International Journal of Current Biotechnology

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1 Gowsiya Shaik and Santosh Kumar Mehar, Allelopathic potentialities of an invasive tree, Prosopis juliflora on germination and seedling growth of rice under laboratory conditions, Int.J.Curr.Biotechnol., 2014, 2(12): International Journal of Current Biotechnology ISSN: Journal Homepage : Allelopathic potentialities of an invasive tree, Prosopis juliflora on germination and seedling growth of rice under laboratory conditions Gowsiya Shaik 1 and Santosh Kumar Mehar 1,2 * 1 Department of Botany, S.V.U. College of Sciences, Sri Venkateswara University, Tirupati Andhra Pradesh, India. 2 Department of Botany, Jai Narayan Vyas University, Jodhpur, Rajasthan, India. A R T I C L E I N F O Article History: Received 10 September 2014 Received in revised form 20 October 2014 Accepted 08 November 2014 Available online 15 December 2014 Key words: Allelopathy; Allelochemicals; Prosopis juliflora; Germination; Shoot growth; Root growth; Rice. A B S T R A C T Prosopis juliflora is known for its invasive nature and allelopathic effect. An attempt was made to analyze, compare and determine allelopathic potentiality of P. juliflora on rice seed germination and seedling growth. The experiment designed in such a way where both the seed germination and seedling growths can be observed easily using agar+extract in testtubes. The aqueous extract from fresh and dried leaves of P. juliflora was used for the bioassay by applying in 0.1%, 1%, 2.5% and 5% concentrations. Germination characteristics and growth parameters such as, root and shoot growths and biomass of rice seedlings were observed. Germination indices, shoot length and seminal root length showed no inhibition when compared to control. Length of the primary root was inhibited only at 5% concentration; however, the biomass was not inhibited, instead it showed higher value than control in some treatments. As results showed, no inhibitory effect of P. juliflora on the growth of rice seedlings up to 5% concentration, when exposed to leaves extract, it s an initial point to where the negative effect will start. We propose that there is a concentration level (a threshold level), where the allelochemicals starts acting negatively. Below that particular concentration it is not inhibitory. Introduction The word Allelopathy was coined by Plant Physiologist Hans Mollisch (1937). The formal definition of allelopathy is, any direct or indirect harmful or beneficial effect by one plant (including microorganisms) on the other, through production of chemical compounds that escape into the environment (Mollisch, 1937; Rizvi and Rizvi, 1992). Several researchers have worked on this chemical interaction between plants/microbes. The chemicals which are released from allelopathic plants are called allelochemicals. These phytotoxic substances have been reported in a large number of plants, with varying concentration in different parts (Evenari, 1949). Abiotic and biotic soil factors are known to further transform the allelochemicals (Huang et al., 1999; Inderjit et al., 1999). In this process of allelochemical transformation, physical, chemical and biological soil barriers limit the phytotoxicity of allelochemicals in many situations (Schmidt and Ley, 1999). There are several plants which exhibit allelopathic characteristics such as Lantana camara, Prosopis juliflora, P. cineraria, Sphenoclea zeylanica, and so on. P. juliflora is an invasive species, widespread in India. Shankhla et al. (1965) reported the inhibitory effect of aqueous extracts on the growth of some plants. Similar results were reported by many workers (Nakano et al., 2001; Noor et al., 1995; Al-Humaid and Warrag, 1997; Warrag, 1995). The major allelochemicals were reported to be the phenolics. The plant parts which fall to the ground are not totally degraded quickly by the microbes due to the high phenol content. Nakano et al. (2001; 2003) isolated L-Tryptophan from the freeze-dried leaves of P. juliflora which inhibited the radicle growth. And they (Nakano et al., 2002) also isolated syringin, (-)- lariciresinol. Syringin inhibited the root and shoot growth of lettuce seedlings and Barnyard grass. Lariciresinol inhibited root and shoot growth of lettuce seedling and