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Crop Protection 23 (2004) 1209–1214
Phytotoxicity of lemon-scented eucalypt oil and its potential
use as a bioherbicide
Daizy R. Batish
a,
*, N. Setia
a
, H.P. Singh
a
, R.K. Kohli
a,b
a
Department of Botany, Panjab University, Chandigarh 160014, India
b
Centre for Environment and Vocational Studies, Panjab University, Chandigarh 160014, India
Abstract
The effect of volatile oil from leaves of Eucalyptus citriodora against some plant species viz.Triticum aestivum,Zea mays,
Raphanus sativus,Cassia occidentalis,Amaranthus viridis and Echinochloa crus-galli was investigated. In a laboratory bioassay seed
germination of test plants was significantly reduced in response to the different concentrations of the eucalypt oil. Maximum
germination inhibition was observed with A. viridis, whereas least effect was seen on R. sativus. Based on the germination response,
dose-response curve was generated and LC
50
values were calculated. It was maximum for R. sativus whereas minimum for A. viridis.
Further, seedling growth of the test plants and the chlorophyll content in the treated seedlings was significantly reduced at
concentrations 0.12 and 0.3 mg/l. Not only the initial growth, but also the spray treatment on the 4-week-old mature plants of two
weedy species viz.C. occidentalis and E. crus-galli adversely affected the chlorophyll content and cellular respiration, thereby
indicating the adverse effect of eucalypt oil on the photosynthetic machinery and the energy metabolism of the target plants. Based
on the study, it is concluded that volatile oil from E. citriodora is phytotoxic and could be utilized as bioherbicide for future weed
management programmes.
r2004 Elsevier Ltd. All rights reserved.
Keywords: Eucalyptus citriodora; Volatile oil; Phytotoxicity; Seed germination; Dose-response; Seedling growth; Cellular respiration; Chlorophyll
content; Weed management; Bioherbicides
1. Introduction
Weed infestation in agricultural fields results in huge
economic losses and low quality crop yields (Appleby
et al., 2000). Worldwide, a large amount of money is
spent every year to control them. While control of weeds
can be achieved through several means such as
mechanical, chemical, biological and cultural, the use
of synthetic herbicides is common and provides an
effective method. Unfortunately, the use of synthetic
herbicides may affect the environment and human
health, and is also leading to increasing herbicidal
resistance among many weed species. Therefore, efforts
to develop alternative means of weed control, which are
not only eco-friendly, but also cost effective and
bioefficaceous are needed (Duke et al., 2002). In this
direction, efforts to utilize natural plant products for
effective weed management are being made (Dayan
et al., 1999;Duke et al., 2002;Singh et al., 2003).
Natural products are not only biodegradable but may
also possess novel molecular target sites different from
synthetic herbicides. Among natural plant products,
volatile essential oils and their constituents have
attracted much attention because of their phytotoxicity
(also providing allelopathic property) and relatively
quicker degradation in the environment (Muller, 1965;
Kohli and Singh, 1991;Dudai et al., 1999;Romagni
et al., 2000;Singh et al., 2002;Tworkoski, 2002).
Terpenoids, particularly monoterpenes and sesquiter-
penes, are the main components of essential oils and are
often responsible for their inhibitory activity. Muller
and Muller (1964) have reported lesser vegetation in the
vicinity of purple sage (Salvia leucophylla Greene),
owing to the presence of volatile compounds such
as terpenes. Kohli and Singh (1991) reported that
the essential oil from hybrid eucalypt (Eucalyptus
ARTICLE IN PRESS
*Corresponding author. Tel.: +91-172-534005; fax: +91-172-
746253.
E-mail address: daizybatish@yahoo.com (D.R. Batish).
0261-2194/$ - see front matter r2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.cropro.2004.05.009
tereticornis Sm.) inhibits the growth of lentil (Lens
culinaris Medik.) seedlings and that from Tasmanian
blue gum (E. globulus Labill.) inhibit the growth of
mung bean (Phaseolus aureus L.), barley (Hordeum
vulgare L.), and oat (Avena sativa L.). In a preliminary
laboratory bioassay, Kohli et al. (1998) reported that the
volatile oil from lemon-scented eucalypt (E. citriodora
Hook.) and Tasmanian blue gum inhibits the germina-
tion and early seedling growth of ragweed parthenium
(Parthenium hysterophorus L.) and pointed that these
could be used for weed management. But not much has
been done in this direction. In view of these reports, the
present investigation was undertaken to assess the
phytotoxicity of lemon-scented eucalypt (E. citriodora
Hook.) volatile oil against some crops and weed species
with a view to exploit it for future weed management.
