

Sagina procumbens 0

Usteria quineensis 0

0 12 24 36 48 60 72 84

0

20

40

60

80

100

Germ

inati

on

(%

)

Storage period (days)

Control Epilobium ciliatum

Primed af ter 12 d