全 文 ：Sedum alfredii:A New Lead_Accumulating Ecotype
HE Bing , YANG Xiao_E , NI Wu_Zhong , WEI You_Zhang , LONG Xin_Xian , YE Zheng_Qian
(Department of Resource Science , Zhejiang University , Hangzhou 310029, China)
Abstract:　In a survey of plant population , Sedum alfredii Hance , a new lead(Pb)_tolerant and lead(Pb)_
accumulating ecotype , was found in an old Pb/Zn mining area in Zhejiang Province of China.The growth and
Pb content of plant ecotypes being able to and unable to accumulate Pb were studied by hydroponic culturewith
different concentrations of Pb(NO3)2.Growth of shoots of accumulating ecotype was not affected by Pb treat-
ments up to 320 mg/L , whereas that of non_accumulating ecotype was inhibited in all Pb treatments.The Pb
concentrations in the roots and shoots of accumulating ecotype increased with increasing of Pb level in the nu-
trient solution.The maximum Pb concentrations in the shoots and roots of accumulating ecotype were 514 mg/
kg and 13 922 mg/kg , 2.27 times and 2.62 times as much as that of non_accumulating ecotype , respectively.
The highest rate of Pb accumulation of accumulating ecotype was 8.62 μg/plant/d , 7.16 times as much as
that of non_accumulating ecotype.Due to its fast growth rate and high Pb_accumulating ability , from a phytore-
mediation perspective , accumulating ecotype of S .alfredii is a potential plant species for Pb removal from
contaminated soils.
Key words:　lead(Pb);pollution;Sedum alfredii
　　It is well known that lead(Pb)is a heavy metal and
extremely toxic to human beings(Li et al , 1999;Wu et
al , 2000).The contamination of this toxic metal in soil ,
streams , and ground water poses a major environmental
hazard to human health.High levels of Pb concentration
have been reported at some severely contaminated sites.
For example , Pb concentrations were recorded as high as
13 825 μg/g in the soil of a mining district according to
our survey.The threat that Pb poses to human and animal
health is aggravated by their long_term and enormous per-
sistence in the environment.
Over the last 10 years there has been increasing in-
terests in developing a plant_based technology (phytoex-
traction)to remediate metal_contaminated soil (Salt et
al , 1995;Scott and Ow , 1996;Garbise and Alkorta ,
2001;Wang et al , 2001).In phytoextraction , plants
take up soil Pb into the roots and translocate it to shoots
that are harvested (Shen and Liu , 1998).This process
results in a gradual reduction in Pb concentration in the
soil.Compared with other remediation methods , phytoex-
traction has many advantages:lower cost , minimal envi-
ronmental disturbance , elimination of secondary air or wa-
ter_borne wastes and public acceptance (Salt et al ,
1995;Scott and Ow , 1996;Garbise andAlkorta , 2001;
Wang et al , 2001).However , the success of phytoex-
traction depends upon the identification of suitable plant
species that hyperaccumulate heavy metals and produce
large amounts of biomass.In general , plants which accu-
mulate more than 1 000 mg Pb/kg are called Pb_hyperac-
cumulators.Only five Pb_hyperaccumulators have been i-
dentified so far (Shen and Liu , 1998).An example of
such plants is Thlaspi rotundifoliun , which was reported
to be able to accumulate Pb in shoots as much as 130-
8 200 mg/kg with a mean of 1 100 mg/kg (Reeves and
Brooks , 1983).However , this plant species , like other
Pb_hyperaccumulating species reported in the literature ,
is not suited for phytoextraction of Pb from contaminated
soils because of its slow growth rate and small biomass(Scott and Ow , 1996).
With a survey of plant population , we found a new
and special ecotype , Sedum alfredii Hance , in an old
Pb/Zn mining area in Zhejiang Province of China.It was
identified that S .alfredii is a Zn_hyperaccumulator(Yang et al , 2001).In our survey , we also found that
S .alfredii was able to accumulate 1 182 mg Pb/kg in
shoots with fast growth rate and relatively large amount of
biomass.The objectives of this study were(1)to compare
Pb_accumulation ability of different plant species from the
mining zone;(2)to compare Pb_accumulation ability of
two ecotypes of S .alfredii;and(3)to identify that S.
alfredii is a new Pb_tolerant and Pb_accumulating eco-
type.
