Journal of Agricultural Technology 2012 Vol.

8(4): 1423-1469
AvailableTechnology
Journal of Agricultural online http://www.ijat-aatsea.com
2012, Vol. 8(4): 1423-1469
ISSN 1686-9141

Allelopathic effects of some botanical extracts on germination

and seedling growth of Sorghum bicolor L.

Mohammed. M. Hassan1, Hussien M. Daffalla2*, Samia O. Yagoub3,

Magdoleen G. Osman2, Migdam E. Abdel Gani1 and Abdel El Gabar E.
Babiker1
1
Environment and Natural Resources Research Institute, Khartoum, Sudan, 2Commission for
Biotechnology and Genetic Engineering, Khartoum, Sudan, 3Sudan University of Science and
Technology, College of Agricultural Studies, Khartoum, Sudan

Mohammed. M. Hassan, Hussien M. Daffalla, Samia O. Yagoub, Magdoleen G. Osman,

Migdam E. Abdel Gani and Abdel El Gabar E. Babiker (2012) Allelopathic effects of some
botanical extracts on germination and seedling growth of Sorghum bicolor L. Journal of
Agricultural Technology 8(4): 1423-1469.

The allelopathic potential of the aqueous extracts and powder of Khella (Ammi majus),
Ghobaish (Guiera senegalensis) and Safsaf (Salix spp.) on germination and seedling growth of
two Sorghum bicolor L. cultivars was studied. Petri-dish trial showed that the different extracts
level reduced total germination percentage (G %) and mean germination time (MGT). Khella
extract sustained the maximum reduction in G % and MGT. Botanical extracts exhibited extra
inhibitory effects on radical emergence than on plumule growth. Pot experiment indicted
variations in seedlings germination and post-germination growth between the two cultivars in
response to different botanical residues. Fatarita seedling emergence improved by Khella and
decreased with Ghobaish and Safsaf. While, Hybrid seedling emergence improved with
Ghobaish and Safsaf and reduced by Khella compared to control. The higher MGT was
recorded in Fatarita in some treatments compared to control. Hybrid exposes a constant MGT
in all treatments. Botanical extracts stimulated some growth parameters and reserve others in
both cultivars. The results suggested that allelopathic potentials of these plants may entitle them
to control specific weeds especially in non-sequential crops by preparing them as natural
herbicides.

Key words: allelopathy, botanical extracts, sorghum germination and growth.

Introduction

Allelochemicals emancipated as residues, exudates and leaches by many

plants from leaves, stem, roots, fruit and seeds reported to interfere with growth
of other plants (Asgharipour and Armin, 2010). These chemicals products
mainly affect plants at seed emergence and seedling levels (Alam and Islam,

