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Encapsulation-Dehydration and Encapsulation-VitrificationBased Cryopreservation of in vitro-Grown Shoot-Tips of Medicinal Plant Astragalus membranaceus

药用植物黄芪离体培养茎尖的包埋脱水法和包埋玻璃化法超低温保存



全 文 :药用植物黄芪离体培养茎尖的包埋脱水法和包埋玻璃化法超低温保存∗
尹明华ꎬ 洪森荣∗∗
(上饶师范学院生命科学学院ꎬ 江西 上饶  334001)
摘要: 为找出一条黄芪种质长期包埋脱水法保存和包埋玻璃化法保存的程序ꎬ 以来源于黄芪离体生长腋芽
的黄芪茎尖并包埋成海藻酸钙珠ꎮ 随后ꎬ 在 MS+0􀆰 75 mol􀅰L-1蔗糖的液体培养基中 25 ℃下预培养 5 d 后ꎬ
放于干硅胶上无菌干燥 5 hꎬ 直至含水量达 23􀆰 1% (以鲜重为基础) 时将材料投入液氮保存ꎮ 保存 1 d 后ꎬ
茎尖在 40 ℃水浴中化冻 2~3 min并转入固体培养基上进行再生培养ꎬ 2周后大约 50%的茎尖可再生出芽ꎮ
黄芪茎尖包埋玻璃化法超低温保存程序也被优化ꎬ 同样包埋成海藻酸钙凝胶珠的茎尖在 MS+1 mg􀅰L-1 6 ̄
BA+0􀆰 05 mg􀅰L-1 NAA+0􀆰 75 mol􀅰L-1蔗糖的液体培养基中 25 ℃预培养 3 dꎬ 用 2 mol􀅰L-1甘油+0􀆰 4 mol􀅰L-1
蔗糖装载液 25 ℃装载 90 min并再用 PVS2在 0 ℃下处理 120 min后直接投入液氮ꎮ 保存 1 d后ꎬ 取出材料
在 37 ℃水浴中化冻 2~3 minꎬ 并用MS+1 mg􀅰L-1 6 ̄BA+0􀆰 05 mg􀅰L-1 NAA+1􀆰 2 mol􀅰L-1蔗糖的液体培养基进
行 10 min的洗涤后转入 MS+1 mg􀅰L-1 6 ̄BA+0􀆰 05 mg􀅰L-1 NAA的固体培养基上进行再生培养ꎮ 茎尖的再生
率接近 80%ꎮ 以上两种超低温保存方式均未造成再生植株形态学上的变化ꎮ 因此ꎬ 包埋脱水法和包埋玻
璃化法两种常规方法对于黄芪茎尖超低温保存来说均具有重要的意义ꎮ
关键词: 超低温保存ꎻ 包埋脱水法ꎻ 包埋玻璃化法ꎻ 黄芪ꎻ 茎尖ꎻ 种质保存
中图分类号: Q 943ꎬ S 632􀆰 3        文献标志码: A          文章编号: 2095-0845(2015)06-767-12
Encapsulation ̄Dehydration and Encapsulation ̄Vitrification ̄Based
Cryopreservation of in vitro ̄Grown Shoot ̄Tips of
Medicinal Plant Astragalus membranaceus
YIN Ming ̄huaꎬ HONG Sen ̄rong∗∗
(College of Life Sciencesꎬ Shangrao Normal Universityꎬ Shangraoꎬ Jiangxi 334001ꎬ China)
Abstract: Shoot tips of A􀆰 membranaceus excised from in vitro ̄grown axillary bud were encapsulated in calcium ̄algi ̄
nate beads. Subsequentlyꎬ shoot tips were precultured in liquid MS medium enriched with 0􀆰 75 mol􀅰L-1 sucrose for
5 d at 25 ℃ and then desiccated aseptically on dried silica gel for 5 h to a water content of 23􀆰 1% (fresh weight ba ̄
sis) prior to immersion in liquid nitrogen (LN) for 1 d. After rewarming at a 40 ℃ water bath for 2-3 min and trans ̄
ferred to solid culture medium for shoot tip recovery. About 50% of cryopreserved shoot ̄tips grew into shoots within
2 weeks after plating. Cryopreservation of Astragalus membranaceus (Fisch.) Bge. shoot tips by encapsulation ̄vitrifi ̄
cation has also been developed. Excised shoot tips were firstly encapsulated into alginate ̄gel beads and then precul ̄
tured in liquid MS medium containing 1 mg􀅰L-1 6 ̄BAꎬ 0􀆰 05 mg􀅰L-1 NAA and 0􀆰 75 mol􀅰L-1 sucrose at 25℃ for 3 d.
After loading for 90 min with a mixture of 2 mol􀅰L-1 glycerol and 0􀆰 4 mol􀅰L-1 sucrose at 25 ℃ꎬ shoot tips were de ̄
hydrated with PVS2 for 120 min at 0 ℃ prior to direct immersion in liquid nitrogen for 1 d. After rapidly thawing at a
37 ℃ water bath for 2-3 minꎬ shoot tips were washed for 10 min with liquid MS medium supplemented with 1 mg􀅰L-1
6 ̄BAꎬ 0􀆰 05 mg􀅰L-1 NAA and 1􀆰 2 mol􀅰L-1 sucrose at 25 ℃ and then post ̄cultured on solid MS medium supplemen ̄
植 物 分 类 与 资 源 学 报  2015ꎬ 37 (6): 767~778
Plant Diversity and Resources                                    DOI: 10.7677 / ynzwyj201515091

∗∗
Funding: The National Natural Science Fund in China (31360072)
Author for correspondenceꎻ E ̄mail: hongsenrong@163􀆰 com
Received date: 2015-05-26ꎬ Accepted date: 2015-09-23
作者简介: 尹明华 (1973-) 女ꎬ 副教授ꎬ 主要从事植物生物技术方面的研究ꎮ
ted with 2 mg􀅰L-1 6 ̄BAꎬ 0􀆰 05 mg􀅰L-1 NAA. The regeneration rate of shoot tips amounted to nearly 80%. Both of
plantlets regenerated from cryopreserved shoot tips were morphologically uniformꎬ which both showed as that of con ̄
trol plants. Thusꎬ this encapsulation ̄dehydration and encapsulation ̄vitrification technique appears promising as a
routine method for the cryopreservation of shoot ̄tips of A􀆰 membranaceus.
