Allelopathic effects of Emex spinosus L . against wheat and mustard

Emex spinosus L. (Family Polygonaceae), a decumbent, branched annual herb, was assayed for its allelopathic potential because of it weedy habit. Aqueous extracts were obtained from powdered shoots and leaves at room temperature and by boiling. Various extracts significantly inhibited the germination and seedling growth of Triticum aestivum and Brassica compestris used as test species. The extracts reduced the development of cells and retarded cell division in root tip. Results revealed that the E. spinosus L. has a strong allelopathic potential at least against tested species. The phytotoxicity depended upon the test species and concentration of extract.

Methanol extract of R. dentatus had alkaloids, saponins, anthraquinones, tannins and flavonoids (Fatima et al., 2009).The allelopathic effect of Emex australis retarded seedling growth and germination of Triticum aestivum (Nadeem et al., 2010).The crude methanolic extracts of Rumex hastatus, R. dentatus, Rumex nepalensis, Rheum australe, Polygonum persicaria and Polygonum plebejum exhibited phytotoxicity against Lemna minor (Hussain et al., 2010b).Allelopathy operates in agro-ecosystems through release of allelochemicals and soil sickness (Alssadawi, 2006).Emex spinosus L. is an annual weed of wheat, Brassica compestris and other crops.The present study assays the phytotoxic effects of the weed and findings will add to the existing weed-corps allelopathy.

MATERIALS AND METHODS
Mature plants of E. spinosus L. were collected from the wheat fields *Corresponding author.E-mail: zamanbotany@yahoo.com. Tel: 92-0938-300187, 0938-300184, 0345-9501066. Fax: 92-0938-300187. of Manki, District Swabi.Plants were dried at room temperature (25 to 30°C), powdered and stored in paper bags.Glassware's were thoroughly washed with water, was sterilized at 170°C for at least 4.There were always 5 replicates, each with 10 seeds of test species.The petridishes were always incubated at 25°C for 72 h.Data were analyzed using ANOVA and means were separated with LSD.

Effect of aqueous extract
5 and 10 g powder of each part were separately soaked in 100 ml distilled water at 25°C for 24 and 48 h and filtered to get aqueous extracts.These extracts were tested against T. aestivum and B. compestris on 2-folds of filter paper in petri dishes (Hussain et al., 2011(Hussain et al., , 2010a)).Germination, growth of plumule and radical were noted after 72 h. 10 were randomly selected for fresh and dry weight determination.Seedlings were dried at 65°C for 72 h.

Effect of hot water extracts
Hot water extract was obtained and tested against the same test species following (Hussain et al., 2011(Hussain et al., , 2010a)).

Effect of mulching
5 and 10 g crushed dried leaves and stems were placed in plastic pots containing sterilized moist sand for test.The control consist of sand and pieces of filter paper.5 replicates, each with 10 seeds was made for each treatment.The plastic pots were incubated at 25°C and observed daily for germination.After germination the pots were transferred to light at room temperature (25 to 30°C).Shoot and root growth was measured after 15 days.10 seedlings were randomly selected for determining fresh and dry weight and moisture contents.

Effect of litter
5 g crushed litter from leaves and shoots were placed in petridish and covered with one fold of filter paper.Filter papers were moistened with 5 ml distilled water.In the control, fine pieces of filter paper were used.For each treatment, 5 replicates, each with 10 seeds were made.The petri dishes were incubated at 25°C.After 72 h, germination, growth of plumule and radical were noted.10 seedlings were randomly selected for fresh and dry weight determination.

