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The Degree of Unsaturation of Plastidic Membrane Lipids is Positively Associated with Tolerance to Imbibitional Chilling in Soybean Seeds

大豆种子吸胀冷害抗性与其质体膜脂不饱和度正相关



全 文 :大豆种子吸胀冷害抗性与其质体膜脂不饱和度正相关∗
禹晓梅1ꎬ2ꎬ4ꎬ 李唯奇1ꎬ3∗∗
(1 中国科学院昆明植物研究所 中国西南野生生物种质资源库ꎬ 云南 昆明  650201ꎻ 2 中国科学院大学ꎬ 北京  100049ꎻ
3. 红河学院生物系ꎬ 云南 蒙自  661100ꎻ 4. 玉溪中烟种子有限责任公司ꎬ 云南 玉溪  653100)
摘要: 吸胀冷害是干种子在吸胀阶段遭受低温造成不萌发的现象ꎬ 结果可能造成农作物损失严重ꎮ 虽然吸
胀过程中细胞膜的修复是关键事件ꎬ 而且细胞膜在响应水分和温度胁迫中扮演重要角色ꎬ 但是种子吸胀过
程中膜变化的过程ꎬ 特别是膜流动性变化过程研究较少ꎮ 本文比较了吸胀冷害耐受型 (LX) 和敏感型
(R5) 两个大豆品种在吸胀冷害过程中膜脂不饱和度 (double ̄bond indexꎬ DBI) 的变化ꎬ 结果发现ꎬ LX
和 R5在常温 (25 ℃) 吸胀时变化趋势一致ꎬ 质体膜脂 DBI 升高ꎬ 质体外膜脂中磷脂酰甘油 (phosphati ̄
dylglycerolꎬ PG) 分子 DBI下降ꎮ LX和 R5在低温 (4 ℃) 吸胀时 DBI变化有很大差异ꎬ 低温吸胀仅仅延
缓了耐受型 LX中质体膜脂 DBI 的升高ꎬ 但是敏感性 R5 质体膜脂 DBI 不仅没有升高反而下降ꎮ 用浓度
33%的聚乙二醇 (polyethylene glycolꎬ PEG) 引发没有直接引起 DBI变化ꎬ 但是所引起的细微而显著的变化
可能为萌发做好准备ꎮ PEG引发处理后的 R5在吸胀冷害后第二和第三阶段质体膜脂 DBI迅速增加ꎬ 这个
增加模式与 LX的 DBI增加相似ꎮ 结果表明ꎬ 吸胀冷害延缓或者阻滞了质体膜脂不饱和度的升高ꎬ 大豆种
子的吸胀冷害抗性与质体膜脂不饱和度正相关ꎬ 提高质体膜质 DBI可以提高吸胀冷害抗性ꎮ
关键词: 大豆种子ꎻ 吸胀冷害ꎻ 膜脂不饱和度ꎻ 渗透调控ꎻ 双键指数
中图分类号: Q 945            文献标识码: A              文章编号: 2095-0845(2014)02-187-10
The Degree of Unsaturation of Plastidic Membrane Lipids is
Positively Associated with Tolerance to Imbibitional
Chilling in Soybean Seeds
YU Xiao ̄Mei1ꎬ2ꎬ4ꎬ LI Wei ̄Qi1ꎬ3∗∗
(1 Germplasm Bank of Wild Species in Southwest Chinaꎬ Kunming Institute of Botanyꎬ Chinese Academy of Sciencesꎬ Kunming
650201ꎬ Chinaꎻ 2 University of Chinese Academy of Sciencesꎬ Beijing 100049ꎬ Chinaꎻ 3. Department of Biologyꎬ
Honghe Universityꎬ Mengzi 661100ꎬ Chinaꎻ 4. Yuxi Zhongyan Tobacco Seed Co.ꎬ Ltdꎬ Yuxi 653100ꎬ China)
Abstract: Injury caused by imbibitional chilling is a common phenomenon during rehydration of desiccated seedsꎬ
and usually causes seriously compromises seedling emergence and crop yield. Restoration of the cell membranes is a
critical event during imbibitionꎬ moreover it is very important in responses to water and temperature stress. Howeverꎬ
the changes in membrane structure during seed imbibitionꎬ especially those related to membrane fluidityꎬ have yet to
be investigated. This study compared changes in the level of unsaturation of membrane lipids (double ̄bond indexꎬ
DBI) between chilling ̄tolerant ‘LX’ and chilling ̄sensitive ‘R5’ soybean cultivars during imbibitional chilling. Af ̄
ter imbibition at normal temperature (25 ℃)ꎬ seeds of LX and R5 showed similar changes in the level of lipid un ̄
saturationꎬ with increased DBI values for plastidic lipids and reduced levels of extraplastidic phosphatidylglycerol
(PG). In contrastꎬ there were dramatic differences in the changes of DBI between LX and R5 following imbibition
under chilling conditions (4 ℃). Chilling only delayed the increase of plastidic DBI in seeds of the tolerant cultivar
植 物 分 类 与 资 源 学 报  2014ꎬ 36 (2): 187~196
Plant Diversity and Resources                                    DOI: 10.7677 / ynzwyj201413095

∗∗
Funding: The National Natural Science Foundation of China (NSFC 30670474ꎬ 30870571ꎬ and 31070262)
Author for correspondenceꎻ E ̄mail: weiqili@mail􀆰 kib􀆰 ac􀆰 cn
Received date: 2013-04-21ꎬ Accepted date: 2013-05-24
作者简介: 禹晓梅 (1984-) 女ꎬ 博士ꎬ 主要从事种子生物学研究ꎮ
LXꎬ whereas plastidic DBI did not increase or even decreased in the sensitive cultivar R5 under these conditions.
Priming of seeds by incubation in 33% polyethylene glycol (PEG) did not directly cause changes in DBIꎬ howeverꎬ
the subtle but significant changes in DBI that it induced prepared the soybean strain for germination. Plastidic DBI
increased during phases II and III of germination in PEG ̄osmoconditioned R5 seeds under imbibitional chilling
stressꎻ this increase was similar to the patterns of increase in DBI of LX. Our results suggest that chilled imbibition
delays or prevents the increase of the degree of unsaturation in plastidic membrane lipidsꎬ that tolerance to imbibi ̄
tional chilling in soybean is positively associated with an increase in the level of unsaturation of plastidic membrane
lipidsꎬ and that increased plastidic DBI could improve tolerance of imbibitional chilling.
Key words: Soybean seedsꎻ Imbibitional chilling injuryꎻ Degree of unsaturation of membrane lipidsꎻ Osmocondi ̄
tioningꎻ Double ̄bond index
  Imbibition is a critical process during seed ger ̄
mination. The uptake of water by a mature dry seed
is triphasic (Bewleyꎬ 1997ꎻ Yin et al.ꎬ 2009ꎻ Han
et al.ꎬ 2013)ꎬ with rapid initial uptake ( phase I)
followed by a plateau phase ( phase II) . A further
increase in water uptake occurs only after germina ̄
tion has been completedꎬ as the embryonic axes e ̄
longate ( phase III) . In dry seedsꎬ cell membrane
systems lose their integrity and adopt a wrinkled and
disordered formꎬ such as the hexagonal II or crystal ̄
line gel forms. Upon rehydrationꎬ these systems re ̄
pair themselves into an orderly and stable configura ̄
tionꎬ which restores integrity and fluidity ( Zhengꎬ
1991). The restoration of the cell membrane occurs
during the phase involving the physical uptake of
water (phase I)ꎬ and it is very important for seed
germination (Bewleyꎬ 1997). It is generally recog ̄
nised that injury caused by imbibitional chilling oc ̄
curs when dry seeds imbibe at a low temperature at
this stage (Zhengꎬ 1988ꎬ 1991). The imbibitional
temperature and rate are the two main factors that
determine the success of membrane reorganization
(Yin et al.ꎬ 2009ꎻ Lyonsꎬ 1973). Low temperature
and rapid uptake of water can severely disturb phos ̄
pholipids and induce a change in their arrangement
from a hexagonal ( dehydrated) to a lamellar ( hy ̄
drated) architecture (Simonꎬ 1974).
