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ASSESSMENT OF ALLELOPATHIC POTENTIAL OF
DIFFERENT WEEDS ON GERMINATION AND
EARLY GROWTH OF AROMATIC RICE
A Thesis
Submitted to
Bangladesh Agricultural University, Mymensingh
In partial Fulfillment of the Requirements
for the Degree of
Master of Science
in
Agricultural Chemistry
By
Monira Yasmin
Roll No.: 10Ag.Chem JD-05M
Registration No.: 32087
Session: 2005-06
Department of Agricultural Chemistry
Bangladesh Agricultural University
Mymensingh
November, 2011
ASSESSMENT OF ALLELOPATHIC POTENTIAL OF
DIFFERENT WEEDS ON GERMINATION AND
EARLY GROWTH OF AROMATIC RICE
A Thesis
Submitted to
Bangladesh Agricultural University, Mymensingh
In partial Fulfillment of the Requirements
for the Degree of
Master of Science
in
Agricultural Chemistry
By
Monira Yasmin
Approved as to style and content by
(Prof. Dr. Md. Mokhlesur Rahman)
Supervisor
(Prof. Dr. Hari Pada Seal)
Co-supervisor
(Dr. Md. Zakir Hossen)
Chairman, BOS and Head
Department of Agricultural Chemistry
November, 2011
ACKNOWLEDGEMENT
All praises are due to the Almighty Allah Whose divine blessing enabled the researcher to complete
her research work and prepare the thesis successfully for the degree of MS in Agricultural
Chemistry.
The author likes to express her gratefulness and indebtedness to her respected supervisor Prof. Dr.
Md. Mokhlesur Rahman, Department of Agricultural Chemistry, Bangladesh Agricultural
University, Mymensingh for his kind advice, valuable guidance and constructive suggestions to
carry out the research work and preparation of this thesis.
The author acknowledges her heartiest gratification and sincere appreciation to her honorable co-
supervisor, Prof. Dr. Hari Pada Seal, Department of Agricultural Chemistry, Bangladesh
Agricultural University, Mymensingh for his sincere advice, planning, upgrading the quality of
the research work and for help in preparing the manuscript of this thesis.
The author humbly desires to acknowledge her sincere gratitude to Prof. Dr. M. Wahid-U-
Zzaman, Prof. Kartik Chandra Saha, Prof. Dr. Md. Akhter Hossain Chowdhury, Dr. Md. Zakir
Hossen, Associate Professor and Head, Dr. Quazi Forhad Kadir, Associate Professor, Dr. Atiqur
Rahman, Assistant Professor, Dr. Razia Sultana, Assistant Professor, Dr. K. M. Mohiuddin,
Assistant Professor, Mrs. Mousumi Akter, Lecturer, Mosammat Hasina Akter, Lecturer and Mr.
Md. Amdad Ali, Lecturer, Department of Agricultural Chemistry for their valuable teaching,
inspiration and encouragement during the whole course of this study.
The author would express her special thanks to the staff members, Department of Agricultural
Chemistry, Bangladesh Agricultural University, Mymensingh for extending all laboratory
facilities for completing research work.
The author is pleased to express her cordial thanks to all of her friends, classmates and well
wishers for their immense inspiration, and kind co-operation during conducting experiment and
writing of the thesis.
The author would like to express heartfelt indebtedness to her respected parents, sisters, friends
and all other relatives for their never ending prayer, encouragement, sacrifice and dedicated efforts
to educate me to this level which can never be forgotten.
The Author
ABSTRACT
A laboratory experiment was carried out at the Department of Agricultural
Chemistry, Bangladesh Agricultural University, Mymensingh to investigate the
allelopathic potential of different weeds on aromatic rice cv. BRRI dhan50. Six
weed species viz., joina (Eimbristylis miliacea), mutha (Cyperus rotundus), khude
shama (Echinochola colonum), sobuj nakful (Cyperus difformis), foskabegun
(Physalis heterophylla) and chapra (Elusine indica) were used in the experiment
to observe their allelopathic effects on seed germination, root length, shoot length
and dry matter production of aromatic rice. Unboiled and boiled weed extracts
reduced the germination and primary growth of aromatic rice. The ranking of
weed species in respect of inhibitory effect on seed germination were Echinochola
colonum > Cyperus difformis > Cyperus rotundus > Elusine indica > Eimbristylis
miliacea > Physalis heterophylla. Khude shama (Echinochola colonum) and sobuj
nakful (Cyperus difformis) had strong detrimental effects on the early growth of
aromatic rice. The relative effect of different weed plant parts (stem, root, leaf and
whole plant) and their concentrations (5, 10 and 25% w/v) were also studied. The
extracts irrespective of plant parts of all weeds inhibited germination and early
growth of aromatic rice. The relative efficiency of reduction of germination and
primary growth by different weed extracts was in the order of stem > root > leaf >
whole plant. The reduction of germination and primary growth of aromatic rice
increased with the increasing extract concentrations. Three unknown compounds
were identified by the TLC technique in extracts of khude shama (Echinochola
colonum) and sobuj nakful (Cyperus difformis). The experimental results proved
that it was important to exclude two allelopathic weeds namely khude shama
(Echinochola colomum) and sobuj nakful (Cyperus difformis) in the aromatic rice
field. It is, therefore, concluded that these two weeds should be avoided from the
aromatic rice field during land preparation.
CONTENTS
Page No.
ACKNOWLEDGEMENT iv
ABSTRACT v
CONTENTS vi
LIST OF TABLES viii
LIST OF FIGURES ix
LIST APPENDICES x
Chapter 1 INTRODUCTION 1
Chapter 2 REVIEW OF LITERATURE 4
2.1 Effect of aqueous extract of different weeds on
germination and primary growth of crops
4
2.2 Effect of different plant parts of weeds on
germination and primary growth of crops
9
2.3 Effect of different concentrations of weed extract on
germination and primary growth of crops
13
Chapter 3 MATERIALS AND METHODS 18
3.1 Test crop 18
3.2 Test weed species 18
3.3 Experimental treatment 18
3.4 Collection of weeds and preparation of weed
extracts
19
3.5 Experimental procedure 19
3.6 Parameters 20
3.7 Experimental data 20
3.7.1 Seed germination 20
3.7.2 Germination time of rice seeds 20
3.7.3 Root and shoot lengths of seedlings 20
3.7.4 Fresh weights of root and shoot of seedlings 20
3.7. 5 Dry weights of root and shoot of seedlings 21
3.8 Identification of chemical compounds 21
3.9 Calculation of Rf values 22
3.10 Data analysis 22
CONTENTS (Contd.)
TITLE Page No.
Chapter 4 RESULTS AND DISCUSSION 23
4.1 Allelopathic effect of different weed species on
aromatic rice
23
4.1.1 Effect of unboiled and boiled weed extracts on
seed germination
23
4.1.2 Effect of unboiled and boiled weed extracts on
primary growth of seedlings
25
4.1.2.1 Root and shoot lengths 25
4.1.2.2 Fresh and dry weights of root 30
4.1.2.3 Fresh and dry weights of shoot 30
4.2 Allelopathic effect of different weed plant parts of on
rice
31
4.2.1 Effect of different weed plant parts on
germination
31
4.2.2 Effect of different weed plant parts on primary
growth
32
4.2.2.1 Root and shoot lengths 32
4.2.2.2 Fresh and dry weights of root 33
4.2.2.3 Fresh and dry weights of shoot 33
4.3 Allelopathic effect of extracts of different weed
plant parts at different concentrations
36
4.3.1 Interaction effect of weed plant parts and
extract concentrations on germination
36
4.3.2 Interaction effect of weed plant parts and
extract concentrations on initial growth
36
4.4 TLC Techniques for extraction of khude shama
(Echinochola colonum) and sobuj nakful (Cyperus
difformis)
40
Chapter 5 SUMMARY AND CONCLUSION 43
REFERENCES 46
APPENDICES 51
LIST OF TABLES
Table TITLE Page No.
4.1 Effect of unboiled weed extracts on germination and
early growth of aromatic rice cv. BRRI dhan50
(Banglamoti)
26
4.2 Effect of boiled weed extracts on germination and early
growth of aromatic rice cv. BRRI dhan50 (Banglamoti)
27
4.3 Allelopathic effect of khude shama extract from
different plant parts on germination and early growth of
aromatic rice cv. BRRI dhan50 (Banglamoti)
34
4.4 Allelopathic effect of sobuj nakful extract from different
plant parts on germination and early growth of aromatic
rice cv. BRRI dhan50 (Banglamoti)
35
4.5 Interaction effect of khude shama extract from different
plant parts on germination and growth of aromatic rice
cv. BRRI dhan50 (Banglamoti)
38
4.6 Interaction effect of sobuj nakful extract from different
plant parts on germination and growth of aromatic rice
cv. BRRI dhan50 (Banglamoti)
39
4.7 TLC of weed extracts and Rf values of the spot 40
LIST OF FIGURES
Figure TITLE Page No.
4.1 Effect of unboiled extract of khude shama (Echinochola
colonum) on aromatic rice seedling
28
4.2 Effect of boiled extract of khude shama (Echinochola
colonum) on aromatic rice seedling
28
4.3 Effect of unboiled extract of sobuj nakful (Cyperus
difformis) on aromatic rice seedling
29
4.4 Effect of boiled extract of sobuj nakful (Cyperus
difformis) on aromatic rice seedling
29
4.5 TLC plates of weed extract of khude shama
(Echinochola colonum) and sobuj nakful (Cyperus
difformis) in ethanol eluted by mixed solvents (A) ethyl
acetate: ethanol (1:1) and (B) benzene : ethyl acetate
(1:1)
41
LIST OF APPENDICES
Figure TITLE Page No.
