INTRODUCTION:

Molish (1937) coined the term allelopathy to refer to biochemical interaction between all types of plants including micro organisms. His discussion indicated that he meant the term to cover both detrimental and beneficial reciprocal biochemical interaction. Lee and Monsi (1963) found a report by Banzan Kumazawa in a Japanese document some 300 yr. ago, that rain or dew washing of the leaves of red pine are harmful to crop growing under the pine. This was substantiated by Lee and Monsi (1963) in a series of experiments.

The phenomenon of one plant having detrimental effect on another through the production of chemical compounds is called allelopathy. The allelopathic effect depends upon a chemical compound being added to the environment by an allelopathic agent (Rice, 1974). These allelopathic chemicals inhibit seed germination or reduce the growth of the other plant species. Some important contributions reporting the analysis and detrimental effect of chemical substances released by plant populations in their environment effecting seed germination as well as seedling growth of neighbouring plants have been described by different workers (Dubey 1968, Rawat 1987, Sharma and Lavonia 1981, Sharma 1974 a, Whittaker and Fenny 1971). Phyllanthus niruri Linn. a member of family Euphorbiaceae, is very common in warm part of the country. It generally thrives on black cotton and alluvial soil and also found in garden and cultivated fields. The distribution of plant is generally found along with kharif crops in different localities of Baghelkhand region of Madhya Pradesh, India .

Review of Literature:

Chen et al.(2016) studied the phytotoxic effects of leaf extract from crofton weed (Eupatorium adenophorum Spreng.) on alligator weed (Alternanthera philoxeroides (Mart.) Griseb.). The aqueous leaf extracts from the crofton weed drastically inhibited the root growth of alligator weed at 0.04g·mL-1 concentration. There was no root or few roots only at the bottom stem node, when the concentration reached to 0.08 g·mL-1. According to Pannacci et al.(2015) the extracts of mugwort inhibited the seed germination and radicle and hypocotyl lengths of Sinapis alba L. and followed the order: leaf extracts > stem extracts > rhizome extracts. The aqueous extract of arial biomass (leaves + stems) of mugwort at the highest concentration (25% w/v) may be considered as a potent inhibitor of seed germination and plant growth of L. multiflorum. The application of aqueous extract on the soil surface as pre-emergence herbicide was found most effective for maximum efficacy against weeds. Ranagalage and Wathugala (2015) to evaluate the allelopathic abilities of 40-Sri Lankan improved rice varieties to control the Echinochloa crus-galli L. (Barnyard grassBYG) using rice/BYG mixed cultures in trays, Double Pot Technique test and a field experiment. In tray experiment, significant inhibition in plant height and dry weight were observed in rice/BYG mixed-cultures than monoculture controls. Varieties which showed highest and lowest inhibition (%) in tray experiment were further tested in Double Pot Technique test and later in field experiment. Among the 40 rice varieties, Ld 365, Ld 368, Ld 408 and Ld 356 proved most inhibitory to BYG growth and 40% inhibition in BYG dry matter accumulation Li et al.(2015) investigated the allelopathic effects of aqueous extracts of seeds and different parts of P. notoginseng on seed germination and seedling growth of soybean (Glycine max) and corn (Zea mays). In soybean, leaf extracts hastened the germination and significantly stimulated the shoot and root length than other extracts. In corn, the minimum germination was observed with P. notoginseng leaf extracts. Corn seeds treated with leaf extract showed the maximum shoot and root length than stem, root and seed extracts and P. notoginseng seed extract strongly increased the dry weight than other extracts, These extracts stimulated both soybean seed germination and seedling growth. The results suggested that the P. notoginseng extracts contain allelochemicals, which affect the germination and seedling growth of corn and soybean, and sowing of soybean instead of corn is a practical approach to avoid inhibition in P. notoginseng cropped soil. Erez and Fidan (2015) studies the allelopathic effects of Sage (Salvia macrochlamys Boiss. et Kotschy) aerial parts on the germination of Portulaca oleracea seeds. Germination of P. oleracea seeds was inhibited by methanol extract of S. macrochlamys at concentrations > 2.5 %. The extract concentrations and germination period significantly influenced the protein profiles of germinated seeds. The increasing concentrations of extract decreased the amylase activity of germinating seeds. The control and lower concentration (2.5%) of extracts increased the gibberellic acid (GA3) levels but higher concentrations (5% and 10%) did not increase GA3 levels. The application of higher extracts concentrations (5 % and 10 %) decreased the abscisic acid (ABA) concentration in P. oleracea seeds. Therefore, different germination response of P. oleracea seeds to applied sage extracts could be due to the perturbed GA3 and ABA amounts and ratio, which further influenced the changes in activities of a- amylase. The main allelochemicals in S. macrochylamis extracts were phenolic compounds and fatty acids. Deng et al. (2014) using different extraction conditions, the allelochemicals in roots, stems, leaves and seeds of A. ordosica were examined and characterized using GC-MS. Irrespective of extraction conditions, all parts of plant have similar allelochemical profile with minor variations although the content of individual allelochemical varied. The stems and leaves had higher content of allelochemicals, than other parts. The compounds found were mainly low molecular weight organic acids, phenols and fatty acids. When aqueous extracts of various plant parts were tested for their effect on germination of Corispermum puberulum seeds, the stems and leaves extracts were most inhibitory than extracts of roots or seeds. Accoding to Kuang (2014) the extracts of Pleioblastus kongosanensis f. aureostriaus were assayed for their effects on seed germination and early seedling growth of V. radiata. All extracts at all concentrations inhibited the seed germination and seedling growth of V. radiata than control, and the degree of inhibition increased with the incremental extracts concentration. Bioassay-guided fractionation of ethyl acetate extract of P. kongosanensis led to the isolation of a phenolic compound named xanthoxyline. The results of this study suggested that P. kongosanensis contain allelochemicals, such as xanthoxyline, which could inhibit the seed germination and seedling growth of V. radiata. Amini and Namdari (2014) evaluated the effects of root exudates and shoot aqueous extract of prostrate amaranth (Amaranthus blitoides S. Wats) on common bean (Phaseolus vulgaris L.). The prostrate amaranth growing for 16 days at density of 24 plants / beaker drastically inhibited the root and shoot length of common bean. Increasing the prostrate amaranth density to > 24 plants/beaker and grown for > 16 days, did not increase its inhibitory effects. The inhibitory effects of prostrate amaranth on root and shoot length of different common bean cultivars were variable. Prostrate amaranth shoot aqueous extract reduced the leaf number and common bean height but there were no significant differences among the extract concentrations. The prostrate amaranth aqueous extract decreased the seed number per plant, seeds weight and grain yield of common bean. The prostrate amaranth extract concentration had the highest and lowest inhibition% on cv. Pak and Gholi, respectively. Chemical screening indicated that sterol + triterpenes, flavonoides and alkaloides were the main allelochemicals present in prostrate amaranth shoot. Sterol + triterpenes and alkaloids were most inhibitory to total root and shoot length of common bean.

OBJECTIVE:

The objective of this study was to investigate the possible allelopathic effects of P. niruri leachates on seed germination and seedling growth of rice.

MATERIALS AND METHODS:

Preparation of leachates:

50gms. of oven dried (60⁰c) powder of each stem; root and leaf of P. niruri were soaked separately in 1000 ml. of distilled water for a period of six days. Leached water was collected and then filtered through a whatman no. 1 filter paper. The filtrate was considered a full strength leachate. Further dilution 1:0, 1:10, 1:20, 1:30 and 1:40 were made by diluting with distilled water. All the solution remained kept in glass Stoppard bottles for experimental purposes. In this process, we have taken pH values of the leachates of every step, using the electric pH meter.

Laboratory Experiments:

(i)Effect of P. niruri leachates on seed germination: Rice seeds were soaked in different dilutions of leachates of different plant parts of P.niruri Linn. Seeds were soaked for 24 hours and then seed surface was sterilized with 0.1 percent mercuric chloride solution. After wards washing with mercuric chloride they kept at a temperature of 25⁰c-30⁰c at 90% humidity for germination. For each set 100 seeds of rice was taken. With all above experiment a water control was used for comparision of the result.