1　Materials and Methods
1.1　Survey of mine
The old Pb/Zn mining area was exploited 300-400
years ago in Zhejiang Province of China.The weather of
mining area is warm , moist and foggy with annual average
temperature of 16.3-17.3 ℃.Sedum alfredii , Viola
yedoensis , V.diffusa , and Prunella vulgaris were col-
lected from the mining area.The shoots of plant samples
were rinsed with deionized water , dried for 2 d at 75 ℃,
and ashed in a muffle furnace at 550 ℃for 5 h.The ash
was dissolved in 1∶1 HCl.The Pb concentration in the
solution was determined by inductively coupled plasma
atomic emission spectrometry (ICP_AES).The soil sam-
ples from the mining area were air_dried and ground.To-
tal Pb and the available Pb in soil were estimated by di-
Received:2001-12-10　Accepted:2002-04-04
Supported by the National Natural Science Foundation of China(39925024)and the Key Project from Education Ministry of China(02180).
植　物　学　报　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　
Acta Botanica Sinica　2002 , 44(11):1365-1370
gestion with HNO3∶HCl(1∶3)and extraction with 0.005
mol/L DTPA respectively , and Pb in the digest and ex-
tract were analyzed by ICP_AES.
1.2　Hydroponic experiment
Accumulating ecotype of S.alfredii was obtained
from the old Pb/Zn mining area in Zhejiang Province ,
China.Non_accumulating ecotype of S.alfredii was ob-
tained from suburb of Hangzhou in Zhejiang Province of
China.Healthy and equal_sized shoots were chosen and
grown for two weeks in the basic nutrient solution contain-
ing 2.00 mmol/L Ca(NO3)2 ·4H2O , 0.10 mmol/L
KH2PO4 , 0.50 mmol/L MgSO4·7H2O , 0.10 mmol/L
KCl , 0.70 mmol/L K2SO4 , 10.00μmol/L H3BO3 , 0.50μmol/L MnSO4·H2O , 1.0μmol/L ZnSO4·7H2O , 0.20μmol/L CuSO4·5H2O , 0.01 μmol/L (NH4)6 Mo7O24 ,
100 μmol/L Fe_EDTA(Yang et al , 2001).Nutrient so-
lution was continuously aerated and renewed every 4 d.
After grown for 14 d , the plants were transferred to
the modified nutrient solution , in which KH2PO4 concen-
tration was adjusted to 0.005 mmol/L in order to prevent
precipitation of lead.The Pb2+ concentrations in the nu-
trient solutions were 0 , 20 , 40 , 80 , 160 , 320 , 480 mg
Pb/L supplied as Pb(NO3)2.Each Pb treatment was
replicated three times.Plants were harvested at 12 d after
treatment.
Roots were immersed in the 20 mmol/L Na_EDTA
for 15 min , and then the whole plants were rinsed with
deionized water.The roots and shoots were dried at 75 ℃
to constant weight , weighed and ground.The dry samples
were digested with concentrated HNO3 at 180-200 ℃for
7 h.The digested samples were diluted to 25 mL and an-
alyzed by flame atomic absorption spectrometry.
2　Results and Discussion
2.1　A survey of ecotypes of S .alfredii accumulat-
ing Pb
The soil from the mining area had high Pb content.
For the all five sites (A -E)of the mining area , the
highest total Pb and available Pb in the soil were 13 825
mg/kg and 1 351 mg/kg , respectively , with the average
of 4 720mg/kg and 1 195mg/kg respectively.The high-
est Pb concentration in shoots of S .alfredii was 1 182
mg/kg , and the average was 518 mg/kg.However , most
plants did not accumulate more than 100 mg Pb /kg in
their shoots regardless of the soil Pb content.It was indi-
cated that not only was S.alfredii able to tolerate high
level of Pb in soil , but also was able to absorb Pb strongly
from soil.The Pb concentrations in shoots of S .alfredii
from the different sites differed greatly , perhaps it was
relevant to the history of being contaminated.For site E ,
Pb concentration in shoot of S .alfredii was 400% that of
V.yedoensis , 1 428% that of V.diffusa , 1 250% that
of P.vulgaris respectively .Moreover , the enrichment
coefficient of S.alfredii was the highest in the four plant
species , which also indicated that S .alfredii was superi-
or to other three plant species in the ability to accumulate
Pb in shoots(Table 1).
