Published Online November 2013 (http://www.scirp.org/journal/ajps)
Department of Crop and Environmental Protection, Faculty of Agricultural Sciences, Ladoke Akintola University of Technology,
Received August 17
, 2013; revised September 17
, 2013; accepted October 15
Copyright © 2013 Gabriel Olulakin Adesina. This is an open access article distributed under the Creative Commons Attribution Li-
cense, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Pot experiment was carried out in the screen house, Ladoke Akintola University Technology Ogbomosho, Nigeria to
determine the possible impact of Tithonia diversifolia on the growth of thirteen selected weed species weeds growing in
its surroundings. The study consisted of two treatments (Tithonia diversifolia infested and Non-Tithonia diversifolia
infested soils) and from the two media, the growth of A. hispidium, B. pilosa E. heterophylla, P. maximum and P.
polystachion was significantly affected in soil infested by T. diversifolia. The number of weed seedling emergence afore
mentioned was significantly lower than what was obtained in soil not infested with T. diversifolia and this accounted for
about 38% of the tested weed species. Germination of four of these weeds species (23%) (A. spinosus, C. viscosa, T.
procumbens and D. gayana) was enhanced by the presence of T. diversifolia. The study further revealed that weed
counts in T. diversifolia infested soil is significantly lower than the ones in soil without T. diversifolia infestation.
Likewise, the vegetative growth of some species (A. spinosus, C. viscosa, T. procumbens and D. gayana) was improved
in this soil. This shows that T. diversifolia infested soil contains allelochemicals that performed both stimulatory and
Keywords: Tithonia diversifolia; Allelopathy; Allelochemical; Asteraceae
Weed infestation is ranked the greatest problem in agri-
cultural systems , causing crop yield losses. Attention
towards reducing dependency on herbicide has height-
ened interest in weed management strategies that com-
bine more efficient use of herbicides with increased use
of biologically based weed management methods .
Chemicals that are released from plants which impose
negative influence on other plants are called al-
lelochemicals or allelochemics . Allelochemicals that
are toxic may inhibit shoot/root growth, nutrient uptake,
or may attack a naturally occurring symbiotic relation-
ship thereby destroying the plant’s usable source of a
nutrient . The consequent effects may be inhibited or
retarded germination rate, reduced root or radicle and
shoot or coleoptile extension, lack of root hairs, swelling
or necrosis of root tips, curling of the root axis, increased
number of seminal roots, discolouration, reduced dry
weight accumulation and lowered reproductive capacity
. Plants in the Asteraceae family like T. diversifolia
and T. rotundifolia have been reported to exhibit allelo-
pathic traits [5,6].
Different plant parts, including flowers, leaves, leaf
litter and leaf mulch, stems, bark, roots, soil and soil
leachates and their derived compounds, can have allelo-
pathic activity that varies over growing seasons [7,8].
When susceptible plants are exposed to allelochemicals,
germination, growth and development may be affected.
The most frequently reported gross morphological effects
on plants are inhibited or retarded seed germination, de-
privative effects on coleoptile elongation and on radicle,
shoot and root development.
Allelopathic inhibition is complex and can involve the
interaction of different classes of chemicals like phenolic
compounds, flavonoids, terpenoids, alkaloids, steroids,
carbohydrates, and amino acids, with mixtures of differ-
ent compounds sometimes having a greater allelopathic
effect than individual compounds alone . Furthermore,
physiological and environmental stresses, pests and dis-
eases, solar radiation, herbicides and less than optimal
allelopathic weed suppression .
The current trend in agricultural practices which dis-
courages the use of inorganic external input in crop and
animal production makes research in allelopathy impor-
tant. This is because the use of inorganic input is con-
tributory to solve many of the problems confronting
adequate food production which is void of many syn-
thethic pesticides (herbicides inclusive). Also, in organic
cropping systems where synthetic herbicides are not used,
crop cultivars with enhanced allelopathic activity could
be part of the weed management strategy. Weed control
mediated by allelopathy—either as natural herbicides or
through the release of allelopathic compounds from a
living crop cultivar or from plant residues is often as-
sumed to be advantageous for the environment compared
to synthetic herbicides. In view of the fact that al-
lelochemicals are derived from natural sources, several
authors were of the opinion that these allelopathic com-
pounds will be biodegradable and less polluting to the
environment than conventional herbicides [10-12].
