Allelopathic effect of waste-land weeds on germination and growth of winter crops

Background: Waste-land weeds present around the fields exert their allelopathic influence on crops through their leaf leachates and rhizospheric soils. Objective: A study was conducted to investigate the phytotoxic action of four common waste-land weeds Parthenium hysterophorus L., Achyranthes aspera L., Lantana camara L. and Withania somnifera L. through their aqueous extracts and rhizospheric soils against winter crops Avena sativa L., Cicer arietinum L., Hordeum vulgare L. and Triticum aestivum L. Methods: Experiments were conducted in Agronomy laboratory in College of Agriculture at the University of Sargodha. In first experiment, 5% (w/v) water extract from entire plant of each weed was applied to germinating seeds of crops whereas in second experiment, crop seeds were subjected to the rhizospheric soil of each weed for germination test. Results: Results revealed that aqueous extracts of weeds were more phyto-inhibitory compared to their rhizospheric soils. Minimum germination percentage (42.5%), germination index (7.4), seedling vigor index (665.3), root length (3.27 cm), seedling length (14.15 cm) and seedling biomass (74.2 mg) of crops were recorded in response to aqueous extract of P. hysterophorus. Root growth of the crops was affected more compared to the shoot growth. Minimum germination percentage was observed in A. sativa (13.3) by the action of L. camara aqueous extract. Rhizospheric soil of L. camara and P. hysterophorus resulted in minimum germination percentages (57.5 and 58.3, respectively) and seedling vigor indices (1472.5 and 2008.4, respectively) of crops. The lowest germination (30%) and germination index (3.7) was observed for T. aestivum seeds germinated in the rhizospheric soil of W. somnifera. Among crops, A. sativa and C. arietinum were more susceptible to the aqueous extracts whereas T. aestivum to rhizospheric ARTICLE INFORMATION Received: December 17, 2016 Accepted: April 2, 2018 SBCPD | Planta Daninha Hayyat MS, et al. Allelopathy of waste-land weeds Planta Daninha 2020;38:e020173626 https://doi.org/10.1590/S0100-83582020380100076 2/8 soils of weeds. Conclusions: It can be concluded that waste-land weeds especially P. hysterophorus and L. camara negatively affect the crops by their allelopathy.


INTRODUCTION
Weed is a plant growing at a place where it is not wanted and not intentionally sown or a plant whose virtues have not yet discovered, plants that are competitive, pernicious, persistent and interfere negatively with crops production. They are primarily competing with crops for nutrient, light, space and water (Muzik, 1970). Allelopathy commonly refers to straight or circumlocutory, injurious or advantageous effect of a plant on nearby plant through during the production of chemical compounds that are released into the environment (Rice, 1984). Allelochemicals are plant's secondary metabolites that are unconfined into the environment through their leachates, volatile compounds, root exudates and decomposition products of plant residues in soil (Khalaj et al., 2013). Allelochemicals are synthesized by more or less all plants but do not have direct function in their development and reproduction (Bertin et al., 2003).
Waste-land weeds in contrast to crop-land weeds, do not interfere directly with crops but remain present in crop surroundings on field borders and water channels. Although they do not compete the crop plants but release allelochemicals into the environment adjacent to crops and therefore supposed to hamper crop growth and yield indirectly. During soil preparation, the soil underneath weeds at field border become mixed with crop field soil and inhibits the germination and growth of current and subsequent crop. Some of the commonly persistent waste-land weeds present in agro-ecological conditions of Sargodha, Pakistan are Parthenium hysterophorus L., Achyranthes aspera L., Lantana camara L. and Withania somnifera L.
Parthenium hysterophorus commonly known as parthenium is highly allelopathic in nature. Phytochemicals comes out from parthenium disturbing many plant species are phenolics, sesquiterpene and lectones (Swaminathan et al., 1990). Parthenin is the foremost sesquiterpene lactone while vanillic, caffeic, chlorogenic, anisic acids and ferulic are the chief phenolics Singh et al., 2002). The phytotoxic influences on growth and germination of mungbean, soybean and maize by water extracts of parthenium were distinguished by Khan et al. (2011) and Safdar et al. (2014). Achyranthes aspera commonly known as prickly-chaff flower belongs to family Amaranthaceae. A. aspera plant has a diversity of allelochemicals like oleonolic acid, alkaloids, dihydroxy ketones, phenolics saponins, and long chain compounds which have been inaccessible from its different parts (Rameshwar and Akito, 2007;Srivastav et al., 2011). Lantana camara is also notorious as lanata, big sage, wild sage, red sage, white sage and tick berry. Lantana belongs to the family Verbenaceae and is one of the well-known allelopathic weed plants (Binggeli and Desalegn, 2002). Its roots, seed and leaf extracts release certain allelochemicals. Lantana can also hamper development of nearby plants by contending for soil nutrients (Dobhal et al., 2010) and subsequently change the microenvironment (e.g. light, temperature) by forming impenetrable thickets (Sharma and Raghubanshi, 2007). Allelopathic effects of L. camara on emergence and development of chickpea and rice was reported by Ahmed et al. (2007) and Bansal (1998). Withania somnifera L. belongs to family Solanaceae. It is a persistent plant also known as winter cherry or ashwagandha. Leaf extract of W. somnifera showed more inhibitory effect compared with stem and roots against emergence and plantlet growth of parthenium (Sherma and Puri, 2015).
Much of the attention of weed scientists remained on the crop-land weeds due to their direct interference with crops. However, very little research has yet been focused on waste-land weeds and the degree of their harmful effect on crops through leaf leachates and rhizospheric soils. To ascertain whether waste-land weeds (P. hysterophorus, A. aspera, W. somnifera and L. camara) exert their influence on nearby winter crops through various means, a trial was designed.