Severe injury caused by imbibitional chilling oc ̄
curs when chilling ̄sensitive seeds absorb water at a
lower temperature. This results in poor germinationꎬ re ̄
duced seedling emergenceꎬ decreased seedling vigourꎬ
and ultimately loss of yield (Pollockꎬ 1969). Such in ̄
jury is a common problem in agriculture and has been
reported for a wide range of cropsꎬ including green
bean and lima bean (Pollockꎬ 1969)ꎬ cotton (Chris ̄
tiaꎬ 1967)ꎬ pea (Powell and Matthewsꎬ 1978)ꎬ cu ̄
cumber (Willing and Leopoldꎬ 1983)ꎬ corn and soy ̄
bean (Obendorf and Hobbsꎬ 1970). On one occasionꎬ
a 25% decrease in soybean yield caused by chilling in ̄
jury was reportedꎬ even though the field seedling den ̄
sity remained the same (Hobbs and Obendorfꎬ 1972).
Osmoconditioning involves the incubation of
seeds in an osmoticumꎬ which is usually a solution
of a salt or polyethylene glycol ( PEG). Priming
seeds for germination by incubating them in solutions
of PEG was previously shown to reduce or eliminate
damage caused by chilled imbibitionꎬ and it also
clearly improved seed vigour (Woodstock and Taoꎬ
1981ꎻ Posmyk et al.ꎬ 2001). Chilling injury and
PEG priming are associated with various biochemical
and metabolic alterations. In chilling ̄sensitive seedsꎬ
the greatest sensitivity to low temperatures occurs
during the first hours of the imbibition phase (Pol ̄
lock and Tooleꎬ 1966ꎻ Christiaꎬ 1967ꎻ Bramlage et
al.ꎬ 1978ꎻ Leopoldꎬ 1980). The leakage of solutes
from chilled imbibing seeds suggests that membrane
reorganisation is impaired at low temperatures (Bram ̄
lage et al.ꎬ 1978)ꎬ and thus that membrane systems
are the cell components that are most vulnerable to
injury by chillingꎻ howeverꎬ only a limited number
of studies have addressed this issue.
Membranesꎬ particularly plasma and chloroplast
membranes are sensitive to environmental stimuli. The
fluidity of cell membranes can influence their stability
881                                  植 物 分 类 与 资 源 学 报                            第 36卷
during exposure to stressꎬ it can be optimised by ad ̄
justment of the membrane lipid or fatty acid composi ̄
tionꎬ structureꎬ and level of unsaturation in response
to stressꎬ which are important determinants of the a ̄
bility to adapt to stress (Navari ̄Izzo et al.ꎬ 1993).
The degree of unsaturation of membrane glycerolipids
(measured as the double ̄bond indexꎬ DBI) is the
major factor that determines membrane fluidity. A
high DBI indicates the presence of more unsaturated
membrane lipids. At low temperaturesꎬ the DBI of
fatty acids is increased. Tolerance of leaves to dehy ̄
dration or desiccation is associated with a decrease in
fatty acid content and alteration in the composition of
unsaturated and saturated fatty acids in various plant
species (Xu et al.ꎬ 2011). Dehydration reduces the
DBI of fatty acids in the plastidic membranes of leav ̄
es (Quartacci et al.ꎬ 2002). Following dehydrative
stressꎬ differences in the DBI values of four cultivars
of grapevine (Vitis vinifera L.) that exhibit different
levels of drought tolerance implied that specific ad ̄
justments in the level of unsaturation of lipids during
stress could compromise stress tolerance ( Toumi et
al.ꎬ 2008 ). The ability to change DBI in order to
maintain membrane integrity and fluidity during peri ̄
ods of stress is of major importance for plant surviv ̄
alꎬ as discussed aboveꎬ and may also be critical for
seed rehydration or regrowth ( Quartacci et al.ꎬ
1995ꎻ Bettaieb et al.ꎬ 2009ꎻ Toumi et al.ꎬ 2008).
Howeverꎬ changes in DBI during imbibitional chill ̄
ing and the effects of these changes on seed germina ̄
tion do not appear to have been reported.
Plant lipidomics analysis based on electrospray i ̄
onization tandem mass spectrometry (ESI ̄MS / MS) can
rapidly measure the relative abundances of hundreds of
different types of lipid molecules in vivo using small
samples (Welti et al.ꎬ 2002)ꎬ this enables accurate
calculation of the DBI of all membrane glycerolipids
measured. Several studies have employed lipidomics to
profile changes in molecular species and DBI during
plant growth and stress. For exampleꎬ Zheng et al.
(2011) used a lipidomics approach to profile the chan ̄
ges in molecular species of membrane glycerolipids and
thus calculated the DBI in four plant species in re ̄
sponse to frequent changes of temperature.
Seeds of most soybean varieties are sensitive to
cold imbibitionꎬ albeit to various extents. Alleviation
of this sensitivity poses one of the most important
challenges to reliable and sustainable soybean pro ̄
duction in Northeast China (Zhengꎬ 1991). We found
two soybean cultivars characterised by different levels
of resistance to imbibitional chilling: ‘LX’ (chill ̄
ing ̄tolerant) and ‘R5’ (chilling ̄sensitive). The pur ̄
pose of this study was to use lipidomic analysis to de ̄
termine: (i) how DBI changes in these two soybean
cultivars during their imbibition at normal and cold
temperaturesꎻ ( ii) how DBI changes during PEG
priming and how DBI changes in PEG ̄primed chill ̄
ing ̄sensitive seeds subsequently imbibed at cold
temperaturesꎻ and (iii) whether chilling tolerance is
associated with a change in DBI during imbibition.
1  Methods and materials
1􀆰 1  Seeds
Soybean seeds of the two cultivarsꎬ LX and R5ꎬ
were obtained from a commercial source. The seeds
were equilibrated to 10% moisture over a saturated
solution of LiCl ( 53% relative humidity) for one
week and then stored at 15 ℃ until analysis.
1􀆰 2  Seed germination and sensitivity to imbibi ̄
tional chilling injury
Seeds of the two cultivars were tested for sensi ̄
tivity to imbibitional chilling. They underwent imbi ̄
bition for 24 h in distilled water at 25 ℃ or 4 ℃ꎬ
and were then transferred to 25 ℃ for four days dur ̄
ing which seed germination was recorded using a
camera. Percent germination was measured to deter ̄
mine the sensitivity to imbibitional chillingꎬ four
replications with 40 seeds each were germinated at
25 ℃ (unpulished data).