Key words: Cryopreservationꎻ Encapsulation ̄dehydrationꎻ Encapsulation ̄vitrificationꎻ Astragalus membranaceus
(Fisch.) Bge.ꎻ Shoot tipsꎻ Germplasm conservation
  Astragalus membranaceus (Fisch.) Bge.ꎬ belong ̄
ing to the family Legumenosae (Xue et al.ꎬ 2008)ꎬ
also known as Huangqi in Chineseꎬ is one of the
most widely commonly used in traditional Chinese
medicine ( TCM) for centuries to enhance the im ̄
mune systemꎬ increase stamina and enduranceꎬ and
to treat many diseases as an immunostimulantꎬ tonicꎬ
diureticꎬ antidiabeticꎬ analgesicꎬ expectorantꎬ and
sedative (Hu et al.ꎬ 2012ꎻ Shibli and Al ̄Jubooryꎬ
2000). To dateꎬ because of excessive commercial
exploitation and collection by people to be used in
the Chinese herbal drug industryꎬ the natural re ̄
sources of this medicinal plant drastically being re ̄
duced hence needs be conserved.
Cryopreservation has been considered to be an i ̄
deal tool of long ̄term storage of germplasmꎬ which
may facilitate the conservation in vitro of plant germ ̄
plasm resource (Sarab et al.ꎬ 2012) and has many
advantages in terms of long ̄term storagecapability and
minimal storage space and maintenance requirements
(Hong and Yinꎬ 2012aꎬb). Nowadaysꎬ cryopreserva ̄
tion has been successfully used for the storage of vari ̄
ous tissue culturesꎬ such as cell suspensionsꎬ calliꎬ
shoot tips of many medicinal species. In additionꎬ
some cryopreservation procedures such as vitrifica ̄
tionꎬ encapsulation dehydrationꎬ encapsulation vitrifi ̄
cationꎬ droplet vitrification have been developed (Ma
et al.ꎬ 2012). Among of these proceduresꎬ the encap ̄
sulation dehydration and encapsulation ̄vitrification
techniques are two methods of the most popular (Khod ̄
damzadeh et al.ꎬ 2011ꎻ Martín et al.ꎬ 2011).
Shoot tips appear as ideal candidates for cryopr ̄
eservation and are preferred over cell and callus cul ̄
tures because the constituent cells of shoot tips are
little differentiated and genetically stable compared
to the callus and suspension cultures ( Florence et
al.ꎬ 1993ꎻ Wang et al.ꎬ 2002ꎻ Erica and Keithꎬ
2012). To dateꎬ cryopreservation of A􀆰 membranaceus
germplasm has also been successfully applied to
hairy root cultures ( Xue et al.ꎬ 2008) and seeds
(Toshiro et al.ꎬ 1995). Howeverꎬ there are no re ̄
ports on the application of cryopreservation to shoot
tips of A􀆰 membranaceus. The objective of the present
study wasꎬ thereforeꎬ to develop respectively a simple
method for cryopreservation of shoot tips of A􀆰 mem ̄
branaceus by encapsulation vitrification and encapsu ̄
lation dehydration.
1  Materials and methods
1􀆰 1  Plant materials
The seeds of A􀆰 membranaceus were purchased
in May 2008 from medicine professional cooperatives
of Wutong Town ( Jingning Countyꎬ Zhejiang prov ̄
inceꎬ People’s Republic of China)ꎬ their origin was
Bozhou City in Anhui province.
1􀆰 2  In vitro culture
Firstlyꎬ the seeds were immersed in 70% etha ̄
nol for 20 s followed by 0􀆰 1% HgCl2 for 12 min and
then washed three times with sterile distilled water.
Finally the seeds were cultured on 1 / 2 ̄strength MS
basal medium which contained 1 / 2 ̄macro ̄ and mi ̄
cro ̄nutrients according to Murashige and Skoog (Mur ̄
ashige and Skoogꎬ 1962)ꎬ supplemented with 30 g􀅰L-1
sucrose and semi ̄solidified with 3􀆰 5 g􀅰L-1 agar. No
plant growth regulators were added. Media were ad ̄
justed to pH 5􀆰 8 prior to autoclaving at 121 ℃ for
20 min. The growth conditions were at (25 ± 1) ℃
under a 14 h light / 10 h dark photoperiod with a light
intensity of 36 μmol􀅰m-2 s-1 provided by cool ̄white
fluorescent tubes (Hong et al.ꎬ 2010). Thereafterꎬ the
seeds germinated after one week and formed plantlets.
867                                  植 物 分 类 与 资 源 学 报                            第 37卷
The plantlets were then cut into nodal segments
(1-2 cm in length) with one axillary bud and cul ̄
tured on 40 mL basal MS medium supplemented with
2 mg􀅰L-1 Kinetin (KT)ꎬ 1 mg􀅰L-1α ̄naphthalene ̄
acetic acid (NAA)ꎬ 30 g􀅰L-1 sucrose and 7􀆰 5 g􀅰
L-1 agar and held at (25 ± 1) ℃ under 14 h light / 10 h
dark photoperiod at 36 μmol􀅰m-2 s-1 . Subculture of
single ̄node stem segments to fresh medium were
made at 4 ̄week intervals. Axillary shoot tipsꎬ about
1 mm in lengthꎬ consisting of an apical dome with 1
-3 leaf primordia were excised under a stereo micro ̄
scope from the stem of 20 ̄day ̄old plantlets (3-5 cm
in height) that had developed from single ̄node stem
segments and used for cryopreservation.
