International Journal of Agriculture and Crop Sciences. Available online at www.ijagcs.com IJACS/2012/4-19/1452-1457 ISSN 2227-670X 2012 IJACS Journal Allelopathic Effects of Wheat Seed Extracts on Seed and Seedling Growth of Eight Selected Weed Species Soheila Porheidar Ghafarbi 1, Sirous Hassannejad 2*, Ramin Lotfi 3 1. MS of weed science 2. Assistant professor of weed science, Department of Plant Eco-physiology, University of Tabriz 3. PhD student of crop physiology, Department of Plant Eco-physiology, University of Tabriz Corresponding author email: sirous_hasannejad@yahoo.com ABSTRACT: Allelochemicals have the potential to create friendly-eco products for weed management. A factorial experiment (using RCBD design) with 3 replication was conducted in 2011, to evaluation seed germination and seedling growth of some weed soaked in distilled water (control) and aqueous extract of wheat (Triticum aestivum L.) seeds. The first factor included different wheat extract concentrations (0, 2.5, 5, 10 and 20 percent) and the second factor was the eight weed species (Rumex crispus L., Datura stramonium L., Sisiymbrium irio L., Daucus Carota L., Peganum harmala L., Cardaria Draba L., Hordeum spontaneum and Avena ludoviciana).whereas wheat extract concentration increased, the inhibitory effect of allelopathic material on seeds germination and seedling growth indices also increased. As seed germination and seedling growth factors of R. crispus, P. harmala and D. carota were reduced by increasing wheat extract concentration, while seed germination of D. stramonium, C. draba, and S. riro in 5%, 5%, and 2.5% of wheat extract concentrations was increased. The results showed that S. riro was most sensitive to aqueous extract of wheat seeds and R. crispus was most resistant. Wheat seeds extract concentration of 20% has inhibitory effect on all seeds and seedling indices. As a result the allelopathic properties of wheat seeds extract can inhibitory effects on weed species. Key words: Allelopathy, Seedling Growth, Seed Germination, Wheat Seeds Extract, Weeds Species. INTRODUCTION Seeds of some crops possess allelopathic potential or weed-suppressing activity, including wheat (Wu et al., 1999). Aqueous extracts of wheat seed were allelopathic to the germination and growth of a number of weed species (Liebl and Worsham, 1983). Allelopathy has been defined as the inhibitory or stimulatory effects of a plant or microorganism on other plants through the release of chemical compounds into the environment. Most allelochemicals are classified as secondary metabolites of the plant (Kruse et al., 2000). However, these stimulatory and inhibitory effects depend on the concentration of the compounds (Bhowmik and Inderjiit, 2003). When susceptible plants are exposed to allelochemicals, germination, growth and development may be affected (Xuan et al., 2004). The most frequent reported gross morphological effects on plants are inhibited or retarded seed germination and effects on coleoptile elongation and shoot and root development (Kruse et al., 2000). Haig (2008) classified allelochemicals into several categories, such as glucosinolates, phenolic compounds, terpenoids, alkaloids, hydroxamic acids, and other compounds (flavonoids, quinones, polyacetylenes). Allelopathy in cereals (cultivated and wild plants of the Poaceae family) was attributed mostly to hydroxamic acids (Sanchez-Moreiras et al., 2004). Many of such natural compounds have been shown to be promising prospects for natural pesticides development (Dayan et al., 2009; Ma et al., 2011). Bio-herbicides represent solution to heavy use of synthetic herbicides which it causes serious threats to the environment, consumers and increases costs of crop production (Asghari and Tewari, 2007). Allelochemicals may be used to develop new tools to combat the evolution of herbicide resistance in weeds (Anjum and Bajwa, 2005). An equally promising way to use allelopathy in weed control is using extracts of allelopathic plants as herbicides (Dayan, 2002; Singh et al., 2005). Because biosynthesized herbicides are easily biodegradable, they are believed to be much safer than synthesized herbicides (Duke et al., 2000). Many authors reported employ plants extracts for controlling weeds with variable success (Hussain et al., 2007; Iqbal et al., 2009; Naseem et al., 2009).