I Analysis of the variance of the data of unboiled weed
extract on seed germination and early growth of
aromatic rice cv. BRRI dhan50
51
II Analysis of the variance of the data of boiled weed
extract on seed germination and early growth of
aromatic rice cv. BRRI dhan50
51
IIIa Analysis of the variance of khude shama extract
obtained from different plant parts of extract
concentration on seed germination and growth of
aromatic rice cv. BRRI dhan50
52
IIIb Analysis of the variance of sobuj nakful extract obtained
from different plant parts of extract concentration on
seed germination and growth of aromatic rice cv. BRRI
dhan50
52
IVa Analysis of the variance of khude shama extract
obtained from different plant parts and extract
concentration on seed germination and growth of
aromatic rice cv. BRRI dhan50
53
IVb Analysis of the variance of sobuj nakful extract obtained
from different plant parts and extract concentration on
seed germination and growth of aromatic rice cv. BRRI
dhan50
53
CHAPTER 1
INTRODUCTION
Allelopathy refers to the beneficial or harmful effects of one plant on another, both
crop and weed species, by the release of chemicals from plant parts in both natural
and agricultural systems. The term has since appeared commonly in literature to
plant/plant biochemical interactions that causes detrimental effects and it has now
been recognized as an important ecological factor in plant interactions (Chou,
1990). Chemicals with allelopathic potential are present (commonly in conjugated
form) in almost all plant parts and in many tissues like leaves, stems, flowers, fruits,
seeds and roots (Putnam, 1988). Under specific conditions, these chemicals are released
into the environment (atmosphere or rhizosphere) by means of volatilization,
leaching, decomposition of residues, root exudation in ample quantities and long
persistence to affect a neighboring of successional plant (Chou, 1990). These
processes are also affected by environmental complex, and are not easy to single
them out (Einhelling, 1987). The science of allelopathy has progressed its descriptive
and foundations to provide a base to aid crop production.
Weed is an undesirable plant and a serious pest of our crops including
aromatic rice. It competes with crop plants for light, moisture, and other essential
nutrients; as a result it reduces the quality and yield of crops. Its infestation
increases the cost of production, which ultimately reduces the net return, where
there is cultivable land there is weed. Subsistent farmers of the tropics spend more
time, energy and money on weed control than in any other aspects of crop
production (Kasasian, 1971). The harmful effect of weed allelopathy on the
growth and development of field crops are well documented. Plant releasing
chemicals may have deleterious or beneficial effects on other plant growing in
their vicinity. The plant-plant chemical interactions are of vital importance in
agriculture. Phytol, vanillin, 3-methoxy-4hydroxy nitrobenzene and 2, 6-dimethoxy
benzoquinone were isolated from palmer amaranth which inhibited germination
and growth of onion and wheat. These compounds are reported to have inhibitory
influence on germination as well as nutrient assimilation. Commonly cited effects of
allelopathy include the reduced seed germination and seedling growth. Like
synthetic herbicides, there is no common mode of action or physiological target site
for all allelochemicals.
Allelopathic potential may also vary in different parts of an individual weed
species (Bansal and Singh, 1986; Rajangam et al., 1997; Oudhia and Tripathi,
2000). The inhibitory substances present in durba responsible for crop seedling
growth inhibition could retain in every part of the plant and the efficiency in growth
inhibition differs based on the part of the plant (Premasthira and Zungsonthiporn,
1995). Not only that the degree of allelopathic activity of weed species depends on
the concentration of weed material which needs to be investigated (Bhatt et al.,
2001). Allelochemical concentrations in the producer plant may also vary over time
and in the plant tissue produced. Different plant parts including flowers, leaves, stems,
roots, soil and soil leachates and their derived compounds can have allelopathic activity
that varies over a growing season. Allelopathic chemicals can also persist in soil,
affecting both neighboring plants as well as those planted in succession.
Therefore, it is also important to know the effects of different parts of weeds on seed
germination and growth of crop plants.
Therefore, the present study has been undertaken to examine the influence
of some important weeds on germination and primary growth of aromatic rice. A
number of weeds grow in aromatic rice field, which compete with crop and reduce
the crop yield. When the weed shows allelopathic effect, the qualitative and
quantitative damage may be severed on the basis of allelochemicals present in the
species. If the allelopathic effect of specific weed species on particular crop can be
known, weed management becomes economically more effective for the crop
grower. By knowing the potentiality of allelopathy in specific weed, we can remove
those species from the crop field before they contribute allelopathy to crop suppression.
All these information emphasize the study on allelopathy of different weed species
on aromatic rice production. With the above views in mind, the present study was
undertaken to fulfill the following objectives:
i. To observe the allelopathic effects of different weed species on seed
germination and primary growth of aromatic rice cv. BRRI dhan50.
ii. To identify the allelochemicals responsible for the allelopathic effect.
CHAPTER 2
REVIEW OF LITERATURE
The aim of this chapter is to review the results of some previous studies related to
the present research work. In Bangladesh, a few works have been done on allelopathy
but a good number of works have been done in abroad. The research reports
related to the present study are mentioned below:
2.1 Effect of aqueous extract of different weeds on germination and primary growth
of crops
Poly (2009) investigated the allelopathic effect of weeds on wheat cv. BARI
wheat-18 and used five weed species viz., mutha (Cyperus rotundus), foskabegun
(Physalis heterophylla), chapra (Elusine indica), biskataly (Polygonum hydropiper)
and nunia (Portulaca oleracea) to observe their allelopathic effects on
seed germination, root length, shoot length and dry matter production of
wheat. Unboiled and boiled weed extracts reduced the germination and
primary growth of wheat. The ranking of weed species in respect of inhibitory
effect on seed germination was Portulaca oleracea > Polygonum hydropiper >
Elusine indica > Cyperus rotundus > Physalis heterophylla. Biskataly
(Polygonum hydropiper) and nunia (Portulaca oleracea) had strong
detrimental effects on early growth of wheat.
Nasrin (2009) studied the effect of weeds on seed germination and early growth of
jute and soybean. Five weed species viz. durba (Cynodon dactylon), katanotey
(Amaranthus spinosus), baradudia (Euphorbia hirta), haldemutha (Cyperus
esculentus) and shama (Echinochola crusgalli) was used for jute cv. 0-9897 and five
weed species viz., durba (Cynodon dactylon), holdemutha (Cyperus eseulentus),
shama (Echinochola arusgalli), foskabegun (Physalis heterophylla) and chapra
(Elusine indica) was used for soybean cv. Shohag. Boiled and unboiled weed
extracts reduced the germination and primary growth of jute and soybean. Durba
(Cynodon dactylon) and katanotey (Amaranthus spinosus) had strong detrimental
effect on primary growth of jute. Durba (Cynodon dactylon) and foskabegun
(Physalis heterophylla) had also strong detrimental effect on primary growth of
soybean.
An investigation was carried out in typical maize growing sandy loam soil at the
Agronomy Laboratory of Bangladesh Agricultural University, Mymensingh during
March to August, 2000 to determine the allelopathic effect of five weed species viz.,
Polygonum hvdropiper L. (WI), Amaranthus spinosus L. (W2), Chenopodium
album L. (W3), Cyperus rotundus L. (W4) and Imperata cylindrica L. (W5) on
corn (cv. Barnali) seed germination, growth and development (Samad et al.,
2008). The trial included dried plant parts of five selected weeds (the whole plant,
stem, leaf, root and five weed mixture) and weeds aqueous extract (whole plant,
stem. leaf; root and five weed mixture) in petridishes at laboratory condition.
These five weed species exhibited inhibition of seedling height and radicle
length. Imperata cylindrica affected the seedling height and seedling dry matter
production severely than others. Radicle length was affected by Amaranthus
spinosus. On the other hand, germination, seedling growth and dry matter
production affected maximum by dried mass of stems of five weed species.
The results demonstrated the allelopathic potential of five weed species and
suggested that those weed species might affect corn seedling growth and
development due to the inhibitory effect of allelochemicals, which were present in
the dried parts and aqueous extracts of weed.
Zoheir et al. (2008) stated that the experiment barley (Hordeum vulgare) contained
water soluble allelochemicals that inhibited the germination and growth of other
species. Greenhouse and laboratory experiments were conducted to determine the
effects of barley leaf, stem, flower and root water extract concentrations on green
loxtail (Setaria viridis) germination and seedling growth. In bioassays, barley
extracts reduced green foxtail hypocotyl length, hypocotyl weight, radicle weight,
seed germination and radicle length when compared with water control.
Khatun (2008) studied the effect of weeds on seed germination and primary growth
of rice and mungbean. Four weed seed species viz., durba (Cynodon dactylon),
shama (Echinochloa crusgalli), biskatali (Polygonum hydropiper), and foskabegun
(Physalis heterophylla) were selected. Boiled and unboiled weed extracts reduced the
germination and primary growth of rice and mungbean. The ranking of weed species
in respect of inhibitory effect on seed germination of BARI Mung-5 and BINA
moog5 was Physalis heterophylla > Cynodon dactvlon > Echinochloa crusgalli >
Polygonum hydropiper. Durba (Cynodon dactylon) and foskabegun (Physalis
heterophylla) had strong detrimental effect on primary growth of these varieties. The
extracts of all parts (e.g. stem, root, leaf; and whole plant) of weeds inhibited
germination and primary growth of this variety.
Hua et al. (2007) investigated a series of experiments to evaluate the phytotoxicity
and to identify the allelochemicals of Ambrosia trifida against wheat (Triticum
aestivum). The results showed that wheat growth could be significantly inhibited
in Ambrosia trifida infested, or residue amended soils in North-East China. Two
carotane-type sesquiterpcnes, l alpha (angeloyloxy) -carotol and l alpha-(2-methyl
butyrovloxy)-carotol were subsequently isolated and identified from the toxic
soils. Both compounds had high inhibitory activity on wheat growth.
A study was carried out by Batiste et al. (2007) to determine the potential and
nature of root-mediated allelopathic interference of Chenopodium murale on
wheat. Early growth of wheat reduced significantly in agar medium where
C. murale seedlings were previously growing as well as in rhizosphere soil of
C. murale. The reduction in wheat growth was due to the presence of inhibitory
metabolites released by roots of C. murale in the growth media. Even the soil
incorporation of root residues also reduced the wheat growth in terms of seedling
length and seedling dry weight. Root residues did not reduce the available
nutrients in the soil, which was rather nutrient rich. These results indicated the
definite role of allelopathy of C. murale roots in retarding wheat growth.
A laboratory experiment was conducted by Roy et al. (2006) to determine the
influence of naturally occurring growth substances in aqueous extracts of some
common weeds of naturally occurring growth substances in aqueous extracts of
some common weeds, i.e. bathua (Chenopodium album), bhijli ghash (Striga
deniflora), shetdrone (Leucus aspera), mutha (Cyperus rotundus), chapra (Elcusine
indicu) and khude anguli (Digitaria ischaemum) on delayed germination and
growth of wheat and jute seeds. Boiled and unboiled extracts of all weed
species significantly reduced and delayed the germination of wheat and jute
seeds. The effect of boiled and unboiled bathua extracts showed the lowest
germination in wheat seeds. Root and shoot lengths of wheat and jute were also
decreased due to the presence of weed extracts.
