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AGRICULTURAL RESEARCH COMMUNICATION CENTRE
www.arccjournals.com / indianjournals.comIndian J. Agric. Res., 47 (1) : 1 - 15, 2013
POTENTIAL ALLELOPATHIC EFFECTS OF LUDWIGIA ADSCENDENS L. ONTHE SEED GERMINATION AND SEEDLING GROWTH OF RICE
Abhishek Mukherjee and Anandamay Barik*
Ecology Research Laboratory, Department of Zoology,The University of Burdwan, Burdwan – 713 104, India
Received: 07-01-2012 Accepted: 02-05-2012
ABSTRACTThe allelopathic potential of Ludwigia adscendens L. was studied under laboratory conditions andpot experiments in field conditions. Different parts (viz. leaf, stem, and leaf+ stem) of the weedexudates at 2.5, 5, and 10% (w/v) concentrations were applied to determine their effect on rice(Oryza sativa cv. Satabdi) seed germination and seedling growth under laboratory conditions.Increasing concentrations of leaf and stem of L. adscendens weed inhibited seed germination andseedling growth of rice. Further, leaf+ stem extract of this weed synergistically also inhibited seedgermination and seedling growth of rice. The plumules of rice seedlings were more sensitive toallelopathic effects than radicles. Increasing concentrations from leaf, stem, and leaf+ stem of thisweed significantly (P< 0.05) inhibited water uptake by rice seeds. The decrease in germination wasalso correlated with increased electrolyte leakage. Dry weed residues (i.e., 2.5, 5, and 10 g per 2.5 kgsoil) incorporation in soil or application on soil surface also inhibited seed germination and seedlinggrowth of rice in pots under field conditions. The germination inhibition was higher under soilsurface placement of dry weed residues, whereas root length and shoot length inhibition was higherunder soil incorporated dry weed residues.
Key words: Allelopathic effects, Bioassay, Exudates, Germination, Ludwigia adscendens, Rice, Seedling growth.
*Corresponding author’s email: [email protected]
INTRODUCTIONLudwigia spp. (Myrtales: Onagraceae), a pan
tropical genus, are among the 200 most aggressiveworld plant invaders and consist of 82 speciesdistributed among 23 sections (Cronk and Fuller,1995). The Onagraceae family is characterized byflower with parts mostly on plan of four (4 sepals, 4petals, 4 or 8 stamens) and the ovary is inferior(Chen et al., 1992). A very diverse assemblage ofLudwigia species occurs in South America, where45 of the 82 species occur and which may havebeen the centre of origin for the genus (Wogu andUgborogho, 2000). Twenty five of these species occurin old world (Ghani, 1998), and a diverseassemblage of Ludwigia species occur in India (King,1974; Sagar, 1974). Generally Ludwigia spp. occurin moist places while a few are predominantlyaquatic, ranging from annual herbs to large shrubs(Wogu and Ugborogho, 2000). One such species ofOligospermum section, Ludwigia adscendens L. is
a mesophytic herb, which is predominantly aquaticand characterized by rooting at nodes and floatingor matting and grows in wet places (Wogu andUgborogho, 2000). It is generally common acrossdifferent districts of West Bengal and also widespreadover Bihar and Assam of India (Nayek and Banerjee,1987). The large tolerance as well as adaptivecapability of this herbaceous creeping weed is oftentroublesome in cultivated lands, especially in riceplantations (Nayek and Banerjee, 1987). This weedcompetes with rice plants for nourishment anddisturbs crop production. Currently, hand picking ofthis weed from rice fields, and herbicide use are thepractices to get relief from the threat of L.adscendens.
Weed infestation is one of the major causesof low yields of rice under field conditions. Reductionof yield and quality of rice is caused throughcompetition by the weed for light, moisture, and
2 INDIAN JOURNAL OF AGRICULTURAL RESEARCH
nutrients (Nayek and Banerjee, 1987). At the sametime, weeds may inhibit germination and seedlinggrowth of rice due to allelochemicals released byleaching of different weed parts, decomposing weedresidues and volatile substances. Hence, it isprerequisite to assess whether there is anyinvolvement of allelopathy in interference potentialof this weed species.
The alleopathic effects of L. peploidesand L. grandiflora of Oligospermum section onjute have been documented by Dandelot et al.(2008). In another study, Sobhana et al. (1990)showed the al lelopathi c po tent ial o f L .perviflora on rice. Further, two studies indicatedthe allelopathic potential of L. adscendens ongreengram (Roy and Barik, 2010) and jute(Sakpere et al., 2010). However, the li teratureon allelopathic potential of L. adscendens weedon rice seed germination and seedling growthis meager. Hence, this study aimed to assessthe allelopathic potential of L. adscendens ongermination and seedling growth of rice underlaboratory and pot conditions.
MATERIALS AND METHODSNaturally growing L. adscendens weeds
were collected randomly from the rice fieldsadjacent. to The University of Burdwan (23°16'N and 87°54' E), West Bengal, India, duringMarch, 2011. The weeds were initially broughtinto the laboratory and rinsed with distilledwater and followed by paper toweling. 2.5, 5,and 10 g of each weed part (viz. leaf and stem)were cut into 0.5–1.0 cm pieces and wereplaced in 100 ml distilled water for 24 h at roomtemperature (28°C). I n order t o ob tainparticulate free supernatant, the exudates ofleaf and stem were then passed throughWhatman No. 1 filter paper, and the filtrateswere centrifuged at 3000 rpm for 20 min. Thesupernatant were then passed throughWhatman No. 41 filter paper, and the filtrateswere stored at 4° C for use in laboratorybioassay. From the prepared leaf and stemexudates of different concentrations (i.e., 2.5,5, and 10%), leaf and stem exudates of eachconcentration were mixed with equal volumeto produce leaf+ stem exudates of differentconcentrations (i.e., 2.5, 5, and 10%). The rice
seeds (cv. Satabdi ) used throughout theexperiment were collected from Hooghly KrishiVigyan Kendra, ICAR, Chinsurah, Hooghly,West Bengal, India.