Understanding the response of weed to allelopathic plants potential for weed control is very important. Therefore, the objective of this study was to determine the effects of wheat extract on seed germination and seedling growth of some its main weeds under lab conditions. MATERIAL AND METHODS In order to determine the effects of wheat seeds extract on seed and seedling growth of its main weeds [Rumex crispus L. (curlydock), Datura stramonium L. (datura), Sisiymbrium irio L. (London rocket), Daucus Carota L. (Carrot), Peganum harmala L. (harmel), Cardaria Draba (L.) Desv. (horay cress), Hordeum spontaneum C. Koch. (Wild barley), and Avena ludoviciana Durieu (oat)], a Factorial experiment (using RCBD design) with three replications was carried out in agronomy laboratory of University of Tabriz. The first factor included different concentrations of the wheat seeds extract (0, 2.5, 5, 10 and 20 percent). The second factor was the eight weed species. Two hundred grams of wheat seeds powder were separately suspended in 1000 ml distilled water and shaken for 24 hours by a horizontal rotary shaker in room temperature to obtain 20 percent concentration of aqueous extract. The solution was diluted appropriately with distilled water to give the other extract concentrations of 2.5, 5 and 10 percent. In this experiment, 16 seeds of each weed species were placed on Whatman filter paper in 9 cm petri dishes. Four ml of distilled water and final wheat seed aqueous extract concentrations were added to each petri dish. Their solutions were applied where required during the course of experiment. Then, their petri dishes were incubated at 20±ºC and germinated seeds (protrusion of radicle by 2 mm) were counted every day up to 7 days. Germination rate (GR) and mean germination time (MGT) were calculated according to Ellis and Roberts (1980): GR= MGT= Where n is the number of seeds germinated on day D, D is the number of days from the beginning of the test and GR is the mean germination rate. Then percentage of germination was also determined. At the end of test, number of root, length and fresh weight of root and shoot were measured. Root and shoot of each sample were then dried in an oven at 80 ºC for 24 hours (Perry 1977) and mean dry weight of root and shoot for each treatment at each replicate was determined. All the data were analyzed on the basis of experimental design, using MSTATC and SPSS-16 software. The means of each trait were compared according to Duncan multiple range test at P0.05 and standard error values. Excel software was used to draw figures. RESULTS Germination percentage of H. spontaneum, A. ludoviciana, R. crispus, P. harmala and D. carota seeds in control (wheat seeds extract concentration of 0%) were significantly higher than that of wheat seeds extract treatments. While, seed germination of D. stramonium, C. draba, and S. riro were stimulated in 5%, 5%, and 2.5% of wheat seeds extract concentrations. However, highest concentration of this extract (20%) has inhibitory effect on seed germination of all weed species (Tab. 1). Difference of mean germination time at H. spontaneum, A. ludoviciana, P. harmala, and C. draba among control and wheat seeds extract treatments were not significant. However, with increasing these extract concentrations, mean germination time at D. stramonium, R. crispus, and D. carota was significantly increased (Tab. 1). Wheat extract treatments were significantly reduced germination rate of H. spontaneum, A. ludoviciana and C. draba seeds, compared with control. In contrast, difference in germination rate of S. riro, D. stramonium, R. cricpus, P. harmala, and D. carota in control and wheat extract treatments was not statistically significant (Tab. 1). Table 1. Effects of wheat seeds extract concentrations on weed species seed germination Treatment Hordeum Sisiymbrium Avena Datura Rumex Peganum Cardaria Daucus