Laboratory based studies were undertaken by Shahid et al. (2006) to assess
the allelopathic effect of different aqueous extracts of plants viz., sorghum
(Sorghum bicolor), sunflower (Helianthus annuus), johnson grass (Sorghum
halepense), eucalyptus (Eucahptus camaldulensis) and acacia (Acacia nilotica)
on wheat and its weeds. Analysis of data (taken twenty days after seedling) revealed
that germination percentage, shoot length, root lengths and biomass plant were
significantly (P < 0.001) inhibited by plant extracts. Sunflower extract was the
most inhibiting to germination, shoot and root length of wheat and to all species
of weeds, while application of johnson grass extract resulted in significantly
minimum biomass plant.
Kayode (2004) investigated to evaluate the effects of 24 and 48 h C.
procera leaf extracts on the radicle and plumule growth of maize cultivars Oba
Super I, II, III and IV. Both extracts showed considerable inhibitory effects on
radicle and plumule growth of the cultivars. The severity of inhibition increased
with an increase in the duration of the extraction. The growth of Oba Super I
was the least inhibited while the growth of Oba Super III was the most inhibited
by the extracts when the growth and development of the plumule were compared
to those of the control.
Agarwal et al. (2002) found that weed extracts of Avena futua, Cyperus rotundus,
Polygonum hydropiper and Solanum nigram inhibited the length of plumule in all
the varieties of wheat.
Ameena and George (2002) assessed the allelopathic effect of aqueous extracts of
purple nutsedge (Cyperus rotundus) on the germination and seedling growth of
okra (Abelmoschus esculentus). Result showed that aqueous extracts of nutsedge
dry plant parts inhibited the germination and seedling growth of okra. Inhibition
was dependent on concentration.
Bhatt et al. (2001) reported the allelopathic influences in bioassays on Glycine
max cv. JS-80-21, Vigna mungo cv. DPU-80-31, Oryza sativa cv. RCPL-129
and Zea mays cv. Vijay. The aqueous extracts of dried and fresh leaves of weeds
significantly suppressed the germination. Toxicity increased with the increased
concentration of extracts. The effect of extracts was greater on germination of Vigna
mungo and Oryza stliva compared to Glycine max and Zea mays.
Binita et al. (2001) performed a study on allelopathic effect of eight important
weeds commonly grown in North East India, namely Amaranthus sp, Argemone
mexicana, Cynodon dactylon, Cyperus rotundus, Imperata cylindrica, Luntunu
curnuru, Parthenium hysterophorus and Chenopodium sp. on different vegetable
production. Of them Cynodon dactylon and Parthenium hysterophorus showed
both stimulatory effect on germination and seedling of growth of vegetables.
Olofsdotter (1999) conducted a research in soybean allelopathy and utilization in
weed management program in Egypt. Korea, India and Sri Lanka and observed that
the allelopathy effect of Glycine max on different concentrations. The leaf extracts
have significant stimulatory or inhibitory effects on germination or seedling vigor
of soybean and shoot elongation of rice.
Oudhia et al. (1999) conducted an experiment and found that the effect of the
aqueous extracts of different plant parts of Blumea lacera produced significant
effects on the germination and seedling vigour of rice. At 3 days after sowing
(DAS), root extracts obtained after 11 days of decay enhanced seed germination.
At 5, 7, 9 and 11 DAS, leaf extracts obtained after 9 days of decay produced
the highest percentage of seed germination. Different parts of I3. lacera failed
to produce any detrimental effect on any weed species.
Oudhia and Tripathi (1998) stated the allelopathic effects of Sesamum inclicum,
Helianthus annus, Catharanthus rosea, Bombax ceiba and Acacia auriculaeformis
on germination and seedling vigour of rice cv. Mahamaya. The fresh samples of
leaves of these plants were cut into line pieces, immersed in water and decayed for
24 h in the ratio of 1:10 (w/v). The extracts were applied to rice seeds. Different
extracts produced significant effect on germination and seedling vigour. C. roseus
extracts gave very low germination after 3 days, although by 5 days after sowing
there were no significant differences between treatments.
Rahman et al. (1996) performed an investigation with aqueous extracts of some
common weeds viz., katanotey (Amaranthus spinosus L.), shama (Echinochloa crusgalli),
durba (Cvnodon dactylon L.), lazzabati (Mimosa pudica L.), mutha (Cyperus rotundus
L.), baradhudhia (Euphorbia hirta L.) and haldemutha (Ctiperus esculentus L.). Boiled
and unboiled extracts of katanotey, durba and lazzabati reduced the germination and
early growth of rice while all the 7 weed species inhibited germination and growth of
jute. The extracts of all weeds delayed the germination of rice and jute seeds.
2.2 Effect of different plant parts of weeds on germination and primary
growth of crops
Sharma (2005) evaluated the allelopathic effects of some newly developed strains
of harar (Terminalia chebula) and reetha (Sapindus mukorossi) on wheat (Triticum
aestivum), maize (Zea mays), gram (Vigna sp.), lentil (Lens culinaris), pea (Pisum
sativum) and brinjal (Solanum melongena). Leaves of 6 strains of Terminalia
chebula and two strains of Sapindus mukorossi were collected and allowed to
shade dry. The treated crops responded differently to aqueous leaf extracts
of Harar and Reetha indicating the presence of different phytoactive compounds
and growth promoters. Some strains had synergistic or no adverse effect on germination
and growth of tested field crops, whereas other had antagonistic effects.
An aqueous leaf and root/tuber extracts of three important medicinal plant
species (e.g. Bergenia ciliates, Hedychium spicatum and Potentilla fulgens) were
tested by Basotra et al. (2005) for their allelopathic effects on germination,
radicle and plumule elongation of Amaranthus caudatus, Eleusine coracana,
Fagopyrum esculenttum, Vigna mungo, Phaseolus vulgaris and Triticum aestivum.
The results revealed that the allelopathic effects increased with increasing
concentration of leachats from 2, 5 to 10%. The susceptible crops were Amaranthrrs
caudatus and Phaseolus mungo whose germination, radicle and plumule growth
were reduced significantly under aqueous extracts of all three medicinal
species.
A greenhouse experiment was conducted by Narwal et al. (2003) to evaluate the
allelopathic effects of different parts of sunflower biomass (stem, leaf infloresence
and root) on winter wheat. Among the different parts of sunflower, stems showed
the highest inhibitory effect on the growth and yield of wheat, followed by the
roots, leaves and infloresences. Increasing doses of sunflower biomass resulted in
significant reductions in the seedling growth and yield of wheat.
Zoheir et al. (2008) stated that increasing the extract concentrations from 4 to 20 g per
100 mL of water of all barley parts significantly increased the inhibition of green
foxtall germination, seedling length and weight. Based on 7-day old green foxtail
redicle length, averaged across all extract concentrations and the degree of toxicity
of different barley plant parts were ranked in the following order of inhibition:
leaves > flowers > mixture of all plant parts > stems > roots.
Khatun (2008) conducted an experiment to observe the allelopathic effect of weeds
on seed germination and primary growth of rice and mungbean. Four weed seed
species viz., durba (Cynodon dactylon), shama (Echinochola crusgali), biskatali
(Polygonum hydropiper) and foskabegun (Physalis heterophylla) are selected. She
also stated that the relative efficiency of inhibition of germination and primary growth
by different weed plant parts was in the order of stem>whole plant> leaf > root.
An attempt was made to evaluate the effect of durba (Cynodon dactylon L.)
extracts on seed germination and early seedling growth of jute and mungbean.
The experiment was conducted by Rahman et al. (2006) during the period between
August and October 2005. Durba plants were collected from the Agronomy Field
Laboratory of Bangladesh Agricultural University on 14 August and extracts of 1,
5, 10 and 25% concentration (w/v) were prepared from leaves, stems, roots
and whole plants. The extracts of different parts of durba plant reduced
germination and early growth of both crops. The relative efficiency of
inhibition of germination and growth by different extracts were in the order of
stem>whole plant>leaf>root. Between the crops, jute was more sensitive to
allelochemical action. The reduction of germination and growth for both crops
increased with increasing extract concentration.
Mulatu et al. (2005) found that aqueous extracts of Parthenium hysterophorus leaf
and flower seriously inhibited seed germination and seedling growth (root and
shoot lengths) of lettuce. Extracts of the root and stem had much less effect.
Lettuce roots were more sensitive to the allelopathic effect than shoots. It
appears that early removal of Parthenium weed from lettuce fields is essential
to avoid poor germination and seedling growth.
Gamez et al. (2002) conducted an experiment on the allelopathic effect of
extracts from the stem and leaves of Cynodon dactylon and Sorghum halepense
on seeds of oat cv. L138, wheat, sorghum and bean. The stem extract decreased the
respiration rate in wheat and oat. Weed extracts inhibited germination and dry
matter accumulation in the crops.
Meena (2001) investigated the allelopathic effect of the aqueous extracts of shoots
and tubers of purple nutsedge (C. rotundus) at 2.5, 5.0, 7.5 and 10% concentration on
germination and seedling growth of pigeon pea and mungbean. An increase
in aqueous extract concentration of shoot and tuber of nutsedge reduced seed
germination and seedling growth of pigeon pea and bean. The negative allelopathic
effect was more pronounced with tuber extract than shoot extract on all growth
attributes of both the pulses i.e. germination, fresh weight, dry weight of radicle
and plumule, redicle length, plumule length, leaves plant-1
and secondary roots
plant-1
.
Allelopathic effects of Parthenium hysterophorus on seed germination of rice
were investigated by Oudhia et al. (1999). Root, stem, leaf and stem + leaf
sections of P. hysterophorus were cut into fine pieces, immersed in water and
left for 120, 168, 216 or 264 h at room temperature (22 ± 1°C) at a ratio of
1:10 (w/v). The extracts were than applied to rice seeds. The extracts had
significant allelopathic effects on rice germination and seedling vigour. At 11
days after sowing (DAS), the 216-h stem + leaf extract and the 120-h stem+
leaf extract resulted in the greatest and lowest levels of germination,
respectively.
Beres and Kazinczi (2000) assessed the effect of aqueous extracts of shoots and
plant residues of Abutilon theophrasti, Amaranthus retroflexus, Asclepias syrica,
Chelidonium majus, Chysvnthemum vulgare, Datura stramonium, Rumex
obtusifolius and Solidago gigruttea on the germination and growth of barley,
maize, soybeans, sunflower and wheat in petridishes and pot experiments.