*
Corresponding author: Hussien M. Daffalla; e-mail: hdaffalla@yahoo.com
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2002; Hussain et al., 2007; Mohamadi and Rajaie, 2009; Naseem et al., 2009).
Allelopathy plays an important role in agricultural ecosystems and in a large
scale, in the plant covers among the crop-crop, crop-weed and tree-crop covers.
These interactions are detrimental and occasionally, are useful and gave
attention to allelopathy in natural and agricultural ecosystems. Today,
allelopathy is recognized as appropriate potential technology to control weeds
using chemicals released from decomposed plant parts of various species
(Naseem et al., 2009).
Sorghum [Sorghum bicolor (L.) Moench] is a very economic important
cereal crop and represent major staple food crop for many developing countries.
Sorghum was severe affected by weeds invention during the four-five weeks
after seeds emergence and seedling growth. As a consequence, severe
uncontrolled weed infestations often cause poor crop establishment or complete
crop failure (Pannacci et al., 2010). Bioherbicides represent solution to heavy
use of synthetic herbicides which it causes serious threats to the environment,
consumers and increases costs of crop production (Asghari and Tewari, 2007).
Unavailability of grass herbicides registered both for pre- and post-emergence
applications (Pannacci et al., 2010). Moreover, continuous use of herbicides for
weeds control causes herbicide resistant (Naseem et al., 2009). Many author
reported employ plants extracts for controlling weeds with variable success
(Hussain et al., 2007; Iqbal et al., 2009; Naseem et al., 2009). However,
allelochemicals might affect both crop and weeds when found together. The
crop was distress directly or indirectly by the allelochemicals and lead to either
stimulation or inhibition of growth (Asgharipour and Armin, 2010). Several
works have demonstrated the harmful influence of application of some plant
species to sorghum including reduced seeds germination, seedlings emergence
and biomass gain. Aqueous extracts of leaves have notably inhibited seed
germination of sorghum with application of Parthenium hysterophorus (Murthy
et al., 1995), Ipomoea cornea (Jadhav et al., 1997) Commelina bengahalensis
and Cyperus rotundus (Channappagoudar et al., 2003) and Eucalyptus
camaldulensis (Mohamadi and Rajaie, 2009). However, the allelochemicals
sometimes have positive affects on sorghum growth. For example, Moringa
oleifera leaf extracts enhanced germination of sorghum by 29% (Phiri, 2010).
The same kind of germination pomotary behaviour was also observed in
extract of Cassia angustifolia (Hussain et al., 2007). Study the allelopathic of
plant organs extract at seed germination and seedling growth stages was
beneficial for it is difficult to separate the allelochemicals effects from that of
competition among crop and allelopathic plants (Asgharipour and Armin,
2010). Understanding the response of crop cultivars to allelopathic plants
potential for weed control is very important. Therefore, the objective of this

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study was to determine the effect of aqueous extracts from some Sudanese
medicinal plants on germination and seedling growth of sorghum under lab and
greenhouse conditions.

Materials and methods

Botanical material

A total of three plants known for ability to produce allelochemicals were

selected for the present study namely Khella, Ammi majus (Umbellifereae),
Ghobaish, Guiera senegalensis (Combretaceae) and Safsaf, Salix spp.
(Salicaceae). Fully grown healthy leaves collected from these plants were
washed thoroughly with distilled water and dried in the open for 14 days. Then
the dried samples were separately ground into fine powder and stored dry until
used. Aqueous leaf extract was prepared by soaking 10 gram of powdered leaf
material in 100 ml distilled water for 24 hours. Then, this extract was filtered
using filter paper (Whatman No. 1). The filtered solutions (stock solutions)
were held in a refrigerator for a short time until experiment start. Stock solution
(10% w/v) was diluted appropriately with distilled water to give the final
concentrations of 25, 50 and 75 %. To evaluate the phytotoxicity of
allelochemicals produced by the plants, the effects of water soluble compounds
on seed germination and powdered leaves on seedling growth was analyzed.
The control treatment, distilled water, was used to estimate potential
germination of seeds.

Plant material

Seeds of two local cultivars, Sorghum bicolor (L.) Moench, viz. Fatarita
and Hybrid were obtained locally. The plant seeds were sterilized with 15:1
water/bleach (commercial NaOCl) solution for 5 minutes and subsequently
washed with distilled water.

Seed germination

Five tests corresponding to the treatments mentioned above were

performed on cultivar Fatarita in a germination test consisting of seeds
incubated on filter paper with; irrigated solely with concentrations of 25, 50, 75
and 100 % along with 0% (control, distilled water). For each treatment, three
different replications were tested. Each replicate was composed of 10 seeds
placed in a 10-cm diameter plastic Petri dish on paper tissues, kept saturated by
regular watering. The Petri dishes were kept in a germinator (25±3° C, 70%
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humidity and constantly dark) for 5 days. The Petri dishes were watered once in
every 2-3 days with either different concentrations of aqueous solution of leaf
extract or distilled water for the control, if necessary.
Germinated seed (considered when radicle emergence ≥ 1 mm) were
daily counted for 5 days or until the last seed germination. To assess the rate of
germination, final germination percentage (G %) and mean germination time
(i.e., time from imbibition to radicle emergence) (MGT) were calculated using
the formulas:

G% = (a/b) 100,

Where, a is the proportion of germinant and b the total number of seeds

germinates in control treatment.