Laboratory bioassayFifty rice seeds of uniform size were
surface-steri lized in 10% household bleachsolution for 15 min followed by rinsing thricein sterile distilled water. The above mentionedseeds were placed in 10 cm diameter Petridishes containing double layers of WhatmanNo. 41 filter paper. Ten ml each of leaf, stem,and leaf+ stem aqueous exudates were addedto Petri dishes, separately. Distilled water wasused as a control. Later on exudates wereadded when needed and not to exceed a totalof 10 ml exudates or distilled water for eachPetri dish. The treatments were replicated 3times in a completely randomized design foreach concent rat ion f rom each weed partexudates. The experiment was conducted at 27± 1°C temperature, 70 ± 10% relative humidityand 12 h ± 1.8 L in a BOD incubator. Thenumber of germinated seeds were recordeddaily from day 3 to 10 and expressed as totalper cent. The seeds were considered germinatedupon radical emergence. Seedling growth (i.e.,root length and shoot length) were measuredon day 10. After taking fresh weight on day 10,the seedlings were dried in a hot air oven at 80± 5°C for 48 h to record dry weight.
Water up take test: To test the water uptakecapacity of rice seeds under 2.5, 5, and 10%exudates from different weed parts (viz. leaf,stem, and leaf+ stem), samples of rice seeds(50) were soaked for 3, 6, 12, and 24 h in theabove graded exudates. Distilled water wasmai ntained as cont ro l . Treatments werearranged in a completely randomized designwith three replicates. The seeds were blottedfor 2 h for each time after soaking, and thenthey were weighed. Water up take wascalculated by subtract ing the original seedweight from the final seed weight and expressedin milli liters.
Electrolyte leakage: Electrolyte leakage from seedsor young seedling for different weed parts (viz.leaf, stem, and leaf+ stem) was measured with a
3Vol. 47, No. 1, 2013
conductivity meter (model: Elico® CM 180). Seeds(20) were placed in 20 cm3 of 2.5, 5, and 10%exudates concentration at room temperature inconstant darkness, and conductivities weremeasured after 2 , 24, and 240 h (i.e., day 10).Distilled water was used as a control. Results areexpressed as (µS cm-1) / % of total leakage from seedsor seedlings boiled for 20 min. All treatments wereset-up in triplicate.
Field experimentsHundred grams each of weed leaf and
stem were air-dried separately. The air-driedleaf and stem parts were grounded separatelyin a mill of 2 mm sieve size, and the powderedleaf and stem parts of equal amount were mixedthoroughly. The soil used for pot experimentswas clay-loam (organic matter 2.7–4.4 %, pH7.6–7.8) which was totally free from presenceof weed. The rice seeds were also surface-sterilized as laboratory bioassay test for all potexper iments. The po t exper i ments wereperformed in field conditions during March-April, 2011 when the mean minimum andmaximum temperatures were 22–30°C.
Soil surface applied dry weed residues: 2.5 lpots were filled with 2.5 kg sieved soil which waswithout any trace of weed. 2.5, 5, and 10 g ofpowdered weed residues were applied on the soilsurface of each pot separately. A control was alsoset up side by side with a pot filled with same volumeof sieved soil without weed residues application.This experiment was also arranged for each amountof dry weed residues in a completely randomizedblock design with three replicates.
Soil incorporated dry weed residues: 2.5, 5, and10 g ground weed residues were mixed thoroughlyin 2.5 l pot filled with 2.5 kg sieved field soil,separately. A pot filled with only sieved soil was usedas a control. Fifty rice seeds were incorporated ineach pot, and germination was recorded daily fromday 3 to 10. After 30 days, the seedlings werecarefully taken out from the soil and followed bysubsequent root length and shoot lengthmeasurement. The fresh weights were taken andsubsequently dry weights were measured asmentioned previously in laboratory bioassayexperiment. Treatments were arranged in a
completely randomized block design with threereplicates.
Data collection and analysis: Data were subjectedto correlation coefficient test (r) to find the effect ofexudates from different weed parts (viz. leaf, stem,and leaf+ stem) on the seed germination, root length,and shoot length of rice seedlings (Zar, 1999). Therate of germination/ emergence (G/ER) wascalculated by the modified formula of Maguire(1962) as:
G/ ER seeds per day =Number of normal seedlings Number of normal
seedlings + K +
Days of first count Days of final count
K= Number of normal seedlings/ days of secondcount + number of normal seedlings/days of thirdcount + … … .. .
Regression equations were deduced for eachweed part exudates against different concentrationsfor seed germination, root length, and shoot lengthof rice seedlings to compare the elevations whetherseed germination, root length, and shoot length ofrice seedlings were decreased with increasing doseof three treatments (viz. leaf, stem, and leaf+ stem)(Zar, 1999). Data for seed germination, root length,shoot length, fresh weight, and dry weight of riceseedlings were also subjected to multiple analysis ofvariance (MANOVA) followed by Tukey test to findany significant allelopathic effect (P< 0.05) in SPSS16.0 software. The data of water uptake by rice seedagainst different exudates concentrations (viz. 2.5,5, and 10%) of leaf, stem, and leaf+ stem againstdifferent times (i.e., 3, 6, 12, and 24 h) weresubjected to three-way ANOVA to find allelopathicpotential of L. adscendens through a regulation ofwater uptake and inhibition of seeds. Three-wayANOVA was also applied to find allelopathicpotential of this weed by electrolyte leakage fordifferent exudates concentrations (i.e., 2.5, 5, and10%) of leaf, stem, and leaf+ stem against differenttimes (i.e., 2, 24, and 240 h).
