全 文 ：入侵植物紫茎泽兰化感作用及其途径研究*
杨明挚, 吕摇 霞, 张摇 婷, 杨摇 晨, 李文君, 史云涛, 张汉波**
(云南大学生命科学学院, 云南 昆明摇 650091)
摘要: 紫茎泽兰广泛入侵中国西南地区, 研究结果表明化感作用是其入侵的重要武器, 但其化感作用的途
径并不十分清楚。 本研究中, 我们发现紫茎泽兰可以通过多种途径对两种栽培植物大麦和玉米的生长产生
化感作用, 这些途径包括了叶挥发物、 叶淋溶物以及根分泌物。 并且在紫茎泽兰幼苗早期就可以检测到这
些化感作用。 然而, 没有实验证据表明紫茎泽兰落叶的微生物降解物对两种测试植物具有化感作用。
关键词: 化感途径; 紫茎泽兰; 入侵植物
中图分类号: Q 945摇 摇 摇 摇 摇 摇 文献标识码: A摇 摇 摇 摇 摇 摇 摇 摇 文章编号: 2095-0845(2011)02-209-05
Allelopathic Potential and Pathway of an Invasive Weed
Eupatorium adenophorum (Asteraceae)
YANG Ming鄄Zhi, LV Xia, ZHANG Ting, YANG Chen, LI Wen鄄Jun,
SHI Yun鄄Tao, ZHANG Han鄄Bo**
(School of Life Science, Yunnan University, Kunming 650091, China)
Abstract: Crofton weed (Eupatorium adenophorum) is one of the most notoriously invasive plants in China. Allel鄄
opathy has been considered to play an important role for population spread. In this study, we demonstrate that this
weed has strong adverse effects on two agronomic cultivars, barley and maize, through a variety of allelopathic path鄄
ways including volatiles, leachates and root exudates. The allelopathic effect was even detected in early growth sta鄄
ges of the weed. However, there was no evidence to indicate that allelochemicals in dead leaf tissue either persisted
or converted into new allelochemicals by naturally colonizing phyllosphere microbes.
Key words: Allelopathic pathways; Eupatorium adenophorum; Invasive plant
摇 摇 Crofton weed (Eupatorium adenophorum Speng
or Ageratina adenophora Sprengel) is one of the
most severely invasive weeds in China. This weed
first invaded the Yunnan Province of China from Bur鄄
ma during the 1940s, and then spread northward and
eastward with an annual speed of about 20 -30 km
(Lu et al., 2005; Wang and Wang, 2006). Cur鄄
rently, it commonly distributes in southwest areas of
China, including Yunnan, Guizhou, Sichuan and
Guangxi Provinces, and produces a great threat to
the local ecological system. Besides China, more
than 30 countries and areas have been invaded by
E. adenophorum ( Qiang, 1998; Lu et al., 2005;
Ding et al., 2008).
Allelopathy is considered to be an important
weapon of many invasive plants for rapidly spreading
in their introduced range (Kong et al., 2002; Bais
et al., 2003). Although there have been reports of
植 物 分 类 与 资 源 学 报摇 2011, 33 (2): 209 ~ 213
Plant Diversity and Resources摇 摇 摇 摇 摇 摇 摇 摇 摇 摇 摇 摇 摇 摇 摇 摇 DOI: 10. 3724 / SP. J. 1143. 2011. 10168
*
**
Foundation items: The Department of Science and Technology of Yunnan Province, China (2007PY01鄄24) and The National Science Foun鄄
dation of China (30560033, 30960077)
Author for correspondence; E鄄mail: zhhb@ ynu. edu. cn; zhbdm@ yahoo. com. cn; Tel: +86鄄0871鄄5034282
Received date: 2010-10-08, Accepted date: 2010-12-07
作者简介: 杨明挚 (1970-) 男, 博士, 副教授, 主要从事植物生理与分子生物学方面的研究。
the allelopathic effects of E. adenophorumv on differ鄄
ent species of plants (Song et al., 2000; Zheng and
Feng, 2005; Li et al., 2007), most of these studies
tested allelopathy of E. adenophorum through directly
extracting the chemicals from fresh below and above鄄
ground tissues using an organic solvent ( Song et
al., 2000; Ding et al., 1999). Currently it is un鄄
clear whether allelopathic chemicals in E. adenopho鄄
rum tissues have the ability to naturally diffuse into
the environment to affect the growth of neighboring
plants. Moreover, there are multiple pathways by
which allelochemicals can affect other plants, inclu鄄
ding volatilization, root exudation, leaching and de鄄
composing plant residues in soil (Ninkovic, 2003);
however, little is known regarding how E. adenopho鄄
rum affects plant growth.