1􀆰 3  Seed priming
Dry seeds underwent imbibition in 33% PEG ̄
6000 solution for three days at 15 ℃ . And then the
seeds were washed three times in distilled water and
then desiccated for three days at room temperature to
9812期      YU and LI et al.: The Degree of Unsaturation of Plastidic Membrane Lipids is Positively Associated 􀆺     
adjust their water content to 10􀆰 3% on average (dry
weight basis)ꎬ which is similar to that of control un ̄
treated seeds. The control seeds and the primed
seeds then underwent imbibition at 4 ℃ for 24 h for
imbibitional chilling treatment. Untreated seeds were
used as controls.
1􀆰 4  Lipid extraction and ESI / MS ̄MS analysis
The process of lipid extractionꎬ ESI ̄MS / MS a ̄
nalysisꎬ and quantification was performed as de ̄
scribed previously with minor modification (Welti et
al.ꎬ 2002ꎻ Li et al.ꎬ 2008ꎻ Zheng et al.ꎬ 2012).
Each sample contained seed axes with a pooled dry
weight of 10 to 20 mgꎻ samples were harvested at the
indicated sampling time. To inhibit lipolytic activityꎬ
seed axes were transferred immediately into 3 mL of
isopropanol with 0􀆰 01% butylated hydroxytoluene in
a 75 ℃ water bath. The tissue was extracted three
times with chloroform / methanol (2 ∶ 1) with 0􀆰 01%
butylated hydroxytolueneꎬ with a week of agitation.
The remaining plant tissue was dried overnight at
105 ℃ and weighed to give the dry weight of the tis ̄
sue. Lipid samples were analysed on a triple quadru ̄
pole MS / MS equipped for ESI. Automated ESI ̄MS /
MS analysis was performed in the Kansas Lipidomics
Research Center Analytical Laboratory as described
previously (Kansas Lipidomics Research Centerꎬ ht ̄
tp: / / www􀆰 k ̄state􀆰 edu / lipid / lipidomics).
1􀆰 5  Data analysis
Data processing was performed as previously
described (Devaiah et al.ꎬ 2006ꎻ Welti et al.ꎬ 2002ꎻ
Zheng et al.ꎬ 2012). DBI were calculated using the
formula: DBI=[∑(N×mol% lipid)] / 100ꎬ where N
is the total number of double bonds in the two fatty
acid chains of each glycerolipid molecule (Zheng et
al.ꎬ 2011ꎻ Osmond et al.ꎬ 1982ꎻ Rawyler et al.ꎬ
1999ꎻ Bakht et al.ꎬ 2006). Five replicates of each
treatment were analysed. The Q ̄test was performed on
the total amount of lipid in each classꎬ and data from
discordant samples were removed. The data were sub ̄
jected to one ̄way analysis of variance ( ANOVA)
with SPSS 13􀆰 0. Statistical significance was tested by
Fisher’s least significant difference (LSD) method.
2  Results and discussion
2􀆰 1  LX and R5 cultivars differ markedly in their
sensitivity to imbibitional chilling
After 24 h of imbibition at 25 ℃ꎬ both cultivars
exhibited a seed germination rate of 100% (Fig􀆰 1ꎬ
Control)ꎬ which indicated that an extremely high
level of viability of these seeds. Howeverꎬ LX and
R5 exhibited contrasting levels of resistance to imbi ̄
bitional chilling (Fig􀆰 1ꎬ Imbibition Chilling): (1)
R5ꎬ chilling ̄sensitive: Imbibition at 4 ℃ caused large
reductions in survival and seedling vigourꎬ and no
germination occurred ( 0 germination rateꎬ unpul ̄
ished data). The seeds were surrounded by a circle
of a light ̄yellowꎬ sticky substanceꎬ which may have
been mildew or fungal rot. (2) LXꎬ chilling ̄resist ̄
ant: Imbibitional chilling had a small effectꎻ a small
reduction of radicle emergence was observed com ̄
pared with the control (unpulished data)ꎬ but nor ̄
mal radicle extension occurred. Thereforeꎬ we used
LX as a chilling ̄resistant cultivar and R5 as a chill ̄
ing ̄sensitive one for further comparative investigation
of the effects of chilled imbibition on germination.
Fig􀆰 1  The sensitivity of soybean cultivars to imbibitional chilling injury
Control: Seeds underwent imbibition for 24 h in distilled water at 25 ℃ꎬ
followed by germination for four days at 25 ℃ . Chilled imbibition:
Seeds underwent imbibition for 24 h in distilled water at 4 ℃ꎬ followed
by germination for four days at 25 ℃ . LXꎬ Liaoxinꎻ R5ꎬ Riben 5
2􀆰 2  Effects of PEG priming on R5 seed germination
Many studies have indicated that osmopriming
can accelerate seed germination. In order to deter ̄
091                                  植 物 分 类 与 资 源 学 报                            第 36卷
mine whether PEG ̄osmoconditioned seeds were
chilling ̄sensitiveꎬ they underwent imbibition at 4 ℃
for 24 h and were then transferred to 25 ℃ . Figure 2
shows that control seeds lost their ability to germi ̄
nate at 25 ℃ after imbibition at 4 ℃ . Howeverꎬ the
germination of PEG ̄osmoconditioned R5 seeds at
25 ℃ was almost unchanged after chilled imbibition
(unpulished data). This experiment indicated that
PEG osmoconditioning has clear advantages for im ̄
proving the tolerance of R5 seeds to imbibitional
chilling. Thereforeꎬ PEG was used to investigate the
mechanisms of injury due to imbibitional chilling in
sensitive seeds.
Fig􀆰 2  Prior imibibition in solutions of PEG protects against
chilling injury in germinating R5 soybean seeds
Controls: R5 seeds without PEG treatment underwent imbibition for
24 h in distilled water at 4 ℃ꎬ followed by germination for four days at
25 ℃ . After PEG treatment: PEG ̄treated R5 seeds underwent imbibi ̄
tion for 24 h in distilled water at 4 ℃ꎬ followed by germination for four
days at 25 ℃
2􀆰 3  Profiling DBI changes during germination
We harvested the embryo axes of LX and R5
seeds after their imbibition in water for 0 h (control)ꎬ
3 hꎬ and 24 h at 25 ℃ or 4 ℃ꎬ and then at one and
three days of germination at 25 ℃ for lipidomics
analysis. Base on the water uptake (unpulished da ̄
ta)ꎬ these sampling times represent the three phases
during germination ( Bewleyꎬ 1997ꎻ Yin et al.ꎬ
2009ꎻ Han et al.ꎬ 2013). Imbibition for 3 h repre ̄
sented the period of rapid initial uptake (phase I)ꎬ
whereas imbibition for 24 h represented the plateau
phase ( phase II) . Penetration of the seed radicles
through the seed coat 1 day after the beginning of
imbibition indicated that the seed had completed
phases I+II and was just starting phase III ( unpul ̄
ished data). Using a lipidomics approach based on
ESI ̄MS / MS (Welti et al.ꎬ 2002ꎻ Li et al.ꎬ 2008)ꎬ
we identified and quantified six head ̄group classes
of phospholipids: phosphatidylcholine (PC)ꎬ phos ̄
phatidylethanolamine (PE)ꎬ phosphatidylinositol (PI)ꎬ
phosphatidylserine (PS)ꎬ phosphatidic acid (PA)ꎬ
and phosphatidylglycerol (PG)ꎬ as well as two head ̄
group classes of galactolipids: monogalactosyldiacyl ̄
glycerol (MGDG) and digalactosyldiacylglycerol (DG ̄
DG) (Welti et al.ꎬ 2002)ꎬ and thus we calculated
their DBI during the three phases of germination
(Table 1). From an overview of the DBIꎬ it can be
seen that there was diversity in the changes in DBI
among the eight classes of lipidsꎬ differences be ̄
tween normal and chilling germinationꎬ and differ ̄
ences between PEG ̄ and non ̄PEG ̄treated R5 seeds
following chilled imbibition. Detailed analysis and
discussion are presented in later sections.