S .alfredii belongs to Crassulaceae family.It is a
kind of perennial herb with clumped population , growing
on moist stones beside the rivulet or under the bamboo
grove (Fig.1).The leaves of S.alfredii are alternate ,
without petiole , juicy , spoon type with 10 -30 cm in
length and 5 -10 cm in width.The inflorescence is
polyumbrella form with two to three branches.Yellow
flowers are small with the same numbers of petal and
carpel in 5.
2.2　Effects of Pb on growth and Pb accumulation of
the two ecotypes of S.alfredii
2.2.1　Growth response of two ecotypes to Pb 　In
the hydroponic experiment , the accumulating ecotype
showed better growth , erect stem , thicker leaf dark
green , while non_accumulating ecotype showed small ,
thin , leaf light green.The epidermis of stem was some-
times purple , and the stem was tender with purple spot or
stripes and tending to creep (Fig.1).Lead did not sig-
nificantly affect the growth and appearance of shoot of the
accumulating ecotype until 320 mg/L (Table 2).In 480
mg/L Pb treatment , the leaves of the accumulating eco-
type showed a slight desiccation and dry weight of the
shoot decreased a little.For non_accumulating ecotype ,
Pb significantly inhibited plant growth (dry weight)and
the color changed from light green to dark green as Pb
concentration in the solution increased from 0 to 20 or 40
mg/L.Desiccation and chlorosis of crispate leaves oc-
curred at Pb≥80 mg/L.The shoot DW of non_accumu-
lating ecotype in 80 mg Pb/L treatment decreased to
three_fourth of that of non_accumulating one in 0mg Pb/L
treatment.With 480 mg Pb/L , the shoot DW was even
half of the control.
Table 1　Lead concentrations of the soil and the shoot of plant from the mining area(mg/kg)
Sample site Plant species
Pb concent ration
in shoot
Soil Pb
Available Pb
in soil
Enrichment coefficient
A Sedum alfredii Hance 63.27 4 958 1 255 0.05
B S.alfredii Hance 152.70 5 540 58.85 2.59
C S.alfredii Hance 57.99 4 860 1 095 0.05
D S.alfredii Hance 616.40 13 825 1 351 0.46
E S.alfredii Hance 1 182.00 3 525 1 081 1.09
E Viola yedoensis Makino 302.90 3 525 1 081 0.28
E V.diffusa Ging. 77.25 3 525 1 081 0.07
E Prunella vulgaris L. 89.35 3 525 1 081 0.08
1366　 植物学报　Acta Botanica Sinica　Vol.44　No.11　2002
Fig.1.　Effect of Pb on growth of two ecotypes.
a.Growth of the Pb_accumulating ecotype of S .alfredii.b.Accumulating ecotype of S .alfredii.c.Non_accumulating ecotype of S.al-
fredii.
Table 2　Effect of Pb on dry weight
Lead treatment
(mg/ L)
Shoot dry weight(mg/plant)
Accumulating ecotype Non_accumulating ecotype
Root dry weight(mg/ plant)
Accumulating ecotype Non_accumulating ecotype
0 202.3±6.8a 104.5±3.4a 13.9±2.3d 9.9±0.4a
20 199.1±10.9a 85.3±2.8ab 22.0±1.3cd 8.4±0.1a
40 198.8±2.1a 90.5±5.5ab 23.9±2.1bcd 9.0±1.6a
80 200.0±8.83a 84.2±4.7b 31.7±1.3b 7.8±0.5a
160 201.3±4.1a 64.7±2.9c 52.9±2.5a 6.6±1.0a
320 187.5±3.3a 57.9±4.8c 29.3±1.7bc 6.6±0.8a
480 157.0±4.0b 55.8±3.1c 18.0±2.0d 7.8±1.1a
　　Pb promoted the emergency of lateral root and growth
of plant of both ecotypes (Fig.2).The number and
length of lateral root of the accumulating ecotype increased
with increasing of Pb from 20 mg/L to 160mg/L , where-
as decreased when Pb was over 320 mg/L and significant-
ly inhibited when Pb was 480 mg/L (Fig.2).The root
dry matter of accumulating ecotype increased with increas-
ing of Pb , highest at 160 mg/L , and then decreased(Table 2).This might suggest that the stimulating effect
on root growth was over the inhibiting effect before the Pb
concentration in the growth media raised up to 160 mg/L ,
and thereafter the inhibiting effect became more obvious.