(ii)Effect of P. niruri lechates on seedling growth: Rice seeds were surface sterilized with 0.1% mercuric chloride, washed and placed in sterilized petri dishes of 10cm. diameter lined with double layer of filter papers. The seed were moistened with 6ml. of the different dilutions of leachates on first day and 3 ml. on subsequent days. Distilled water was used as control. The petridishes were kept at a temperature of 20⁰c-30⁰c. The criterion of seedling growth was estimated by measuring the length of plumule and radicle of 10 seedlings of each petridishes.

DISCUSSION AND RESULT:

(i) pH of leachates : Observation given in Table- 1 and 2 reveal that most of aqueous leachates come out in water within a period of six days. Rates of leaching of exudates were more similar in leaves, root and stem of P. niruri Linn. In all cases there is a slight increase in pH and then it stabilises. On the basis of pH measurements, leachates may be arranged in the following decreasing order root > leaf > stem.

Table 1: Effect of periodic changes on pH of leachates of different plant parts of P. niruri Linn.

S. No	Plant part leachates	Periodic change in pH
S. No	Plant part leachates	I day	II day	III day	IV day	V day	VI day
1	Leaf	5.7	5.1	4.9	4.7	4.6	4.4
2	Stem	5.8	5.5	5.2	4.9	4.7	4.6
3	Root	5.6	5.3	4.7	4.5	4.4	4.1

Table 2: Effect of dilution on pH of leachates of different plant parts of P.niruri Linn.

S. No.	Plant part leachates	Changes on pH
		dilutions of leachates (leachates : water)
		1 : 10	1 : 20	1 : 30	1: 40	(Stan. Solu.pure)
1	Leaf	4.7	5.3	6.0	6.7	4.4
2	Stem	5.1	5.6	6.4	6.9	4.6
3	Root	4.6	5.2	5.9	6.6	4.1

Table 3: Germination percentage of rice seeds after treatment with different concentration of different plant parts leachtes of P. niruri Linn.

S. No.	Con. of leachates	% of germination of rice seeds
S. No.	Con. of leachates	Leaf	Leachates Stem	Root
1	1 : 0	21	24	17
2	1 : 10	36	40	30
3	1 : 20	46	51	42
4	1 : 30	65	69	57
5	1 : 40	79	81	70

Fig.1: Germination percentage of rice seeds after treatment with different concentration of different plant parts leachtes of P. niruri Linn.

Table- 4: Effect of root leachates of P. niruri Linn. on length of radicle and plumule of Rice seedling (cm.)

S. No	Time interval after germination (In hours)	Rice
		Root leachtes concentration
		Control		1 : 0		1 : 10		1 : 20		1 : 30		1 : 40
		P	R	P	R	P	R	P	R	P	R	P	R
1	24	1.7	1.6	0.4	0.4	0.6	0.5	0.8	0.7	1.0	0.9	1.3	1.1
2	48	2.4	2.0	0.6	0.5	0.8	0.7	1.1	1.0	1.2	1.1	1.7	1.4
3	72	3.0	2.5	0.8	0.7	1.0	0.9	1.3	1.1	1.5	1.4	2.3	1.8
4	96	3.8	3.0	1.1	0.9	1.3	1.2	1.7	1.4	1.9	1.7	2.9	2.4
5	120	4.8	3.6	1.4	1.3	1.6	1.5	2.0	1.8	2.6	2.2	3.7	2.9

Fig.2: Effect of root leachates of P. niruri Linn. on length of radicle and plumule of Rice seedling (cm.)

Table- 5: Effect of stem leachate of P.niruri Linn. on length of radicle and plumule of Rice seedling (in cm.)

S.No	Time interval after germination (In hours)	Rice
		Stem leachtes concentration
		Control		1 : 0		1 : 10		1 : 20		1 : 30		1 : 40
		P	R	P	R	P	R	P	R	P	R	P	R
1	24	1.7	1.6	0.7	0.6	0.8	0.7	1.0	0.9	1.2	1.0	1.4	1.2
2	48	2.4	2.0	1.0	0.8	1.0	0.9	1.3	1.1	1.6	1.4	1.9	1.6
3	72	3.0	2.5	1.3	1.2	1.4	1.3	1.7	1.5	2.2	1.8	2.4	2.0
4	96	3.8	3.0	1.7	1.5	1.8	1.6	2.0	2.0	2.8	2.3	3.0	2.5
5	120	4.8	3.6	2.1	1.9	2.3	2.1	2.8	2.4	3.4	2.4	4.0	3.0

Fig.3: Effect of stem leachate of P.niruri Linn. on length of radicle and plumule of Rice seedling (in cm.)