2. Materials and methods
2.1. Extraction of volatile oil
Essential volatile oil from fresh, mature and healthy
leaves of lemon scented eucalypt (E. citriodora Hook.)
was extracted by steam distillation, using Clevenger’s
apparatus as per the details given in Kohli et al. (1998).
For this, leaves were collected from the E. citriodora
trees growing in the Botanical Garden, Panjab Uni-
versity, Chandigarh. Two hundred and fifty grams of
fresh leaves were chopped into pieces and mixed with 1 l
distilled water in a 2 l round bottom flask and fitted with
condenser. Mixture was boiled for 1 h and oil was
collected from the nozzle of condenser.
2.2. Procurement of test material
For growth studies, seeds of wheat (Triticum aestivum
L.), maize (Zea mays L.), radish (Raphanus sativus L.)
were purchased from Punjab Agricultural University,
Ludhiana and seeds of weeds viz., barnyard grass
(Echinochloa crus-galli [L.] Beauv.), coffee weed (Cassia
occidentalis L.) and green amaranth (Amaranthus viridis
L.) were collected locally from Punjab University
campus.
2.3. Dose-response studies
Seeds of all these test plants were germinated in Petri
dishes (15 cm diameter) on a filter paper (Whatman No.
1) wetted with 7 ml of distilled water. To test the
inhibitory effect of oil, different amounts of oil were
loaded on the inner side of cover of Petri dish (so as to
get 0.03, 0.06, 0.12, 0.30, 0.60 and 1.20 mg/l) after
spacing the seeds on the base and then sealed
immediately with tape. Control was kept without
loading oil. For each concentration, five replicates were
maintained. All the Petri dishes were kept in a growth
chamber maintained at 16/8 h light/dark period at
2572C temperature. After 7 days, the number of seeds
that germinated was counted and on this basis LC
50
(least concentration for 50% inhibition) was calculated.
Based on the dose-response study, two concentrations—
i.e. 0.12 and 0.30 mg/l—of eucalypt oil were selected for
further growth studies.
2.4. Growth studies
Seeds of test plants were allowed to germinate for 18 h
on a filter paper moistened with distilled water and when
the radicle was 2 mm, these were subjected to growth
studies in response to 0.12 and 0.30 mg/l (as described
above). Five replications were kept for each treatment
including control (water instead of oil). After eight days,
the seedling length and dry weights of the germinated
seeds were measured, and the amounts of total
chlorophyll and cellular respiration were estimated.
The entire experiment was repeated twice.
2.5. Greenhouse studies
Another experiment was planned to establish the
herbicidal activity of eucalypt oil, against 4-week-old
plants of the weedy species E. crus-galli and C.
occidentalis under controlled greenhouse conditions.
Plants of E. crus-galli and C. occidentalis were raised
from locally collected seeds in 15 cm diameter pots in a
growth chamber at 2572C temperature, 7572%
relative humidity, 16/8 h light/dark photoperiod and
photon flux density of approximately 150 mmole
photons m
2
s
1
. For this 1200 g of garden soil
(soil:sand, 3:1, w/w) was taken in each pot and five
seeds of E. crus-galli and C. occidentalis were sown in
each pot, respectively. A week after emergence, pots
were thinned to two plant per pot. When the plants were
4-week-old, they were spray treated with 2.5, 5.0 and
7.5% solution of eucalypt oil (or distilled water to serve
as control) in such a manner that each plant received
2 ml of treatment solution. For each treatment five
replications were maintained. On the next day after
treatment, the leaves were plucked and used for the
estimation of chlorophyll content and determination of
respiratory activity.
2.6. Field study
To test the herbicidal activity of the volatile oil from
E. citriodora under field conditions, experiments were
conducted in the agricultural fields selected on the
outskirts of Chandigarh in 2002. The soil was sandy
loam in nature with pH 6.65, electrical conductivity
160.2 mS, organic matter 1.12%, available nitrogen,
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D.R. Batish et al. / Crop Protection 23 (2004) 1209–12141210
phosphorus, and potassium 160.4, 52.7, and 70.9 kg/ha,
respectively.