Many crop cultivars show strong allelopathic proper-
ties, of which rice (Oryza sativa) has been most studied.
Beet (Beta vulgaris L.), lupin (Lupinus lutens L.), maize
(Zea mays L.), wheat (Triticum aestivum L.), oats (Avena
sativa L.), barley (Hordeum vulgare L.) and Cucumis
sativus are other crops which have been studied that
show allelopathic effect on other crops [7,13-15].
Reference  examined the toxic effect of four leg-
umes and reported that the aqueous leachates (1%) of all
the four legumes exhibited strong phytotoxic effect on
the radical growth of barnyard grass (Echinochloa crus-
of Ipomoea was described by [17,18] identified Tricol-
orin A as the major phyto-growth inhibitor from the resin
glycoside mixture of the plants.
According to references  isothiocyanates contained
in Brassica spp were strong suppressants of germination
on some tested weed species Spiny sow thistle (Sonchus
asper L. Hill), Scentless mayweed (Matricaria inodora
L.), Smooth pigweed (Amaranthus hybridus L.), Barn-
yard grass (Echinochloa crusgalli L. Beauv.), Black
grass (Alopecurus myosuroides Huds.) and wheat crop
(Triticum aestivum L.). Reference  studied the al-
lelopathic effect of black mustard (Brassica nigra L.) on
germination and seedling growth of wild oat (Avena
fatua L.); these authors found that germination and radi-
cle length were affected by extracting solutions and the
inhibitory effect on germination increased with increas-
ing concentration of extract solution of the fresh plant
Congress grass (Parthenium hysterophorus L.) was
found to show allelopathic effect due to the presence of
parthenin, a sesquiterpene lactone of pseudoguanolide
nature in various parts of the plant [21-23]. Parthenin is
known to have specific inhibitory effects on root and
shoot growth of Crotalaria mucronata L., Cassia tora L.,
Oscimum basilicum L., Oscimum americanum L. and
barley (Hordeum vulgare L.) [24,25]. Various phenolic
compounds identified in Parthenium (caffeic, vanillic,
ferulic, chlorogenic and anisic acid) [21,26,27] may be
responsible for growth reduction of test crops in
Reference  investigated the allelopathic effects of
Croton bonplandianum weed on seed germination and
seedling growth of crop plants (Triticum aestivum L.,
and weed plants (Melilotus alba Medik, Vicia sativa L.
and Medicago hispida Gaertn). Leaf extract was found to
be the most allelopathic and growth inhibition effect was
found to increase with increasing concentrations of dif-
ferent aqueous extracts.
Russian knapweed (Acroptilon repens L.) is a widely
distributed and problematic weed of the Western United
State. [29,30] found that the roots of A. repens inhibited
the root growth of many plants including some weed
species such as Lactuca sativa, Medicago sativa, Echi-
nochloa crusgalli and Panicum miliaceum by 30% at
concentrations comparable to those found in the soil sur-
rounding of A. repens plants. Moreover, the germination
of Agropyron smithii and Bromus marginatus was inhib-
ited by aqueous leaf extracts of A. repens at high level
concentrations, however, according to , germination
was induced by lower concentrations. The objective of
this study, therefore, is to determine whether Tithonia
its surroundings and identify the affected weed species.
The experiment was carried out in the screen house,
Ladoke Akintola University Technology Ogbomosho,
Seeds of thirteen weed species were collected from the
wild in the previous season (2011) from Teaching and
Research Farm Ogbomoso. The collected weed species
were: Euphorbia heterophylla, Pennisetum polystachion,
Bidens pilosa and Ancanthospermum hispidium. Others
were Amaranthus spinosus, Cleome viscosa, Fibristylis
A plot heavily infested by Tithonia diversifolia was se-
lected for soil sampling for the experiment. The plot was
Open Access AJPS
tuting more than 90% of the total identifiable weed spe-
cies. Other weed species present on the plot were Imper-
ata cylindrica, Boerhavia diffusa, and Ageratum cony-
zoides. Non Tithonia infested soil has no T. diversifolia
growing on it. Soil sampling of the T. diversifolia in-
fested field and Non T, diversifolia infested field was
done at the depth of 0 - 15 cm of the soil.