Whereas, MGT was calculated according to Ganaie et al. (1992) as:

MGT = Σ (n × d)/N,

Where, n is the number of seeds which germinated after each period in days (d)
and N is the total number of seeds germinated at the end of the experiment.
Radicle and plumule growth elongation measurements were recorded after the
5 th day.

Seedling growth

In order to test the short-term allelopathy of the three plants, effect of

botanical residues incorporated with soil was studied. For incorporation
treatments, residues of dried botanicals were mixed with a silt soil per 50 cm3
pot. The amount of plant residues incorporated in a soil medium was 0.0, 0.5
and 1.0 g/pot. In each pot 10 seeds of the two cultivars were sown at a depth of
1 cm. Pots were kept under green house condition with daily irrigation. After 2
days of incubation, seeds start to germinate and seedlings emergence was
counted each day for a period of 9 days to calculate G% and MGT as above.
The length of shoot (seedling height) was measured. At the end of the
experiment, all plants were harvested to determine the dry weight of roots and
shoots of seedlings. The experiment was performed in three replicates with 8
seeds in each.

Statistical analyses

Germination and seedling growth bioassays were conducted in a complete

randomized design (CRD) with three replications. All experiments repeated

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twice and the data were subjected to analysis of variance (ANOVA). The
significant differences between treatments means were separated using LSD
test (P< 0.05).

Results and discussion

Results of variance analysis for germination experiment showed that

germination, plumule and radicle growth and dry biomass of sorghum plant was
significantly affected by different concentrations of botanical extract
(allelopathic chemical).

Seed germination

Seed germination is considered to be the most critical stage especially

under stress conditions. During germination, biochemical changes take place,
which provide the basic framework for subsequent growth and development.
Aqueous crude extracts of the three plants leaves appreciably affected
germination and growth of the Sorghum bicolor cultivar Fatarita (Figure 1).
However, there were considerable variations on parameters measured in
responses to different treatments at all concentrations. Different botanical
extracts revealed different influence on Fatarita seeds germination (Figure 1 a).
Among the botanical extracts, Khella displayed the lowest germination (52.5%)
and therefore showed greater inhibition on germination as compared to control
(96.3%), Ghobaish (85.5%) and Safsaf (85.0%). No correlation between
germination percentage (G %) and time to germination (MGT) was found
(Figure 1 a). Results displayed that when concentration of extract increased the
G % decreased while MGT increased. This representing that seeds in higher
concentrations need more time to germinate (i.e. has lower germination rate). In
consequent, control has the lower MGT with 2 days indicating high
germination rate. Nevertheless, Ghobaish increase MGT to around 3 days
almost in all concentrations. The leaves extract inhibited the shoot and root
length sorghum Fatarita seedlings, compared to the related controls. The
inhibitions were relatively enhanced with the increasing amount of each extract
concentrations. Fatarita shoot length showed less effect with application of
Khella at 25% (Figure 1b). Results indicated that root length was relatively
more sensitive to allelochemicals compared to the shoot elongation (Figure 1c).
Ghobaish has same effect under all concentrations. Safsaf leaf extracts
proved to have more allelopathic effect in comparison to other extracts. Effect
of botanical extracts on sorghum seed germination was reported through several
experimentations. This study is in agreement with other studies which showed
that sorghum seeds germination was significantly reduced when treated with
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Eucaliptus camaldulensis (Mohamadi and Rajaie, 2009) and Spina christi,
Sesbania sesban and Tamarindus indica (Mubarak et al., 2009). In contrast,
Moringa oleifera, Khaya senegalensis and Albizia lebek leaf extracts found to
have no significant effects on seed germination of sorghum (Mubarak et al.,
2009; Phiri, 2010). The differences in the germination percentage between the
cultivars could be attributed to differences in the selective permeability of the
seeds coat of sorghum to inhibitory substances (Zakaria and Razak, 1990).
Therefore, effects of allelochemicals on seeds germination appear to be
mediated through a disruption of normal cellular metabolism rather than
through damage or organelles (Mohamadi and Rajaie, 2009). It can be
summarized from the results that extract concentrations of allelochemcial will
reduce sorghum seeds germination and ultimately results in reduction in yield.
These results are in agreement with those of Singh et al. (1992), Nandal et al.
(1999 a, b) and Patel et al. (2002) who all observed reduction in germination
percentage with extract/ leachates application to wheat seed.