Shoot extracts of S. gigantea and A. theophrasti reduced germination of wheat
by 7.6 and 18.3%, respectively, and germination of barley by 9.8 and 2.7%.
Extracts of A. svriaca, C. vulgare and D. stramonium reduced germination of
maize by 34, 30 and 44%, respectively. The extracts of all weeds studied, except
A. retrofexus, reduced germination of sunflower and soybean. In bioassays, extracts
of A. syriaca, A. theophrasti and S. gigantea increased the fresh weight of wheat
plants. The weight of barley was increased by extracts of 5 weeds. In pot experiments
with weed residues, germination of test crops was inhibited, but fresh weight of
crop seedlings was stimulated.
Kalita et al. (1999b) reported that the aqueous extracts of Cynodon dactylon
and Cyperus rotundus at concentrations of 1:5 and 1:10 w/v had significant
allelopathic effects on seed germination of rice. Aqueous shoot extracts were
inhibitorier than root extracts at the same concentration.
Bora et al. (1999) studied the allelopathic effect of fresh extracts of Acacia
aurculiformis on seed germination and radicle and plumule elongation of rice (Oryza
sativa), mustard (Brassica campestris) and gram (Cicer arietinum). The inhibitory
effect of leaf extract on germination was proportional to the concentration of the
extracts. The elongation of radicle and plumule was reduced in all treatments, with
effects much more pronounced on plumule than radicle elongation.
Oudhia and Tripathi (2000) conducted an experiment on allelopathic effect of
Lantuna camara on rice and reported that the extracts of root, stem, leaf and
stem + leaf tissue of L. camara had significant effects, increasing rice germination
rates and seedling vigour.
2.3 Effect of different concentrations of weed extract on germination and
primary growth of crops
Channappagoudar et al. (2005) studied the allelopathic effects of extracts of
Cyperus rotundus, Commelina benghalensis, Parthenium hysterophorus and
Prosopis julilora leaves collected from karnataka, India at two concentrations (5 and
10% w/v) on sorghum, wheat, green gram, soybean, sunflower and groundnut in
the laboratory. The results revealed that Commelina and Cyperus extracts had
greater inhibitory effect on germination, seedling length and seedling vigour
index than the leaf extracts of the other crops.
Laboratory experiments were conducted by Yao et al. (2006) to study the potential
role of allelopathy in plant interference and in the successful invasion of
alien species Salidago canadensis. Aqueous and ethanolic extracts were used
as treatment solutions to assess their effects on seed germination and
seedling growth in four target species, mulberry (Morns alba), morning glory
(Pharbitis nil), wheat (Triticum aestivum) and rape (Brassica campestris).
Reduction and/or growth in germination and growth of the target plant
species in the presence of both aqueous and ethanolic extracts at different
concentrations indicated that the responses were species-specific and concentration
dependent. Generally, ethanolic extracts (especially from leaves) imposed stronger
effects on both seed germination and seedling growth. Extracts with lower concentration
at 0.001 g mL-1
dry weight could stimulate seedling growth of rape and morning
glory, where as extracts at the higher concentrations have inhibitory effects on
mulberry.
Khatun (2008) studied the effect of weeds on seed germination and primary
growth of rice and mungbean. Four weed seed species viz., durba (Cynodon
dactylon), shama (Echinochloa crusgalli), biskatali (Polygonum hydropiper) and
foskabegun (Physalis heterophylla) were selected. Boiled and unboiled weed
extracts reduced the germination and primary growth of rice and mungbean.
The ranking of weed species in respect of inhibitory effect on seed germination
of BARI Mung-5 and BINA moog5 was Physalis heterphylla> Cynodon dactylon >
Echinochloa crusgalli > Polygonzun hydropiper. Durba (Cynodon dactylon) and
foskabegun (Physalis heterophylla) had strong detrimental effect on the primary
growth of these varieties. The extracts of all parts (e.g. stem, root, leaf, and whole
plant) of weeds and their concentrations (5, 10 and 25% w/v) inhibited germination
and primary growth of this variety. She also conducted that the reduction of
germination and primary growth for both crops increased with increasing extract
concentration.
Hassan and Samy (2007) conducted the experiment to study the effect of dry
leaf water extraction (5, 10, 20, 40 and 60%) of Calotropis procera plants on
the germination of barley (Hordeum vulgare L.), wheat (Triticum aestivum L.),
cucumber (Cucumis satirus) L., fenugreek (Trigonella foenum graecum L.) and
alssana (Senna occidentalis L. Link). The results showed that the germination
delayed at the higher concentrations and the final germination percentage was
decreased by increasing leaf extract concentration. Generally, the radicle and
plumule growth was sensitive to different levels of leaf extraction whereas,
the radicle length was decreased by increasing the extract concentration.
Dongre and Yadav (2005) performed an experiment to observe the inhibitory
effect of leaf leachates on seed germination of pea (Pisum sativum). Seeds of
pea (Pisum sativum) cultivars, Arpan and Malviya 2 sapana were treated with
different concentrations of aqueous leaf leachates of 8 dominant weeds (Ageratum
conzoides, Anagallis arvensis, Eclipta alba, Lippia nodiflora, Parthenium hyterophorus,
Phyllanthus niruri, Pluchea lanceolata and Polygonum plebejum) to assess their
allelopathic effects on seed germination. Fifty seeds of each cultivar were
placed equidistantly in 10 cm diameter petridish plates with 2 layers of filter paper.
Approximately 15 mL of 10, 20, 30 and 40% leachates from each weed species
were poured into the specified petri plate. Leachates of all weed species inhihited
both percent seed germination and seedling growth of both test cultivars at 10%
concentration was invariably associated with further decrease in germination performance
of each test cultivar irrespective of weed species.
Deka et al. (2004) conducted an experiment to study the effect of leaf
extracts and leachates of the weeds namely Dryinaria cordata and Oplismenus sp. on
the germination and growth of seeds of Raphanus sativus. The extract and leachate
were diluted with distilled water and applied at 1:2, 1:4, 1:8 and 1:16, and
1:10, 1:20, 1:40 and 1:80 v/v, respectively. Higher inhibition of seed germination by
D. cordata extracts showed that the allelochemicals from D. cordata were more
toxic on radish seed than Oplismenus sp.
Veenapani et al. (2004) performed an experiment to study the effect of
Paspalum scrobiculatum and Echinochloa colonum on rice seed germination. Rice
seeds were placed in petridish lined with three layers of filter paper
moistened with aqueous leachates (1:0, 1:5, 1:10, 1:25, 1:50, 1:100, 1:250 and
1:500 dilutions) from leaves, stem, roots and seeds of both weeds. The
percentage of reduction in germination was 39.6, 36.0, 10.0 and 5.0% with
leaf, steam, root and seed extracts of P. scrobiculatum and 60.0, 3.0, 7.0 and
20.0% with leaf, stem, and root and seed extracts of E. colonum. These results
indicated the allelopathic effects of both weeds on rice seed germination.
Meena (2001) conducted an experiment to assess the allelopathic effect of the
aqueous extracts of shoots and tubers of purple nutsedge (C. rotundus) at 2.5, 5.0,
7.5 and 10% concentration on germination and seedling growth of pigeon pea
and mungbean. An increase in aqueous extract concentration of shoot and tuber of
nutsedge reduced seed germination and seedling growth of pigeon pea and mungbean.
Kalita et al. (1999a) performed an experiment to assess the allelopathic effect of four
common upland rice weed species (Ageratum conzoides, Borreria hispida, Cynodon
dactylon and Cyperus rotundus) on leaf area per plant, total leaf chlorophyll content
and leaf nitrate reductase activity of potted rice plants at 25 to 50 days after sowing
(DAS). The weeds were sundried, ground and mixed with rice potting soil at rates of
1:5, 1:10, and 1:20 w/w. The greater the concentration of weed residue, the greater
was the reduction of all tested parameters in rice plants at both 25 and 50 DAS.
Casini et al. (1998) performed an experiment to study the effects of four aqueous
extracts (0, 1.0, 2.0, and 3.0% w/v) of itch grass (Rottboellia cochinchinensis) and
cogon grass (Imperata brasiliensis) on rice germination and the effects of residues
(0, 1.0, 2.0, and 3.0% w/w) incorporated in the growth medium on early rice plant
development were tested. Allelochemicals present in weed extracts reduced germination
of rice by 11-15% at the highest concentration. A different effect of residues on total
dry matter of seedlings was observed. The lowest concentration of water extracts of
weeds increased epicotyl length and reduced the germination index.
Rajangam (1997) evaluated that the allelopathic effects of the weed Heliotropiwn
indicum on germination, growth and biochemical composition of paddy. The experiment
was conducted in petridishes and pots in the laboratory. An aqueous extract
of fresh leaves, shoots and roots of H. indicum inhibited germination of the rice
varieties IR-20 and Ponmani.
This review suggested that the potentiality of allelopathy may vary in different plant
parts of an individual weed species. Allelopathic substances are most commonly found
in plant extracts. A number of weed species possess allelopathic potential which suppress
the growth of field crops including rice, wheat, jute, soybean, mungbean, lentil and so
on. The per cent reduction also depends on the concentration of the aqueous extracts
of weed species. Therefore, the allelopathic effects of six weed species on aromatic rice
seed germination were studied and at the same time, the effects of different plant
parts were also taken into consideration with different concentrations.
CHAPTER 3
MATERIALS AND METHODS
An experiment was conducted at the Departmental Laboratory of Agricultural Chemistry,
Bangladesh Agricultural University, Mymensingh during the period from September
to November 2011 to evaluate the allelopathic effect of weed extracts on germination
and primary growth of aromatic rice.
3.1 Test crop
Aromatic rice cv. BRRI dhan50 (Banglamoti) was used as test crop in this
experiment.
3.2 Test weed species
The following common weed species were selected for this study:
Sl.
No.
Bengali name English name Scientific name
1 Joina Cogon grass Eimbristylis miliacea
2 Mutha Purple nutsedge Cyperus rotundus
3 Khude shama Small burnyardgrass Echinochola colonum
4 Sobuj nakful Smallflowered umbrellagrass Cyperus difformis
5 Foskabegun Clammy groundcherry Physalis heterophylla
6 Chapra Indian goosegrass Elusine indica
3.3 Experimental treatment
The boiled and unboiled extracts of the selected weeds were used for test crop. Stem,
leaf, root and whole plant extracts of different weed species were considered in this
experiment. For each weed 5, 10 and 25% of plant part extracts including control
(only water) were applied.