Independent-Samples T test was performedfor all data on pot to assess any significantdifferences between treatment and control. FurtherT test was also performed to find whether theallelopathic effect on seed germination, root length,
4 INDIAN JOURNAL OF AGRICULTURAL RESEARCH
and shoot length, fresh weight and dry weight of riceseedlings were same between the effects of soilincorporated versus surface applied dry weedresidues.
RESULTS AND DISCUSSIONLaboratory bioassay
The exudates of L. adscendens weed leaf,stem, and leaf+ stem inhibi ted the seedgermination (%), root length, and shoot length ofrice seedlings (Fig-1 & Table-1). The correlationcoefficient (r) revealed a significant (P< 0.05)negative relationship with concentrations ofexudates and germination (%) of rice seeds (forleaf, r = -0.937; for stem, r = -0.923 andleaf+ stem = -0.955), root length (for leaf, r = -0.921; stem, r = -0.963 and leaf+ stem, r = -
0.921) and shoot length (for leaf, r = -0.919; stem,r = -0.830 and leaf+ stem, r = -0.784). Thepresent results agree with reports on greengram(Roy and Barik, 2010). The germination rate ofrice seeds was lower in leaf exudates of this weedthan stem exudates at all concentrations (Fig-2).This is in agreement with the earlier report ofWakjira (2009) who recorded that inhibition ofgerminat ion rate o f onion was higher inparthenium leaves than stems at di fferentconcentrations. Furthermore, the leaf and stemexudates in synergy at all concentrations exhibitedlowest germination rate for rice seeds (Fig-2)(Gopal and Goel, 1993; Sakpere et al., 2010).Since the slopes of the regression lines for seedgermination (%) and shoot length of rice seedlingsagainst different weed parts (leaf, stem, and
Conc. (% of
exudates)
Fresh weight (g %)
Dry weight (g %)
Weed parts
Weed parts
Leaf Stem Leaf+ Stem Leaf Stem Leaf+ Stem
2.5
5.943 ± 0.100
5.396 ± 0.042
5.052 ± 0.033
0.957 ± 0.004
0.915 ± 0.012
0.881 ± 0.006 5
4.956 ± 0.064
5.033 ± 0.068
4.638 ± 0.088
0.919 ± 0.003
0.883 ± 0.006
0.857 ± 0.005
10
4.846 ± 0.052
4.750 ± 0.009
4.326 ± 0.052
0.883 ± 0.009
0.850 ± 0.006
0.827 ± 0.011
TABLE 2: Effects of different parts of L. adscendens weed exudates on fresh weight and dry weight of rice seedlings.Water control for fresh weight= 6.915 ± 0.169 g % and dry weight = 1.039 ± 0.031g %.
Values are mean ± standard error, N = 3.
TABLE 1 . Effects of different parts of L. adscendens weed exudates on root length and shoot length of rice seedlings.Water control for root length= 5.835 ± 0.343 cm and shoot length = 7.432 ± 0.44 cm.
Values are mean ± standard error, N = 3.
Conc. (% of exudates)
Root length (cm)
Shoot length (cm)
2.5 5 10
Regression equation
Weed parts Weed parts Leaf Stem Leaf+ Stem Leaf Stem Leaf+ Stem
5.537 ±.0.813 5.662 ± 0.058 5.151 ± 0.411 5.413 ± 0.941 5.42 ± 0.97 4.73 ± 0.056 4.817 ± 0.0767 4.58 ± 0.089 4.445 ± 0.155 Y = 5.8351- 0.0993 (X) leaf r2= 0.849; F = 39.292, df = 1,7; P< 0.0004 Y = 6.07955-0.148 (X) stem r2= 0.927; F = 89.5041, df = 1,7; P< 0.00003 Y = 5.295- 0.0899 (X) leaf+ stem r2= 0.848; F = 39.12, df = 1,7; P< 0.0004
6.421 ± 0.107 6.781 ± 0.081 6.069 ± 0.119 5.85 ± 0.026 6.614 ± 0.165 5.473 ± 0.138 5.34 ± 0.155 6.031 ± 0.119 5.252 ± 0.155 Y = 6.6725 - 0.1375 (X) leaf r2= 0.844; F = 37.901, df = 1,7; P< 0.0004 Y = 7.0721 – 0.1024 (X) stem r2= 0.6887; F = 15.4895, df = 1,7; P< 0.005 Y = 6.1804 – 0.09984(X) leaf+ stem r2= 0.614; F = 11.152, df = 1,7; P< 0.01
5Vol. 47, No. 1, 2013
FIG. 1 . Effects of L. adscendens weed leaf, stem, and leaf+ stem exudates on rice seed germination (%). The regression
equations are for leaf [Y= 96.014 – 1.843 (X) leaf, r2 = 0.876, df = 1, 7; F = 50.6771, P< 0.0002]; stem [Y = 100.001 –
1.905 (X) stem, r2 = 0.851, df = 1, 7; F = 40.1984, P< 0.0003] and leaf+ stem [Y = 90.1333 – 1.5893 (X) leaf+ stem, r2 =
0.9126, df = 1,7; F = 73.101, P< 0.00005.
FIG. 2 . Effects of L. adscendens weed leaf, stem, and leaf+ stem exudates on rice seed germination rate (seeds/day).