1􀆰 3  Cryopreservation procedure by encapsula ̄
tion dehydration
The shoot tips were suspended in calcium ̄free
MS medium supplemented with 2% sodium alginate
(Viscosity: 200 ± 20 mpa􀆰 s / 1 Kgꎻ Shanghai Yuanye
Biotechnology Co. Ltd. 9005 ̄38 ̄3) and 0􀆰 4 mol􀅰L-1
sucrose. The solution containing the shoot tips was
dispensed with a wide mouth sterile pipette into 0􀆰 1
mol􀅰L-1 CaCl2 solution containing 0􀆰 4 mol􀅰L
-1 su ̄
crose at (25 ± 1) ℃ for 40 minꎬ to allow solidifica ̄
tion of the calcium alginate beads (about 4 mm in di ̄
ameter)ꎬ each bead containing one shoot ̄tip. The me ̄
dium was poured off and the beads washed three times
with MS basal medium. The beads were then precul ̄
tured in MS basal medium but containing various su ̄
crose concentrations (0ꎬ 0􀆰 25ꎬ 0􀆰 5ꎬ 0􀆰 75ꎬ 1mol􀅰L-1)
on a rotary shaker at 30 r / min at (25 ± 1) ℃ under a
14 h light / 10 h dark photoperiod with a light intensi ̄
ty of 36 μmol􀅰m-2 s-1ꎬ 5 d in each sucrose concen ̄
tration. After removing any remaining liquid precul ̄
ture medium by sterile pipetteꎬ the precultured beads
were rapidly surface ̄dried on sterile filter paper and
transferred in sealed petri dishes containing sterile
dried silica ̄gel (50 g / 20 beads) for 5 h. Tempera ̄
ture and relative air humidity during desiccation
were controlled to (25 ± 1) ℃ and 14%-15%ꎬ re ̄
spectively as determined with a Thermo recorderꎬ
and remained stable among treatments.
In other parallel experimentsꎬ to determine the
effects of preculture time with MS basal medium sup ̄
plemented with 0􀆰 75 mol􀅰L-1 sucroseꎬ dehydration and
exposure time to LN on the recovery of shoot tips after
cryopreservationꎬ the preculture periods of beadsꎬ the
dehydration time and conservation time of precultured
beads were ranged from 0 to 7 dꎬ 0 to 11 h and 1 to
150 dꎬ respectively. We also determined the percent ̄
age of water loss from fresh and precultured ( for 3
days) beads after 0-9 h of drying. A water content
curve was obtained by weighing every two hours. Each
point of curve is based on three replicates of five
beads each. The water content of the beads ( on a
fresh ̄weight basis) was assessed by drying them in an
oven at 80 ℃ for 48 h to constant weight after dehy ̄
dration. Following desiccationꎬ approximately 10 dried
beads were transferred into 10 ̄ml cryotubes and di ̄
rectly immersed in liquid nitrogen (LN) for 1 d.
After rewarming in a water bath at 25℃ꎬ 30℃ꎬ
40 ℃ꎬ 45 ℃ for 2-3 minꎬ respectivelyꎬ cryopreserved
beads were removed from the cryovial and directly
transferred to culture. One half of the beads were
surface ̄dried by blotting on sterilized filter paper and
then plated on solid MS medium supplemented with
2 mg􀅰L-1 6 ̄BAꎬ 0􀆰 05 mg􀅰L-1 NAA at (25 ± 1) ℃
in the dark for 3 days and then transferred to the
light conditions (under 14 h photoperiod at 36 μmol􀅰
m-2 s-1)ꎬ The other half were surface ̄dried and then
plated on solid MS medium supplemented with 2 mg􀅰
L-1 6 ̄BAꎬ 0􀆰 05mg􀅰L-1 NAA at (25 ± 1) ℃ under 14
h photoperiod at 36 μmol􀅰m-2 s-1 without 3 ̄day
dark incubation.
Shoot tips were recorded as regrowing if they
showed obvious signs of growthꎬ such as expansion
of leaves. Survival percentage of the shoot tips was
recorded as a percentage of the total number of shoot
tips forming normal shoots 4 weeks after plating. Sur ̄
viving shoot tips were extracted from the alginate
beads one week after post ̄culture and then trans ̄
ferred to fresh solid MS medium with 2 mg􀅰L-1 KTꎬ
1 mg􀅰L-1 NAA for plant regeneration (under 14 h
photoperiod at 36 μmol􀅰m-2 s-1) (Yin and Caoꎬ
9676期      YIN and HONG: Encapsulation ̄Dehydration and Encapsulation ̄Vitrification ̄Based Cryopreservation of 􀆺     
2011). The morphological index ( i􀆰 e. the height of
plantletꎬ the length of internode and the number of
leaf and root) of cryopreserved plantlets and non ̄
cryopreserved plantlets ( i􀆰 e. samples without any
treatment) was compared after 60 days.
1􀆰 4  Cryopreservation procedure by encapsula ̄
tion ̄vitrification
Excised shoot tips were suspended in calcium ̄free
MS inorganic medium supplemented with 2% Na ̄algi ̄
nate and 0􀆰 4 mol􀅰L-1 sucrose. The mixture including
shoot tips were picked up using 1 mL sterile wide ̄
mouth pipette and then dispensed into 0􀆰 1 mol􀅰L-1
CaCl2 solution supplemented with 0􀆰 4 mol􀅰L
-1 su ̄
crose and kept in calcium chloride solution for 40 min
for polymerization at 25 ℃ to form beads about 4 mm
in diameterꎬ each bead containing one shoot tip.