Barnyard grass seedling. Sen & Chawan (1972) reported that the aqueous extracts of P. juliflora were stimulatory at low concentration. It was also reported elsewhere (El- Keblawy and Al-Rawai, 2007), that the effect of P. juliflora on the associated flora significantly depended on the density and size of canopy; wherein larger individuals and greater densities have significantly greater negative impacts on the associated plants. The present study attempted to assess the affect of P. juliflora aqueous crude extract of leaves on the growth parameters of rice. Both the fresh and dried leaves were used for the comparative analysis in the present study. *Corresponding author. address: santoshkumar.1@rediffmail.com Phone: Volume 2; Issue 12; December, 2014 Int.J.Curr.Biotechnol. 22

2 Materials and Methods Collection of plant materials Seeds of Rice (Oryza sativa) variety Kurnool Sona BPT 4205 were used as testing plant material. This is a rice variety which has great agronomic value in the study area (Andhra Pradesh, India). The mature leaves of P. juliflora DC leaves were collected from the P. juliflora trees located in SV University campus in Tirupati, Chittoor Dist., at the longitude and latitudes of N and E. These served as the allelopathic plant material. Part of the leaf sample collected was kept for drying in shade and was used to prepare dry leaves extract, the other part of the sample was used to prepare fresh extract for use in the experiment. Extract preparation Dried leaves extract The leaves were shade dried after collection and powdered. This powder was sieved with 2mm sieve and mixed with distilled water (DW) in the ratio of 1:20 (10 grams of leaves in 200ml of DW), and kept for incubation for 7 days at room temperature (28 o C ±2). Fresh leaves extract The fresh leaves were macerated with the help of pestle and mortar in the same ratios (1:20) as dried leaves and kept for incubation for 7 days in similar conditions. On the 7 th day, both the solutions were filtered with Watman No.1 filter paper and stored at 4 o C for further use. The extracts served as stock solutions. The EC and ph of the dried leaves extract were 0.12 ms and 9.3 respectively. The EC and ph of the fresh leaves extract are as 0.35 ms and 7.38, respectively. Experimental design From both the stock solutions various concentrated solutions i.e., 0.1%, 1%, 2.5% and 5% were prepared with the help of sterilized DW and adding agar (20 g/l) for preparing the media in the test tubes. In 50ml of test tubes, 20 ml of each solution (0.1%, 1%, 2.5% and 5%) was added in separate test tubes. These served as uniform concentration treatments. For testing the effect of different concentrations of the extract on growth and development of rice seedlings, layers of the media were prepared with different concentrations ranging from 0.1 % to 5 %. For this in test tubes, 5ml of 5% solution was added and cooled (by keeping the tubes immersed in ice cold water), than 2.5%, 1%, and ultimately 0.1% solutions were added in the test tube from bottom to the top of the test tube in succession and cooled simultaneously. This served as increasing concentration treatment (because the seeds at the top were exposed to increasing concentrations of the extract in the test tube during their growth (as the roots developed). For making the decreasing concentration treatment, same extract solutions were added in the test tubes, but in the reverse order from what was used to make increasing concentration treatment. Same pattern was followed for both the fresh and dried leaves extract. Distilled water with agar without the extract was used as control. After proper cooling and solidification of the solutions in all the test tubes, rice seeds were inoculated in the test tubes after surface sterilization (0.1% mercuric chloride for 60 seconds, rinsed and washed with DW several times). Two seeds were inoculated in each test tube. All the test tubes were kept for incubation at constant temperature of 25±2 o C, with light (12 hours light and dark periods) for 15 days. Growth patterns and germination was observed and recorded during the incubation. All the treatments were replicated thrice. Collection of data Germination data everyday for 6 days (because by this time all the seeds germinated) On the 15 th day, the plants