6 INDIAN JOURNAL OF AGRICULTURAL RESEARCH
TABLE 3. The results of multiple analysis of variance (MANOVA) showing allelopathic potential of different weed parts(viz. leaf, stem, and leaf+ stem) at different concentrations against rice seeds germination (%) and seedlings growth along
with the results of Tukey test (| q| = Studentized t value, values in bold indicates significance at P < 0.01).
Source
Dependent Variable
Type III Sum of Squares
df
Mean Square
F
Weed Part
Germination Root length Shoot length Fresh weight Dry weight
286.872363 1.28337735 3.6263488
0.38816235 0.00465896
2 2 2 2 2
143.4361813 0.641688674 1.813174399 0.194081176 0.00232948
45.502 37.264 33.948 66.843 55.087
Conc.
Germination Root length Shoot length Fresh weight
886.481852 3.29071602 3.50076597 0.8082744
2 2 2 2
443.2409258 1.64535801
1.750382984 0.404137198
140.608 95.550 32.772
139.189 Dry weight 0.00461809 2 0.002309043 54.604
Weed part * Conc.
Germination Root length Shoot length Fresh weight
11.5801964 0.28643367 0.24958902 0.09494949
4 4 4 4
2.895049111 0.071608418 0.062397255 0.023737373
0.918 4.158 1.168 8.175
Dry weight 8.9467E-05 4 2.23667E-05 0.529
Error
Germination Root length Shoot length Fresh weight
56.741584 0.30995884 0.96138638 0.05226297
18 18 18 18
3.152310222 0.017219936 0.053410354 0.002903499
Dry weight 0.00076117 18 4.2287E-05
Total
Germination Root length
196422.77 702.878319
27 27
Shoot length Fresh weight
974.21624 169.642052
27 27
Dry weight 5.30805331 27
Corrected Total
Germination Root length
1241.67599 5.17048588
26 26
Shoot length Fresh weight
8.33809016 1.34364921
26 26
Dry weight 0.01012768 26
leaf+ stem) for different concentrations are notsignificantly different, it is apparent that germination(%) [F0.05(1)2,21= 0.710 , P> 0.05] and shoot length(F0.05(1)2,21= 0.652, P> 0.05) decreased withincreasing concentration in a similar way for thethree treatments (viz. leaf, stem, and leaf+ stem) (datanot given). However, the slopes of the regression linesfor root length did not differ significantly [F0.05(1)2,21=4.280, P> 0.05], which is indicative of the fact thatroot length inhibition was same with increasingconcentrations for the three weed parts (data notgiven). Our results are consistent with the reportson allelopathic effects in li terature of seed
germination, root length, and shoot length of othercrop seedlings that effect of exudates wereconcentration dependent (data not given) (Ghani,1998; Roy and Barik, 2010; Sakpere et al., 2010;Wakjira, 2009; Zhang and Fu, 2010).
The values obtained for fresh weight and dryweight of rice seedlings for the control werenormalized to 100% (i.e., the values obtained forfresh weight and dry weight of rice seedlings wereexpressed as 100 g); it is seen that the inhibitoryeffects of exudates of different weed parts (viz. leaf,stem, and leaf+ stem) on fresh weight and dry weightof rice seeds were concentration dependent (Table-2).
7Vol. 47, No. 1, 2013
Values at bold indicates significance at P< 0.05; Weed part, i.e., leaf (1) , stem (2) , and leaf+ stem (3).
Dependent variable Weed part (I) Weed part (J) | (I)-(J)| = | q|
Germination 1 2 3.624 1 3 4.349 2 3 7.973 Root length 1 2 0.036 1 3 0.479 2 3 0.443 Shoot length 1 2 0.604 1 3 0.272 2 3 0.877 Fresh weight 1 2 0.094 1 3 0.288 2 3 0.194 Dry weight 1 2 0.018 1 3 0.032 2 3 0.013
Values at bold indicates significance at P< 0.05; Concentration of Weed exudates, i.e., 2.5% (1), 5% (2), and 10% (3).
Dependent variable Conc. of aqueous extract(I)
Conc. of aqueous extract(J)
| (I)-(J)| = | q|
Germination 1 2 7.732 1 3 14.010 2 3 6.279 Root length 1 2 0.263 1 3 0.836 2 3 0.573 Shoot length 1 2 0.446 1 3 0.882 2 3 0.436 Fresh weight 1 2 0.294 1 3 0.411 2 3 0.118 Dry weight 1 2 0.016 1 3 0.032 2 3 0.016
The MANOVA results revealed that the reduction ingermination (%), root length, and shoot length, andfresh weight and dry weight of seedlings weresignificantly (P< 0.05) different among the threeweed parts (viz. leaf, stem, and leaf+ stem) anddifferent concentrations of exudates from the threeweed parts (Table-3). The germination (%) inhibitionwas higher in leaf exudates than stem exudates, butweed leaf and stem exudates (i.e., leaf+ stem) insynergy exerted more phytotoxic or allelopathiceffects in rice (Fig-1) (Gopal and Goel, 1993;Sakpere et al., 2010). The interaction amongdifferent weed parts (viz. leaf, stem, and leaf+ stem)and different concentrations (i.e., 2.5, 5 and 10%)demonstrated that the allelopathic effect ongermination (%), shoot length, and dry weight of
rice seedlings were same (P> 0.05) for different weedparts at different concentrations, whereas allelopathiceffect by different weed parts at dif ferentconcentrations for root length inhibition and freshweight of rice seedlings were significant (P< 0.05)(Table-3).