Pb has stronger positive effects on lateral root growth of
the accumulating ecotype than that of the non_accumulat-
ing ecotype.The emergency and growth of lateral root of
the non_accumulating ecotype were inhibited at Pb≥160
mg/L(Fig.2).
Kochian(1972)thought that tolerant ecotypes were
HE Bing et al:Sedum alfredii:A New Lead_Accumulating Ecotype 1367　
less affected by an increase in toxic ions than non_tolerant
ones.Accumulating ecotype of S .alfredii would seem to
be superior to non_accumulating ecotype of S.alfredii
under the Pb treatment , since biomass of shoots and roots
even at the 320 mg/L were similar to that with the 0 mg/
L treatment , and it did not show toxic symptoms in roots
when Pb ≤160 mg/L.
2.2.2　Uptake of Pb　For both ecotypes , the Pb con-
centrations in roots and shoots in 160 mg Pb/L treatment
were higher than that in other Pb treatments.The amount
of lead accumulated by most plant species is very limited(Kochain , 1972).Accumulating ecotype of S.alfredii ,
however , was shown to accumulate appreciable amount of
Pb.The highest Pb concentrations in both shoots(514.
13 mg/kg)and roots(13 922.27 mg/kg)were attained
by accumulating ecotype (Table 3).At the same time ,
the variable levels of Pb more than 320mg/L in the nutri-
ent solution did not significantly affect the shoot DW of
accumulating ecotype.Therefore , it is suggested for accu-
mulating eco_type that the mechanism of accumulating Pb
might be positive.Compared with accumulating ecotype ,
non_accumulating ecotype was a plant species poorer in
Pb uptake and accumulation , the Pb concentration did not
exceed 226.62 mg/kg in shoots and 5 191.54 mg/kg in
roots(Table 3).
The mobility of Pb from root to shoot of plant is usu-
ally low(Kochian , 1972;Begonia et al , 1998).When Pb
enters the plant root , it encounters the neutral pH , high
phosphate , and high carbonate environment of the intercel-
lular spaces.Under these conditions , Pb precipitates as
phosphate or carbonate and does not reach the xylem for
translocation(Malone et al , 1974;Qureshi et al , 1986).
However , a higher shoot/ root ratio of heavy metal concen-
tration in plant is important in practical phytoremediation of
heavy metal_contaminated soils.It has been shown that Pb
hyperaccumulators usually have a higher shoot/ root ratio(0.04-0.10)of Pb concentration in plant than the non_
hyperaccumulators(Kumar et al , 1975).In this study ,
accumulating ecotype treated with 20 -160 mg Pb/L
showed 0.04-0.18 shoot/ root ratio of Pb concentration ,
while those of the non_accumulating ones did not exceed 0.
04.It was demonstrated that accumulating ecotype was
more effective in transporting Pb from roots to shoots than
non_accumulating one (Table 4).
Fig.2.　Effect of Pb on root growth of two ecotypes.