The samples were passed through just three stages of
processing before being subjected to laboratory analysis:
1) Crushing; Large soil clods were crushed to facilitate
drying; 2) Air drying of the soil samples from the two
different locations separately for a week under a condi-
tion that prevented contamination and finally; 3) Sieving
of the soil samples through a 2 mm brass sieve.
The physical and chemical properties of the two soil lo-
cations were determined at the International Institute of
Tropical Agriculture (IITA), Ibadan, Nigeria.
A total of 104 pots were used for the experiment with 52
pots for each treatment replicated four times. These pots
were perforated at the base to prevent water logging and
filled with 2 kg soil each. The pots were laid-out in a
Completely Randomized Design (CRD).
Twenty seeds of each of the test weeds were sown in
each of the treatments and replicated four times. Pots
were irrigated every other day to facilitate germination.
Emergence of young seedlings was observed from two
weeks after planting (WAP).
Data were collected every week after seedling emergence
on population of weed seed that emerged in each of the
The collected data was subjected to Analysis of Variance
(ANOVA) and means were separated using LSD at 5%
probability level. The result soil chemical analysis of the
two locations (Tithonia-infested and Non-Tithonia-infested
soils were correlated with weed seedling emergence at 6
WAP to determine the relationship between soil chemical
parameters and weed seed emergence.
The result of Physico-chemical parameters of soil in the
two locations where soil samples were collected is shown
in Table 1. From the result, the two soils differed in
terms of pH and exchangeable acidity, but the level of
Nitrogen, and Potassium were very close. The pH values
show that the location with Tithonia diversifolia infesta-
tion was alkaline (8.4) while the location without T. di-
infested soil was higher in Ca, Zn and Fe composition
(4.68, 188.59 and 136.89 ppm) respectively than the lo-
cation without T. diversifolia infestation (1.07, 24.17 and
84.73 ppm) respectively but lower in Cu composition.
The sand, silt, and clay composition of these locations
were the same.
3.2. Weed Emergence
The performances of the 13 weed species planted in
shown in Table 2. Amongst the weeds, 69% of the thir-
teen species were broadleaved while the remaining 31%
were grasses. Out of the weed lot, the growth of A. his-
by T. diversifolia. The number of weed seedling emer-
gence afore mentioned were significantly lower than
what was obtained in soil not infested with T. diversifolia
and this account for about 38% of the tested weed spe-
cies. At 1 WAP A. hispidium, an average of almost five
(5) plants were recorded in Non-Tithonia infested soil
while less than one plant (<1) on the average was re-
corded in soil infested with T. diversifolia. This trend
continued until 6 WAP when 16 seedlings of A. his-
were recorded in Non-T. diversifolia infested soil while
only approximately four seedling of A. hispidium was
recorded in T. diversifolia infested soil. The same trends
was observable in the growth pattern of B. pilosa, E. het-
erophylla, P. maximum, P. polystachion and W. indica. It
was also noted that statistically, the seedling emergence
of W. indica in both T. diversifolia infested and Non-T.
diversifolia infested soil media were not statistically sig-
nificant for 1 WAP and 3 WAP but subsequently signifi-
cant difference were observed.
The presence of T. diversifolia favoured the germina-
tion and seedling emergence of four of these weeds spe-
cies (23%) and these include A. spinosus, C. viscosa, T.
the experiment, A. spinosus almost have no seedling
emergence on the average for the six weeks except week
two when average of two seedlings were recorded but
these seedlings withered before the end of the experiment
Table 1. Physico-chemical properties of the experimental soils.