were harvested. For the analysis of growth the different parameters were recorded as listed below: Length of Primary Root (PRL) Length of Shoot (SL) Length of Seminal Root (SRL) Fresh Weights of Root, Shoot and Seed (FW of R, FW of Sh, FW of S) Dry weights of Root, Shoot and Seed (DW of R, DW of Sh, DW of S) Calculations and statistical analysis From the above data, germination data was used to calculate, germination indices i.e., Total germination (GT), Speed of Germination(S), Speed of accumulated Germination (AS), Co-efficient of the rate of Germination (CRG) as per Chiapusio et al. (1997). All the germination indices values for all the treatments were compared with control using Mann-Whitney U-Test. All the other values such as PRL, SRL, SL, FW of R, FW of SH, FW of S and Number of Seminal roots (No. of SR) were compared with control by paired t-test. The percentage of control values were calculated in case of Dry weights. This helped in knowing the percent contribution of different plant parts i.e. root, shoot and seed in complete plant biomass. Pearson s Correlation test was used to know the relationship among different parameters. Results and Discussion There was no inhibitory affect on the germination of seeds. Variation between control and treatments for different germination indices were not significant, in both fresh and dried leaves extracts at all the concentrations used in the experiment. Values of all the germination indices are shown in Table 1. There are several reports of both inhibitory and stimulatory effect of different plant extracts on various target species by using different concentration of the extract. L. camara water extracts at the concentrations of 1%, 5%, 10%, inhibited the germination percentage of seeds of E. colonum, D. sangualis, P. psilopdium. But the inhibitory effect was alleviated by the same plants at the same concentrations when the activated charcoal was added along with the water extracts of L. camara. Interestingly, there was no inhibitory effect of the same extracts at the same concentrations, on the seeds of 4 rice varieties namely, Himalaya-1, Himalaya-2, Himdhan, China-988 at the same concentrations without the addition of charcoal (Bansal, 1988). The same plant extract can be inhibitory to some plants and can have stimulatory effect on some other plants, or could not show any noticeable effect. In general, the effect of plant extracts on the test plants depends on the target and test plant combination, and so also on the eco-physiological conditions effective during the experiment. To know the allelopathic affect of P. juliflora, Sen and Chawan (1970) tested effect of extract from fresh, dried and autoclaved extracts prepared from stem, leaves and fruits on the growth of E. cardifolia in two lots. The results varied with the plant part used and the 23 Int.J.Curr.Biotechnol. Volume 2; Issue 12; December, 2014

3 Figure - 1: Percentage of control of all parameters in different treatments (SL- Length of the shoot; PRL- Length of the Main root; SRL- Length of Seminal Root; No. of SR- number of seminal roots; FW of R- Fresh Weight of Root; FW of S- Fresh Weight of seed; FW of Sh- Fresh Weight of shoot; DW of R- Dry Weight of Root; DW of S- Dry Weight of seed; DW of Sh- Dry Weight of shoot) Figure - 2: Contribution of seed, root, shoot to total seedling biomass with reference to control Table - 1: Germination indices values of different treatments Treatments GT S AS CRG Control C % Dried 1% leaves 2.50% extract 5% %-1%-2.5%-5% %-2.5%-1%-0.1% % Fresh 1% leaves 2.50% extract 5% %-1%-2.5%-5% %-2.5%-1%-0.1% (Values are the percentage of control) Volume 2; Issue 12; December, 2014 Int.J.Curr.Biotechnol. 24

4 Table - 2: p-values of different treatments in comparison with control Treatments L of Shoot F of Shoot L PR of No. of SR L SR of FW of Root FW of Seed 0.10% * % Dried Leaves Extract 2.50% % * Fresh Leaves Extract 2.50% * 5% * %-1%-2.5% * % 5%-2.5%-1%- 0.1% % * % %-1%-2.5%- 5% 5%-2.5%-1%- 0.1% 14_0.1 v/s 21_ * Dried v/s Fresh Leaves extract 14_1 v/s 21_ _2.5 v/s * 21_2.5 14_5 v/s 21_ * _Inc 21_Inc 14_Dec 21_Dec (*Significant at the 0.05 level) v/s v/s * Table - 3: Pearson s Correlation test results SL PRL SRL No. SR FW R FW Seed FW Shoot SL PRL SRL No. SR ** FW R FW Seed * FW Shoot * (2-tailed, N=13; *Correlation is significant at the 0.05 level; **Correlation is significant at the 0.01 level) 25 Int.J.Curr.Biotechnol. Volume 2; Issue 12; December, 2014