In these fields plots of 1 10 m size were prepared.
Seeds of both the weed species viz. C. occidentalis and E.
crus-galli were sown manually in four rows at the
spacing of 25 cm each and nearly 2 cm deep in soil.
Eucalypt oil was applied when the weeds were nearly
25 cm in height. These were sprayed with emulsions of
eucalypt oil at the concentrations of 1, 2.5, 5.0, and 10%
(prepared in water with the help of Surfactant Tween-
80, conc. 0.05%, v/v) on the weeds with a backpack-type
CO
2
sprayer.
Weed injury was visually noted on the 1 and 21 days
after the treatment (DAT). It was rated on the scale of 0
(with no injury) to 5 (with complete mortality). Plants
were harvested 21 DAT, and their dry weight was
determined after keeping them in oven at 70C for 72 h.
2.7. Estimation of chlorophyll content
Chlorophyll from 25 mg of treated or control leaves
were extracted in 4 ml of dimethyl sulphoxide (DMSO)
as per the method of Hiscox and Israelstam (1979).It
was quantified spectrophotometrically using the equa-
tion of Arnon (1949) and expressed on dry weight basis
as suggested by Rani and Kohli (1991).
2.8. Determination of cellular respiration
Respiratory activity was determined indirectly using
2,3,5-triphenyl tetrazolium chloride following the meth-
od of Steponkus and Lanphear (1967) wherein the red
formazan formed traps the oxygen released through
respiratory chain and thus respiration can be measured
indirectly. The absorbance was read at 530 nm and the
values were expressed with respect to control.
2.9. Statistical analysis
All the experiments were performed in a completely
randomized block design and repeated twice. For each
treatment five replications were maintained. The data
collected from dose-response study was subjected to log
transformations so as to generate dose-response curves
and calculate LC
50
concentrations. The data from other
experiments was subjected to one-way ANOVA fol-
lowed by separation of means at Po0.05 besides
calculation of correlation coefficients.
3. Results and discussion
The volatile essential oil from E. citriodora reduced
the germination of test plants in a dose-response
relationship (Fig. 1). At lower concentrations (ranging
from 0.03 to 0.12 mg/l) of volatile oil, very little
difference in germination of treated seeds was observed
compared to control. However, at 0.30 or higher
concentrations, the germination was significantly re-
duced in response to eucalypt oil compared to control.
The test plants responded differently to eucalypt oil
exhibiting a differential species- specificity. In case of A.
viridis none of the seed germinated even at lower
concentration of 0.30 mg/l, whereas in maize and radish
no complete inhibition in germination was obtained
even at highest concentration used, i.e. 1.20 mg/l (Fig.
1). Inhibition of seed germination in response to volatile
essential oil from a number of aromatic plants has also
been reported by Singh et al. (1991) and Dudai et al.
(1999). From the dose-response curve, LC
50
(the amount
of oil required to cause 50% inhibition of germination)
values were determined. LC
50
was calculated to be
maximum for radish followed by maize and least for A.
viridis sp. (Table 1). These values are of importance,
especially when further physiological studies are to be
undertaken in order to determine the mechanism of
action of this oil.
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0.01 0.1 1 10
0
20
40
60
80
100
LC50 values
T. aestivum
Z. mays
R. sativus
C.occidentalis
A. viridis
E. crus-galli
Germination (%)
Concentration (log10)
Fig. 1. Effect of different concentration of eucalypt oil on the
germination of test plants.
Table 1
LC
50
concentrations of the volatile oil from E. citriodora
Plant species LC
50
(mg/l)
T. aestivum 0.32
Z. mays 0.41
R. sativus 1.20
C. occidentalis 0.53
E. crus-galli 0.40
A. viridis 0.17
D.R. Batish et al. / Crop Protection 23 (2004) 1209–1214 1211
Seedling growth of the germinated seeds was also
affected in response to the treatment of 0.12 and
0.30 mg/l concentration of eucalypt oil (Table 2). Similar
observations as regards the effect of volatile oil have
been made by Muller (1965) and Elakovich and Stevens
(1985) wherein radicle growth of test seedlings was
adversely affected by the volatile essential oils from
Salvia leucophylla and mat grass (Lippia nodiflora [L.]