2􀆰 4  Patterns of changes in levels of extraplastidic
and plastidic DBI differ after imbibition at 25 ℃
To understand better the patterns of DBI change
during germinationꎬ we profiled the DBI phase by
phase from dry seeds to three days of germination in
LX and R5 seeds imbibed at the normal temperature
tested (25 ℃). Table 1 shows that LX and R5 had
the same patterns of change after imbibition at 25 ℃ꎻ
namelyꎬ the content of total DBI increased with time.
After three days of germinationꎬ the contents of MG ̄
DG and DGDG increased markedlyꎬ whereas levels
of PG significantly decreasedꎻ howeverꎬ the contents
of PIꎬ PEꎬ PCꎬ PAꎬ and PS changed very little.
The eight classes of lipids can be divided into
extraplastidic and plastidic types. Plastidic lipids in ̄
clude MGDG and DGDGꎬ which are the dominant
components of chloroplast membranes (Jarvis et al.ꎬ
2000ꎻ Dubots et al.ꎬ 2010). Five of the other clas ̄
ses of lipids (PCꎬ PEꎬ PIꎬ PSꎬ and PA) belong to
the extraplastidic type (Li et al.ꎬ 2008 ). PG lipids
include both classes: 34 ∶ 4 PG ( total carbon num ̄
ber: double ̄bond number)ꎬ which harbours a 16∶1
acyl chainꎬ is part of the plastidic membraneꎬ whereas
1912期      YU and LI et al.: The Degree of Unsaturation of Plastidic Membrane Lipids is Positively Associated 􀆺     
both 34∶1 PG and 34 ∶ 2 PG are extraplastidic lipids
(Welti et al.ꎬ 2002ꎻ Marechal et al.ꎬ 1997). In soy ̄
bean seed axesꎬ PG includes 34 ∶ 1 PGꎬ 34 ∶ 2 PGꎬ
and 34∶3 PGꎬ but not 34 ∶ 4 PG (data not shown).
Accordinglyꎬ in this caseꎬ PG can be classified as
extraplastidic lipids. As suchꎬ the data obtained in
this study indicate that extraplastidic and plastidic
lipids are affected differently by imbibition at 25 ℃.
These differences may be associated with the special
biological significance of extraplastidic and plastidic
membranes. Dry seeds had very low levels of plastidic
DBI (Table 1)ꎬ which confirmed that plastids were
scarce in dry seeds. The content of plastidic mem ̄
brane DBI increased along with seed germination.
This suggested that MGDG and DGDG synthesis and
chloroplast development occurred during this period.
Because MGDG and DGDG are the dominant compo ̄
nents of thylakoid membranesꎬ they are the main con ̄
tributors to membrane unsaturation because they also
harbour a relatively high level of trienoic fatty acids.
For all glycerolipid classesꎬ the changes in DBI
were small at phases I and II. Howeverꎬ during
phase IIIꎬ dramatic alterations took place in both the
extraplastidic and plastidic lipids of the two culti ̄
vars. This was probably becauseꎬ during imbibition
(phases I and II)ꎬ seeds mainly adjust their lipid
composition using existing substances in order to re ̄
spond to the level of hydrationꎬ whereas enzymes
initiate metabolism and the synthesis of new polyun ̄
saturated or saturated fatty acids in order to restore
their integrity and fluidity state post ̄germination
(phase III) . Thereforeꎬ the DBI changed little du ̄
ring imbibitionꎬ but displayed significant changes at
phase IIIꎻ in additionꎬ chloroplast development was
the main occurrence during post ̄germination.
2􀆰 5  The effects of chilled imbibition on the DBI
in chilling ̄tolerant seeds
To study how chilled imbibition affects DBIꎬ we
compared the DBI values of LX seeds imbibed at 25℃
and those imbibed at 4 ℃ . The patterns of changes
in the DBI of extraplastidic and plastidic lipids were
similar between seeds imbibed at normal and cold
temperatures ( Table 1). Increases in the plastidic
membrane DBI and decreases of extraplastidic PG
DBI after imbibition at 4 ℃ imbibition were slower
than those observed after imbibition at 25 ℃ . For ex ̄
ampleꎬ the DGDG DBI after imbibition at 4℃ (4􀆰 57)
was lower than that at 25 ℃ (4􀆰 90) after one day of
germination ( Table 1 ). Howeverꎬ there was no
difference after three days of germination. These re ̄
sults indicate that chilling delayed an increase in the
DBI of plastidic lipids.
2􀆰 6   Differential changes in DBI between LX
and R5 following chilled imbibition
Severe injury occurred in R5 seeds after imbibi ̄
tion at a low temperature. To reveal whether DBI
change is associated with imbibitional chilling inju ̄
ryꎬ we compared the extraplastidic and plastidic DBI
of R5 with those of LX seeds subjected to chilled im ̄
bibition (Table 1). The DBI of the two cultivars ex ̄
hibited different changes. In seeds of the tolerant
cultivar LXꎬ imbibition at 4 ℃ caused dramatic in ̄
creases in the levels of total DBI and plastidic DBI
(MGDG and DGDG)ꎬ with MGDG increasing from
3􀆰 75 (control) to 5􀆰 76 (germination 3 d). Howev ̄
erꎬ MGDG and DGDG did not increase or even de ̄
creased in the sensitive cultivar R5 following imbibi ̄
tional chilling: MGDG decreased from 5􀆰 21 ( con ̄
trol) to 4􀆰 65 (germination 3 d). This indicated that
the DBI of R5 seeds after imbibition at 4 ℃ differed
markedly from that of LX seeds with normal germina ̄
tion. Low DBI levels of MGDG and DGDG in R5
seeds could be associated with their severe injury
due to chilled imbibition. In other wordsꎬ changes in
the degree of unsaturation of membrane lipids of soy ̄
bean seeds were suggested to be related to the toler ̄
ance of imbibitional chilling.
Given that dry seeds do not contain chloroplasts
for photosynthesisꎬ the development of chloroplasts
to provide ATP during seed germination is essential
for seeds to overcome imbibitional chilling and to
grow. Photosynthesis requires high levels of mem ̄
brane polyunsaturation (Mcconn and Browseꎬ 1998).
A high DBI helps to maintain the fluidity of mem ̄
291                                  植 物 分 类 与 资 源 学 报                            第 36卷
branes in order to sustain the functional activity of
membrane proteins and the membranes themselves.
MGDG and DGDGꎬ the dominant components of thy ̄
lakoid membranesꎬ are the main contributors to
membrane unsaturation because they harbour a rela ̄
tively high level of trienoic fatty acids.