Control Khella A
Ghobais Safsaf
100 4
90
3
80
70 3
Germination %

MGT (day)
60 2
50
40 2

30 1
20
1
10
0 0
1 2 3 4 5 6 7 8 9 10 11 12 13

4.0
3.5
Shootl length (cm )

3.0 B
2.5
2.0
1.5
1.0
0.5
0.0
0 25 50 75 100 25 50 75 100 25 50 75 100

Kela Gobaish Safsaf

Botanical extracts concentration

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 Journal of Agricultural Technology 2012, Vol. 8(4): 1423-1469

10
9 C
Radical length (cm ) 8
7
6
5
4
3
2
1
0
0 25 50 75 100 25 50 75 100 25 50 75 100

Kela Gobaish Safsaf

Botanical extracts concentration

Fig.1. Effect of botanical extracts on Fatarita (a) seed G% (column) and MGT (line), (b) shoots
length and (c) radicle length. Bars at the tip of columns indicate + standard errors of means.

Results showed that the two sorghum cultivars differed in their reaction in
seed emergence with botanical residues application (Figure 2). Germination
percentage (G %) of Fatarita consistently increased when Khella was added to
the substrate, whereas decreased with Ghobaish and Safsaf compared to
control. On the other hand, germination of Hybrid was increased in order of
Safsaf > Ghobaish > Khella > Water. Germination rate considered when the
G% increased. However, Fatarita gave better seeds germination than Hybrid in
all treatments excluding Safsaf 1.0g. The differences in the tolerance levels
between the two sorghum cultivars Fatarita and Hybrid could possibly be due to
the selective permeability of the seed coat to the inhibitory substances
(Mubarak et al., 2009). Experiment on effect of M. oleifera leaf extracts on
sorghum indicated 15.3% reduction in survival seedlings (Phiri, 2010). The
leaches of E. camaldulensis (Mohamadi and Rajaie, 2009) and many plant
extracts (Mubarak et al., 2009) were also reported to reduce seedlings growth
of sorghum.
The mean days to germination (MGT) was relatively decreased (i.e.
germination rate increased) by botanical application compared to control
(Figure 2). The fastest MGT exhibited in Fatarita by the Safsaf with 2.6 days.
Fatarita has wide range in MGT between 2.6 to 11.7 days. Also, seeds
germinated rapidly (MGT improved) in all of treatments (except Ghobaish
1.0g) than control. The mean time to germination of all treatments on Hybrid
was almost same and near to 4 days.
Comparison results in seeds germination percentages between Petri dish
and pot experiments, displayed that seeds were germinated better in pot
experiment as compared to Petri dishes. Allelochemicals might be inactivated
in the soil by different factors such as chelation with ions, complexation with

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soil colloids, decomposition by micro-organisms or mechanical forces
(Mubarak et al., 2009).

Fatarita Hybrid
MGT Fatarita MGT Hybrid

100 14
90
12
80
Seed emergence (%)

70 10

MGT (day)
60 8
50
40 6
30 4
20
2
10
0 0
0 0.5 1 0.5 1 0.5 1

Khela Ghobaish Safsaf

Botanical extracts (g)

Fig. 2. Effect of botanical extracts on seed emergence and mean germination time of Fatarita
and Hybrid. Bars at the tip of columns indicate + standard errors of means.