Michx.), respectively. The exact mechanism by which
germination and seedling growth is affected by eucalypt
volatile oil is not known. However, it could be due to the
inhibition of mitosis in the growing cells, as essential oil
are reported to inhibit the sprout growth in potato by
killing meristematic cells (Vaughan, 1991). The amount
of total chlorophyll content and the respiratory activity
in the treated seedlings were drastically reduced in
response to eucalypt oil (Figs. 2 and 3). At 0.12 mg/l
concentration of eucalypt oil, both chlorophyll content
and cellular respiration were reduced by over 50% in all
the test plants. Maximum inhibitory effect was observed
in A. viridis sp. (Figs. 2 and 3).
Likewise, in the 1-month-old mature plants of C.
occidentalis and E. crus-galli spray treated with the
eucalypt oil, both chlorophyll content and respiratory
activity were drastically affected (Fig. 4). In response to
spray treatment of 2.5% eucalypt oil, respiratory
activity and chlorophyll content in C. occidentalis was
reduced by over 85%.
Under field conditions, the plants spray-treated with
different concentrations of eucalypt oil exhibited vary-
ing levels of injury. Nearly 80% injury was recorded on
the C. occidentalis treated with 5% eucalypt oil, whereas
only 40% injury was observed in E. crus-galli plants
(Fig. 5). At lower concentration of 0.5 and 1.0%
eucalypt oil very little effect was observed in both the
weeds. However, at the higher concentration i.e. 7.5 and
10%, there was complete killing of C. occidentalis even
on the 1 DAT, whereas in contrast the injury level in E.
crus-galli varied from around 50% to 76% (Fig. 5). In
order to check any delayed effect of eucalypt oil, the
injury levels were also measured 21 DAT. It was
observed that none of the plants of C. occidentalis,
which were earlier killed showed any recovery or
regrowth (Fig. 5).
Euclaypt oil was more phytotoxic to C. occidentalis (a
broad-leaved weed) than to E. crus-galli (a grassy weed)
under both greenhouse and field conditions. Such an
observation is not surprising, since the volatile oil from
E. citriodora comprise mainly citronellal (>75%) while
other monoterpenes such as cineole and citronellol are
in much lower concentration. Citronellal is observed to
ARTICLE IN PRESS
Table 2
Effect of eucalypt oil on the seedling length (cm) of test plants
Plant species Control 0.12 mg/l 0.30 mg/l
T. aestivum 14.370.03
a
9.170.26
b
7.070.02
c
Z. mays 22.371.04
a
5.970.24
b
5.270.05
b
R. sativus 12.170.38
a
7.170.14
b
6.770.25
b
C. occidentalis 6.770.15
a
4.970.08
b
3.270.08
c
E. crus-galli 11.670.33
a
6.470.05
b
4.770.24
c
A. viridis 7.770.48
a
2.570.02
b
—
Different superscripts in a row represent significant difference at
Po0.05.
-0.1 0.0 0.1 0.2 0.3
-1
0
1
2
3
4
5
6
7
8
9
10
r=-0.817
r=-0.819
r=-0.840
r=-0.935
r=-0.894
r=-0.953
T. aestivum
Z. mays
R. sativus
C. occidentalis
A. viridis
E. crus-galli
Chlorophyll Content (µg/mg)
Concentration
(
m
g
/l
)
Fig. 2. Effect of eucalypt oil on the total chlorophyll content in the
seedlings of test plants. rrepresents values of correlation coefficient
between concentration and chlorophyll content
0.0 0.1 0.2 0.3
0
20
40
60
80
100
r=-0.819
r=-0.898
r=-0.885
r=-0.869
r = -0.843
r=-0.853
T. aestivum
Z. mays
R. sativus
C. occidentalis
A. viridis
E. crus-galli
Percent Cell Respiration
Concentration
(
m
g
/l
)
Fig. 3. Effect of eucalypt oil on the respiratory activity in the seedlings
of test plants. rrepresents values of correlation coefficient between
concentration of eucalypt oil and respiratory activity.