The desaturation of lipids in plants starts with
the synthesis of 16 ∶ 0 and 18 ∶ 0 fatty acids (Wallis
and Browseꎬ 2002ꎻ Zheng et al.ꎬ 2011). Desaturation
is mediated by a series of desaturases that are located
Table 1  Changes in the double ̄bond index (DBI) of each lipid class at 25 ℃ or 4 ℃ in LX and R5
Seeds underwent imbibition in water at 25 ℃ or 4 ℃ for 3 h and 24 hꎬ and were then transferred to 25 ℃ for germination for one and three
days. Values are means ± SE (n= 4 or 5) . Values in the same row with different letters are significantly different (P < 0􀆰 05) . DBI=(∑[N
× mol% molecular species]) / 100ꎬ where N is the number of double bonds in each molecular species. LXꎬ Liaoxinꎻ R5ꎬ Riben 5
Lipid
class Treatment / ℃
Double ̄bond index (DBI)
Control Imbibition3 h: phase I)
Imbibition
24 h: phase II
Germination
1 d: phase III
Germination
3 d: phase III
PG
LX 254
2􀆰 37 ± 0􀆰 03b
2􀆰 37 ± 0􀆰 03b
2􀆰 48 ± 0􀆰 02a
2􀆰 40 ± 0􀆰 03b
2􀆰 36 ± 0􀆰 01b
2􀆰 48 ± 0􀆰 03a
1􀆰 69 ± 0􀆰 05c
1􀆰 88 ± 0􀆰 08c
1􀆰 64 ± 0􀆰 02c
1􀆰 59 ± 0􀆰 04d
R5 254
2􀆰 43 ± 0􀆰 01a
2􀆰 43 ± 0􀆰 01a
2􀆰 43 ± 0􀆰 03a
2􀆰 33 ± 0􀆰 01b
2􀆰 41 ± 0􀆰 02a
2􀆰 44 ± 0􀆰 03a
1􀆰 98 ± 0􀆰 06b
2􀆰 09 ± 0􀆰 03c
1􀆰 59 ± 0􀆰 06c
1􀆰 93 ± 0􀆰 05d
PI
LX 254
2􀆰 51 ± 0􀆰 01ab
2􀆰 51 ± 0􀆰 01b
2􀆰 52 ± 0􀆰 01a
2􀆰 54 ± 0􀆰 02a
2􀆰 50 ± 0􀆰 01b
2􀆰 53 ± 0􀆰 01a
2􀆰 42 ± 0􀆰 01d
2􀆰 38 ± 0􀆰 01c
2􀆰 68 ± 0􀆰 02c
2􀆰 52 ± 0􀆰 02ab
R5 254
2􀆰 53 ± 0􀆰 02b
2􀆰 53 ± 0􀆰 02a
2􀆰 54 ± 0􀆰 01b
2􀆰 54 ± 0􀆰 02a
2􀆰 49 ± 0􀆰 01c
2􀆰 56 ± 0􀆰 01a
2􀆰 36 ± 0􀆰 01d
2􀆰 39 ± 0􀆰 02b
2􀆰 70 ± 0􀆰 01a
2􀆰 36 ± 0􀆰 01b
PE
LX 254
3􀆰 29 ± 0􀆰 03a
3􀆰 29 ± 0􀆰 03a
3􀆰 24 ± 0􀆰 06b
3􀆰 28 ± 0􀆰 03a
3􀆰 24 ± 0􀆰 03b
3􀆰 24 ± 0􀆰 07ab
3􀆰 13 ± 0􀆰 02c
3􀆰 19 ± 0􀆰 01b
3􀆰 28 ± 0􀆰 01ab
3􀆰 21 ± 0􀆰 04b
R5 254
3􀆰 34 ± 0􀆰 01b
3􀆰 34 ± 0􀆰 01a
3􀆰 37 ± 0􀆰 03a
3􀆰 30 ± 0􀆰 05a
3􀆰 28 ± 0􀆰 01c
3􀆰 34 ± 0􀆰 04a
3􀆰 16 ± 0􀆰 01d
3􀆰 22 ± 0􀆰 02b
3􀆰 28 ± 0􀆰 02c
3􀆰 24 ± 0􀆰 01b
PC
LX 254
3􀆰 45 ± 0􀆰 04bc
3􀆰 45 ± 0􀆰 04bc
3􀆰 41 ± 0􀆰 03c
3􀆰 47 ± 0􀆰 03b
3􀆰 41 ± 0􀆰 04c
3􀆰 39 ± 0􀆰 01d
3􀆰 47 ± 0􀆰 07b
3􀆰 43 ± 0􀆰 03c
3􀆰 67 ± 0􀆰 01a
3􀆰 56 ± 0􀆰 01a
R5 254
3􀆰 48 ± 0􀆰 01b
3􀆰 48 ± 0􀆰 01ab
3􀆰 46 ± 0􀆰 02b
3􀆰 49 ± 0􀆰 02a
3􀆰 49 ± 0􀆰 05b
3􀆰 45 ± 0􀆰 03b
3􀆰 42 ± 0􀆰 03c
3􀆰 46 ± 0􀆰 02ab
3􀆰 65 ± 0􀆰 02a
3􀆰 35 ± 0􀆰 03c
PA
LX 254
3􀆰 34 ± 0􀆰 03b
3􀆰 34 ± 0􀆰 03b
3􀆰 41 ± 0􀆰 03a
3􀆰 43 ± 0􀆰 02a
3􀆰 41 ± 0􀆰 06a
3􀆰 43 ± 0􀆰 02a
3􀆰 20 ± 0􀆰 04c
3􀆰 26 ± 0􀆰 05c
3􀆰 35 ± 0􀆰 01b
3􀆰 29 ± 0􀆰 05c
R5 254
3􀆰 40 ± 0􀆰 01b
3􀆰 40 ± 0􀆰 01c
3􀆰 58 ± 0􀆰 04a
3􀆰 47 ± 0􀆰 02b
3􀆰 45 ± 0􀆰 02b
3􀆰 55 ± 0􀆰 02a
3􀆰 30 ± 0􀆰 06c
3􀆰 38 ± 0􀆰 04c
3􀆰 29 ± 0􀆰 03c
3􀆰 31 ± 0􀆰 04d
PS
LX 254
2􀆰 24 ± 0􀆰 02c
2􀆰 24 ± 0􀆰 02b
2􀆰 30 ± 0􀆰 03b
2􀆰 32 ± 0􀆰 09a
2􀆰 29 ± 0􀆰 03b
2􀆰 26 ± 0􀆰 01ab
2􀆰 22 ± 0􀆰 01c
2􀆰 24 ± 0􀆰 01b
2􀆰 37 ± 0􀆰 02a
2􀆰 30 ± 0􀆰 01ab
R5 254
2􀆰 27 ± 0􀆰 03c
2􀆰 27 ± 0􀆰 03b
2􀆰 35 ± 0􀆰 06ab
2􀆰 50 ± 0􀆰 16a
2􀆰 32 ± 0􀆰 02b
2􀆰 30 ± 0􀆰 01b
2􀆰 22 ± 0􀆰 02d
2􀆰 25 ± 0􀆰 01b
2􀆰 38 ± 0􀆰 02a
2􀆰 25 ± 0􀆰 01b
MGDG
LX 254
3􀆰 95 ± 0􀆰 16d
3􀆰 95 ± 0􀆰 16d
4􀆰 33 ± 0􀆰 11c
4􀆰 02 ± 0􀆰 48cd
4􀆰 36 ± 0􀆰 06c
4􀆰 37 ± 0􀆰 04c
5􀆰 54 ± 0􀆰 04b
5􀆰 29 ± 0􀆰 14b
5􀆰 80 ± 0􀆰 01a
5􀆰 76 ± 0􀆰 02a
R5 254
5􀆰 21 ± 0􀆰 05b
5􀆰 21 ± 0􀆰 05a
4􀆰 40 ± 0􀆰 09d
4􀆰 09 ± 0􀆰 16d
4􀆰 44 ± 0􀆰 09d
4􀆰 36 ± 0􀆰 03c
4􀆰 99 ± 0􀆰 10c
4􀆰 68 ± 0􀆰 01b
5􀆰 79 ± 0􀆰 01a
4􀆰 65 ± 0􀆰 13b
DGDG
LX 254
4􀆰 56 ± 0􀆰 07c
4􀆰 56 ± 0􀆰 07b
4􀆰 48 ± 0􀆰 10c
4􀆰 60 ± 0􀆰 08b
4􀆰 27 ± 0􀆰 02d
4􀆰 34 ± 0􀆰 05c
4􀆰 90 ± 0􀆰 06b
4􀆰 57 ± 0􀆰 06b
5􀆰 13 ± 0􀆰 01a
5􀆰 17 ± 0􀆰 03a
R5 254
4􀆰 66 ± 0􀆰 10b
4􀆰 66 ± 0􀆰 10b
4􀆰 60 ± 0􀆰 02b
4􀆰 82 ± 0􀆰 13a
4􀆰 46 ± 0􀆰 02c
4􀆰 59 ± 0􀆰 06b
4􀆰 49 ± 0􀆰 08c
4􀆰 27 ± 0􀆰 01c
5􀆰 11 ± 0􀆰 01a
4􀆰 24 ± 0􀆰 07c
Total
LX 254
3􀆰 17 ± 0􀆰 02c
3􀆰 17 ± 0􀆰 02c
3􀆰 19 ± 0􀆰 08c
3􀆰 24 ± 0􀆰 05b
3􀆰 20 ± 0􀆰 03c
3􀆰 22 ± 0􀆰 03b
3􀆰 31 ± 0􀆰 01b
3􀆰 24 ± 0􀆰 03b
3􀆰 74 ± 0􀆰 02a
3􀆰 58 ± 0􀆰 03a
R5 254
3􀆰 20 ± 0􀆰 02d
3􀆰 20 ± 0􀆰 02ab
3􀆰 28 ± 0􀆰 02c
3􀆰 28 ± 0􀆰 03a
3􀆰 24 ± 0􀆰 04cd
3􀆰 26 ± 0􀆰 01a
3􀆰 39 ± 0􀆰 03b