MATERIALS AND METHODS
Plant and soil bioassay experiments were performed to investigate the phyto-inhibitory influence of plant water extracts and soils from rhizosphere of four waste-land weeds viz., parthenium (Parthenium hysterophorus), prickly chaff-flower (Achyranthes aspera), lantana (Lantana camara) and winter cherry (Withania somnifera) against four winter crops viz., barley (Hordium vulgare), gram (Cicer arietinum), oat (Avena sativa) and wheat (Triticum aestivum). The study was conducted under controlled conditions in the Agronomy Laboratory of University College of Planta Daninha 2020;38:e020173626 -https://doi.org/10.1590/S0100-83582020380100076 3/8 Agriculture, University of Sargodha, Pakistan during year 2015. In plant bioassay, 5% (w/v) aqueous extracts from whole plants of these weeds were applied to germinated seeds of crops whereas in soil bioassay, rhizospheric soils adjacent to roots of these weeds were used as germination media of crop seeds. Both experiments were repeated and results of the second repeat were considered and presented.
Preparation of aqueous extracts: Parthenium hysterophorus, W. somnifera, L. camara and A. aspera plants were uprooted near their maturity from the research area of University College of Agriculture, University of Sargodha, Sargodha (32.08 o latitude, 72.67 o longitude and 190 m altitude), Pakistan during month of March and plants specimens were brought to laboratory. They were exposed to preliminary room temperature drying and then whole plants were kept for oven-drying at 70 o C for 48 hours. Desiccated plants of each weed were chopped into small pieces (3-5 cm) and were dipped into distilled water with 1:20 (w/v) plant material: water ratio through 24 hours duration at room temperature (Hussain and Gadoon, 1981). After 24 hours they were shaken well. To obtain aqueous extract of each weed, its plant-water mixture was filtered through muslin cloth. The filtrate (aqueous extract) of each weed was preserved at room temperature.
Collection of rhizospheric soils: Soils adjacent to roots of uprooted plants of P. hysterophorus, W. somnifera, L. camara and A. aspera were collected from the investigate area of University College of Agriculture, University of Sargodha, Sargodha, Pakistan during march, 2015. The rhizospheric soil of each weed was put in separate plastic bags and kept in laboratory. Before using, soils were sieved. The 300 grams of soil was filled in each plastic pot (12 cm diameter and 6 cm depth) which was used as germination medium for crop seeds.