P (ppm) 58.395
Zn (ppm) 188.59
Cu (ppm) 1.72
Mn (ppm) 32.55
Fe (ppm) 136.89
Table 2. Seedling emergence response of thirteen weed species on T. diversfolia and non-T. diversfolia infested soils for a pe-
Name of the weed
1.0 0.0 1.3
4.0 2.0 1.6
0.8 4.8 1.3
0.8 6.5 0.8
0.5 8..0 2.8
0.5 9.8 2.0
2.5 1.0 1.3
4.8 2.3 1.4
5.5 10.3 1.5
7.8 12 2.4
Fibristylis littoralis 0.0 0.0 0.0
0.0 0.0 0.0
1.3 1.5 0.5 1.3
Hyptis suaveolens 1.8 3.8 2.6
3.3 4.0 1.5
0.5 0.8 0.8
Tridax procumbens 6.0 0.0 2.6
7.0 0.0 1.8
6.3 4.3 0.0
7.3 6.0 1.5
Panicum maximum 1.0 4.8 2.0
2.5 6.0 2.8
4.5 5.8 1.2
5.5 7.8 0.8
0.0 0.5 0.9
0.0 1.3 2.0
Key: TIS: T. diversfolia Infested Soil; TNS: Non-T. diversfolia Infested Soil; LSD: Least Significant Difference; NS: Non Significantly different;
on non-T. diversifolia infested soil. When this result was
fested soil, A. spinosus seed germinated and seedling
emerged from one (1) at 1 WAP to four seedings be-
tween 4 - 6 WAP. The same observation was made on C.
these weed seeds (A. spinosus, C. viscosa, T. procumbens
and D. gayana) that emerged on soil not infested with T.
diversifolia was significantly lower than the number of
weed seed that emerged on soil infested with T. diversi-
Germination of Fibristylis littoralis, Hyptis suaveolens
weed species were not responsive in either T. diversifolia
infested soil or Non-T. diversifolia infested soil. It was
observed that the first emergence on Fibristylis littoralis
pots was noticed on the third week when an average of
less than one (<1) seedling was recorded in the two soil
media. Senna occidentalis has lower germination from
the first week but did not increase appreciably through-
out the 6 week experimental period.
Based on the response of weed species to their growth
in the two media, A. hispidium, B. pilosa, P. maximum
and P. polysachion showed the highest response to the T.
the study with reduced number of seedling that emerged
when compared with Non-T. diversifolia infested soil
(Table 3). A. hispidium, on infested soil, has as low as
0.8 plant/pot average seedling during the first week after
planting and 3.5 plants/pot was recorded at 6 WAP while
in non-infested soil, 4.8 plants/pot was recorded in first
weed after planting and was significantly greater than the
number of seedling recorded at 6 WAP for T. diversifolia
infested soil. At 6 WAP, an average of 78% (15.5
plants/pot) of A. hispidium seeds planted in soil not in-
fested with T. diversifolia soil germinated. The same
trend was observed for B. pilosa, P. maximum and P.
polysachion which belong to the category of weed that
were significantly affected by T. diversifolia infested
Statistically, the mean of seedling recorded at E. het-
ferential in average number of seedling recorded. For
example, at 1 WAP, the number of E. heterophylla seed-
ling for both T. diversifolia infested and non T. diversifo-
and at 6 WAP, the average number of E. heterophylla
seedlings was 10.5 and 16.5 plants/pot for T. diversifolia
infested and non T. diversifolia infested soil respectively.
The seedling emergence of A. spinosus, C. viscosa, T.
procumbens and D. gayana were not affected by T. di-
versifolia infested soil. Among all the weed seeds planted,
F. littoralis had average of 0.3 and 0.8 plants/pot in both
T. diversifolia infested soil and non T. diversifolia in-
fested soil respectively at 3 WAP. There was no emer-
gence of the weed at 1 and 2 WAP. A highest average of
1.5 plants/pot was recorded on soil not infested soil.
Correlation between soil physico-chemical parameters
and weed emergence in the two soil media were shown
in Tables 4 and 5. The correlation of soil with T. diver-
two weed species (C. viscosa and F. littoralis) showed
correlation that was significant (Table 4). It was obvious
Table 3. Rating of thirteen weed species in Tithonia infested soil.