3􀆰 24 ± 0􀆰 03a
3􀆰 76 ± 0􀆰 04a
3􀆰 16 ± 0􀆰 04b
3912期      YU and LI et al.: The Degree of Unsaturation of Plastidic Membrane Lipids is Positively Associated 􀆺     
in the endoplasmic reticulum and chloroplastsꎻ these
molecules have similar catalytic sequences within
their active sites. Although little is known about the
enzymatic mechanism by which desaturated fatty acids
are saturatedꎬ low DBI levels in R5 seeds could result
from inhibition of lipid synthesis processes at a low
temperature. Accordinglyꎬ higher levels of unsaturat ̄
ed lipids in plastidic membrane might account for the
tolerance of LX seeds to chilled imbibition.
2􀆰 7  Effects of PEG priming on DBI of membrane
lipids
The above experiment indicates that PEG os ̄
motic pretreatment ( priming or osmoconditioning)
reduced the damage due to imbibitional chilling in
R5 seeds. We profiled the DBI in R5 seeds os ̄
moconditioned for one and three days as well as
PEG ̄treated dry seeds to test whether PEG treatment
changed the seed DBI (Table 2). The results indi ̄
cate that PEG osmopriming slightly but significantly
changed the DBI of membrane lipids in chilling ̄sen ̄
sitive seeds ( R5)ꎬ with the small changes being
very similar to the pattern of LX imbibition at 25 ℃
during phase I. This finding suggested that PEG
priming did not directly cause the main changes in
DBIꎬ but rather induced changes in DBI in prepara ̄
tion for germination.
2􀆰 8  Dramatic changes in DBI profiles occur in
PEG osmoconditioned R5 seeds under imbibitional
chilling stress
To examine how the effects of PEG osmoprim ̄
ing occur under imbibitional chillingꎬ we analysed
the DBI of membrane lipids in PEG ̄treated R5 seeds
during imbibition at 4 ℃ for 3 and 24 hꎬ followed by
germination at 25 ℃ for one and three days (Table
3). Levels of the plastidic lipids MGDG and DGDG
increased continually over the period studied: MG ̄
DG increased from DBI of 5􀆰 13 (control) to 5􀆰 72
(germination 3 d)ꎬ whereas DGDG increased from
Table 2  Changes in double ̄bond index (DBI) of each lipid class in R5 soybean seeds during the PEG priming. Values are means ± SE
(n= 4 or 5) . Values in the same row with different letters are significantly different (P < 0􀆰 05)
Lipid class
Double ̄bond index (DBI)
Control PEG 1 d PEG 3 d After PEG priming
PG 2􀆰 44 ± 0􀆰 07c 2􀆰 62 ± 0􀆰 06b 2􀆰 77 ± 0􀆰 04a 2􀆰 78 ± 0􀆰 05a
PI 2􀆰 52 ± 0􀆰 02b 2􀆰 52 ± 0􀆰 01b 2􀆰 53 ± 0􀆰 02b 2􀆰 58 ± 0􀆰 02a
PE 3􀆰 50 ± 0􀆰 03a 3􀆰 37 ± 0􀆰 02b 3􀆰 39 ± 0􀆰 01b 3􀆰 39 ± 0􀆰 02b
PC 3􀆰 55 ± 0􀆰 03a 3􀆰 38 ± 0􀆰 03b 3􀆰 35 ± 0􀆰 02b 3􀆰 41 ± 0􀆰 03b
PA 3􀆰 35 ± 0􀆰 02a 3􀆰 34 ± 0􀆰 01a 3􀆰 31 ± 0􀆰 01b 3􀆰 28 ± 0􀆰 02b
PS 2􀆰 47 ± 0􀆰 06b 2􀆰 51 ± 0􀆰 03b 2􀆰 67 ± 0􀆰 07a 2􀆰 55 ± 0􀆰 09ab
MGDG 4􀆰 93 ± 0􀆰 12b 4􀆰 92 ± 0􀆰 11b 5􀆰 21 ± 0􀆰 08a 5􀆰 13 ± 0􀆰 17ab
DGDG 4􀆰 59 ± 0􀆰 13a 4􀆰 48 ± 0􀆰 08ab 4􀆰 51 ± 0􀆰 11ab 4􀆰 34 ± 0􀆰 08b
Total 3􀆰 19 ± 0􀆰 03a 3􀆰 13 ± 0􀆰 01b 3􀆰 11 ± 0􀆰 02b 3􀆰 12 ± 0􀆰 02b
Table 3  Changes in double ̄bond index (DBI) of each lipid class during imbibitional chilling and post ̄germination for R5 soybean seeds after
PEG priming. Values are means ± SE (n= 4 or 5) . Values in the same row with different letters are significantly different (P < 0􀆰 05)
Lipid class
Double ̄bond index (DBI)
After PEG treatment Imbibition 3 h Imbibition 24 h Germination 1 d Germination 3 d
PG 2􀆰 78 ± 0􀆰 05a 2􀆰 73 ± 0􀆰 11a 2􀆰 78 ± 0􀆰 05a 1􀆰 96 ± 0􀆰 01b 1􀆰 53 ± 0􀆰 01c
PI 2􀆰 58 ± 0􀆰 03b 2􀆰 58 ± 0􀆰 03b 2􀆰 64 ± 0􀆰 01a 2􀆰 37 ± 0􀆰 01c 2􀆰 61 ± 0􀆰 01b
PE 3􀆰 39 ± 0􀆰 02a 3􀆰 38 ± 0􀆰 01a 3􀆰 37 ± 0􀆰 02a 3􀆰 18 ± 0􀆰 02c 3􀆰 29 ± 0􀆰 01b
PC 3􀆰 41 ± 0􀆰 03c 3􀆰 38 ± 0􀆰 04c 3􀆰 52 ± 0􀆰 02b 3􀆰 42 ± 0􀆰 01c 3􀆰 67 ± 0􀆰 04a
PA 3􀆰 28 ± 0􀆰 02b 3􀆰 21 ± 0􀆰 03c 3􀆰 47 ± 0􀆰 06a 3􀆰 20 ± 0􀆰 03c 3􀆰 31 ± 0􀆰 06b