spontaneum riro ludoviciana stramonium crispus harmala draba carota G% 0 97.92 a 14.58 mno 95.83 a 10.42 no 50.00 fghi 70.83 cde 87.50 abc 91.67 a 2.5 97.92 a 31.2 jklm 91.67 a 16.67 lmno 45.83 ghij 64.58 def 81.25 abcd 60.42 efgh 5 89.58 ab 6.250 o 89.58 ab 27.08 klmn 43.75 hijk 62.50 efg 89.58 ab 45.83 ghij 10 66.67 def 0.00 o 72.92 bcde 8.33 o 8.33 o 62.50 efg 33.33 ijkl 12.50 no 20 2.08 o 0.00 o 0.00 o 6.250 o 6.25 o 10.42 no 0.00 o 2.08 o MGT 0 0.2167 g 1.777efg 0.2200g 4.833cde 1.183 g 0.5267 g 0.3800 g 0.5000 g 2.5 0.1733 g 0.9467g 0.2500 g 1.390 fg 1.403 fg 0.5300 g 0.5000 g 0.9300 g 5 0.3200 g 5.000 cd 0.2133 g 1.910 defg 1.450 fg 0.5700 g 0.4667 g 0.9600 g 10 0.7633 g 0.0000 g 0.4033 g 7.000 bc 8.333 ab 0.6433 g 1.300 fg 4.500 cdef 20 0.3333 g 0.0000 g 0.0000 g 5.000 cd 10.33 a 1.667 fg 0.0000 g 3.333 defg GR 0 5.250 b 0.5833 fg 5.333 b 0.2200 fg 0.9133 efg 1.977 defg 2.633 cdef 2.110 defg 2.5 9.000 a 1.133 efg 4.057 bcd 0.3333 fg 0.7333 fg 1.923 defg 2.057 defg 1.080 efg 5 3.347 bcde 0.2067 fg 4.777 bc 0.5467 fg 0.7000 fg 1.857 defg 2.157 defg 1.047 efg 10 2.057 defg 0.0000 g 2.58 cdef 0.1567 fg 0.1333 fg 1.640 defg 0.7933 fg 0.2300 fg 20 0.3333 fg 0.0000 g 0.0000 g 0.1000 fg 0.1133 fg 0.2767 fg 0.0000 g 0.03333 g G%: germination percentage, MGT: germination mean time and GR: germination rate. Different letter in each column indicate significant difference at p0.05 Mean length of root and shoot at H. spontaneum, S. riro, A. ludoviciana, R. crispus, P. harmala, C. draba, and D. carota seedling by increasing of wheat extract concentrations were significantly decreased. However, in seedling of D. stramonium, highest root and shoot length were obtained from wheat extract concentrations of 2.5% (Tab. 2). Treatment Table 2. Effect of wheat seeds extract concentrations on MLR and MLS in seedling weeds Hordeum Sisiymbrium Avena Datura Rumex Peganum Cardaria spontaneum riro ludoviciana stramonium crispus harmala draba Daucus carota MLR 0 11.41 a 0.5133 defg 10.50a 0.04667 g 2.433 b 1.160def 0.9933 defg 2.267 bc 2.5 2.193bc 0.0000 g 1.320 cde 0.1000 fg 0.7533 0.4267 0.0000 g 0.0000 g defg defg 5 1.487bcd 0.0000 g 0.2800 efg 0.0000 g 0.0000 g 0.0000g 0.0000 g 0.0000 g 10 0.6867defg 0.0000 g 0.1400 fg 0.0000 g 0.0000 g 0.0000g 0.0000 g 0.0000 g 20 0.0000 g 0.0000 g 0.0000g 0.0000 g 0.0000 g 0.0000g 0.0000 g 0.0000 g MLS 0 12.24 a 0.7867 fg 7.740b 0.1867 g 3.000 de 1.567efg 3.500 d 3.000 de 2.5 10.95 a 0.3467 fg 6.027 c 0.9333 fg 1.700efg 0.7467 fg 1.167 fg 0.900 fg 5 6.887 bc 0.0000g 1.827 efg 0.3133 g 1.033fg 0.1533 g 0.7133 fg 0.1733 g 10 2.120 def 0.0000 g 1.013 fg 0.0000 g 0.05333 g 0.1133 g 0.1933g 0.0266 g 20 0.0000 g 0.0000 g 0.0000 g 0.0000 g 0.0000 g 0.02000 g 0.0000g 0.0000 g MLR: means length of root and MLS: means length of shoot. Different letter in each column indicate significant difference at p0.05 Means numbers of root was stimulated with increasing of wheat seeds extract concentrations at H.spontaneum up to 5% and at A. ludoviciana and P. harmala up to 2.5%. In seedling of S. riro, D. stramonium, R. crispus, C. draba, and D. carota, number of root in control were significantly higher than that of wheat extracts treatments. This indicated that H.spontaneum, A. ludoviciana, P. harmala were most resistant species than that of S. riro, D. stramonium, R. crispus, C. draba, and D. carota (Fig. 1).
Means number of root Wheat seeds extract concentrations H. spontaneum S. riro A. ludoviciana D. stramonium R. crispus P. harmala C. draba D. carota Figure 1. Effect of wheat seeds extracts concentration on means number of root on seedling of weed species; Bar=±SE, P<0.05. Fresh weight of root and shoot at H. spontaneum and A. ludoviciana seedling were reduced by increasing of wheat extract concentrations. Fresh weight of root at D. stramonium, R. crispus, P. harmala, and D. carota seedling was also reduced in this condition. While, difference of fresh weight of shoot in seedling of S. riro, D. stramonium, R. crispus, P. harmala, C. draba and D. carota between control and wheat extracts treatments was not significant (Tab. 3). Table 3. Effect of wheat seeds extract concentrations on FWR and FWS in seedling weed species Treatment Hordeum spontaneum Sisiymbrium riro Avena ludoviciana Datura stramonium Rumex crispus Peganum harmala Cardaria draba Daucus