D.R. Batish et al. / Crop Protection 23 (2004) 1209–12141212
be more effective against broad-leaved weeds than
cineole (Singh et al., 2002), whereas cineole is more
effective against grassy weeds (Romagni et al., 2000).
The present study is thus in conformity with these
observations.
As regards the loss in chlorophyll content, nothing is
known whether it is due to decreased synthesis or
enhanced degradation, however, it is likely to affect the
photosynthetic efficiency of plants. Polova and Vicher-
kova (1986) and Vicherkova and Polova (1986) ob-
served that eucalypt oil alter the leaf diffusibility,
transpiration rate and stomatal aperture in test plants
and these might also affect photosynthesis. The loss of
respiratory ability measured through 2,3,5-triphenyl
tetrazolium chloride can probably change cellular
energy production leading to growth retardations.
Eucalypt oil is a complex mixture of a number of
volatile monoterpenes (Kohli, 1990). There are reports
that the monoterpenes such as cineole, citronellol,
citronellal, and linalool—the constituent of eucalypt
oil, affect photosynthesis by reducing chlorophyll
content (Romagni et al., 2000;Singh et al., 2002).
Abrahim et al. (2000) have reported that interference of
monoterpenes with respiratory ability can lead to
impairment of germination and growth of plants. The
phytotoxicity of eucalypt oil on the test species could
thus may be due to impairment of photosynthesis and
respiratory ability by the constituent monoterpenes. The
constituent monoterpenes might be acting synergisti-
cally like other allelochemicals (Einhellig, 1996). The
solubility of monoterpenes, in general being water
insoluble, is a limiting factor in imparting toxicity to
other plants. However, monoterpenes are generally
active at concentrations far below their maximum
solubility (Weidenhamer et al., 1993). Besides, these
can be brought into solution form with the help of some
surfactants (Muller, 1965).
From the present study, it could therefore be
concluded that volatile oil from E. citriodora show
strong phytotoxicity and possesses weed-suppressing
ability. Hence, these could be one useful natural plant
products for developing bioherbicides. However, re-
garding their commercialization, the feasibility is lesser
owing to their rapid volatilization. But it could be taken
care by chemical alterations/modifications of its con-
stituents so as to decrease rapid volatilization as has
been done in case of cinmethylin. Moreover, there is a
need to explore whether the addition of adjuvants or
preparation of its formulations can further enhance its
herbicidal activity.
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0246810
0
20
40
60
80
100 21 DAT
r=0.980
r=0.941
Visible Injury (%)
Concentration (%)
0246810
0
20
40
60
80
100 1 DAT
r=0.991
r=0.954
C. occidentalis
E. crus-galli
Visible Injury (%)
(a)
(b)
Fig. 5. Visible injury levels observed in C. occidentalis and E. crus-galli
on the 1 and 21 DAT under field conditions after spray treatment of
eucalypt oil. rrepresents values of correlation coefficient between
concentration and the value of visible injury level.
0 2 4 6 8
20
40
60
80
100
r=-0.913
r=-0.786
Cellular Respiration (%)
Concentration (%)
0 2 4 6 8
0
3
6
9
12
15
r=-0.959
r=-0.827
C. occidentalis
E. crus-galli
Chlorophyll Content (µg/mg)
Fig. 4. Effect of spray treatment of eucalypt oil on the photosynthetic
and respiratory activity of C. occidentalis and E. crus-galli in the
greenhouse. rrepresents values of correlation coefficient between
concentration and value of parameter.
D.R. Batish et al. / Crop Protection 23 (2004) 1209–1214 1213
Acknowledgements
Nidhi Setia is thankful to CSIR, New Delhi for
financial assistance in the form of JRF.
References
Abrahim, D., Braguini, W.L., Kelmer Bracht, A.M., Ishi-Iwamoto,
E.L., 2000. Effects of four monoterpenes on germination, primary
root growth and mitochondrial respiration of maize. J. Chem.
Ecol. 26, 611–623.
Appleby, A.P., M.uller, F., Carpy, S., 2000. Weed control. In: M.uller,
F. (Ed.), Agrochemicals. Wiley-VCH, New York, pp. 687–709.
Arnon, D.I., 1949. Copper enzymes in isolated chloroplasts: poly-
phenylperoxidase in Beta vulgaris. Plant Physiol. 24, 1–15.