Table 3　Lead(Pb)concentrations of roots and shoots of the two ecotypes
Pb treatment
(mg/ L)
Shoot Pb(mg/ kg)
Accumulating ecotype Non_accumulating ecotype
Root Pb(mg/ kg)
Accumulating ecotype Non_accumulating ecotype
0 18.6±1.5a 14.7±1.6a 184.4±13.5a 78.3±7.6a
20 213.5±7.0bc 97.5±4.7b 1 210.5±31.4ab 2 245.5±201.7b
40 240.0±9.9c 150.8±13.6c 2 183.6±156.2b 4 304.3±178.7cd
80 281.9±21.0d 158.1±14.9c 4 817.2±490.1c 4 358.0±211.8cd
160 514.1±11.9e 226.6±14.6d 13 922.2±394.2e 5 191.5±442.8d
320 185.0±4.8b 99.5±8.2b 9 660.5±481.6d 4 843.2±412.3cd
480 165.4±12.6b 114.3±4.1b 5 822.1±192.2c 3 613.0±367.0c
1368　 植物学报　Acta Botanica Sinica　Vol.44　No.11　2002
Table 4　Effect of Pb on shoot/ root ratio of lead(Pb)concentra-
tion
Treatment(mg/ L) Shoot/ root ratio of Pb concentration
Accumulating ecotype Non_accumulating ecotype
20 0.18 0.04
40 0.11 0.04
80 0.06 0.04
160 0.04 0.04
320 0.02 0.02
480 0.03 0.03
2.3　Efficiency of Pb removal and phytoremediation
perspective
Due to the great difference in the accumulation of
biomass in the shoots of the two ecotypes , it is important
to take account of such accumulation when the two eco-
types are compared for their efficiency of removing trace
elements.For this reason , we calculated the rate of trace
element accumulation of the two ecotypes as the amount of
Pb accumulated per plant per day (Fig.3).Compared
with non_accumulating ecotype , accumulating ecotype had
higher rates (3_ to 7_fold higher)of Pb accumulation in
the treatments of most Pb levels.This is attributed to the
fact that accumulating ecotype exhibited the higher
biomass accumulation and attained higher concentrations
of Pb in shoot.If the major goal of the phytoremediation
process is to remove the maximum amount of element in
the shortest time possible , the selection should be based
on the rate of element accumulation in harvestable tissues
as well as on plant biomass accumulation.Under this
standard , accumulating ecotype would be perfect for the
extraction of Pb from the contaminated soils.
Fig.3.　Rate of Pb accumulation by shoots of the two ecotypes.
3　Conclusion
There are only five Pb hyperaccumulators discovered
up to the present (Shen and Liu , 1998).Until recent
time , however , no Pb hyperaccumulating plants have
been reported in China , though some investigations into a
number of wild plant species have been conducted.In our
survey in an old Pb/Zn mining area in Zhejiang Province
of China , accumulating ecotype of S .alfredii was found
to be able to accumulate 1 182 mg/kg Pb in the shoot.
The response of accumulating ecotype to Pb was quite dif-
ferent from that of non_accumulating ecotype.Accumulat-
ing ecotype had higher Pb concentration both in root and
shoot.Besides , the increase of plant dry matter of shoot
and root in accumulating ecotype did not decrease even
when treated with Pb concentration up to 320mg/L.Our
data showed that S.alfredii was a Pb_tolerant and Pb_ac-
cumulating species , and may be a material available for
studying on the mechanism of Pb uptake and accumulation
by plant.Besides , from phytoremediation perspective ,
accumulating ecotype seems to be perfect for the extraction
of Pb from the contaminated soil.
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HE Bing et al:Sedum alfredii:A New Lead_Accumulating Ecotype 1369　
一种新的铅富集植物———富集生态型东南景天
何　冰　杨肖娥　倪吾钟　魏幼璋　龙新宪　叶正钱
(浙江大学环境与资源学院资源科学系 , 杭州 310029)
摘要:　对浙江一古老铅锌矿区的土壤和植物种群进行调查后发现一种新的具有耐铅特性和铅富集能力的植物
———景天科景天属东南景天(Sedum alfredii Hance), 称为铅富集生态型植物。进一步比较和分析了不同浓度硝酸铅
处理对富集和非富集生态型东南景天的生长及其对铅的吸收特性的影响。结果表明 , 320 mg Pb/ L处理对富集生
态型的地上部分生长无显著影响 ,而非富集生态型在 20 mg Pb/ L时即出现受害症状。富集和非富集生态型的地上
部分铅含量 、根系铅含量以及单株铅积累速率均随处理浓度的增加而表现出先升后降的变化趋势。 其中富集生态
型的地上部分铅含量 、根系铅含量以及单株铅积累速率最高可达到 514 mg/kg 、13 922 mg/kg 和 8.62 μg/ plant/ d , 分
别是非富集生态型的 2.27 、2.62 和 7.16倍。由于具有生长速度快和高积累铅的能力 , 从植物修复的观点来说 , 东
南景天铅富集生态型在铅污染土壤的修复方面具有巨大的潜力。
关键词:　铅;污染;东南景天
中图分类号:Q945　　　文献标识码:A　　　文章编号:0577-7496(2002)11-1365-06
收稿日期:2001-12-10　接收日期:2002-04-04
基金项目:国家自然科学基金(39925024);国家教育部重点基金(02180)。
(责任编辑:贺　萍)
1370　 植物学报　Acta Botanica Sinica　Vol.44　No.11　2002