Seedling growth

The data on sorghum seedling growth indicated considerable differences

due to different botanicals and their concentrations (Table 1). Among the two
cultivars the concentrations of the three botanical residues decreases the shoot
length of Fatarita as compare to control (distilled water). The control showed
15.9 ± 0.8 cm for shoot length where the highest length produced by botanical
was (15.7 ± 0.8) in Ghobaish treatment. Likewise, cultivar Hybrid treated with
botanicals leaf powder enhanced shoot growth of Khella at 0.5g (10.6 ± 1.3
cm), Ghobaish at 1.0g (8.5 ± 1.1 cm) and Safsaf at 0.5 (9.1 ± 0.6 cm) over the
control (8.3 ± 1.3 cm).
With respect to plant biomass, Khella and Ghobaish reduced shoot and
root dry weight of cultivar Fatarita as compared to the control (Table 1).
However, Safsaf decreased shoot dry weight of sorghum Fatarita although it
enhanced its root dry weight. In among all treatments, sorghum Hybrid treated
with botanical extracts displayed the highest shoot dry weight except Ghobaish
at 0.5g as compared to the control (0.029 ± 0.00 cm). However, all botanical
treatments decreased root dry weight compared to control. From these results it

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can be stated that (Table 1), the botanical materials reveal negative effects on
seedling growth but with variation between the two cultivars. Sorghum treated
with Safsaf increased shoot and root dry weight of both Hybrid and Fatarita.

Table 1. Effect of botanical residues on shoot length and dry biomass of

Sorghum cultivars after 2 weeks of germination

Botanical Shoot length (cm) Shoot dry weight (g) Root dry weight (g) (Means ±
Residue (Means ± SE) (Means ± SE) SE)
(g/pot) Fatarita Hybrid Fatarita Hybrid Fatarita Hybrid
0.0 15.9 ± 0.8 8.3 ± 1.3 0.066 ± 0.00 0.029 ± 0.00 0.037 ± 0.01 0.046 ± 0.02
Khella
0.5 14.5 ± 1.0 10.6 ± 1.3 0.054 ± 0.01 0.031 ± 0.01 0.018 ± 0.01 0.031 ± 0.02
1.0 12.4 ± 0.7 8.7 ± 1.3 0.051 ± 0.01 0.030 ± 0.01 0.014 ± 0.00 0.026 ± 0.01
Ghobaish
0.5 15.7 ± 0.8 7.0 ± 0.9 0.064 ± 0.01 0.027 ± 0.00 0.036 ± 0.004 0.031 ± 0.00
1.0 15.7 ± 0.1 8.5 ± 1.1 0.063 ± 0.00 0.033 ± 0.00 0.026 ± 0.00 0.035 ± 0.02
Safsaf
0.5 12.8 ± 1.5 9.1 ± 0.6 0.050 ± 0.02 0.031 ± 0.01 0.051 ± 0.01 0.028 ± 0.00
1.0 12.6 ± 0.3 8.2 ± 0.5 0.057 ± 0.00 0.030 ± 0.00 0.040 ± 0.002 0.025 ± 0.01
LSD(p=0.05)
Cultivar (V) 1.2 0.01 0.01
Botanical (B) 1.4 0.01 0.01
Conc. (C) 1.4 0.01 0.01
V*B*C Interaction 2.5 0.01 0.02

The reduction of biomass was correlated with seedling height growth.

This reduction may be due to stunted and reduced seedlings growth (Garcı´a et
al., 2002). A reduction of 31% in dry matter of sorghum by leaf leaches of E.
camaldulensis (20%) had been reported (Mohamadi and Rajaie, 2009). Khella,
Ammi majus is known for its high coumarin content, particularly
furanocoumarins, Coumarin, umbelliferone, bergapten, xanthotoxin,
isopimpinellin, imperatorin and isoimperatorin (Garcı´a et al., 2002). It is
inhibitors of seeds germination and seedling growth.
In conclusion, results of this study showed that most leaves aqueous
extracts and residues of Khella (Ammi majus), Ghobaish (Guiera senegalensis)
and Safsaf (Salix spp.) have phytotoxic effects on seeds germination and
seedling growth of sorghum. Allelopathic potentials of these plants which
induces identifying and purification of allelopathic substances, may entitle them
to control specific weeds especially in non-sequential crops by preparing them
as natural herbicides.

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(Published in July 2012)

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