Germination and growth conditions:
In Petri plate experiment, ten seeds, each of oat, wheat, barley and gram were sown in 9 cm diameter Petri plates with dual layer of filter paper at bottom and moistened with 3 mL of aqueous extracts of weeds. In case of control, distilled water with a same quantity was used instead of aqueous extract. In pot-based soil bioassay experiment, crop seeds were sown in rhizopheric soils of waste-land weeds filled in plastic pots with 6 cm depth and 12 cm diameter. The completely randomized design with a factorial arrangement was used for both experiments. Petri plates and pots were placed in germinator at 25 o C for 12 days.

Data recording and calculations:
In both the plant and soil bioassay experiments, day by day count was performed regarding germination/emergence for the period of 12 days. After complete emergence, shoot and root lengths of crop seedlings were taken. Seedling roots and shoots were weighed after oven drying at 70 o C for 24 h. Data of daily germination/ emergence count were used to calculate a variety of vigor parameters as detailed below: Germination/emergence percentage (GP/EP) was worked out by following formula: where N T : proportion of germinated/emerged seeds in each treatment for the final measurement, and N: Number of seeds used in bioassay.
The germination/emergence index (GI/EI) was worked out by formula as described by as described by Scott et al. (1984): where N 1 : number of seeds germinated/emerged on 1st count, D 1 : days to 1st count, N L : number of seeds germinated/emerged on last count, and D L : days to last count.
Mean germination/emergence time (MGT/MET) was worked out by equation as given by Dezfuli et al. (2008): where n: Number of seeds which were germinated/ emerged on day D, D: Number of days counted from the beginning of germination/ emergence.
Time to 50% germination/emergence (T 50 ) was worked out according to the formula modified by Farooq et al. (2005): where N: final number of germination/emergence, n i , n j : cumulative number of seeds germinated/emerged by adjacent counts at times t i and t j when n i <N/2<n j .

RESULTS AND DISCUSSION
Plant bioassay: Data presented in Table 1 indicated that different germination parameters including germination percentage (GP), germination index (GI), mean germination time (MGT) and time to 50% germination (T 50 ) of crops were affected significantly by water extracts of weeds. Among weeds, P. hysterophorus and L. camara imparted the highest inhibitory effect as aqueous extracts of these weeds resulted in significantly lower GP (42.5 and 50.8%) and GI (7.4 and 9.5), respectively in crops. The GP of these treatments was reduced to 52 and 34% compared to the distilled water (control). The weed-specific crop germination response as revealed by the weed × crop interaction means showed A. sativa to be the most sensitive crop regarding germination percentage to all weeds. This is manifested by its lowest GP (13.3 to 23.3%) and GI (5.0) beneath the influence of aqueous extracts of weeds. The GP of C. arietinum by the application of P. hysterophorus extract remained statistically at par with these values. Among crops, A. sativa and C. arietinum were proved to be the most susceptible to phytotoxic inhibitory effect of weeds as seeds of these crops showed the maximum values of MGT (3.9 and 3.7 d, respectively) and T 50 (3.3 d) that were significantly different from those of other crops. Data concerning growth of crops as affected by water extracts of weeds are shown in Table 2. All the weeds except W. somnifera expressed significant inhibitory effect in seedling biomass of crops by producing their lowest seedling biomasses (63.33, 74.17 and 81.67 g) in response to A. aspera, P. hysterophorus and L. camara, respectively. However, the values of crop seedling lengths remained 14.2, 16.5 and 16.2 mm by growing their seeds in aqueous extracts of P. hysterophorus, W. sominfera and A. aspera, respectively that were significantly lower than the distilled water treated control. The root growth of crop seedlings was more suppressed than their shoot growth by the phytotoxic effect of weeds. Seedling vigor index of crop was also significantly reduced in response to the aqueous extracts of all weeds in comparison to control. Among crops, seedling growth of C. arietinum and A. sativa were proved to be more susceptible to phytotoxic action of weeds aqueous extracts.
The higher deleterious effect of P. hysterophorus and L. camara on germination and seedling growth of crops was probably due to the strong allelopathic potential caused by their aqueous extracts. Rashid et al. (2008) also reported a decline in the seed germination of barley due to the application of parthenium extract. Safdar et al. (2014) also reported significant phytotoxic action of various parts of parthenium plant against emergence and seedling growth of maize. In addition, the strong allelopathic effect of water extracts of all parts of plant L. camara on the emergence of Pennisetum americanum, Lactuca sativa, Setaria italica and Vigna radiata has also been demonstrated by Hussain et al. (2011) and Maiti et al. (2010). Tables 3  and 4, respectively. Data indicated that significant reductions in GP of crops was observed in seeds sown in rhizospheric soils of L. camara and P. hysterophorus that were 32.35 and 31.4% lower than the control (Table 3). However, crops germination speed in terms of MGT and T50 was significantly enhanced in rhizospheric soils of all weeds compared to the control soil. Whereas, there was no effect of rhizopheric soils of wasteland weeds on GI of crop seeds. Among crops, T. aestivum and C. arietinum were proved to be sensitive to allelopathic effect of rhizospheric soils of weeds as these crops gave significantly lower GP (48.7 and 64%, respectively) than other crops. However, these crops hastened their germination by showing significantly the lower GI (7.4 and 10) compared to the rest of crops. Regarding seedling growth, shoot length of crops was significantly reduced by sowing their seeds in rhizospheric soils of A. aspera (16.9 mm), L. camara (18.6 mm) and P. hysterophorus (18.1 mm) (Table 4). However, significantly lower root lengths (6.6 and 10.8 mm) and seedling lengths (25.2 and 27.7 mm) were measured from seeds sown in rhizospheric soils of L. camara and A. aspera, respectively. While, the seedlings germinated in rhizospheric soil of L. camara showed the lowest seedling vigor index (1472.5) that varied significantly among weeds. It is also obvious from the data that phytotoxic inhibitory effect of rhizospheric soils of weeds was more pronounced against shoot growth than root growth of crop seedlings.