Tukey test indicated significant differencesin germination (%) of rice seeds between leaf andstem (| q| = 3.624, P< 0.01; | q| = Studentized tvalue), leaf and leaf+ stem (| q| = 4.349, P < 0.01)and stem and leaf+ stem (| q| = 7.973, P< 0.01)(Table-3). The inhibition of root length differssignificantly between leaf and leaf+ stem (| q| =0.479, P< 0.01), stem and leaf+ stem (| q| = 0.443,P< 0.01), whereas the allelopathic effect on root
8 INDIAN JOURNAL OF AGRICULTURAL RESEARCH
length inhibition was same between leaf and stem(| q| = 0.036, P> 0.01) (Table-3). At the same time,the inhibition of shoot length differs significantlybetween leaf and stem (| q| = 0.604, P< 0.01), stemand leaf+ stem (| q| = 0.877, P< 0.01), but thereduction of shoot length was same between stemand leaf+ stem (| q| = 0.272, P < 0.01) (Table-3).Tukey test demonstrated that significant allopathiceffect by this weed parts on fresh weight of riceseedlings between leaf and stem (| q| = 0.094,P< 0.01), between leaf and leaf+ stem (| q| = 0.288,P < 0.01) and stem and leaf+ stem (| q| =0.194, P< 0.01) (Table-3). Similarly, Tukey testindicated significant allopathic effect on dryweight of rice seedlings between leaf and stem(| q| = 0.018, P< 0.01), leaf and leaf+ stem(| q| = 0 .032, P< 0.01) and stem andleaf+ stem (| q| = 0.013, P< 0.01) of this weed(Table-3).
The leaf exudates of this weed at allconcentrations showed greater allelopathiceffect on root length and shoot length of riceseedlings than was stem exudates of this weed.However, the allelopathic effects of leaf andstem (i.e., leaf+ stem) exudates in synergyproduced higher allelopathic activity on rootlength and shoot length of rice seedlings thanwas leaf exudates of this weed (Gopal andGoel, 1993; Sakpere et al., 2010). Plumulelength was more sensitive to allelopathic effectsof L. adscendens weed than radicle length ofrice seedlings. These results are contradictoryto Wakj i ra (2009) who found that onionradicles are more sensitive than plumules toparthenium exudates. The fresh weight and dryweight of ri ce seedlings were also highlyaffected by leaf and stem exudates (i .e.,leaf+ stem exudates) in synergy (Gopal andGoel, 1993; Sakpere et al., 2010).
The increase in concent rat ion o fexudates from different parts of the weed (viz.leaf , stem, and leaf+ stem) signi f i cant lyinhibited water uptake when compared withthat of control (Table-4 and 5). The results ofthree-way ANOVA revealed that water uptakeby the rice seeds differed significantly (P< 0.05)among the weed parts, concentrations, andtimes (Table-5). Further, water uptake of rice
TA
BLE
4 .
Wat
er u
ptak
e by
ric
e se
eds
soak
ed in
L.
adsc
ende
ns w
eed
leaf
, st
em,
and
leaf
+st
em e
xuda
tes
in d
iffer
ent
conc
entra
tions
at d
iffer
ent
times
. Wat
er c
ontr
ol
for
rice
seed
s at
3 h
= 0
.254
± 0
.004
ml,
6 h
=0.
313
± 0
.007
ml,
12 h
= 0
.439
± 0
.006
ml,
24 h
= 0
.573
± 0
.019
ml.
Valu
es a
re m
ean
± st
anda
rd e
rror
, N
= 3
.
5
9Vol. 47, No. 1, 2013
seeds differed significantly (P< 0.05) among theweed parts on different concentrations andtimes. Hence, it is concluded that allelopathicityby water uptake of rice seeds among the weedpart s (o r concent rat i ons o r t i mes) aredependent of the other two factors. From theseresults, it can be assumed that allelopathicityof L. adscendens weed may be mediatedthrough regulat ion o f water uptake andinhibition of seeds (Ashrafi et al., 2008). Thism i gh t be caused d u e t o l o ss o f seedprotease act ivi ty, which plays a key role inprotein hydrolysis during germination andwhich is related to water uptake of seeds.
Electrical conductivity of the alleopathystressed rice seeds or seedlings increasedgradually with the increasing concentrations and
durations of the experiment (Table-6). The leafexudates exhibited substantial increase inelectrolyte leakage than stem exudates, whereasleaf and stem exudates in synergy (i.e., leaf+ stem)showed higher electrolyte leakage than leafexudates. The results of three-way ANOVArevealed that electrolyte leakage by the rice seedsdiffered significantly (P< 0.05) among the weedparts, concentrations, and t imes (Table-7).Furthermore, it is concluded that allelopathicityby electrolyte leakage of rice seeds among theweed parts (or concentrations or times) aredependent of the other two factors. Increasedelectrolyte leakage indicated loss in membraneintegrity of rice seeds or seedlings in the increasingconcentrations of leaf, stem, and leaf+ stemexudates of this weed. From this observation, it
TABLE 5 . The results of three-way Anova showing response of water uptake by rice seeds soaked by L. adscendensweed leaf, stem, and leaf+ stem exudates at different concentrations and at different times along with the results of Tukey test
(| q| = Studentized t value).
Values at bold indicates significance at P< 0.05.
Source
Type III Sum of Squares
df
Mean Square
F
Weed part Conc. Time Weed part * Conc. Weed part * Time Conc. * Time Weed part * Conc. * Time Error Total Corrected Total
0.027690967 0.041916692 0.525996269 0.001421574 0.004272588 0.010769982 0.00383334 0.008500051 9.262376457 0.624401462
2 2 3 4 6 6
12 72
108 107
0.013845 0.020958 0.175332 0.000355 0.000712 0.001795 0.000319 0.000118
117.279 177.529
1485.157 3.01
6.032 15.205 2.706
Values in bold indicates significance at P< 0.01; Weed part: leaf (1), stem (2), leaf+ stem (3); Concentration: 2.5% (1), 5%(2), 10% (3); Time: 2 h (1), 24 h (2), 240 h (3).