3.4 Collection of weeds and preparation of weed extracts
Weed species collected from the Agronomy Field Laboratory, Bangladesh Agricultural
University, Mymensingh were joina (Fimbristylis miliacea), mutha (Cyperus
rotundus), khude shama (Echinochola colonum), sabuj nakful (Cyperas
difformis), foskabegun (Physalis heterophylla) and chapra (Elusine indica).
After collection, they were washed, chopped and macerated. In a set, fresh weed
mass (250 g) of each weed species was boiled in 1 L water and kept for 3
days with intermittent stirring. The extracts were filtered through filter paper
(Whatman No. 1). The filtrates were used as boiled extracts of weeds. In another set,
250 g fresh weed mass were decomposed in 1 L water for 7 days at normal room
temperature. The extracts were filtered and used as unboiled extract. Thus boiled and
unboiled extracts of each weed species were prepared and used in this experiment
following the technique as stated by Prasad and Srivastava (1991).
In another trial, the collected weed plants were separated into four portions viz.,
leaves, stems, roots and whole plants. Fresh weed portions were chopped and
macerated and 125 g of each portion were decomposed in 500 mL, distilled water
for 7 days at room temperature (28 ± 1°C) with intermittent stirring. The extracts
were filtered through filter paper (Whatman No. 1). From the filtrate 5, 10 and
25% (w/v) extract solutions were prepared from each portion of selected weeds.
3.5 Experimental procedure
The effect of weed extracts on the germination of aromatic rice cv. BRRI dhan 50
seeds were tested in petridishes in the laboratory. Two sets of trial, with
boiled and unboiled extracts were performed. Twenty five seeds of aromatic
rice were placed in each petridish lined with double layer of filter paper and
treated with weed extracts. Fifteen milliliter aqeous extracts of different weeds
were put in each petridish and a control set with distilled water was run
simultaneously every time. The filter papers were kept constantly moist with
distilled water. The experiment was arranged in a completely randomized design
with 3 replications at room temperature (28 1°C).
3.6 Parameters
The following parameters were considered in this study:
a) Germination (%)
b) Days to complete germination
c) Seedling growth and weight
i) Root and shoot lengths
ii) Root and shoot weights
In this experiment, 10 plants were selected to each parameter and the average
results were calculated from these collected plants.
3.7 Experimental data
Experimental data were collected on the following parameters.
3.7.1 Seed germination
The number of germinated seeds was counted from the beginning of seed
germination up to completion of the seed germination.
3.7.2 Germination time of rice seeds
Mean germination time was calculated after counting germination.
3.7.3 Root and shoot lengths of seedlings
The root and shoot lengths of aromatic rice seedling were measured after
7 and 14 days, respectively.
3.7.4 Fresh weights of root and shoot of seedlings
The fresh weights of respective root and shoot of aromatic rice seedling were
measured after 7 and 14 days of the germination setting.
3.7. 5 Dry weights of root and shoot of seedlings
The dry weights of respective root and shoot of aromatic rice seedling were
measured after 7 and 14 days of the germination setting.
3.8 Identification of chemical compounds
Thin layer chromatography (TLC) was developed to identify the compound using
different polar and nonpolar solvent systems such as chloroform, petroleum ether,
ethyl acetate and methanol following the technique as stated by Chopra and Kanwar
(1980) and Ahuja (2003). Thin layer chromatographic (TLC) technique was employed
for the identification of the number of compounds present in extracts of khude shama
(Echinochola colonum) and sabuj nakful (Cyperus difformis). The chromatographic
plates were prepared by spreading a suspension of finely powdered silica gel for TLC
on glass plates of suitable sizes (5 1 0.3 cm3). About 50 g silica gel was mixed
thoroughly with 125 mL of water in a beaker. This was then spread unifomly on clear
glass plates with the help of a spreader. The silica coated plates were then dried in an
oven at 105 ± 5°C for about 12 hours before use. Freshly prepared plates were always
used for TLC.
A number of solvent chambers were prepared by solvents of low to high polarity
and by some mixed solvents of expected polarities. For obtaining a chromatogram, a
minute drop of khude shama (Echinochola colonum) and sabuj nakful (Cyperus
difformis) extract in a suitable solvent (ethanol, boiling and normal distilled
water) was applied with a capillary tube along a bare line along at the bottom of
the plate. This was then developed in a TLC tank containing selected solvent or
mixed solvents. The sample gave both coloured and colourless spots on the TLC
plate in ordinary conditions. To locate colourless spots, the developed plates were
further treated in various ways and kept for some time in gaseous iodine chamber.
TLC of extracts using different solvents as eluent gave spots for different compounds
present in the extracts. Considering the Rf values and the respective polarities of
the eluent, the polar nature of the compound and its extent was ascertained. TLC
of the extracts was made using different solvents and mixed solvents. A number
of spots were observed for different compounds and their Rf values were determined.
3.9 Calculation of Rf values
When solvent passed more than half of the TLC plate, it was marked and the
plates were taken out and allowed to dry. The plants were then placed in iodine
chamber and Rf (Ratio of flow) values were calculated as follows:
pointstartingthefromfrontsolventthebytraveledDistance
pointstartingthefrommoleculescomponentthebytraveledDistancef
R
3.10 Data analysis
The collected data on various parameters were statistically analyzed. The means
for all treatments were calculated and analysis of variance for all characters was
performed by F-test. The significance of difference between the pairs of means
was calculated by LSD as reported by Gomez and Gomez (1984).
CHAPTER 4
RESULTS AND DISCUSSION
This chapter depicts the presentation of the experimental data through different
forms of illustrations. The possible interpretation of major findings has also been
made. The experimental results have been presented and discussed in this chapter.
The whole discussion has been categorized as the effect of weed extracts on seed
germination, shoot and root lengths, fresh and dry weights of root and shoot of
aromatic rice cv. BRRI dhan50 (Banglamoti) as follows:
4.1 Allelopathic effect of different weed species on aromatic rice
4.1.1 Effect of unboiled and boiled weed extracts on seed germination
The experimental data on the effect of unboiled and boiled weed extracts on seed
germination have been shown in Tables 4.1- 4.2, Figs. 4.1-4.2 and Appendix is I-
II. It was found that seed germination varied significantly due to the effect of
unboiled and boiled weed extracts on seed germination of aromatic rice cv. BRRI
dhan50.
Aromatic rice germination was reduced significantly by the allelopathic effect of
different weed species (Table 4.1). In case of unboiled extract, maximum germination
rate (96.2%) was observed in control and minimum rate (80.8 %) was found in khude
shama (Echinoahla colonum) extract treated seeds (Table 4.1). It was observed that
germination rate was comparatively higher due to less allelopathic effect of
Physalis heterophylla (93.0%), Eimbristylis miliacea (91.6%), Elusine indica
(91.0%), Cyperus rotundus (89.3%) and Cyperus difformis (82.5%) extract treated
seeds. The ranking of weed species in respect of inhibitory effect on seed
germination of aromatic rice seed was Echinochola colonum > Cyperus difformis
> Cyperus rotundus > Elusine indica > Eimbristylis miliacea > Physalis heterophylla.
Again, days required to complete the germination of seeds was also affected significantly
by weed extracts. Minimum days (3.00 days) required to complete the germination
was recorded in control treatment where as maximum days (7.00 days) was due to the
effect of Echinochola colonum extract treated seeds. Therefore, the effect of unboiled
extracts of different weed species induced statistically significant variation in germination
rate and number of days required to complete the germination of aromatic rice seeds.
In case of boiled extract, maximum germination rate (95.5%) was observed in
control and minimum rate (75.5%) was found in khude shama (Echinochola
colonum) extract treated seeds (Table 4.2). It was observed that germination rate
was comparatively higher due to less allelopathic effect of Physalis heterophylla
(92.8%), Embristyis miliacea (91.2%), Elusine indica (90.3%), Cyperus rotundus
(90.3%) and Cyperus difformis (83.3%) weeds had strong inhibitory effect on
seed germination of aromatic rice. The ranking of selected weed species in respect
of inhibitory effect on seed germination of aromatic rice was Echinochola colonum
> Cyperus difformis > Cyperus rotandus > Elusine indica > Eimbristyis miliacea
> Physalis heterophylla. Similar inhibitory effect was noted by Roy (1995). Agarwal
et al. (2002) found the inhibitory effect on germination and seedling growth of all
varieties of mustard. Results of this study suggested that the germination of
aromatic rice seed in the field might be reduced by the presence of weed species,
especially Echinochola colonum and Cyperus difformis due to their allelopathic
influence.
Again, days required to complete the germination of seeds was also affected
significantly by weed extracts. The lowest number of days (3.00 days) required to
complete the germination was recorded from control treatment and extract treated
seeds whereas maximum days (7.00 days) was due to the effect of Echinochola
colonum extract treated seeds (Table 4.2).
In case of boiled extract, days required to complete the germination of seeds was
also affected significantly by weed extracts. The lowest number of days (4.10 days)
required to complete the germination was recorded from control treatment and
weed extract treated seeds whereas maximum days (6.23 days) was due to the
effect of khude shama (Echinochola colonum) extract treated seeds (Table 4.2).
4.1.2 Effect of unboiled and boiled weed extracts on primary growth of
seedlings
4.1.2.1 Root and shoot lengths
The result revealed that unboiled and boiled weed extracts reduced root and shoot
lengths of aromatic rice cv. BRRI dhan50 significantly (Tables 4.1-4.2 and Appendix
is I-II). Root and shoot lengths of aromatic rice were affected significantly by the
allelopathic effect of different weed species. Root and shoot lengths of aromatic rice
showed significant reduction due to the treatment of seeds with unboiled and
boiled weed extracts. In case of unboiled extract, the highest root length (8.25 cm) of
aromatic rice seeding was observed in control treatment and the lowest root length (3.50
cm) was obtained in khude shama (Echinochola colonum) extract treated aromatic rice
seedling (Table 4.1). In case of boiled extract, the highest root length (8.00 cm) of
aromatic rice was observed in control treatment and the lowest root length (3.25 cm)
was found in khude shama (Echinochola colonum) extract treated aromatic rice
seedlings (Table 4.1).
Fig. 4.1 Effect of unboiled extract of khude shama (Echinochola
colonum) on aromatic rice seedling.