Soil bioassay: Data showing the effect of rhizospheric soils of wasteland weeds on emergence and growth of crops have been presented in
The decrease in germination percentage and seedling length of crops in response to rhizospheric soils of weeds seems to be the deleterious effect of allelochemicals present in those soils. However, phytotoxic substances present in minute concentration in soils could be responsible for the little inhibitory or triggering effect on germination parameters like MGT and T 50 . Safdar et al. (2014) found the presence of total and individual phenolic concentrations in rhizospheric soils of P. hysterophorus considerably lower than those detected in the water extracts of different plant parts. The reduction in germination percentage and seedling growth in maize due to the toxic effect of rhizospheric soil of P. hysterophorus has also been noticed by Safdar et al. (2014). Biswas et al. (2010) reported that emergence of rice seedlings was significantly reduced by different concentrations of P. hysterophorus weed debris. Enyew and Raja (2015) reported that L. camara leaf powder mixed in soil with 2.5, 5.0 and 7.5% (w/v) ratios significantly inhibited the germination index, stem thickness, seedling biomass, shoot and root lengths, and germination percentage of wheat and maize crops owing to its strong allelopathic nature. Previous studies also showed that rhizospheric soils of weeds due to their enrichment with allelochemicals caused growth inhibition by reduction in cell division (Hussain et al., 1984;Rice, 1984;Putnam and Chung-Shih, 1986).

CONCLUSIONS
In terms of germination and seedling growth inhibition among winter crops, P. hysterophorus and L. camara could be ranked first. However, P. hysterophorus imparted the maximum phytoinhibition through its aqueous plant extract whereas L. camara through its rhizospheric soil. The overall inhibitory effect of aqueous plant extracts of weeds was more pronounced than their rhizospheric soils. Similarly, crops showed a higher suppression in their root growths in response to weed aqueous extracts whereas shoot growths in response to their rhizospheric soils. Among crops, A. sativa, C. arietinum and T. aestivum were more susceptible to allelopathicity of weeds.

CONTRIBUTIONS
MSH: performed the experiments, data collection, analyzed the data, MES: designed the experiments, manuscript writing, MA: revised the manuscript, AT: final reading and approval, RQ and LA: interpreted the results, HHA, NF, HMRJ and ZHT: literature review and literature search.

ACKNOWLEDGEMENTS
Authors of this manuscript greatly acknowledge Laboratory staff of Agronomy Department, College of Agriculture, University of Sargodha, Pakistan for his