5 concentration of the extract applied. Fresh stems extract showed inhibitory affect on the plants except in 1:16 dilutions and had insignificant effect on some plants. However, the dried stems extract (5%, 2.5%, 1%) caused no inhibition, which is similar to the results obtained in the present study. Dried leaf extract was inhibitory in higher concentrations and slightly stimulatory at 1% (with and without autoclaving). Fresh fruits extract was inhibitory at all concentrations. This indicates that the variability in seed germination depends on other factors also besides the extract to which the seeds are subjected. Germination responses were mixed and dependent on many aspects such as; extract source, extract concentration and weed species. Along with inhibitory effects, several workers have reported stimulatory affects of allelochemicals on the germination of seeds (Hoffman et al., 1996; Liu and Lovett, 1993; Panasiuk et al., 1986). In the present experiment, lengths of the shoot and seminal root in both the dried and fresh leaves extract treated seeds were comparable to control. The length of PR varied in some treatments. Seedlings grown in 0.1% of dried and fresh leaves extract had longer roots than control. Both the 5% concentration extracts inhibited the PR growth slightly in comparison with control. When the treatments of fresh and dried leaves were compared with each other (such as 0.1% v/s 0.1%, 1% v/s 1%, and so on), except for the 5% concentration treatment, rest were insignificant. The length of PR of the seedlings grown in fresh leaf extract was significantly inhibited when compared with the seeds grown in dried leaf extract (Table 2). When the values of SRL, PRL and SL were analyzed for difference as percentage of control, SRL was promoted except in Dried 0.1%, Dried 1%, Fresh 1%, Fresh Decreasing ordered treatments. SL was also promoted except in the fresh 5% treatment. PRL was inhibited in all except in fresh and dried 0.1%, and in fresh D (Fig.1). Parvez et al. (2003) carried out bioassays of tamarind leaves on edible crop species and reported that the growth inhibition was higher in weed species than the edible crop species tested. When the tamarind leaves crude water-soluble extract was applied, the inhibition of seedling growth was stronger in weed species than edible crop species and ranged between 22-80% (radicle) and 21-76% (hypocotyls). They also reported that the largest inhibitory effects in all the plants were observed in the higher concentrations i.e. 10% (w/v). Chug et al. (2001) isolated some phenolic acids, including O-Hydroxy phenyl acetic acid from rice straw and 9 phenolic acids from rice hulls. These chemicals inhibited seed germination and seedling growth of barnyard grass at concentrations of M, and sometimes even at lower concentrations (Chug et al., 2002). Extracts of Lantana at concentrations of 1%, 5%, 10%, inhibited the root lengths of E. colonum, Digitaria sangualis, P. psilopodium, with and without the addition of activated charcoal to the extract. Shoot lengths were also inhibited, but when charcoal was added D. sangualis showed greater shoot growth in lower concentrations (1%). Whereas the litter of L. camara had no significant inhibitory effects on heights of the plants, Cyperus rotandus, E. colonum, P. psilopodium, Commalina benghalensis and 4 rice varieties (Bansal, 1988). This shows that the effect of the allelochemical depends on the concentration of the extract, donor plant material, the form of application of allelopathic material and also on the plant species tested. The same results were found when Calicarpa acuminate aqueous leachate was applied; tomato seedling growth was inhibited (47%), but there was no effect on radicle growth of bean and maize seedlings (90.4% & 100% of control growth, respectively) (Ortega et al., 2002). Aqueous extracts of P. juliflora leaves showed inhibitory affects on both the radicle and plumule lengths of Cynodon dactylon (Al-Humaid & Warrag, 1998). The radical growth was affected greatly at higher concentrated of extracts of P. juliflora. But when the allelopathic effect of P. juliflora was tested on