In this study we tested the allelopathic effects
on the growth of two agronomic cultivars, barley
(Hordeum vulgare L. ) and maize (Zea mays L. ).
We also evaluated possible pathways involved in E.
adenophorum忆s effect on plant growth, including vol鄄
atiles, leaf leachates, root exudates and dead tissues
of this weed.
Materials and methods
Plant Materials摇 Fresh leaves, stems and seeds
of E. adenophorum were collected in April from the
north urban area of Kunming, Yunnan Province, Chi鄄
na. Barley (Hordeum vulgare L. ) and maize (Zea
mays L. ) were chosen as indicator plants in the allel鄄
opathy bioassay, and were purchased at the market.
Allelopathy of Root Exudates, Leaf Leachates
and Residues摇 To collect E. adenophorum root exu鄄
dates, about 200 grains of surface鄄sterilized seeds
(>90% germination rate) were germinated on three
layers of moisten filter paper in a 9 cm鄄diameter Petri
dish at 25益, with 12 h / 12 h light / dark cycle. Fil鄄
ter papers were moistened by adding 10 mL of dis鄄
tilled water every day. Ten days after germinating,
10 mL of 1 / 4 MS nutrient solution was applied to
support the growth of seedlings. Seedlings and root
residues were removed at 2, 4 and 6鄄leaf stages.
Filter papers were collected and dried at room tem鄄
perature on a clean bench. To collect leaf leachates,
fresh mature leaves obtained from the wild were
soaked with distilled water (w / v: 5 / 100) and solu鄄
tions were filtrated. To obtain allelochemical from
residues, ablated and senescent leaves were collect鄄
ed from the wild and dried at room temperature.
Crushed leaf debris was moistened with sterilized wa鄄
ter (water content: 抑30% ). Moistened leaf debris
was filled into 12 flasks (50 g per bottle) and cov鄄
ered with plastic membranes. Leaf debris was al鄄
lowed to decompose by naturally associating phyllo鄄
sphere microbes at 28益 . At the following day 5, 10
and 20 the degraded residues were taken out and
rapidly wind鄄dried at 40益 . Subsequently, allelo鄄
chemicals in the residues were extracted for 10 mi鄄
nutes by sterilized water (w 颐 v =5 颐 100). Extracts
were filtrated and condensed to 1 / 2 volume. All fil鄄
ter papers, leaf leachates and residue extracts ob鄄
tained were stored at 4益 until further use.
To test root exudate effects, two papers collect鄄
ed from the same layer were put into every Petri dish
and evenly moistened using 10 mL of distilled water.
In the other two assays, two new sterilized papers
were put into each Petri dish, and a 10 mL of leaf
leachate with concentrations of 50% , 100% (v 颐 v)
or condensed residue extracts were added. Papers
with 10 mL of pure distilled water were used as con鄄
trols. For each assay, 30 grains of germinated barley
seeds (or 20 grains for maize) were put onto filter pa鄄
pers in each Petri dish and incubated at 25益 with 14
h / 10 h light / dark cycle. Filter papers were moistened
by supplying 10 mL of distilled water twice every day.
Three repeats were prepared for each treatment.
Seedling height (SH), leaf length (LL), root
length (RL) and fresh weight (FW) were measured
for each seedling after 5 days忆 growth of indicator
plant. The average values in every Petri dish were
used in statistical analysis.
Allelopathy of Volatiles 摇 A glass container
(diameter: 30 cm; height: 60 cm) was designed to
test the allelopathy of volatiles (Fig. 1). Acting as
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the donor plant, fresh materials ( leaves and stems)
from E. adenophorum were put into the lower cham鄄
ber. Surface鄄sterilized barley seeds served as indica鄄
tor plants and were cultured on moistened filter pa鄄
pers in Petri dishes and put in the upper chamber.