carota FWR 0 0.4900 a 0.0000 d 0.2400 b 0.01667 cd 0.01000 cd 0.01667 cd 0.0000 d 0.006 cd 2.5 0.1067 c 0.0000 d 0.06000 cd 0.04667 cd 0.000 d 0.01000 cd 0.0000 d 0.0000 d 5 0.07000 cd 0.0000 d 0.02000 cd 0.0000 d 0.0000 d 0.0000 d 0.0000 d 0.0000 d 10 0.04333 cd 0.0000 d 0.0000 d 0.0000 d 0.0000 d 0.0000 d 0.0000 d 0.0000 d 20 0.0000 d 0.0000 d 0.0000 d 0.0000 d 0.0000 d 0.0000 d 0.0000 d 0.0000 d FWS 0 0.6233 a 0.006667 e 0.2800 cd 0.03000 e 0.05667 e 0.06333 e 0.06000 e 0.0233 e 2.5 0.4233 b 0.0000 e 0.2200 d 0.05333 e 0.04000 e 0.03333 e 0.03000 e 0.0266 e 5 0.3333 c 0.0000 e 0.07333 e 0.01333 e 0.03000 e 0.1067 e 0.02000 e 0.0133 e 10 0.2633 cd 0.0000 e 0.04000 e 0.0000 e 0.0000 e 0.01000 e 0.01333 e 0.0000 e 20 0.0000 e 0.0000 e 0.0000 e 0.0000 e 0.0000 e 0.0000 e 0.0000 e 0.0000 e WFR: fresh weight of root and FWS: fresh weight of shoot. Different letter in each column indicate significant difference at p0.05. Dry weight of root and shoot in seedling of H. spontaneum, A. ludoviciana and D. stramonium were significantly affected by aqueous extracts from seeds of wheat and their trait were reduced with increasing extract concentrations (Tab. 4). Treatment Table 4. Effect of wheat seeds extracts concentrations on DWR and DWS in seedling weeds Hordeum Sisiymbrium Avena Datura Rumex Peganum Cardaria spontaneum riro ludoviciana stramonium crispus harmala draba Daucus carota DWR 0 0.0200 a 0.00 f 0.0166 b 0.0000 f 0.00 f 0.00 f 0.00 f 0.00 f 2.5 0.0100 c 0.00 f 0.0066 d 0.0033 e 0.00 f 0.00 f 0.00 f 0.00 f 5 0.0100 c 0.00 f 0.0000 f 0.0000 f 0.00 f 0.00 f 0.00 f 0.00 f 10 0.0066 d 0.00 f 0.0000 f 0.0000 f 0.00 f 0.00 f 0.00 f 0.00 f 25 0.0000 f 0.00 f 0.0000 f 0.0000 f 0.00 f 0.00 f 0.00 f 0.00 f DWS 0 0.0533 a 0.00 h 0.0200 e 0.0033 g 0.00 h 0.00 h 0.00 h 0.00 h 2.5 0.0500 b 0.00 h 0.0133 f 0.0000 h 0.00 h 0.00 h 0.00 h 0.00 h 5 0.0333 c 0.00 h 0.0000 h 0.0033 g 0.00 h 0.00 h 0.00 h 0.00 h 10 0.0266 d 0.00 h 0.0000 h 0.0000 h 0.00 h 0.00 h 0.00 h 0.00 h 25 0.0000 h 0.00 h 0.0000 h 0.0000 h 0.00 h 0.00 h 0.00 h 0.00 h DWR: dry weight of root and DWS: dry weight of shoot.different letter in each column indicate significant difference at p0.05.
DISCUSSION As the wheat seeds extract concentrations increased, the germination and seedling indices of the target weed species significantly decreased and reached the lowest percentage compared with the control. This is in agreeing with the findings of other researchers (Chaves et al. 2001, An et al. 2001, Wu et al. 2001, Asghari and Tewari 2007). Ahn and Chung (2000) have found an inverse relationship between rice hull water extract concentration and target weed seed germination. This finding also agrees with the work of Chaves et al. (2001) who have found that by increasing the concentration of Cistus ladanfer aqueous extracts, the percentage of seed germination, and root and cotyledon length of Rumex crispus were decreased. Mlakar et al. (2012) showed that extract of weeds have stronger inhibitory effect on the germination process and root elongation. Also, similarly result reported by Lai et al. (2012) on tobacco seeds. In some case, extract of wheat seeds have positive effect on germination and seedling indices. This finding is in agreement with that of Swaminathan et al. (1989) who reported a positive effect of seed extracts on radical growth. Nikneshan et al. (2011) reported that with increasing extract concentration from 25 to 100% the inhibitory effect on germination indices increased, while in 25% extract concentration it have incitement effects on seed germination. Boz (2003) also found that allelopathic materials in wheat has no effect on other plants, but may inhibited on some of their most important annual weeds. Results of this experiment showed the effects of wheat seeds extract on germination process are lower than seedling growth indices. Similarly Smith (1991), Smith and Martin (1994) and Ben-Hammouda et al. (1995) found aqueous extracts of several species have suppressed seedling growth in target plants more than seed germination. 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