E. caducifolia by Sen and Chawan, the fresh stem (1:16) extracts promoted the growth of radicle and hypocotyls. The paired t-test of fresh weights of seedlings i.e., seed, shoot and root when compared with control, did not vary significantly in most of the treatments (Table 2). Results were similar in both fresh and dried extracts at all concentrations. According to earlier reports, most of the workers considered dry weights as a good measurement of growth. In the present experiment, when the dry weights were compared to control, most of the treatments showed stimulatory effect on biomass except fresh-5%-root, fresh-0.1% root and seed, 1%-root, seed, shoot, fresh- 5%-shoot, fresh increasing order treatment seed; although they were not significant statistically (Fig.1). When the dry weights were taken as the percentage of control, most of the treatments (Dried 0.1%, 1%, 2.5%, DT, Fresh-2.5%, IT, DT) showed more contribution of root in total seedling biomass. Seed contribution was similar in all the treatments. However, the contribution of shoot varied in different treatments (Fig.2). The results indicate that the extract from dried leaves had positive effect on the growth the seedlings. When Jennifer et al. (2005) tested the affect of allelopathic extracts of Minced autumn olive on Sycamore against water as control; they found significant reduction in biomass of root by 35%. A gradual decrease in both fresh and dry weights was observed with increasing concentrations in all the plant species tested with tamarind leaves when compared with control. The reduction in the fresh and dry weights ranged from 33-42% and 40-53% in the radicle and hypocotyle respectively (Drost and Doll, 1980; Parvez et al., 2003). Zhu et al. (2009) reported that the Populus tomentosa extracts inhibited the fresh and dry weights of its own seedlings. The 20-year old plants treatment lowered 14.01%-51.62% and % of fresh and dry weights respectively. The 45-years old P. tomentosa plants extract lowered the dry and fresh weights by 18.19%-58.97% and % respectively. It was also mentioned that, greater the concentration of aqueous leaf extracts, lower was the fresh and dry weights of seedlings when compared with their respective controls. In comparison with the dry weights of the seedlings, the inhibitory effect was greater on the fresh weight. But in the present experiment, results indicate that only the dry weights were affected by the treatments, and not fresh weights. After analyzing the results, it was clear that there was some correlation between lengths and biomass of different parts of the seedling, and to delve deeper in this, Pearson s co-relation test was carried out (Table 3). The results showed that there was significant negative co-relation between PR length and FW of seed at 0.05% significance level; FW of root and FW of shoot had Volume 2; Issue 12; December, 2014 Int.J.Curr.Biotechnol. 26

6 positive correlation at 0.05% significance level; and, the correlation between SRL and number of SR was positive at 0.01% significance level. It means the FW of seed and PR Length was inversely proportional to each other. Most of the workers had given importance only to the main root/radicle and considered its measurements as the growth of the complete root system, and ignored the seminal roots. SR is also a significant part of root system and has greater importance than primary root particularly in the case of monocotyledons. In the present study we observed that the number of seminal roots did not vary significantly in comparison to control, indicating it is not affected by the extracts (Table 2). After analysis of the results it is clear that there is a concentration level (a threshold level), where the allelochemical extracts starts acting in a negative way. Below that particular concentration there is no inhibitory effect, and thereafter the negative effect will increase with increase in the concentration of the extract. The inhibitory effect could only be seen in PRL of 5% treatment. The results of the other workers also indicated that at lower concentrations, effect of most of the allelochemicals was stimulatory or neutral. The effect of growth inhibiting substance becomes more evident at higher concentrations and the promoting influence become more prominent with higher dilutions