Between donor and indicator plants, a sandwich
structure filled with cotton or activated carbon was
used to stop ( filled with activated carbon) or allow
(filled with cotton) E. adenophorum volatiles to pass
Fig. 1摇 The glass container used in allelopathy
bioassay by volatilization pathway
Fresh tissues of donor plant (E. adenophorum) were put into the lower
chamber and indicator plants were put into the upper chamber. The
lower and upper chambers were separated by sandwich filled with cot鄄
ton or activated carbon grains. Air was pumped into the chamber from
the bottom and out from the top of the container. An airtightness door
was designed in lower chamber for renewing donor plant tissues.
through. Containers were incubated at 25益 with 14
h / 10 h light / dark cycle. Filter papers were mois鄄
tened by supplying 1 / 4 MS nutrient solution every
day. The donor plant ( fresh tissues of E. adenopho鄄
rum) was renewed every two days. After 5 and 8
days of incubation, the indicator plant was taken out
to measure SH, LL and RL.
Statistical Analysis摇 Allelopathy potential was
assessed as response index (RI) = 1鄄C / T (when T
逸C) or T / C鄄1 (when T
presents the control and “ T冶 represents the treat鄄
ment. RI>0 means there is an enhancing effect and
RI<0 means there is an inhibitory effect. The Pro鄄
tected Least Significant Difference ( PLSD) test,
using SPSS10. 0 software package, was used to test
statistical significance.
Results and discussion
There are many potential pathways by which E.
adenophorum can adversely affect the growth of the
indicator plant, such as root exudates, leaf
leachates, and volatiles. Barley and maize were
used as indicator plants to detect the allelopathic po鄄
tential of E. adenophorum root exudates (Table 1).
Filter papers obtained from the upper to lower
layers showed a decreasingly inhibitory effect on both
maize and barley in seedling height, root length and
plant fresh weight. Therefore, the allelpathic potential
Table 1摇 Response index (RI) of E. adenophorum root exudates on barley and maize seedlings
Filter
papers
SH
barley摇 maize摇
LL
barley摇 maize摇
RL
barley摇 maize摇
FW
barley摇 maize 摇
玉1 -0. 32** -0. 45** -0. 43** -0. 82** -0. 13 -0. 35** -0. 15 -0. 19*
玉2 -0. 13** -0. 36* -0. 18** -0. 47** -0. 02 -0. 26* -0. 06 -0. 15
玉3 -0. 10* -0. 16 -0. 13 -0. 21 -0. 01 -0. 06 -0. 22* -0. 10
域1 -0. 15** -0. 24 -0. 18** -0. 38** -0. 08 -0. 09 -0. 15 -0. 21*
域2 -0. 10* -0. 19 -0. 14* -0. 20 -0. 05 -0. 18 +0. 10 -0. 01
域3 +0. 01 -0. 07 -0. 01 -0. 05 +0. 06 -0. 04 -0. 02 -0. 09
芋1 -0. 45** -0. 12** -0. 63** -0. 16 -0. 26** -0. 19** -0. 49** -0. 10
芋2 -0. 13** -0. 07 -0. 19** -0. 04 -0. 11** +0. 09 -0. 29* -0. 07
芋3 -0. 01 -0. 10* +0. 05 -0. 11 -0. 11** -0. 01 -0. 27* -0. 12
* P<0. 05; ** P<0. 01. I, II and III indicate filter papers with root exudates collected at 2, 4 and 6鄄leaf stages of E. adenophorum, respectively;
1, 2 and 3 indicate the first, second and third layer of filter paper (counting from the top layer which directly contact with the roots of E. adenopho鄄
rum) . SH: seedling height; LL: leaf length; RL: root length; FW: fresh weight
1122 期摇 摇 YANG Ming鄄Zhi et al. : Allelopathic Potential and Pathway of an Invasive Weed Eupatorium adenophorum …摇 摇
declines with decreased exudate concentrations.
Moreover, strong allelopathy of root exudates
can be detected in a very early growth stage (cotyle鄄
don stage) of E. adenophorum seedlings, suggesting
that allelopathy may play a role during its population
establishment. However, we cannot determine the
extent to which allelopathy helps single or few seeds
establish new populations in the wild, since root
exudates collected from high densities of E. adeno鄄
phorum seedlings were tested in this experiment.
Interestedly, root exudates of cotyledon and
four鄄leaf stages of E. adenophorum had nearly two
times the inhibitory effect on maize than on barley
seedlings. However, when root exudates of six鄄leaf
stage were used, there was stronger inhibition in
barley compared to maize seedlings. This suggests
that E. adenophorum produces different allelochemi鄄
cals during different developmental stages.