PS 2􀆰 55 ± 0􀆰 09a 2􀆰 50 ± 0􀆰 07a 2􀆰 27 ± 0􀆰 02b 2􀆰 21 ± 0􀆰 02c 2􀆰 30 ± 0􀆰 02b
MGDG 5􀆰 13 ± 0􀆰 17b 4􀆰 70 ± 0􀆰 19c 4􀆰 38 ± 0􀆰 05d 5􀆰 32 ± 0􀆰 13b 5􀆰 72 ± 0􀆰 01a
DGDG 4􀆰 34 ± 0􀆰 08c 4􀆰 48 ± 0􀆰 13c 4􀆰 25 ± 0􀆰 13c 4􀆰 77 ± 0􀆰 08b 5􀆰 15 ± 0􀆰 03a
Total 3􀆰 12 ± 0􀆰 02d 3􀆰 17 ± 0􀆰 01c 3􀆰 35 ± 0􀆰 01b 3􀆰 39 ± 0􀆰 04b 3􀆰 54 ± 0􀆰 02a
491                                  植 物 分 类 与 资 源 学 报                            第 36卷
4􀆰 34 (control) to 5􀆰 15 (germination 3 d). For ex ̄
traplastidic lipidsꎬ the levels of PG decreased con ̄
tinuallyꎬ from 2􀆰 78 (control) to 1􀆰 53 (germination
3 d). These remarkable changes occurred mainly
during phase III. These patterns were the same as
those for the imbibition of LX and R5 seeds at 25 ℃ .
These results indicate that PEG osmopriming had a
large effect on DBI in chilling ̄sensitive seeds during
phases II and III. The effect of PEG priming was to
increase the degree of unsaturation of plastidic mem ̄
brane in order to enhance the tolerance of imbibi ̄
tional chilling. PEG ̄osmoprimed R5 seeds could
synthesise desaturases under chilled imbibition in or ̄
der to change their membrane fluidity and enhance
photosynthesis. This result further demonstrates that
the DBI of seed membrane lipids is positively corre ̄
lated with their resistance to imbibitional chilling.
3  Conclusion
The present study provides evidence that the
level of unsaturation of membrane lipids is involved
in the tolerance of soybean seeds to imbibitional
chilling. Extensive increases in the extent of total
lipid unsaturation occurred during imbibition and af ̄
ter germination. LX exhibited similar changes to R5
after imbibition at 25 ℃ . The content of total DBI in ̄
creased during germinationꎬ which was mainly due
to the marked increase in the content of plastidic
DBI. There were increases of plastidic DBI in LX af ̄
ter imbibition at 4 ℃ꎬ but these increases were sig ̄
nificantly slower than those after imbibition at 25 ℃ .
Howeverꎬ the patterns of change in R5 significantly
differed from the patterns that occurred upon normal
imbibitionꎬ when even plastidic DBI decreased. PEG
priming slightly changed the DBI in sensitive seeds
(R5). It improved their resistance to injury due to
imbibitional chillingꎬ mainly by increasing their
plastidic DBI during phases II and III. Given that in ̄
creases of plastidic DBI favor the resistance of mem ̄
branes to low temperature injuryꎬ those seeds with
higher DBI values for plastidic lipids might be more
likely to germinate after imbibitional chilling stress.
The delay or prevention of an increase in the degree
of unsaturation in plastidic membrane lipids was thus
the cause of injury due to imbibitional chilling. The
increase in the DBI of plastidic lipids is associated
with the restoration of functional chloroplastic mem ̄
branes needed to support photosynthesis and mem ̄
brane fluidity.
The results of this study suggested that an in ̄
crease in the degree of unsaturation in plastidic
membrane lipids is positively associated with the to ̄
lerance to imbibitional chilling in soybeans. These
findings have not been reported previously for soy ̄
bean seedsꎬ and should provide further insight into
the mechanisms of adaptation toꎬ and survival ofꎬ
imbibitional chilling. Such insights might guide the
development of chilling ̄resistant seeds. Further ana ̄
lyses should be undertaken to study the mechanisms
that underlie differences between these two cultivars
in the way that chilled imbibition affects DBI.
Acknowledgments: The authors thank Mary Roth (Kansas
Lipidomics Research Center) for lipid analysis.
References:
Bakht Jꎬ Bano Aꎬ Dominy Pꎬ 2006. The role of abscisic acid and low
temperature in chickpea ( Cicer arietinum) cold tolerance. II.