Dependent variable Response of water uptake by
seeds Weed part (I) Weed part (J) | (I)-(J)= | q|
1 2.0000 0.016 1 3.0000 0.023 2 3.0000 0.039
Conc. (I) Conc. (J) | (I)-(J)= | q| 1 2 0.026 1 3 0.048 2 3 0.021 Time (I) Time (J) | (I)-(J)= | q|
1 2 0.022 1 3 1.115 2 3 0.172
-
10 INDIAN JOURNAL OF AGRICULTURAL RESEARCHT
AB
LE 6
: E
lect
roly
tic le
akag
e by
ric
e se
eds
soak
ed in
L.
adsc
ende
ns w
eed
leaf
, st
em, a
nd le
af+
stem
exu
date
s in
diff
eren
t con
cent
ratio
ns a
t di
ffere
nt t
imes
. W
ater
cont
rol f
or r
ice
seed
s at
2 h
= 3
.333
± 0
.333
, 24
h =
6 ±
0.2
89, 2
40 h
= 1
02.8
33 ±
1.1
67 (
µS c
m-1)
/ % o
f se
ed a
t 25
°C.
Valu
es a
re m
ean
± s
tand
ard
erro
r, N
= 3
.
can be assumed that an inability to maintaincoherent membranes of rice seeds or seedlingsresults in loss of germinability. These findings arecongruent with the data obtained on mustardseeds germination treated wi th increasingsunflower exudates (Bogatek et al., 2006).
Pot experimentsThe incorporation of dry weed residues in
the soil or application of dry weed residues on thesoil surface at different amounts demonstrated thatgermination (%), root length, and shoot length werereduced over the control (Fig-3 and Table-8).The co rrelat ion coef f i cient ( r ) revealedsignificant (P< 0.05) negative relationship withconcentrat ions of dry weed residues wi thgermination (%) when dry weed residues wereapplied on the soil surface (r = -0.883) or whenincorporated in soil (r = -0.912). The reductionin germination (%) of rice seeds increased withthe increasing amount of L. adscendens dryweed residues when incorporated in soil orapplied on soil surface (Alsadawi and Salih,2009; Qasem, 2001; Wang et al., 2009).
Independent-Sample T test demonstratedthat application of dry weed residue on surfacesoil against control exhibited reduction in seedgermination (%) [t0.05(1)8 = 6.859, P< 0.01], rootlength [ t0.05(1)8 = 5.723, P< 0.01], shoot length[t0.05(1)8 = 6.031, P< 0.01], fresh weight [t0.05(1)8 =6.507, P< 0.01] and dry weight [t0.05(1)8 = 13.356,P< 0.01] of rice seedling over control (from thedata of Table-8). This is in good agreement withprevious reports (Chon et al., 2005; Obaid etal., 2005; Tawaha and Turk, 2003; Wakjira,2009) that found an increase in inhibitoryeffects with increasing amount of dry weedresidues when applied on soil surface. Similarly,T test indicated that incorporation of dry weedresidues in soi l signi ficantly reduced seedgermination [t0.05(1)8 = 6.313, P< 0.01], root length[t0.05(1)8 = 14.295, P< 0.01], shoot length [t0.05(1)8= 18.885, P< 0.01], fresh weight [t0.05(1)8 = 13.084,P< 0.01], and dry weight [t0.05(1)8 = 23.222, P< 0.01] of rice seedling over control (from thedata of Table-8). This is supported by earlierreports that found an increase in inhibitoryeffects with increasing amount of weed residues
11Vol. 47, No. 1, 2013
TABLE 7 . The results of three-way Anova showing response of electrolyte leakage by rice seeds soaked by L.adscendens weed leaf, stem, and leaf+ stem exudates in different concentrations and at different times along with the results
of Tukey test (| q| = Studentized t value).
Values at bold indicates significance at P< 0.05.
Source Type III Sum of Squares
df Mean Square F
Weed parts 3499.240741 2 1749.62037 1461.023 Conc. 5525.166667 2 2762.583333 2306.899 Time 370738.7407 2 185369.3704 154793 Weed parts * Conc. 308.1481481 4 77.03703704 64.329 Weed parts * Time 4262.296296 4 1065.574074 889.809 Conc. * Time 5644.37037 4 1411.092593 1178.335 Weed parts * Conc. * Time 519.2592593 8 64.90740741 54.201 Error 64.66666667 54 1.197530864 Total 656474 81 Corrected Total 390561.8889 80
when incorporated in soil (Alsadawi et al.,2009; Qasem, 2001; Wakjira, 2009; Wang etal . , 2009). Fur ther T t ests betweenincorporation of dry weed residues in soil andapplication of dry weed residues on the soilsur face revealed that reduct ion o f seedgermination [ t0.05(1)8 = 5.159, P< 0.01], rootlength[t0.05(1)8 = 7.473, P< 0.01], shoot length[t0.05(1)8 = 9.339, P< 0.01], fresh weight [t0.05(1)8 =8.499, P< 0.01] and dry weight [t0.05(1)8 = 7.425,P < 0.01] of rice seedlings are not same (from thedata of Table-8).