These beads were surface ̄dried by plating them
on a sterilized filter paper and then precultured in
liquid basal MS media containing 0􀆰 75 mol􀅰L-1 su ̄
crose supplemented with 1 mg􀅰L-1 6 ̄BAꎬ 0􀆰 05 mg􀅰
L-1 NAA for 0ꎬ 1ꎬ 3ꎬ 5 or 7 days on a rotary shaker
at 30 r / min at (25 ± 1) ℃ under 14 h photoperiod at
36 μmol􀅰m-2s-1 . The effects of the preculture on the
survival of cryopreserved shoot tips were also meas ̄
ured at a range of sucrose concentrations (0ꎬ 0􀆰 25ꎬ
0􀆰 5ꎬ 0􀆰 75 and 1 mol􀅰L-1) in liquid basal MS medi ̄
um supplemented with 1 mg􀅰L-1 6 ̄BAꎬ 0􀆰 05 mg􀅰L-1
NAA for 3 days.
Following precultureꎬ the beads were surface ̄
dried by plating them on a sterilized filter paper and
loaded in a loading solution in a 100 ̄ml Erlenmeyer
flask for various durations ranging from 0 to 180 min
at 25 ℃ . The loading solution was composed of liq ̄
uid basal MS medium supplemented with 0􀆰 4 sucrose
and 2 mol􀅰L-1 glycerol (Matsumoto et al.ꎬ 1994).
The encapsulated shoot tips were then rapidly
surface ̄dried by plating them on a sterilized filter
paper and directly dehydrated with a highly concen ̄
trated plant vitrification solution2 ( PVS2) solution
(Sakai et al.ꎬ 1990) in a 100 ̄ml Erlenmeyer flask
at 24 ℃ or 0 ℃ for various lengths of time (0-180
min). PVS2 contains 30% glycerolꎬ 15% ethylene
glycol and 15% dimethylsulfoxide (DMSO) in MS
medium with 0􀆰 4 mol􀅰L-1 sucrose (pH 5􀆰 8). After
dehydrationꎬ the beads were rapidly surface ̄dried by
blotting on cellulose tissue and then 10 beads were
transferred into a 10 ̄ml cryotube containing 2􀆰 5 mL
fresh PVS2 and immersed directly in liquid nitrogen
(LN) for at least 1 d.
After cryopreservationꎬ cryotubes were rapidly
rewarmed in a water bath at 25 ℃ꎬ 37 ℃ and 45 ℃
for 2-3 min respectively. PVS2 solution was drained
from the cryotubes and replaced with 0ꎬ 0􀆰 4ꎬ 0􀆰 8ꎬ
1􀆰 2ꎬ 1􀆰 6 mol􀅰L-1 sucrose prepared in liquid MS
medium supplemented with 1 mg􀅰L-1 6 ̄BAꎬ 0􀆰 05 mg
􀅰L-1 NAA at 25 ℃ꎬ which was changed three timesꎬ
every time held for 10 min. One half of the beads
were surface ̄dried by blotting on sterilized filter pa ̄
per and then plated on solid MS medium supplemen ̄
ted with 2 mg􀅰L-1 6 ̄BAꎬ 0􀆰 05 mg􀅰L-1 NAA at (25
± 1) ℃ in the dark for 3 days and then transferred to
the light conditions (under 14 h photoperiod at 36
μmol􀅰m-2 s-1)ꎬ The other half were surface ̄dried and
then plated on solid MS medium supplemented with 2
mg􀅰L-1 6 ̄BAꎬ 0􀆰 05 mg􀅰L-1 NAA at (25 ± 1) ℃
under 14 h photoperiod at 36 μmol􀅰m-2 s-1 without
3 ̄day dark incubation.
Shoot tips were recorded as regrowing if they
showed obvious signs of growthꎬ such as expansion of
leaves. Survival rate of the shoot tips was recorded as
a percentage of the total number of shoot tips forming
normal shoots 2 weeks after plating. Surviving shoot
tips were extracted from the alginate beads one week
after post ̄culture and then transferred to solid MS
medium with 2 mg􀅰L-1 KTꎬ 1 mg􀅰L-1 NAA for plant
regeneration (under 14 h photoperiod at 36 μmol􀅰
m-2 s-1) (Yin and Caoꎬ 2011). The morphological
index (i􀆰 e. the height of plantletꎬ the length of in ̄
ternode and the number of leaf and root) of cryopre ̄
served plantlets and the plantlets without cryopreser ̄
vation was compared after 60 days.
1􀆰 5  Statistical analysis
Each cryopreservation experiment included at
least 15 shoot tips. Each cryopreservation experiment
077                                  植 物 分 类 与 资 源 学 报                            第 37卷
was repeated three times. All data were subjected to
analysis of variance (one way ANOVA) and signifi ̄
cance (P < 0􀆰 05) was determined with Duncan’ s
multiple range test. Statistical tests were performed
by the help of SPSS statistical software (19􀆰 0).
2  Results
2􀆰 1  Cryopreservation by encapsulation dehydration
2􀆰 1􀆰 1  Effect of preculture on survival  All the shoot ̄
tips without preculture treatment died after cryopreser ̄
vation (Fig􀆰 1-2). Significant variations in survival of
cryopresrved shoot tips were obtained along with the
different concentrations of sucrose (0-1 mol􀅰L-1) in
the preculture medium. Maximum survival percentage
(52􀆰 6%) of cryopreserved shoot tips was recorded
when precultured with 0􀆰 75 mol􀅰L-1 sucrose (Fig􀆰 1).