Effect of aqueous extracts
The germination and the radical growth of the test species was strongly inhibited at all concentrations (Table 1) especially in concentrated extracts.Similarly, the fresh and dry weights of the test species were significantly reduced under test condition.The germination of B. compestris was more affected than the T. aestivum.The results suggest that the aqueous extracts of E.spinosus exhibited inhibitory effect, similar to some earlier studies on allelopathy (Azirak and Karaman, 2008;Dongre and Singh, 2007;Dongre and Yadav, 2005;Rafiqul Hoque et al., 2003;Iqbal et al., 2003;Monfared and Rasheed, 2006;Nazir et al., 2007;Zhang et al., 2009) who reported that allelochemicals are released from the various parts of the plant that inhibited the germination and growth of the test species.The toxicity of the plant material depended upon the duration of plant material soaked, concentration and the test species.Similar results were reported by Alam and Shaikh (2007) and Iannuci (2007) for other allelopathic plants.

Effect of hot water
Hot water extract from shoots and leaves inhibited the germination and seedling growth of the test species.Using hot water extract seems unusual but hot water extracts have been used by many workers in allelopathic studies (Lodhi and Nikell, 1973).The germination of B. compestris were more affected than T. eastivum (Table 3).5 g hot water extract was more inhibitory than 10 g hot water extract (Table 3).It is suggested that, the hot water extract had more inhibitory effect than the cold water extract (Table 3).Similar results were reported for Cenchrus ciliarus and Bothriochloa pertusa (Hussain et al., 2010a).Thus, our findings are in line with them.Furthermore, the extracts from leaves were more inhibitory than shoot extract.Fresh weight, dry weight and moisture content were also reduced by hot water extract especially concentrated ones.

Effect of mulching
Allelochemical compound are released directly or indirectly from dead parts of the plants with phytotoxic effects (Saffari et al., 2010).These compounds accumulate in the soil, causing soil sickness and disturb the physiological activities of the susceptible plants (Alssadawi, 2006;Jim and Hodel, 2000).Various plants released phytochemicals from dead tissue into soil this process is accelerated by leaching thus, facilitating their effect (Hussain et al., 2010a(Hussain et al., , 2010b;;Inderjit and Duke, 2003).When E. spinosus mulch was tested against test species the germination, radical growth and plumule growth were significantly retarded (Table 2).However, the effects were specific as inhibition was more pronounced against B. compestris than T. eastivum.The fresh and dry weights were also reduced in both test species.

Effect of litter
The litter when used as growth medium significantly reduced the germination, radical and plumule growth of the test species.Fresh and dry weight were also reduced (Table 2).These results are agree with those of the earlier results regarding the litter-mediated allelopathic effects (Chenlu and Fu, 2010;Rashid et al., 2010;Hussain et al., 2011).The most common effect of    allelochemicals is the death of cells that causes growth reduction (Wu et al., 2003).The toxins might also reduce the chlorophyll contents of the susceptible plant which leads to the reduction of plant growth (Inderjit and Duke, 2003).E. spinosus contain some allelochemicals which retard the growth of test species.The present study suggests that E. spinosus is an allelopathic plant which retards the germination and growth of various test species.The allelopathic effect depends upon the part assayed, test species and physiological process involved.These results although obtained from laboratory assays yet suggest that E. spinosus exhibit allelophatic substances which released into the environment.Field experiment must be carried out to test the effectiveness of the allelopathic potential under natural condition.Further investigations are required to test its efficiency as weeds and disease control.

Table 1 .
Effect of aqueous extract on germination, plumule and radical growth, fresh and dry weight and moisture contents of test species.Each value is a mean of 5 replicates each with 10 seedlings.Significantly different from control at alpha 0.050 according to LSD method in one way ANOVA. *

Table 2 .
Effect of litter and mulching on germination, plumule and radical growth, fresh and dry weight and moisture contents of test seedlings.Each value is a mean of five replicates, each with 10 seedlings.

Table 2 .
Contd.Significantly different from control at alpha 0.050 according to LSD method in one way ANOVA. *

Table 3 .
Effect of hot water extract on germination, plumule and radical growth, fresh and dry weight and moisture contents of test of test species.Each value is a mean of 5 replicates each with10 seedlings.Significantly different from control at alpha 0.050 according to LSD method in one way ANOVA. *