The reduction of germination (%) (Fig-3) and germination rate (Fig.-4) were higher
under soil surface applied dry weed residuesthan under soil incorporated dry weed residues,whereas root length and shoot length inhibitionof rice seedlings were greater when dry weedresidues were incorporated in soil (Table-8).This is in partial agreement with the earlierreports o f Ismai l and Chong (2009) andWakjira (2009), where seed germination (%)and rate, and seedling growth were moreinhibited on soil surface placed weed residues.The root length and shoot length inhibitionwere higher in soil incorporated dry weedresidues probably due to more inhibi toryeffect of allelochemicals released from the soil
Values in bold indicates significance at P< 0.01; Weed part: leaf (1), stem (2), leaf+ stem (3); Concentration: 2.5% (1), 5%(2), 10% (3); Time: 2 h (1), 24 h (2), 240 h (3).
Dependent variable Response of electrolyte leakage by rice seeds
Weed part (I) Weed part (J) | (I)-(J)= | q|
1 2 7.630 1 3 8.463 2 3 16.093
Conc. (I) Conc. (J) | (I)-(J)= | q| 1 2 9.611 1 3 20.222 2 3 10.611 Time (I) Time (J) | (I)-(J)= | q| 1 2 2.407 1 3 144.703 2 3 142.296
12 INDIAN JOURNAL OF AGRICULTURAL RESEARCH
TABLE 9 . Effects of L. adscendens soil incorporated and soil surface placed dry weed residues on rice seedling weight.Control fresh weight = 13.55 ± 0.190 g % and dry weight = 3.383 ± 0.116 g %.
Values are mean ± standard error, N = 3.
Dry weed Fresh weight (g %) Dry weight (g %)residue (g)
Soil surface Soil incorporated Soil surface Soil incorporated
2.5 12.69 ± 0.009 11.556 ± 0.211 2.87 ± 0.028 2.43 ± 0.0375 12.398 ± 0.165 10.583 ± 0.028 2.77 ± 0.048 2.305 ± 0.11110 11.379 ± 0.22 10.195 ± 0.039 2.71 ± 0.120 2.233 ± 0.038
incorporated dry weed residues (Belgz, 2008;Teasdale and Mohler, 2000; Wakjira, 2005 and2009).
The al lelochemicals, i .e. , tannins,triterpenes, flavonoids, polyphenols, alkaloids,linoleic acid and saponins, etc. released fromL. adscendens weed are diverse (Ghani, 1998;Gopal and Goel, 1993) that can in synergyexert either phytotoxic or allelopathic effects(Singhvi and Sharma,1984). This might bepossib le explanat ions fo r the cur rentallelopathic inhibitory effect of L. adscendenson rice seed germination and seedling growth.The inhibitory activity of leaf+ stem exudatesof this weed on rice seed germination andseedling growth was higher than leaf or stemexudates due to synergi st i c ef fect s o f
allelochemicals that might be absent when leafor stem exudates were used separately.However, there is the need for further studiesthat which chemical or a combinat ion ofchemicals of L. adscendens might serve asinhibitory allelochemicals on rice seeds.
CONCLUSIONThe present studies on L. adscendens weed
revealed that exudates from leaf, stem, andleaf+ stem, and incorporation of dry weed residuesin the soil and application of dry weed residues onthe soil surface had allelopathic effect on rice seeds.Overal l, the allelopathic potential o f thisweed in reduction of rice seed germinationand seed l i ng gr o w t h i ncr eased w i t hincreasing concentration. Hence, for betteryield of rice, careful considerations should
TABLE 8 . Effects of L. adscendens soil incorporated and soil surface placed dry weed residues on rice seedling growth.Control root length = 8.299 ± 0.023 cm and shoot length = 12.51 ± 0.103 cm.
Values are mean ± standard error, N = 3.
Dry weed residue (g)
Root length (cm)
Shoot length (cm)
Soil surface Soi l incorporated
Soi l surface Soil incorporated
2.5 7.665 ±0.104
6.351 ±0.215
11.43 ±0.156
9.364 ±0.149
5 7.249 ±0.210
5.86 ±0.196
10.893±0.169
8.702±0.189
10 6.34 ±0.158
5.37 ±0.161
9.31 ±0.067
8.08 ±0.119
Regression Y= 8.1204 – 0.1778 (X) soil surface Y= 12.222 – 0.288 (X) soil surface
equation r2 = 0.851, F = 40.1484, df = 1,7; P< 0.0004 r2 = 0.948, F = 126.514, df = 1,7; P< 0.000009
Y= 6.5915 – 0.1255 (X) soil incorporated Y= 9.6748 – 0.1645 (X) soil incorporated
r2 = 0.657, F = 13.4, df = 1, 7; P< 0.008 r2 = 0.815, F = 30.802, df = 1, 7; P< 0.0008
13Vol. 47, No. 1, 2013
FIG. 3 . Effects of L. adscendens soil incorporated and soil surface placed dry weed residues on rice seed germination (%).
The regression equations are for soil surface placed weed residues [Y= 94.6216 – 1.935 (X), r2 = 0.779, df = 1, 7; F =
24.7201, P< 0.0016] and soil incorporated dry weed residues [Y= 96.925 – 1.7138 (X), r2 = 0.832, df = 1, 7; F =
34.7804, P< 0.0006].
FIG. 4 . Effects of L. adscendens soil incorporated and soil surface placed dry weed residues on rice seed germination rate(seeds/day).
14 INDIAN JOURNAL OF AGRICULTURAL RESEARCH
REFERENCESAlsadawi, I.S and Salih, N.M.M. (2009). Allelopathic potential of Cyperus rotundus L. I. Interference with crops.
Allelopathy J., 23:297–304.Ashrafi, Y.Z.; Sadeghi, S.; Mashhadi, R.H. and Hassan, A.M. (2008). Allelopathic effect of sunflower (Helianthus
annuus) on germination and growth of wild barley (Hordeum spontaneum). J. Agric. Technol.,4:219–229.