There was a significant effect of preculture with 0􀆰 75
mol􀅰L-1 sucrose for different periods (0-7 days) on
survival of cryopreserved shoot tipsꎬ prolonged precul ̄
ture was found to improve survival significantly and the
greatest survival (49􀆰 6%) was obtained when cryopre ̄
served shoot tips were precultured for 5 days (Fig􀆰 2).
2􀆰 1􀆰 2  Effect of desiccation on survival  The initial
water content of the precultured beads was 76􀆰 8%
on a fresh weight basis (after preculture in 0􀆰 75 mol
􀅰L-1 sucrose for 3 days)ꎬ but abruptly decreased to
36􀆰 5% within the first 3 h and then gradually dropped
to approximately 25􀆰 3% after 5 hꎬ 23􀆰 1% after 7 hꎬ
17􀆰 9% after 9 h and 15􀆰 4% after 11 h ( Fig􀆰 3).
Meanwhileꎬ survival percentage of cryopreserved shoot ̄
tips greatly changed with the water content of beads
during dehydration periods ranging from 0 to 11 h
(Fig􀆰 4). Under conditions of no dehydration no sur ̄
vival was obtained after exposure to LN. For survival
of the shoot tips the water content of the precultured
beads had to be 25􀆰 3% or lessꎬ which was reached
Fig􀆰 1  Effect of sucrose concentration in the preculture medium on
survival of cryopreserved A􀆰membranaceus shoot tips by Encapsulation ̄
dehydration. Bars correspond to SE of means of three replications.
Values with different letters are significantly different using
Duncan’s Multiple Range Test (P<0􀆰 05)
Fig􀆰 2  Effect of preculture time on survival of cryopreserved
A􀆰 membranaceus shoot tips by Encapsulation ̄dehydration. Bars
correspond to SE of means of three replications. Values with
different letters are significantly different using Duncan’s
Multiple Range Test (P<0􀆰 05)
Fig􀆰 3  A desiccation curve of encapsulated precultured beads.
Bars correspond to SE of means of three replications. Values
with different letters are significantly different using
Duncan’s Multiple Range Test (P<0􀆰 05)
Fig􀆰 4  Effect of water content on survival of cryopreserved A􀆰 membr ̄
anaceus shoot tips by Encapsulation ̄dehydration. Bars correspond to SE
of means of three replications. Values with different letters are signifi ̄
cantly different using Duncan’s Multiple Range Test (P<0􀆰 05)
1776期      YIN and HONG: Encapsulation ̄Dehydration and Encapsulation ̄Vitrification ̄Based Cryopreservation of 􀆺     
by 5 h of dehydration. The highest survival percent ̄
age (53􀆰 4%) was obtained at 23􀆰 1% water content
(dried for 7 h).
2􀆰 1􀆰 3  Effect of conservation time on survival  As is
showed in Fig􀆰 5ꎬ extending storage duration in LN 1
to 150 days did not cause significant change in the
survival percentage of cryopreserved shoot tips.
2􀆰 1􀆰 4  Effect of rewarming on survival   From the
results shown in Fig􀆰 6ꎬ the highest survival percent ̄
age was obtained at 40 ℃ .
2􀆰 1􀆰 5  Effect of dark culture after LN exposure on
survival  As is showed in Fig􀆰 7ꎬ culture condition
after cryopreservation affected the survival of shoot
tips. When cryopreserved shoot tips were cultured in
the dark for 3 days and then transferred to the light
conditions (under 14 h light / 10 h dark photoperiod
at 36 μmol􀅰m-2 s-1)ꎬ the survival percentage in ̄
creased to 54􀆰 4%.
2􀆰 1􀆰 6  Plant regeneration  Successfully cryopreserved
shoot tips began to turn green after 3 days and re ̄
sumed growth after 7 days and developed normal
shoots within 14 days without intermediary callus for ̄
mation. The shoots were subsequently extracted from
the alginate beads one week after post ̄culture and
then transferred to solid MS medium with 2 mg􀅰L-1
KTꎬ 1 mg􀅰L-1 NAA. After 30 days rooting occurred
and formed complete plants (Fig􀆰 8). No morpholog ̄
ical abnormalities were observed in the cryopreserved
and the controlled plantlets (P > 0􀆰 05) (Fig􀆰 9).
2􀆰 2  Cryopreservation by encapsulation ̄vitrification
2􀆰 2􀆰 1  Effect of preculture on survival  Survival rate
of shoot tips significantly increased as the sucrose
concentration in the preculture medium increased and
the highest survival rate (72􀆰 6%) was obtained with
0􀆰 75 mol􀅰L-1 sucrose (Fig􀆰 10). At the same timeꎬ
the survival rate of cryopreserved shoot tips remained
continuous increase and up to a maximum value (a ̄
bout 78􀆰 5%) as the preculture period increased from
1 to 3 daysꎬ and then started to decrease (Fig􀆰 11).
2􀆰 2􀆰 2  Effect of loading time on survival  As shown
in Fig􀆰 12ꎬ survival of shoot tips was markedly af ̄
fected by loading time. Without loading treatmentꎬ
no shoot tips survived freezing in LNꎬ whereas a
loading time of 90 min gave the highest survival rate
of shoot tips (about 72􀆰 9%).