Control Khude shama (UBE)
Control Khude shama (BE)
Fig. 4.2 Effect of boiled extract of khude shama (Echinochola
colonum) on aromatic rice seedling.
Fig. 4.3 Effect of unboiled extract of sobuj nakful (Cyperus
difformis) on aromatic rice seedling.
Control Sobuj nakful (BE)
Control Sobuj nakful (UBE)
Fig. 4.4 Effect of boiled extract of sobuj nakful (Cyperus difformis)
on aromatic rice seedling.
Again, maximum shoot length (9.87 cm) of aromatic rice seedling was noted in
control treatment and minimum shoot length (4.00 cm) was recorded in unboiled
extract of khude shama (Echinochola colonum) and joina (Eimbristylis miliacea)
. Again, maximum shoot length (9.50 cm) of aromatic rice seedling was noted in
control and minimum shoot length (3.80 cm) was recorded in boiled extract of
khude shama (Echinochola colonum) as presented in Tables 4.1-4.2. Similar results
were reported by Prasad and Srivastava (1991) and Qasem (1993). Reduced shoot
and root lengths were observed in this experiment was possibly due to the effect
of allelochemicals of weed species under investigation.
4.1.2.2 Fresh and dry weights of root
The effect of unboiled and boiled extracts of weeds on aromatic rice seedling
reported in Tables 4.1-4.2 indicating significant reduction on fresh and dry
weights of root of seedlings. In case of unboiled weed extract, maximum fresh
(5.81 mg) and dry (4.25 mg) weights of root were recorded in control treatment.
On the other hand, minimum fresh (2.17 mg) and dry (1.53 mg) weights were
recorded in unboiled extract of khude shama (Echinochola colonum).
In case of boiled weed extract, maximum fresh (6.25 mg) and dry weights (4.15
mg) were observed in control treatment. Minimum fresh (2.16 mg) and dry (1.20
mg) weights of root were found in boiled extract of Echinochola colonum (Table
4.2). Fresh and dry weights of root of aromatic rice seedling were inhibited significantly
by allelopathic effect of different weed species.
4.1.2.3 Fresh and dry weights of shoot
Fresh and dry weights of shoot of aromatic rice seedlings were affected significantly
by the allelopathic effect of different weed species. Maximum reduction of shoot
weight was found due to the treatment of seeds within Echinochola colonum
extract. Maximum fresh (8.28 mg) and dry (5.15 mg) weights of shoot were found in
control (no weed extract). On the other hand, minimum fresh (3.19 mg) and dry
(2.56 mg) weights were recorded in unboiled extract of Echinochola colonum
(Table 4.1).
In case of boiled extract, maximum fresh (8.71 mg) and dry (5.29 mg) weights of
shoot were recorded in control and minimum fresh (2.75 mg) and dry (1.50 mg)
weights of shoot were recorded in extract of Echinochola colonum (Table 4.2).
4.2 Allelopathic effect of different weed plant parts on rice
Khuda shama (Echinochola colonum) and sobuj nakful (Cyperus difformis) showed
more inhibitory effect as compared to other weed species, these two weed species
were selected for further investigation.
4.2.1 Effect of different weed plant parts on germination
Aromatic rice seed germination was affected significantly by allelopathic effect of
different weed plant parts (Tables 4.3-4.4). The highest germination (96.0%) was
observed in control (no weed extract) and the lowest germinations (70.5% and
78.8%) were recorded in stem extracts of khude shama (Echinochola colonum)
and sobuj nakful (Cyperus diformis), respectively. Days required to complete
germination were minimum (3.00 days) in control treatment and maximum (7.87
days) in whole plant extract of khude shama. Again days required to complete
germination were minimum (3.00 days) in control treatment and maximum (7.12
days) in stem extract of sobuj nakful (Cyperus difformis). When the effects of
different plant parts of weeds were compared, it was found that the highest reduction
was caused by stem extracts of different weeds and the lowest reduction was caused
by root extracts. The type and age of plant tissues are extremely important since
compounds are not uniformly distributed in the plants. Here, variation in allelopathic
effect of different weed plant parts might be due to type and age weed plant
(Gamez et al., 2002). Roy (1995) found that dried mass of stem of weeds like
Polygonum hydropiper, Amaranthus spinosus, Chenopodium album, Cyperus
rotundus and Imperata cylindrica were more detrimental than leaf and root. Kalita
et al. (1999) also found that shoot extracts of C. dactylon and C. rotundus was
more inhibitory than root extracts. Sharma et al. (2005) evaluated the allelopathic
effects of some newly developed strains of harar (Terminalia chebula) and reetha
(Sapindus mukorossi) on wheat (Triticum aestivum), maize (Zea mays), lentil
(Lens culinaris), pea (Pisum sativum) and brinjal (Solanum melongena). The
treated crops responded differently to aqueous leaf extracts of harar and reetha
indicating the presence of different phytoactive compounds which were either
phytotoxic or germination and growth promoters.
4.2.2 Effect of different weed plant parts on primary growth
4.2.2.1 Root and shoot lengths
Root and shoot lengths differed significantly due to the effect of extracts of different
plant parts of two weed species viz., khude shama (Echinochola colonum) and sobuj
nakful (Cyperus difformis). These two weed species were selected as per their
inhibitory effects on aromatic rice crops under investigation as reported in Tables
4.3-4.4 and Appendix is IIIa-IIIb, respectively.
Root and shoot lengths of aromatic rice seedling were affected significantly by the
allelopathic effect of different plant parts. Results revealed that the highest root
length (8.13 cm) of aromatic rice seedling was recorded in control treatment. The
lowest root length (2.73 cm) was recorded in root extract of khude shama (Echinochola
colonum) and minimum root length (1.25 cm) was found in stem extract of sobuj
nakful (Cyperus difformis). Again, the lowest shoot length (0.70 cm) was recorded
in root extract of khude shama and minimum shoot length (1.30 cm) was found in
stem extract of sobuj nakful (Tables 4.3-4.4). Agarwal et al. (2002) observed that
the weed extracts of C. rotundus and P. hydropiper inhibited the length of plumule in
all varieties of rice. Aqueous extracts of C. rotundus was found to reduce the
germination and seedling growth of okra (Ameena and George, 2002). Similar
inhibitory effect of the weed on vegetables was also noted by Binita et al. (2001).
4.2.2.2 Fresh and dry weights of root
Fresh and dry weights of root of aromatic rice seedling varied significantly due to
the effect of extract of different weed plant parts (Tables 4.3-4.4 and Appendix
IIIa-IIIb). Aromatic rice seeds with weed extract reduced fresh and dry weights of
root. Maximum fresh (7.00 mg) and dry (4.50 mg) weights of root was recorded
in control treatment and minimum fresh (3.19 mg and 1.08 mg) and dry (2.22 mg
and 0.90 mg) weights was due to stem extract of two weeds (Tables 4.3-4.4). Fresh
and dry weights of root of aromatic rice seedling were significantly affected due to
the allelopathic effect of weed plants parts.
4.2.2.3 Fresh and dry weights of shoot
Fresh and dry weights of shoot of aromatic rice seedling were significantly reduced
due to the allelopathic effect of weed plant parts as shown in Tables 4.3-4.4 and
Appendix is IIIa-IIIb. Maximum fresh (8.50 mg) and dry (5.72 mg) weights of
shoot were recorded in control while minimum fresh (1.53 mg and 2.95 mg) and
dry (0.48 mg and 2.11 mg) weights were observed due to the root and stem extracts
of two weeds, respectively. This finding might be due to the allelopathic potential
of these two weeds under consideration.
Table 4.1 Effect of unboiled weed extracts on germination and early growth of aromatic rice cv. BRRI dhan50 (Banglamoti)
Experimental treatments
Germination
(%)
Days to
complete
germination
Root
length
(cm)
Shoot
length
(cm)
Fresh
weight of
root (mg)
Dry weight
of root
(mg)
Fresh weight
of shoot
(mg)
Dry weight
of shoot
(mg)
Control 96.2 3.00 8.25 9.87 5.81 4.25 8.28 5.15
Joina (Eimbristylis miliacea) 91.6 4.75 4.13 4.00 2.90 2.10 5.33 4.35
Mutha (Cyperus rotundus) 89.3 4.33 4.85 5.35 3.85 2.18 4.91 3.10
Khude shama (Echinochola colonum) 80.8 7.00 3.50 4.00 2.17 1.53 3.19 2.56
Sobuj nakful (Cyperus difformis) 82.5 6.00 3.89 4.40 2.50 2.00 3.50 2.90
Foskabegun (Physalis heterophylla) 93.0 4.28 7.80 8.00 5.40 3.39 8.12 5.12
Chapra (Elusine indica) 91.0 5.10 6.80 7.48 4.80 3.00 7.12 4.95
LSD 0.8 0.15 0.24 0.23 0.27 0.15 0.22 0.16
Level of significance ** ** ** ** ** ** ** **
CV (%) 6.3 6.2 5.3 6.2 7.1 6.1 6.3 8.2
** Significant at 1% level of probability
Table 4.2 Effect of boiled weed extracts on germination and early growth of aromatic rice cv. BRRI dhan50 (Banglamoti)
Experimental treatments
Germination
(%)
Days to
complete
germination
Root
length
(cm)
Shoot
length
(cm)
Fresh
weight of
root (mg)
Dry weight
of root
(mg)
Fresh weight
of shoot
(mg)
Dry weight
of shoot
(mg)
Control 95.5 4.10 8.00 9.50 6.25 4.15 8.71 5.29
Joina (Eimbristylis miliacea) 91.2 4.00 4.10 3.80 2.80 2.00 5.10 4.00
Mutha (Cyperus rotundus) 90.3 4.25 4.00 4.10 2.50 1.98 4.05 3.33
Khuda shama (Echinochola colonum) 75.5 6.23 3.25 4.00 2.16 1.20 2.75 1.50
Sobuj nakful (Cyperus difformis) 83.3 5.80 3.60 4.25 2.79 1.56 2.89 1.73
Foskabegun (Physalis heterophylla) 92.8 4.00 7.40 7.80 5.33 3.20 8.00 5.00
Chapra (Elusine indica) 90.3 4.75 6.40 7.25 4.50 2.90 7.11 4.73
LSD 0.3 0.41 0.43 0.24 0.23 0.11 0.10 0.57
Level of significance ** ** ** ** ** ** ** **
CV (%) 7.7 17.7 7.4 9.9 2.4 4.7 4.3 4.1
** Significant at 1% level of probability
4.3 Allelopathic effect of extracts of different weed plant parts at different
concentrations
4.3.1 Interaction effect of weed plant parts and extract concentrations on
germination
The germination of aromatic rice was significantly influenced due to the interaction
effect of weed plant parts and different concentrations of extract (Tables 4.5-4.6
and Appendix is IVa-IVb). The highest germination (97.0%) was found in control
treatment while the lowest germination (64.0%) was found in 25% stem extract of
Echinochola colonum (Table 4.5). Again, the highest number of days (8.00 days)
required to complete germination was found in 25% stem extract of Echinochola
colonum (Table 4.5). The concentration of 25% was observed the most inhibitory
than those of 5% and 10% concentrations. This might be due to the fate of increasing
concentration of allelochemicals. Bora et al. (1999), Kalita et al. (1999a) and
Ameena and George (2002) noted more or less similar findings. Channappagoudar et
al. (2005) and Yao et al. (2006) found that increasing concentration of weed extracts
increased degree of inhibition for many plant species. The lowest number of days
(3.00 days) was found in control treatment. These findings indicated that the
presence of weed plant parts of Echinochola colonum had the retarding effect on
aromatic rice germination. This influence might be found due to its allelopathic
characteristics.