Belgz, R.G. (2008). Stimulation versus inhibition-bioactivity of parthenin, a phytochemical from Partheniumhysterophorus L. Dose Response, 6:80–96.
Bogatek, R.; Gniazdowska, A.; Zakrzewska, W.; Oracz, K. and Gawronski, S. W. (2006). Allelopathic effects ofsunflower extracts on mustard seed germination and seedling growth. Biol. Plant., 50:156–158.
Chen, C.J.; Hoch, P. C. and Raven, P. H. (1992). Systematics of Epilobium (Onagraceae) in China. System Bot.Monogr., 34:1–209.
Chon, S.U.; Jang, H.G.; Kim, D.K.; Kim, Y.M.; Boo, H.O. and Kim, Y.J. (2005). Allelopathic potential in lettuce(Lactuca sativa L.) plants. Sci. Hortic., 106:309–317.
Cronk, Q. C. B and Fuller, J. L. (1995). Plant Invaders: The threat to natural ecosystems. Chapman and Hall,London.
Dandelot, S.; Robles, C.; Pech, N.; Cazaubon, A. and Verlaque, R. (2008). Allelopathic potential of two invasivealien Ludwigia spp. Aquat. Bot., 88:311–316.
Ghani, A. (1998). Medicinal plants of Bangladesh: Chemical constituents and uses. Asiatic Society of Bangladesh,Dhaka.
Gopal, B and Goel, U. (1993). Competition and allelopathy in aquatic plant communities. Bot. Rev.599:155–210.
Ismail, B.S and Chong, T.N. (2009). Allelopathic effects of Dicranopteris linearis debris on common weeds ofMalaysia. Allelopathy J., 23:277–286.
King, L.J. (1974). Weeds of world: Biology and Control. First Willey Eastern Reprint, New Delhi, India.Maguire, J.D. (1962). Speed of germination-aid in selection and evaluation for seedling emergence and vigour.
Crop Sci., 2:176–177.Nayek, T.K and Banerjee, T.C. (1987). Life history and host specificity of Altica cyanea (Coleoptera:
Chrysomelidae), a potential biological control agent for water primrose, Ludwigia adscendens.Entomophaga, 32:407–414.
Obaid, K.A and Qasem, J.R. (2005). Allelopathic activity of common weed species on vegetable crops grown inJordan. Allelopathy J., 15:221–235.
Qasem, J.R. (2001). Allelopathic potential of white top and Syrian sage on vegetable crops. Agron. J., 93:64–71.Roy, N and Barik, A. (2010). Allelopathic potential of Ludwigia adscendens (L.) on germination and seedling
growth of greengram, Vihna radiata (L.) cultivated after rice. Agric. Sci. Digest, 30:192–196.Sagar, G.R. (1974). On the ecology of weed control. In: Biology, Pest and Disease Control (Eds., D.P. Jones and
M.E. Solomon), Halsted Press, New York. Pp. 42–56.Sakpere, A.M.; Oziegbe, M. and Bilesanmi, A. (2010). Allelopathic Effects of Ludwigia decurrens and L. adscendens
subsp. diffusa on germination, seedling growth and yield of Corchorus olitorious L. Not. Sci. Biol., 2:75–80.Singhvi, N. R and Sharma, K. D. (1984). Allelopathic effects of Ludwigia adscendens L. and Ipomoea aquatica
Forsk. on seedling growth of pearl millet (Pennisetum typhoidium Rich.). Transactions ISDTUCDS, 9:95–100.Sobhana, S.; George, S. and Sheela, K. R. (1990). Preliminary studies on allelopathic effect on weeds in rice of
seed germination. Oryza, 27:94–95.Tawaha, A.M and Turk, M.A. (2003). Allelopathic effects of Black mustard (Brassica nigra) on germination and
growth of wild barley (Hordeum spontaneum). J. Agron. Crop Sci., 189: 298–303.
be taken for early removal of this weed fromthe rice f ields.
ACKNOWLEDGEMENTThe authors are thankful to Hooghly
Kr i shi Vigyan Kendra, ICAR, Chinsurah,Hooghly for providing the rice seeds throughout
the experiments. We are also thankful to Head,Department of Zoology, The Universi ty ofBurdwan and DST-FIST for p rov i d i ngnecessary inst rumental faci l i t i es. Specialthanks to Mr. Nayan Roy for his technicalassistance during this study.
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Teasdale, J.R and Mohler, C.L. (2000). The quantitative relationship between weed emergence and the physicalproperties of mulches. Weed Sci., 48:385–392.
Wakjira, M.; Berecha, G. and Bulti, B. (2005). Allelopathic effects of Parthenium hysterophorus extracts on seedgermination and seedling growth of lettuce. Trop. Sci., 45:159–162.
Wakjira, M. (2009). Allelopathic effects of Parthenium hysterophorus L. on germination and growth of onion.Allelopathy J., 24:351–362.
Wang, J.C.; Wu, Y.; Wang, Q.; Peng, Y.L.; Pan, K.W.; Luo, P. and Wu, N. (2009). Allelopathic effects of Jatrophacurcas on marigold (Tagetes erecta L.). Allelopathy J., 24:123–130.
Wogu, A and Ugborogho, R. E. (2000). Seed morphology, germination and seedling characters in Ludwigiaspecies (Onagraceae) in Nigeria as aids to identification. Seed Sci. Technol., 28: 657–697.
Zar, J.H. (1999). Biostatistical Analysis. 4th Edition. Prentice Hall. Upper Saddle River, USA.Zhang, C and Fu, S. (2010). Allelopathic effects of leaf litter and live roots exudates of Eucalyptus species on
crops. Allelopathy J., 26:91–100.