Fig􀆰 5  Effect of conservation time on survival of cryopreserved
A􀆰 membranaceus shoot tips by Encapsulation ̄dehydration. Bars
correspond to SE of means of three replications. Values with
different letters are significantly different using Duncan’s
Multiple Range Test (P<0􀆰 05)
Fig􀆰 6  Effect of rewarming temperature on survival of cryopreserved
A􀆰 membranaceus shoot tips by Encapsulation ̄dehydration. Bars
correspond to SE of means of three replications. Values with
different letters are significantly different using Duncan’s
Multiple Range Test (P<0􀆰 05)
Fig􀆰 7  Effect of dark culture after LN exposure on survival of cryop ̄
reserved A􀆰 membranaceus shoot tips by Encapsulation ̄dehydration.
Bars correspond to SE of means of three replications. Values
with different letters are significantly different using
Duncan’s Multiple Range Test (P<0􀆰 05)
277                                  植 物 分 类 与 资 源 学 报                            第 37卷
Fig􀆰 8  Plantlets regenerated from cryopreserved shoot tips
Fig􀆰 9  Comparison of morphological indexes of plantlets regenerated
from cryopreserved shoot tips and non ̄cryopreserved shoot tips of
A􀆰 membranaceus. Mean of each of the indexes between the two
types of plantlets were not significant (P>0􀆰 05)
Fig􀆰 10  Effect of sucrose concentration in preculture medium on
survival of cryopreserved A􀆰 membranaceus (Fisch.) Bge. shoot tips
by encapsulation vitrification. Bars correspond to SE of means of
three replications. Values with different letters are significantly
different using Duncan’s Multiple Range Test (P<0􀆰 05)
Fig􀆰 11  Effect of preculture time on survival of cryopreserved A􀆰 me ̄
mbranaceus (Fisch.) Bge. shoot tips by encapsulation vitrification.
Bars correspond to SE of means of three replications. Values with
different letters are significantly different using Duncan’s
Multiple Range Test (P<0􀆰 05)
Fig􀆰 12  Effect of loading time on survival of cryopreserved A􀆰 me ̄
mbranaceus (Fisch.) Bge. shoot tips by encapsulation vitrification.
Bars correspond to SE of means of three replications. Values with
different letters are significantly different using Duncan’s
Multiple Range Test (P<0􀆰 05)
2􀆰 2􀆰 3  Effect of time and temperature of exposure to
PVS2 on survival   At 24 ℃ꎬ the survival rate of
shoot tips was increased considerably between 30
and 60 min and reached a maximum (about 74􀆰 5%)
at 90 min (Fig􀆰 13). At 0 ℃ꎬ shoot tips treated with
PVS2 for 120 min retained the highest survival rate
(Fig􀆰 14). Moreoverꎬ the survival rate of shoot tips
dehydrated with PVS2 at 0 ℃ was much higher than
that of shoot tips dehydrated with PVS2 at 24 ℃ (P
<0􀆰 05).
3776期      YIN and HONG: Encapsulation ̄Dehydration and Encapsulation ̄Vitrification ̄Based Cryopreservation of 􀆺     
Fig􀆰 13  Effect of time of exposure to PVS2 at 24 ℃ on survival
of cryopreserved A􀆰 membranaceus (Fisch.) Bge. shoot tips by
encapsulation vitrification. Bars correspond to SE of means of
three replications. Values with different letters are significantly
different using Duncan’s Multiple Range Test (P<0􀆰 05)
Fig􀆰 14  Effect of time of exposure to PVS2 at 0 ℃ on survival
of cryopreserved A􀆰 membranaceus (Fisch.) Bge. shoot tips by
encapsulation vitrification. Bars correspond to SE of means of
three replications. Values with different letters are significantly
different using Duncan’s Multiple Range Test (P<0􀆰 05)
2􀆰 2􀆰 4  Effect of freezing conservation time on survival
As shown in Fig􀆰 15ꎬ there were some differ ̄
ence in the survival rate of shoot tipsꎬ but the differ ̄
ences were not significant (P>0􀆰 05).
2􀆰 2􀆰 5  Effect of thawing temperature on survival
As shown in Fig􀆰 16ꎬ the optimal thawing tem ̄
perature was 37 ℃ . The temperatures above and be ̄
low 37 ℃ both resulted in reduced viability and
showed poor survival rates.
2􀆰 2􀆰 6   Effect of sucrose concentration in washing
medium on survival  As are shown in Fig􀆰 17ꎬ when
the sucrose concentration was increased up to 1􀆰 2
mol􀅰L-1ꎬ the survival rate was maximum (76􀆰 8%).
Howeverꎬ the survival rate began to decrease with
higher sucrose concentration.
2􀆰 2􀆰 7  Effect of dark culture after freezing on survival
As shown in Fig􀆰 18ꎬ when cryopreserved shoot
tips were incubated in the light conditions (under
14 h photoperiod at 36 μmol􀅰m-2 s-1) subsequent to
a 3 ̄d darkꎬ the survival rate was significantly higher
than that of shoot tips incubated in the light condi ̄
tions (under 14 h photoperiod at 36 μmol􀅰m-2 s-1)
without a 3 ̄d dark.
2􀆰 2􀆰 8  Plant regeneration   Successfully encapsula ̄
ted vitrified shoot tips resumed growth in about 7 days
and developed vigorous morphologically normal shoots.
The shoots were subsequently extracted from the algi ̄
nate beads one week after post ̄culture and then trans ̄
ferred to solid MS medium with 2 mg􀅰L-1 KTꎬ 1 mg􀅰
L-1 NAA. After 30 days rooting also occurred and
formed complete plants (Fig􀆰 19). Almost all of the
surviving shoots formed roots and no morphological
abnormalities were observed in the plantlets developed
from cryopreserved shoot tips (Fig􀆰 20ꎬ P>0􀆰 05).