4.3.2 Interaction effect of weed plant parts and extract concentrations on
initial growth
Significant variation in root and shoot lengths of aromatic rice cv. BRRI dhan50
seed was observed due to the interaction effect of weed plant parts and extract
concentrations of weed plant parts (Tables 4.5-4.6). The highest root (8.10 cm)
and shoot (9.25 cm) length were found in control treatment. The lowest root (0.98
cm) and shoot (1.09 cm) lengths were obtained in 25% stem extract of Cyperus
difformis. The lowest root length was statistically similar with the effect of 25%
stem extract of Echinochola colonum and 10% stem extract, 10% and 25% root
extracts of Echinochola colonum (Tables 4.5-4.6).
A significant interaction between weed plant parts and extract concentration was
observed on fresh and dry weights of root of aromatic rice seedling. Maximum fresh
(6.13 mg) and dry (4.50 mg) weights of root were found in control treatment and
minimum fresh (0.55 mg) and dry (0.50 mg) weights of root were recorded in 25%
root extract of Echinochola colonum. Maximum fresh (6.13 mg) and dry (4.50 mg)
weights of root were found in control treatment and minimum fresh (1.04 mg) and
dry (0.58 mg) weights of root were recorded in 25% stem extract of Cyperus
difformis. Here, it was noted that fresh weight of root was statistically similar with
5% and 10% root extract; 5%, 10% and 25% leaf extract; 5%, 10% and 25% stem
extract and 10% and 25% whole plant. Again, dry weight was statistically similar
with 25% stem extract, 25% whole plant extract, 25% leaf extract and 10% root
extract of Echinochola colonum (Table 4.5).
Significant interaction between weed plant parts and extract concentrations was
observed on fresh and dry weights of shoot of aromatic rice seedling (Table 4.5).
Maximum fresh weight of shoot (8.60 mg) was found in control and minimum weight
of shoot (3.15 mg) was observed 25% stem extract of Echinochola colonum (Table
4.5). Maximum dry weight of shoot (5.40 mg) was found in control and minimum
dry weight of shoot (2.00 mg) was recorded in 25% stem extract of Echinochola
colonum. Again, maximum fresh weight of shoot (8.60 mg) was found in control and
minimum weight of shoot (2.25 mg) was observed 25% leaf extract of Cyperus
difformis (Table 4.5). Maximum dry weight of shoot (5.40 mg) was found in
control and minimum dry weight of shoot (0.89 mg) was recorded in 25% leaf
extract of Cyperus difformis (Table 4.6).
Table 4.3 Allelopathic effect of khude shama extract from different plant parts on germination and early growth of aromatic rice cv.
BRRI dhan50 (Banglamoti)
Treatments
Germination
(%)
Days to
complete
germination
Root
length
(cm)
Shoot
length
(cm)
Fresh weight
of root
(mg)
Dry weight
of root
(mg)
Fresh weight
of shoot
(mg)
Dry weight
of shoot
(mg)
Control 96.0 3.00 8.13 9.25 7.00 4.50 8.50 5.72
Leaf 78.0 7.00 2.83 1.15 3.45 2.90 1.75 0.70
Stem 70.5 7.00 2.98 0.97 3.19 2.22 1.61 0.68
Root 80.6 7.60 2.73 0.70 3.52 2.79 1.53 0.48
Whole plant 74.5 7.87 3.16 0.92 3.50 2.96 1.75 0.72
LSD 1.7 0.67 0.16 0.09 0.33 0.24 0.26 0.05
Level of
significance ** ** ** ** ** ** ** **
CV (%) 12.1 3.6 6.2 4.5 8.9 7.6 10.1 6.9
** Significant at 1% level of probability
Table 4.4 Allelopathic effect of sobuj nakful extract from different plant parts on germination and early growth of aromatic rice cv.
BRRI dhan50 (Banglamoti)
Treatments
Germination
(%)
Days to complete
germination
Root length
(cm)
Shoot length
(cm)
Fresh weight
of root (mg)
Dry weight
of root (mg)
Fresh weight
of shoot (mg)
Dry weight
of shoot (mg)
Control 96.0 3.00 8.13 9.25 7.00 4.50 8.50 5.72
Leaf 80.0 6.60 1.89 1.96 1.82 1.47 3.62 2.98
Stem 78.8 7.12 1.25 1.30 1.08 0.90 2.95 2.11
Root 83.8 6.73 1.73 2.20 1.73 1.19 3.20 2.90
Whole plant 81.3 6.41 2.10 1.95 1.96 1.52 2.98 2.11
LSD 1.7 0.24 0.14 0.21 0.11 0.23 0.09 0.18
Level of
significance ** ** ** ** ** ** ** **
CV (%) 8.3 8.2 5.2 9.8 9.2 7.5 7.4 4.1
** Significant at 1% level of probability
4.4 TLC Techniques for extraction of khude shama (Echinochola colonum)
and sobuj nakful (Cyperus difformis)
TLC plates of alcoholic extracts were developed by three pure solvents and three
mixed solvents. Pure solvents were ethanol (100%), methanol (100%) and mixed
solvents were ethanol: methanol (1:1), ethyl acetate: ethanol (1:1) and benzene :
ethyl acetate (1:1). Rf values of different spots appeared under iodine vapour have
been presented in Table 4.7. The developed TLC plates have been presented in
Fig. 4.5.
Table 4.5 Interaction effect of khude shama extract from different plant parts on germination and growth of aromatic rice cv. BRRI
dhan50 (Banglamoti)
Plant parts × Extract
concentration
Germination
(%)
Days to complete
germination
Root length
(cm)
Shoot length
(cm)
Fresh weight
of root (mg)
Dry weight
of root (mg)
Fresh weight
of shoot (mg)
Dry weight
of shoot (mg)
Control 97.0 3.00 8.10 9.25 6.13 4.50 8.60 5.40
Leaf
5% 80.0 7.79 2.50 2.70 1.15 0.80 3.80 2.95
10% 75.0 7.70 2.15 2.35 1.05 0.70 3.73 2.81
25% 70.0 7.30 2.00 2.30 0.83 0.50 3.58 2.49
Stem
5% 81.2 7.79 1.25 3.00 1.12 0.88 3.35 1.83
10% 68.5 7.75 1.23 2.78 0.97 0.77 3.25 2.15
25% 64.0 8.00 0.98 2.65 0.65 0.63 3.15 2.00
Root
5% 78.0 7.30 1.50 2.75 0.82 0.59 3.50 2.81
10% 72.0 7.45 1.40 2.70 0.65 0.55 3.43 2.70
25% 66.0 7.60 1.30 2.55 0.55 0.50 3.33 2.62
Whole plant
5% 82.0 6.80 1.45 3.15 1.75 0.90 3.60 2.79
10% 80.0 6.90 1.43 2.95 1.25 0.70 3.50 2.83
25% 75.0 7.30 1.35 2.78 0.98 0.50 3.43 2.75
LSD 0.98 0.07 0.06 0.29 1.38 0.06 0.13 0.16
Level of significance ** ** ** ** ** ** ** **
CV (%) 1.6 6.6 29.0 17.6 37.1 46.6 13.0 14.2
** Significant at 1% level of probability
Table 4.6 Interaction effect of sobuj nakful extract from different plant parts on germination and growth of aromatic rice cv.
BRRI dhan50 (Banglamoti)
Plant parts × Extract
concentration
Germination
(%)
Days to complete
germination
Root length
(cm)
Shoot length
(cm)
Fresh weight
of root (mg)
Dry weight
of root (mg)
Fresh weight
of shoot (mg)
Dry weight of
shoot(mg)
Control 97.0 3.00 8.10 9.25 6.13 4.50 8.60 5.40
Leaf
5% 81.2 6.45 1.90 2.11 2.15 1.55 2.95 2.25
10% 79.9 6.55 1.53 1.87 1.96 1.50 2.30 1.96
25% 77.0 6.60 1.45 1.80 1.70 1.20 2.25 0.89
Stem
5% 73.3 6.88 1.35 1.35 1.53 1.05 2.90 1.99
10% 73.2 6.96 1.12 1.27 1.32 0.88 2.84 1.71
25% 70.2 7.11 0.98 1.09 1.06 0.70 2.51 1.39
Root
5% 80.1 6.53 2.11 2.11 2.12 0.93 2.99 1.70
10% 78.1 6.68 1.19 1.71 1.90 0.79 2.83 1.73
25% 73.9 6.73 0.97 1.15 1.04 0.58 2.42 1.52
Whole plant
5% 83.0 6.23 1.60 2.15 1.97 1.15 3.12 1.80
10% 81.2 6.32 1.79 1.90 1.70 0.85 2.80 1.10
25% 79.7 6.40 1.60 1.68 1.55 0.65 2.40 1.10
LSD 0.98 0.29 0.17 0.09 0.14 0.08 0.04 0.16
Level of significance ** ** ** ** ** ** ** **
CV (%) 1.4 6.5 29.1 26.8 23.4 33.5 17.4 23.6
** Significant at 1% level of probability
Table 4.7 TLC of weed extracts and Rf values of the spot
Weeds Extracting
solvent
Carrier solvent Rf values
C1 C2 C3
Khude shama
(Echinochlola colonum)
Ethanol
Ethanol (100%) 0.83 0.78 0.087
Methanol (100%) 0.86 0.85 0.043
Ethyl acetate (100%) 0.87 0.72 0.80
Ethanol : Methanol (1:1) 0.77 0.75 0.025
Ethyl acetate :
Ethanol (1:1) 0.83 0.80 0.82
Benzene : Ethyl
acetate (1:1) 0.53 0.55 0.54
Sobuj nakful
(Cyperus difformis)
Ethanol (100%) 0.75 0.74 0.104
Methanol (100%) 0.89 0.88 0.034
Ethyl acetate (100%) 0.83 0.80 0.81
Ethanol : Methanol (1:1) 0.76 0.76 0.021
Ethyl acetate :
Ethanol (1:1) 0.83 0.81 0.80
Benzene : Ethyl
acetate (1:1) 0.54 0.55 0.50
A B
Fig. 4.5 TLC plates of weed extract of khude shama (Echinochola colonum) and
sobuj nakful (Cyperus difformis) in ethanol eluted by mixed solvents (A)
ethyl acetate: ethanol (1:1) and (B) benzene : ethyl acetate (1:1)
Thin layer chromatographic (TLC) studies of the extracts indicated that compounds
present had high to low polarity. Their Rf values have been reported in Table 4.7.