The above鄄ground parts of mature E. adenopho鄄
rum also significantly inhibit the growth of indicator
plants by leachates (Table 2) and volatiles (Table
3). Both long鄄lasting and high concentrations of
leaching solution had stronger inhibition on the
growth of barley seedlings. Although different growth
rates were found between barley seedlings cultured
in containers with cotton and those with activated
carbon filled in sandwich (Table 3), volatiles had
no influence on the germination ratio ( data not
shown). Compared to previous methods (Ninkovic,
2003), the equipment used in this study convenient鄄
ly provided a way to control indicator and donor
plants at an environment similar to natural atmos鄄
phere (Fig. 1).
Because E. adenophorum can adversely affect
neighboring plants忆 growth by both leachates (Table
2) and volatiles (Table 3), and considering the fact
that many organic chemicals previously extracted
from above鄄ground tissues of E. adenophorum have
been shown to be allelopathic (Song et al., 2000;
Li et al., 1997; Ding et al., 1999; Dayan et al.,
2003), it is possible that allelochemicals still re鄄
main active after dead leaves or stems fall back into
the soil. Results indicate that allelochemicals were
unlikely to persist or be converted into new allelo鄄
chemicals by phyllosphere microbes, because no ad鄄
verse effect was detected in fermented residues (Ta鄄
ble 4). Interestedly, the allelopathic potential disa鄄
ppeared after 5 days of microbial decomposition.
Based on the significant benefits to growth of barley
seedlings (Table 4), the fermented residues appear
to be utilized as nutrients by the indicator plant.
Therefore, allelopathy via a degradation pathway un鄄
likely occurs in E. adenophorum residues.
Table 2摇 Response index (RI) of E. adenophorum
leaf leachates on barley seedlings
Leaching
time
(s)
Concentra鄄
tions(v / v)
(% )
SH LL RL FW
10 50100
-0. 137**
-0. 145**
-0. 266**
-0. 343**
-0. 040摇
-0. 191**
-0. 206
-0. 022
60 50100
-0. 145* 摇
-0. 271**
-0. 370**
-0. 568**
-0. 315**
-0. 493**
-0. 176
-0. 382
*P<0. 05; **P<0. 01. Other notes see Table 1
Table 3摇 Response index (RI) of E. adenophorum
volatiles on barley seedlings
Treating duration SH LL RL
5 days -0. 035 -0. 053 -0. 072
8 days -0. 055 -0. 121** -0. 097*
*P <0. 05; **P<0. 01. Other notes see Table 1
To date, strategies including applying pathogen
(Dai et al., 2004) or gall (Li et al., 2006) con鄄
trols, and native plant replacement (Wang et al.,
2006) have been used to block the spread of E. ade鄄
nophorum in southwest China, but none has been
proven to be effective. The finding that allelochemi鄄
cals in E. adenophorum can be completely degraded
by microbes offers a potentially effective way to con鄄
trol this weed: harvest it as organic fertilizer after
microbial fermentation.
In this study, allelopathy for two agricultivars ex鄄
isted under experimental conditions, however, it is yet
to be determined that allelopathy facilitates E. adeno鄄
phorum spread in the wild. In the future, growth in鄄
hibition to several native plants should be evaluated.
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Table 4摇 Response index (RI) of E. adenophorum leaf residues on barley seedlings
Degrading
days
SH
5 mL摇 10 mL摇
LL
5 mL摇 10 mL摇
RL
5 mL摇 10 mL摇
FW
5 mL摇 10 mL摇
0 -0. 25** -0. 44** -0. 39** -0. 46** -0. 47** -0. 79** -0. 37** -0. 91**
5 +0. 188** +0. 285** +0. 235** +0. 335** +0. 191** +0. 198** +0. 188 +0. 167
10 +0. 202** +0. 239** +0. 258** +0. 284** +0. 129* +0. 068 +0. 185 +0. 068
20 +0. 226** +0. 280** +0. 290** +0. 326** +0. 132** +0. 130** +0. 031 +0. 144
* P <0. 05; **P<0. 01. 摇 5 mL and 10 mL indicate the volume of condensed solution used in bioassay. Other notes see Table 1.
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3122 期摇 摇 YANG Ming鄄Zhi et al. : Allelopathic Potential and Pathway of an Invasive Weed Eupatorium adenophorum …摇 摇