Fig. 15  Effect of freezing conservation time on survival of
cryopreserved A􀆰 membranaceus (Fisch.) Bge. shoot tips by
encapsulation vitrification. Bars correspond to SE of means
of three replications. Mean comparisons of each of the
survivals in 1-150 d were not significant (P>0􀆰 05)
Fig􀆰 16  Effect of thawing temperature on survival of cryopreserved
A􀆰 membranaceus (Fisch.) Bge. shoot tips by encapsulation vitri ̄
fication. Bars correspond to SE of means of three replications.
Values with different letters are significantly different using
Duncan’s Multiple Range Test (P<0􀆰 05)
477                                  植 物 分 类 与 资 源 学 报                            第 37卷
Fig􀆰 17  Effect of sucrose concentration in washing medium on survival
of cryopreserved A􀆰 membranaceus (Fisch.) Bge. shoot tips by
encapsulation vitrification. Bars correspond to SE of means of
three replications. Values with different letters are significantly
different using Duncan’s Multiple Range Test (P<0􀆰 05)
Fig􀆰 18  Effect of dark culture after freezing on survival of cryopre ̄
served A􀆰 membranaceus (Fisch.) Bge. shoot tips by encapsulation
vitrification. Bars correspond to SE of means of three replications.
Values with different letters are significantly different using
Duncan’s Multiple Range Test (P<0􀆰 05)
Fig􀆰 19  Plantlets regenerated from cryopreserved shoot tips
Fig􀆰 20  Evaluation of morphological indexes of plantlets regenerated
from A􀆰membranaceus (Fisch.) Bge. shoot tips treated with and without
cryopreservation by encapsulation vitrification. Bars correspond
to SE of means of three replications. Mean comparisons of
each of the morphological indexes between the two types
of plantlets were not significant (P>0􀆰 05)
3  Discussion
3􀆰 1  Cryopreservation by encapsulation dehydration
At presentꎬ the encapsulation ̄dehydration tech ̄
nique is easy to apply to cryopreservation of shoot tips
of a wide range of plant species ( Pawlowska and
Bachꎬ 2011). In this techniqueꎬ sucrose is the only
cryoprotector ( Engelmannꎬ 2011 ). Many studies
showed that preculture duration significantly influ ̄
enced the survival of cryopreserved shoot tips. The
positive effect of extending duration of the preculture
with high sucrose concentrations has been reported
for Rabdosia rubescens (Ai et al.ꎬ 2012)ꎬ wild Shih
(Sarab et al.ꎬ 2012) and white mulberry (Padro et
al.ꎬ 2012). The present study obtained a similar re ̄
sult: survival of cryopreserved A􀆰 membranaceus shoot
tips increased to about 50% when they were precul ̄
tured with 0􀆰 75 mol􀅰L-1 sucrose for 5 days (Fig􀆰 1ꎬ
Fig􀆰 2)ꎬ as it was observed to promote maximum
survivability of cryopreserved A􀆰 membranaceus hairy
root cultures in the earlier experiment using encapsu ̄
lation vitrifcation method (Xue et al.ꎬ 2008).
The water content of encapsulated shoot ̄tips is
5776期      YIN and HONG: Encapsulation ̄Dehydration and Encapsulation ̄Vitrification ̄Based Cryopreservation of 􀆺     
a crucial factor affecting survival and shoot formation
(Marco ̄Medina et al.ꎬ 2010). In this studyꎬ the in ̄
itial water content of A􀆰 membranaceus encapsulated
shoot tips precultured with 0􀆰 75 mol􀅰L-1 sucrose for
5 days was 76􀆰 8% (Fig􀆰 3)ꎬ which was required to
further treatment with silica ̄gel. When the water
content closed to 23􀆰 1%ꎬ 53􀆰 4% of cryopreserved
shoot ̄tips could survival and regenepercentage shoots
(Fig􀆰 4). Similarlyꎬ water content around 20% was
preferable for cryopreservation of several plant spe ̄
cies such as pear with 20% (Se ̄Chan et al.ꎬ 2013)ꎬ
Olive with 21􀆰 1% (Ruzˇic and Vujovicꎬ 2012)ꎬ apple
with 21% (Paul et al.ꎬ 2000) and grapevine with
20􀆰 6% (Wang et al.ꎬ 2002).
The culture conditions after LN exposure were
very efficient. Culture in the dark immediately after
rewarming may have improved recovery by limiting
the detrimental oxidative effects of light. In this re ̄
portꎬ 54􀆰 4% of A􀆰 membranaceus shoot tips exhibited
regrowth 2 weeks after rewarming were they had
been subjected to 3 days of dark incubation prior to
14 h photoperiodꎬ while directly exposure to 14 h
photoperiodꎬ the survival percentage was only 42􀆰 1%
(Fig􀆰 8). Similar results were reported by Nair and
Reghunath (Nair and Reghunathꎬ 2009) with 62􀆰 2%
regrowth of Indigofera tinctoria (L.). Burritt (2008)
reported Begonia xerythrophylla exhibited greater than
50% regrowthꎬ and Wang et al. (2005) reported 75%
regrowth of raspberry.
3􀆰 2  Cryopreservation by encapsulation ̄vitrification
Preculture of explants in suitable medium can
increase tolerance to both desiccation and freezing in
LN (Mohanty et al.ꎬ 2012). In the present studyꎬ it
was found that all the shoot tips withstood a sucrose
concentration as high as 0􀆰 75 mol􀅰L-1 . However
further increase of sucrose concentration resulted in
decrease of survival rate (Fig􀆰 10ꎬ Fig􀆰 11). our re ̄
sults was similar to observations made in the hairy
root cultures of A􀆰 membranaceus in which a 6% sur ̄
vival rate were obtained when subjected to 3 ̄day pre ̄
culture in medium with 0􀆰 3 mol􀅰L-1 sucrose (Xue et
al.ꎬ 2008).