The concentrations of these compounds in weed extracts were low. So, for obtaining
higher concentration of the compounds in the extracts had also for better bioactivity,
vigorous extract conditions seemed to be needed. The bioactivities of extracts were due
to the high polar organic compounds present in these weed extracts. Another observation
of TLC technique, of these extracts indicated that organic solvents and vigorous extract
conditions were better for extraction of these weeds. In TLC techniques, three unknown
compounds were identified from both extracts of khude shama (Echinochola colonum)
and sobuj nakful (Cyperus difformis). Probably, one or mixture of compounds of
high polarity from the detected compounds might be responsible for the allelopathic
effect on germination and growth of the test crop. Further investigation is needed to
identify the specific or actual compounds responsible for allelopathic action.
CHAPTER 5
SUMMARY AND CONCLUSION
A laboratory experiment was conducted at the Department of Agricultural Chemistry,
Bangladesh Agricultural University, Mymensingh to evaluate the allelopathic potential
of six selected weed species viz., joina (Eimbristylis miliacea), mutha (Cyperus
rotundus), khude shama (Echinochola colonum), sobuj nakful (Cyperus difformis),
foskabegun (Physalis heterophylla) and chapra (Elusine indica) on seed germination
and primary growth of aromatic rice cv. BRRI dhan50 (Banglamoti). The effect of
different weed plant parts e.g. root, stem, leaf and whole plant and three concentrations
viz., 5, 10 and 25% (w/v) of the extracts were evaluated.
Weed species were collected from the Agronomy Field Laboratory, Bangladesh
Agricultural University, Mymensingh. Weed species were washed, chopped and
macerated. In a set, 250 g fresh weed mass of each weed species was boiled in 1 L
water and kept for 3 days with intermittent stirring. After filtration, the filtrates
were used as boiled extracts of weeds. In another set, 250 g fresh weed mass were
decomposed in 1 L water for 7 days at room temperature. The extracts were filtered
and used as unboiled extract. In another trail, the collected plants were separated
into four parts such as leaves, stems, roots and whole plants. Fresh weed plants
parts were chopped and decomposed in 500 mL distilled water for 7 days at room
temperature (28 1°C) with intermittent stirring. After filtration 5, 10 and 25%
(w/v) extract solutions were prepared from each part of two selected weeds.
Germination of aromatic rice seeds was studied by petridish method. Measurement of
shoot and root lengths were started on 14 days after seed placement. After 2 days,
seedlings were collected and fresh and dry weights were recorded.
The aqueous extracts of different weed species exhibited significant inhibitory
influence on aromatic rice. The ranking of weed species in respect of inhibitory
effect on seed germination aromatic rice was Echinochola colonum > Cyperus difformis
> Cyperus rotundus > Elusine indica > Eimbristylis miliacea > Physalis heterophylla.
Khude shama (Echinochola colonum) and sobuj nakful (Cyperus difformis) had strong
detrimental effect on the primary growth of aromatic rice. The effect of unboiled
and boiled extracts of these weed species showed significant reduction in germination
and initial growth of aromatic rice.
The aqueous extract of different parts (root, stem, leaf and whole plant) of the selected
weed species reduced seed germination, root length, shoot length and dry matter
production and increased days to complete seed germination of aromatic
rice. The highest reduction in aromatic rice seed germination was caused by
Echinochola colonum and the lowest reduction was caused by Physalis heterophylla.
In case of root and shoot lengths, the harmful effect of Echinochola colonum was
greater than all other selected weeds. The highest reduction was noticed from the
high concentration (25%) of the extract. The dry matter production was also affected
by extracts of the selected weeds due to their differential allelopathic effects.
Thin layer chromatographic (TLC) technique was developed to identify the
chemical using different polar and non polar solvent systems such as ethanol,
methanol, ethyl acetate and benzene. In TLC technique, three unknown compounds
were identified in the extracts of khude shama (Echinochola colonum) and sobuj
nakful (Cyperus difformis). Probably, one or mixture of the detected compounds
might have special constituents which would be responsible for the allelopathic effect
on germination and early growth of the test crop.
It is, therefore, concluded that all selected weeds had more or less inhibitory effect on
seed germination, number of days to complete germination, root and shoot lengths,
fresh and dry weights of root and shoot of aromatic rice BRRI dhan50. Among the
plant parts, stem extract was the most inhibitory. From the above findings of present
experiment, it could be suggested than khude shama (Echinochola colonum) and
sobuj nakful (Cyperus difformis) had strong detrimental effect on aromatic rice. Therefore,
the cited weeds must be taken into well care and it should be avoided from the aromatic
rice field during land preparation. The experimental results proved that it was
important to exclude these allelopathic weeds especially khude shama (Echinochola
colonum) and sobuj nakful (Cyperus difformis).
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APPENDICES
Appendix I. Analysis of the variance of the data of unboiled weed extract on
seed germination and early growth of aromatic rice cv. BRRI
dhan50
Source of
variation
Degrees
of
freedom
Mean square
Germination
(%)
Root
length
(cm)
Shoot
length
(cm)
Fresh wt.
of root
(mg)
Dry wt.
of root
(mg)
Fresh wt.
of shoot
(mg)
Dry wt.
of
shoot
(mg)
Day of
complete
germination
Treatment 6 114.184** 24.737** 29.004** 12.895** 5.275** 13.992** 3.723** 7.05**
Error 12 12 1 0.014 0.008 0.008 0.009 0.007 0.0419
**Significant at 1% level of probability
Appendix II. Analysis of the variance of the data of boiled weed extract on seed
germination and early growth of aromatic rice cv. BRRI dhan50
Source of
variation
Degrees
of
freedom
Mean square
Germination
(%)
Root
length
(cm)
Shoot
length
(cm)
Fresh wt.
of root
(mg)
Dry wt.
of root
(mg)
Fresh wt.
of shoot
(mg)
Dry wt.
of
shoot
(mg)
Day of
complete
germination
Treatment 6 160.08** 22.822* 28.399* 12.648** 4.847** 14.298** 3.767** 4.976**
Error 12 1 0.008 0.018 0.01 0.009 0.01 0.015 0.028
**Significant at 1% level of probability and *Significant at 5% level of probability
Appendix IIIa. Analysis of the variance of khude shama extract obtained from
different plant parts of extract concentration on seed
germination and growth of aromatic rice cv. BRRI dhan50
Source of
variation
Degrees
of
freedom
Mean square
Germination
(%)
Root
length
(cm)
Shoot
length
(cm)
Fresh wt.
of root
(mg)
Dry wt.
of root
(mg)
Fresh
wt. of
shoot
(mg)
Dry wt.
of
shoot
(mg)
Day of
complete
germination
Treatment 3 57.39** 0.074** 0.1** 0.046** 0.455** 0.051** 0.042** 0.351**
Error 8 0.75 0.003 0.001 0.005 0.001 0.001 0.004 0.006
**Significant at 1% level of probability
Appendix IIIb. Analysis of the variance of sobuj nakful extract obtained from
different plant parts of extract concentration on seed
germination and growth of aromatic rice cv. BRRI dhan50
Source of
variation
Degrees
of
freedom
Mean square
Germination
(%)
Root
length
(cm)
Shoot
length
(cm)
Fresh
wt. of
root
(mg)
Dry
wt.
of
root
(mg)
Fresh
wt. of
shoot
(mg)
Dry
wt.
of
shoot
(mg)
Day of
complete
germination
Treatment 3 18.37** 0.432** 0.38** 0.39** 0.3** 0.212** 0.677 0.218NS
Error 8 0.76 0.008 0.008 0.003 0.008 0.005 0.008 0.758
**Significant at 1% level of probability and NS = Not significant
Appendix IVa. Analysis of the variance of khude shama extract obtained from
different plant parts and extract concentration on seed
germination and growth of aromatic rice cv. BRRI dhan50
Source of
variation
Degrees
of
freedom
Mean square
Germination
(%)
Root
length
(cm)
Shoot
length
(cm)
Fresh
wt. of
root
(mg)
Dry wt.
of root
(mg)
Fresh
wt. of
shoot
(mg)
Dry wt.
of
shoot
(mg)
Day of
complete
germination
Treatment 12 232.74** 10.166** 9.432** 7.473** 2.905** 6.016** 2.064** 2.821**
Error 26 1 0.003 0.083 1.986 0.003 0.016 0.025 0.004
**Significant at 1% level of probability
Appendix IVb. Analysis of the variance of sobuj nakful extract obtained from
different plant parts and extract concentration on seed
germination and growth of aromatic rice cv. BRRI dhan50
Source of
variation
Degrees
of
freedom
Mean square
Germination
(%)
Root
length
(cm)
Shoot
length
(cm)
Fresh
wt. of
root
(mg)
Dry wt.
of root
(mg)
Fresh
wt. of
shoot
(mg)
Dry wt.
of
shoot
(mg)
Day of
complete
germination
Treatment 12 137.464** 10.084** 12.906** 4.746** 2.582** 7.936** 3.567** 1.693**
Error 26 0.995 0.028 0.006 0.021 0.005 0.001 0.025 0.085
**Significant at 1% level of probability