Table-6: Effect of leaf leachate of P. niruri Linn. On length of radicle and plumule of Rice seedling (in cm.)

S.No	Time interval after germination (In hours)	Rice
		Leaf leachtes concentration
		Control		1 : 0		1 : 10		1 : 20		1 : 30		1 : 40
		P	R	P	R	P	R	P	R	P	R	P	R
1	24	1.7	0.6	0.5	0.5	0.7	0.6	0.8	0.7	1.1	1.0	1.4	1.3
2	48	2.4	2.0	0.7	0.6	0.8	0.7	1.2	1.0	1.3	1.2	1.9	1.6
3	72	3.0	2.5	0.9	0.8	1.0	0.9	1.6	1.3	1.7	1.5	2.4	2.0
4	96	3.8	3.0	1.2	1.1	1.3	1.2	2.0	1.6	2.3	2.0	3.1	2.5
5	120	4.8	3.6	1.6	1.5	1.9	1.6	2.3	1.9	3.1	2.4	3.9	3.0

Fig.4: Effect of leaf leachate of P. niruri Linn. on length of radicle and plumule of Rice seedling (in cm.)

Above observation confirmed the work of Overland (1966) where she observed that barley inhibits seed germination and growth of selected plant species even in the absence of competition. This occurred in mixed cultures receiving adequate nutrients and water in germinating tests. Water soluble root exudates of barley caused inhibition of germination, indicating inhibitory substance. Chandramohan, Purushothamann and Kothandarman (1973) isolated vanilic acid from rice field soil of Annamalainagar. Kimber (1973) investigation offers a good model to follow in research on plant interference. There is cutively too much emphasis by some researchers on just competition and too much emphasis by other on just allelopathy. It is beginning to appear that contain aspect of competition and allelopathy operates in plant interaction. Tang and Waiss (1978) reported that major compounds produced in decomposing wheat straw were salts of acetic, propionic and butyric acids, traces of isobutyric, pentanoic and isopentanoic acids were also identified. Amounts increased gradually up to 12 days and the toxicity of the straw extracts to wheat seedlings increased accordingly, Zobyalyendzik (1973) investigated the mutual interactions of Fagopyrum and Lupinus, Brassica and Avena in field and greenhouse experiments.They reported that yields of tops of Fagoplyrum were 30-35% and grain yields 12-35% greater in crops with other components than in pure strains. Water soluble not exudates of Lupins and Mustered stimulated growth and development of Fagopyrum. Water soluble root exudates of Oats, however inhibited growth and yield of Fagopyrum. Anaya and Gomez – Pompa (1971) demonstrated that extracts of leaves and fruits of Schinus molic are strongly inhibitory against seed germination and seedling growth of Cucumis satires L. and reported Schinus molic is a pernicious weed of crop plants in some plant of Maxico and it is possible; therefore that allelopathy may play a role in its interference. Sharma (1974) reported that Digera arvensis which is a common weed in crops in Rajkot, (India), produces toxins which inhibit seed germination and radical elongation and reduce dry waight of Bajra which is a important crop of Rajkot. In the present study the effect of P. niruri weed on seed germination of the Rice crop, it was observed that leachtes treatment inhibit the seed germination. In the same way leachates play a negative role and inhibit germination of seedling growth of Rice. Present results are in conformity of the early results of different workers from time to time on the effect of weeds on crop. In fact the extracts of a plant are inhibitory to other plants; however it does not indicate that these plant extracts have allelopathic action against other plants. An essential part of allelopathy is the movement of the potential allelopathic agent into the environment. Thus for any suspected allelopathic species, leachates of its leaves, roots should be tested against potential receptor species of same locality.

REFERENCES:

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Received on 10.02.2017 Modified on 18.02.2017

Res. J. Pharmacognosy and Phytochem. 2017; 9(2): 77-82.

DOI: 10.5958/0975-4385.2017.00014.0