Dayan, F., Romagni, J., Tellez, M., Rimando, A., Duke, S., 1999.
Managing weeds with natural products. Pestic. Outlook 10,
185–188.
Dudai, N., Mayer, A.M., Putievsky, E., Lerner, H.R., 1999. Essential
oil as allelochemicals and their potential use as bioherbicides.
J. Chem. Ecol. 25, 1079–1089.
Duke, S.O., Dayan, F.E., Rimando, A.M., Schrader, K.K., Aliotta,
G., Oliva, A., Romagni, J.G., 2002. Chemicals from nature for
weed management. Weed Sci. 50, 138–151.
Einhellig, F.A., 1996. Interactions involving allelopathy in cropping
systems. Agron. J. 88, 886–893.
Elakovich, S.D., Stevens, K.L., 1985. Volatile constituents of Lippia
nodiflora. J. Nat. Prod. 48, 504–506.
Hiscox, J.D., Israelstam, G.F., 1979. A method for extraction of
chlorophyll from leaf tissue without maceration. Can. J. Bot. 57,
1332–1334.
Kohli, R.K., 1990. Allelopathic potential of eucalyptus.Project
Report—Man and Biosphere Programme. Department of Envir-
onment, India, 199pp.
Kohli, R.K., Singh, D., 1991. Allelopathic impact of volatile
components from Eucalyptus on crop plants. Biol. Plant. 33,
475–483.
Kohli, R.K., Batish, D.R., Singh, H.P., 1998. Eucalypt oil for the
control of parthenium (Parthenium hysterophorus L.). Crop Prot.
17, 119–122.
Muller, W.H., 1965. Volatile materials produced by Salvia leucophylla:
effects on seedling growth and soil bacteria. Bull. Torr. Bot. Club
92, 38–45.
Muller, W.H., Muller, C.H., 1964. Volatile growth inhibitors produced
by Salvia species. Bull. Torr. Bot. Club 91, 327–330.
Polova, M., Vicherkova, M., 1986. Leaf diffusibility changes of bean
and sunflower plants treated with essential oil vapours. Scr. Facult.
Scient. Nat. Univ. Park. Brun (Biologia) 16, 119–128.
Rani, D., Kohli, R.K., 1991. Fresh matter is not an appropriate
relation unit for chlorophyll content: experience from experiments
on effects of herbicides and allelopathic substances. Photosynthe-
tica 25, 655–657.
Romagni, J.G., Allen, S.N., Dayan, F.E., 2000. Allelopathic effects of
volatile cineoles on two weedy plant species. J. Chem. Ecol. 26,
303–313.
Singh, D., Kohli, R.K., Saxena, D.B., 1991. Effect of Eucalyptus oil on
germination and growth of Phaseolus aureus Roxb. Plant Soil 137,
223–227.
Singh, H.P., Batish, D.R., Kaur, S., Ramezani, H., Kohli, R.K., 2002.
Comparative phytotoxicity of four monoterpenes against Cassia
occidentalis. Ann. Appl. Biol. 141, 111–116.
Singh, H.P., Batish, D.R., Kohli, R.K., 2003. Allelopathic interactions
and allelochemicals: new possibilities for sustainable weed manage-
ment. Crit. Rev. Plant Sci. 22, 239–311.
Steponkus, P.L., Lanphear, F.R., 1967. Refinement of triphenyl
tetrazolium chloride method of determining cold injury. Plant
Physiol. 42, 1423–1426.
Tworkoski, T., 2002. Herbicide activity of essential oil. Weed Sci. 50,
425–431.
Vaughan, S.F., 1991. Natural compounds from spices could replace
chemical patoto-sprouting inhibitors. Ind. Bioprocess. 13, 5.
Vicherkova, M., Polova, M., 1986. Effect of essential oil vapours of
different concentrations upon leaf transpiration of bean and
sunflower. Scr. Facult. Scient. Nat. Univ. Park. Brun. (Biologia)
16, 109–118.
Weidenhamer, J.D., Macias, F.A., Fischer, N.H., Williamson, G.B.,
1993. Just how insoluble are monoterpenes? J. Chem. Ecol. 19,
1799–1807.
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