In cryopreservation procedures by encapsula ̄
tion ̄vitrificationꎬ a loading treatment of 2 mol􀅰L-1
glycerol and 0􀆰 4 mol􀅰L-1 sucrose was essential (Sa ̄
kai and Engelmannꎬ 2007). In the present studyꎬ
loading with a mixture of 2 mol􀅰L-1 glycerol and 0􀆰 4
mol􀅰L-1 sucrose significantly increased osmotoler ̄
ance of shoot tips and improved the survival rate
(Fig􀆰 12). But the survival rate of the hairy root cul ̄
tures of A􀆰 membranaceus in the case of loading solu ̄
tion treatment of 2 mol􀅰L-1 glycerol and 0􀆰 4 mol􀅰
L-1 sucrose was significantly lower than that in the
case of loading solution treatment missingꎬ changing
from 6􀆰 6% to 0 (Xue et al.ꎬ 2008). These results
indicated the loading of 2􀆰 0 mol􀅰L-1 glycerol and
0􀆰 4 mol􀅰L-1 sucrose was valid for the cryopreserva ̄
tion of the A􀆰 membranaceus shoot tipsꎬ whereas
completely ineffective on that of A􀆰 membranaceus
hairy root culturesꎬ which also support the sugges ̄
tion of Huang et al. (1995) that the positive effect
of loading treatment may be materials ̄specific.
In the encapsulation vitrification methodꎬ lower
temperatures such as 0 ℃ can reduce toxicity of the
vitrification solution and usually enhance survival
(Hong and Yinꎬ 2012a). In the present study a sig ̄
nificance increase in survivability was noticed when
A􀆰 membranaceus shoot tip were dehydrated in PVS2
at 0 ℃ for 120 min with a survival rate of 78􀆰 6%
(Fig􀆰 13ꎬ Fig􀆰 14). Howeverꎬ in the cryopreservation
of A􀆰 membranaceu hairy root culturesꎬ dehydration by
exposure to PVS2 was found completely ineffective
and no cells survived (Xue et al.ꎬ 2008).
In the present studyꎬ when the cryopreserved
shoot tips were rapidly rewarmed in a water bath at
37 ℃ for 2-3 minꎬ the survival rate of shoot tips sig ̄
nificantly increased. The temperatures above and be ̄
low 37℃ both resulted in reduced viability and showed
poor survival rates (Fig􀆰 16). Xue et al. (2008) re ̄
ported when cryopreserved A􀆰 membranaceu hairy
root cultures were were thawed in water bath at 40 ℃
for 2 minꎬ the survival rates was up to 6%. Howeverꎬ
Toshiro et al. (1995) reported rapid thawing resulted
into the germination and survival rate of seeds and
677                                  植 物 分 类 与 资 源 学 报                            第 37卷
seedlings of A􀆰 membranaceus decreased remarkably.
The present investigation also indicates that
76􀆰 8% of the shoot tips of A􀆰 membranaceus can sur ̄
vive and continue to growꎬ following washing with
1􀆰 2 mol􀅰L-1 sucrose in liquid MS medium supple ̄
mented with 1 mg􀅰L-1 6 ̄BAꎬ 0􀆰 05 mg􀅰L-1 NAA for
10 min ( Fig􀆰 17). As for the cryopreservation of
A􀆰 membranaceus hairy root culturesꎬ when the post ̄
thaw hairy root cultures were incubated for 30 min in
MS liquid medium with 1􀆰 2 mol􀅰L-1 sucrose for 10
minꎬ the survival rate of cryopreserved hairy root
cultures significantly increased (Xue et al.ꎬ 2008).
Light conditions may be an important determinant of
shoot ̄tip development after freezingꎬ which presuma ̄
bly attributed to damage repair of tissues that might
take place during darkness (Benson et al.ꎬ 1989).
In the present studyꎬ when cryopreserved shoot tips
of A􀆰 membranaceus were incubated under a 14 h
photoperiod subsequent to a 3 ̄d dark periodꎬ the
survival of shoot tips was significantly better than
that of shoot tips directly incubated under a 14 h
photoperiod without a 3 ̄d dark period (Fig􀆰 18).
In conclusionꎬ the methods described in this
paper offers two simple and useful methods for cryo ̄
preservation of A􀆰 membranaceus shoot tips that should
be applicable to other shoot tips of the Legumenosae.
Howeverꎬ this encapsulation vitrification method ap ̄
pears to be more promising technology for the cryopr ̄
eservation of A􀆰 membranaceus shoot tip because of
its higher survival rate. At the same timeꎬ it is also
important that cryopreserved cells and meristems be
capable of producing plants identical to the non ̄trea ̄
ted phenotype (Wang et al.ꎬ 2005ꎻ Mohanty et al.ꎬ
2012). In the present studyꎬ shoot tips cryopre ̄
served by encapsulation ̄dehydration and encapsula ̄
tion vitrification regained green color and resumed
growth 7 days after plating and normally developed
shoots without intermediately callus formation. Re ̄
generated plants from cryopreservation were morpho ̄
logically uniform and normal. In additionꎬ A􀆰 membr ̄
anaceus shoot tips maintained in LN for 5 months re ̄
mained stable and were not affected by cryopreserva ̄
tion. On the basis of observationꎬ we may consider
that no major variations were induced during the cry ̄
ogenic process. The same results were reported in
many species (Ai et al.ꎬ 2012ꎻ Maria et al.ꎬ 2012).
Previous work has demonstrated that conservation
time generally does not affect the survival rate after
cryopreservation. Our works also support the view ̄
point (Fig􀆰 9 and Fig􀆰 20). Howeverꎬ it remains to
be determined whether the two approaches preserve
stable germplasms of A􀆰 membranaceus with respect
to phenotype and molecular biology.
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