Effects on plasma membrane structure and function [J] . Journal
of Experimental Botanyꎬ 57 (14): 3707—3715
Bettaieb Iꎬ Zakhama Nꎬ Wannes WA et al.ꎬ 2009. Water deficit
effects on Salvia officinalis fatty acids and essential oils composi ̄
tion [J] . Scientia Horticulturaeꎬ 120 (2): 271—275
Bewley JDꎬ 1997. Seed germination and dormancy [ J] . The Plant
Cellꎬ 9 (7): 1055—1066
Bramlage WJꎬ Leopold ACꎬ Parrish DJꎬ 1978. Chilling stress to soy ̄
beans during imbibition [J] . Plant Physiologyꎬ 61 (4): 525—
529
Christia Mꎬ 1967. Periods of sensitivity to chilling in germinating cot ̄
ton [J] . Plant Physiologyꎬ 42 (3): 431—433
Devaiah SPꎬ Roth MRꎬ Baughman E et al.ꎬ 2006. Quantitative profi ̄
ling of polar glycerolipid species from organs of wild ̄type Arabi ̄
dopsis and a PHOSPHOLIPASE D alpha 1 knockout mutant
[J] . Phytochemistryꎬ 67 (17): 1907—1924
Dubots Eꎬ Audry Mꎬ Yamaryo Y et al.ꎬ 2010. Activation of the chlo ̄
roplast monogalactosyldiacylglycerol synthase MGD1 by phospha ̄
tidic acid and phosphatidylglycerol [ J] . Journal of Biological
Chemistryꎬ 285 (9): 6003—6011
5912期      YU and LI et al.: The Degree of Unsaturation of Plastidic Membrane Lipids is Positively Associated 􀆺     
Han Cꎬ Yin XJꎬ He DL et al.ꎬ 2013. Analysis of proteome profile in
germinating soybean seedꎬ and its comparison with rice showing
the styles of reserves mobilization in different crops [ J] . PloS
ONEꎬ 8 (2): e56947
Hobbs PRꎬ Obendorf RLꎬ 1972. Interaction of initial seed moisture
and imbibitional temperature on germination and productivity of
soybean [J] . Crop Scienceꎬ 12 (5): 664—667
Jarvis Pꎬ Dormann Pꎬ Peto CA et al.ꎬ 2000. Galactolipid deficiency
and abnormal chloroplast development in the Arabidopsis MGD
synthase 1 mutant [ J] . Proceedings of the National Academy of
Sciences of the United States of Americaꎬ 97 (14): 8175—8179
Leopold ACꎬ 1980. Temperature effects on soybean imbibition and
leakage [J] . Plant Physiologyꎬ 65 (6): 1096—1098
Li WQꎬ Wang Rꎬ Li MY et al.ꎬ 2008. Differential degradation of ex ̄
traplastidic and plastidic lipids during freezing and post ̄freezing
recovery in Arabidopsis thaliana [ J ] . Journal of Biological
Chemistryꎬ 283 (1): 461—468
Lyons JMꎬ 1973. Chilling injury in plants [ J] . Annual Review of
Plant Physiology and Plant Molecular Biologyꎬ 24: 445—466
Marechal Eꎬ Block MAꎬ Dorne AJ et al.ꎬ 1997. Lipid synthesis and
metabolism in the plastid envelope [J] . Physiologia Plantarumꎬ
100 (1): 65—77
Mcconn Mꎬ Browse Jꎬ 1998. Polyunsaturated membranes are required
for photosynthetic competence in a mutant of Arabidopsis [ J] .
The Plant Journalꎬ 15 (4): 521—530
Navari ̄Izzo Fꎬ Quartacci MFꎬ Melfi D et al.ꎬ 1993. Lipid composition
of plasma membranes isolated from sunflower seedlings grown un ̄
der water ̄stress [ J] . Physiologia Plantarumꎬ 87 (4): 508—
514
Obendorf RLꎬ Hobbs PRꎬ 1970. Effect of seed moisture on tempera ̄
ture sensitivity during imbibition of soybean [J] . Crop Scienceꎬ
10 (5): 563—566
Osmond DLꎬ Wilson RFꎬ Raper CDꎬ 1982. Fatty ̄acid composition
and nitrate uptake of soybean roots during acclimation to low ̄
temperature [J] . Plant Physiologyꎬ 70 (6): 1689—1693
Pollock BMꎬ 1969. Imbibition temperature sensitivity of lima bean
seeds controlled by initial seed moisture [ J] . Plant Physiologyꎬ
44 (6): 907—911
Pollock BMꎬ Toole VKꎬ 1966. Imbibition period as the critical tem ̄
perature sensitive stage in germination of lima bean seeds [ J] .
Plant Physiologyꎬ 41 (2): 221—229
Posmyk MMꎬ Corbineau Fꎬ Vinel D et al.ꎬ 2001. Osmoconditioning
reduces physiological and biochemical damage induced by chill ̄
ing in soybean seeds [ J] . Physiologia Plantarumꎬ 111 ( 4):
473—482
Powell AAꎬ Matthews Sꎬ 1978. The damaging effect of water on dry
pea embryos during imbibition [J] . Journal of Experimental Bot ̄
anyꎬ 29 (5): 1215—1229
Quartacci MFꎬ Glisic Oꎬ Stevanovic B et al.ꎬ 2002. Plasma mem ̄
brane lipids in the resurrection plant Ramonda serbica following
dehydration and rehydration [ J] . Journal of Experimental Bota ̄
nyꎬ 53 (378): 2159—2166
Quartacci MFꎬ Pinzino Cꎬ Sgherri CL et al.ꎬ 1995. Lipid ̄composition
and protein dynamics in thylakoids of two wheat cultivars differ ̄
ently sensitive to drought [ J] . Plant Physiologyꎬ 108 ( 1):
191—197
Rawyler Aꎬ Pavelic Dꎬ Gianinazzi C et al.ꎬ 1999. Membrane lipid in ̄
tegrity relies on a threshold of atp production rate in potato cell
cultures submitted to anoxia [ J] . Plant Physiologyꎬ 120 (1):
293—300
Simon EWꎬ 1974. Phospholipids and plant membrane permeability
[J] . New Phytologistꎬ 73 (3): 377—420
Toumi Iꎬ Gargouri Mꎬ Nouairi I et al.ꎬ 2008. Water stress induced
changes in the leaf lipid composition of four grapevine genotypes
with different drought tolerance [ J] . Biologia Plantarumꎬ 52
(1): 161—164
Wallis JGꎬ Browse Jꎬ 2002. Mutants of Arabidopsis reveal many roles
for membrane lipids [ J] . Progress in Lipid Researchꎬ 41 (3):
254—278
Welti Rꎬ Li WQꎬ Li MY et al.ꎬ 2002. Profiling membrane lipids in
plant stress responses: Role of phospholipase D alpha in freezing ̄
induced lipid changes in Arabidopsis [ J] . Journal of Biological
Chemistryꎬ 277 (35): 31994—32002
Willing RPꎬ Leopold ACꎬ 1983. Cellular expansion at low ̄tempera ̄
ture as a cause of membrane lesions [ J] . Plant Physiologyꎬ 71
(1): 118—121
Woodstock LWꎬ Tao KLꎬ 1981. Prevention of imbibitional injury in
low vigor soybean embryonic axes by osmotic control of water ̄up ̄
take [J] . Physiologia Plantarumꎬ 51 (1): 133—139
Xu LXꎬ Han LBꎬ Huang BRꎬ 2011. Membrane fatty acid composition
and saturation levels associated with leaf dehydration tolerance
and post ̄drought rehydration in kentucky bluegrass [ J] . Crop
Scienceꎬ 51 (1): 273—281
Yin GKꎬ Sun HMꎬ Xin X et al.ꎬ 2009. Mitochondrial damage in the
soybean seed axis during imbibition at chilling temperatures [J] .
Plant and Cell Physiologyꎬ 50 (7): 1305—1318
Zheng GWꎬ Chen Jꎬ Li WQꎬ 2012. Profiling of membrane lipids of
Arabidopsis roots during catechin treatment [ J] . Plant Diversity
and Resources (植物分类与资源学报)ꎬ 34 (4): 383—390
Zheng GWꎬ Tian Bꎬ Zhang FJ et al.ꎬ 2011. Plant adaptation to fre ̄
quent alterations between high and low temperatures: remodelling
of membrane lipids and maintenance of unsaturation levels [ J] .
Plant Cell and Environmentꎬ 34 (9): 1431—1442
Zheng GHꎬ 1988. Studies on the imbibitional chilling injury and the
reparation of damaged membrane systems in soybean seeds [J] .
Science China Chemistryꎬ 31 (8): 936—936
Zheng GHꎬ 1991. Physiologicalꎬ biochemical and ultrastructural as ̄
pects of imbibitional chilling injury in seeds: a review of work
carried out at the Beijing Botanical Garden [J] . Seed Science Re ̄
searchꎬ 1 (02): 127—134
691                                  植 物 分 类 与 资 源 学 报                            第 36卷