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