Score of allelopathic Response o weeds to Tithonia infested soil
Key to Rating: High: < 30% of seeds planted/pot in T. diversifolia infested soil germinated by sixth week; Moderate: <50% of the seeds planted/pot in T.
the growth of the weed seeds.
Weed Emergence (6 WAP)
−0.67082 0.32285 0.67082
(p = 0.8039)
−0.89709 0.23663 0.75907
−0.79559 0.74786 0.99449
that there was significant positive correlation between C.
coefficient of 0.99. Moreover, F. littoralis was positively
correlated to calcium (Ca) 0.95 and negatively correlated
to Fe with coefficient of −0.95.
In non T. diversifolia infested soil (Table 5), only two
weed species showed significant correlation to soil
chemical properties. C. viscosa was positively correlated
to pH (0.99) and D. gayana was positively correlated Ca
(0.95) and Zn (0.95) and negatively correlated to acidity
(−0.94). The rest were not statistically significant.
The presence of T. diversifolia on arable field could sug-
gest several changes which may be taken place within
such ecosystem as indicated in this study. From the soil
analysis carried out on the soil of the two locations (T.
diversifolia infested soil and Non T. diversifolia infested
soil), the differential pH in soils from the two locations
could be one of the factors that affect the germination of
the weed seeds. References  reported that the germi-
nation of Texas weed (Caperonia palustris) increased at
pH between 4 and 8 and decreasing germination at pH
levels of 9 and 10. This differential pH could be as a re-
sult of impact of crop architecture of T. diversifolia
which control the degree of exposure to environmental
factors like erosion and other weathering activities since
introduced in T. diversifolia infested soil were sup-
pressed at varying degrees.
E. heterophylla showed average susceptibility to
T.diversifolia suppression as 50% of its total seeds in-
troduced emerged. Although, it was observed that leaves
of E. heterophylla appeared to be healthier in T. diversi-
folia infested soil than in soil without T. diversifolia. This
may however be an indication of stimulatory effect of
allelopathy. Reference  reported that T. diversifolia
Weed Emergence (6 WAP)
Calcium (Ca) Acidity Zinc (Zn) Iron (Fe)
(p = 0.2002)
−0.11066 −0.36515 0.88679
−0.94388 0.95346 −0.57208
−0.77460 0.73030 −0.73030
is a potential green manure and organic fertilizer for
B. pilosa was the most susceptible to T. diversifolia
suppression out of the selected weed plants as only 5%
emerged. The result obtained in this study was similar to
the work of  who studied the allelopathic potential of
aqueous extracts from the aerial part of L. leucocephala
on Desmodium purpureum, B. pilosa and Amaranthus
were the most sensitive species to the extract in the bio-
assays. However, some workers have also observed in-
hibitory effects of some plants on other test plants. Ref-
erences  reported that Chromolaena odorata contains
a large amount of allelochemicals especially in the leaves,
which inhibit the growth of many plants in nurseries and
plantations. Reference  has demonstrated that aque-
ous extract and shoot extract of T. diversifolia was in-
hibitory to the germination and growth of Amaranthus
bark, leaf and leaf extract of Quercus glauca and Q. leu-
and radicle length of wheat (Triticum sp.) and mustard
seeds. Earlier investigators have suggested that al-
lelochemicals or toxins are released from the weed by the
action of micro-organisms during decomposition, which
may interfere with the plant growth processes .
This study reveals that weed counts in T. diversifolia
infested soil is significantly lower than the ones in soil
without T. diversifolia infestation. Likewise, the vegeta-
tive growth of some species (A. spinosus, C. viscosa, T.
This shows that T. diversifolia infested soil contain al-
lelochemicals that performed both stimulatory and in-
It is clear from our discussion that there is immense
Open Access AJPS
ment tool. Impacts of allelopathy on different weed spe-
cies have been identified. In spite of that, some factors
have to be considered before application of allelochemi-
cals as natural herbicide and such factors include soil
properties, type of weed species to be controlled and time
of application of the allelopathic mechanism in control-
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