of the extracts (Sen and Chawan, 1970). A very important point concerning allelopathy is that effect depends on the chemical compound being added to the environment (Hunter and Menges, 2009). Khailov (1974) demonstrated conclusively that the effect of any given compound can be inhibitory or stimulatory depending on the concentration of the compound in the surrounding medium. And, many inhibitory compounds can be stimulatory in small concentrations (Barnes et al., 1987; Hoffman et al., 1996). Conclusion We conclude that the generalization that one plant negatively affects other plants, should be used with caution. The influence of one plant on the other plant depends on many factors, among them the litter is only one factor. The other factors range from physicochemical properties of soil, climatic features, moisture in the soil, soil microbial community etc., besides the target species on which the effect is being tested. In most of the cases the concentration of the so called allelochemicals in the soil is determined by several factors; the concentration gradually builds up only under the canopy of the plant. If the litter of such plants is applied in the field for testing the effect on crops, its application rate could hardly reach the level where it can cause reduction in the growth of the crop plants. Hence, in the era of eroding soil fertility mainly due to decrease in the organic matter content of the soil, easily affordable litter sources should be used in proper manner to augment the paucity of nutrients in soil, because litter of most of the species of plants is stimulatory albeit the dosage should be decided cautiously. References Al-Humaid A.I., Warrag M.O.A., Allelopathic effects of mesquite (Prosopis juliflora) foliage on seed germination and seedling growth of bermudagrass (Cynodon dactylon). J. Arid. Environ. 38: Bansal G.L., Allelopathic effect of Lantana camara on rice and associated weeds under the midhill conditions of Himachal Pradesh, India, in: Olofsdotter, M. (Eds.), Allelopathy in rice. IRRI Barnes J.P., Putnam A.R., Burke B.A., Aasen A.J., Isolation and characterization of allelochemicals in rye herbage. 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7 ecology: allelochemical interactions. CRC, Boca Raton, Fla Khailov K.M., Biochemical trophodynamics in marine coastal ecosystems, Naukova Dumka, Kiev. Liu D.L., Lovett J.V., Biologically active secondary metabolites of barley. I. Developing techniques and assessing allelopathy in Barley. J. Chem. Ecol. 19: Warrag M.O.A., Autotoxic potential of foliage on seed germination and early growth of mesquite (Prosopis juliflora). J. Arid. Environ. 31: Zhu M., Wang Y., Liu B., Zhang L., Wang H., Yuan Y., Du K., Effects of aqueous leaf extracts of Populus tomentosa at different ages on the growth and photosynthetic characteristics of its own seedlings. Front. Agric. China. 32: Mollisch H., Der Eingfluss einer Pflanze aufdie andere- Allelopathie, Fischer, Jena. Nakano H., Fujji Y., Suzuki T., Yamada K., Kosemura S.S., Yamakura S., Suzuki T., Hassegawa K., A growth inhibitory substance exuded from freeze-dried mesquite (Prosopis juliflora (Sw) DC) leaves. Plant. Growth. Regul. 33: Nakano H., Fujji Y., Yamada K., Kosemura S., Yamamura S., Hasewaga K., Suzuki T., Isolation and identification of plant growth inhibitors as candidate(s) for allelopathic substance(s) from aqueous leachate from mesquite (Prosopis juliflora (Sw) DC) leaves. Plant. Growth. Regul. 37: Nakano H., Nakajima E., Fujji Y., Yamada K., Shigemori H., Hasegawa K., Leaching of allelopathic substance, L-tryptophan from the foliage of mesquite (Prosopis juliflora (Sw) DC) plants by water spraying. Plant. Growth. Regul. 40: Noor M., Salam U., Khan A.M., Allelopathic effects of Prosopis juliûora Swartz. J. Arid. Environ. 31: Jennifer O.S.P., Rudgers A.A., Clay K., Invasive plants can inhibit native tree seedlings: testing potential allelopathic mechanisms. Plant. Ecol. 181: Panasiuk O., Bills D.D., Leather G.R., Allelopathic influence of Sorghum bicolor on weeds during germination and early development of seedlings. J. Chem. Ecol. 12: Parvez S.S., Parvez M.M., Nishihara E., Gemma H., Fujji Y., Tamaridus indica L. leaf is a source of allelopathic substance. Plant. Growth. Regul. 40: Rizvi S.J.H., Rizvi V., Allelopathy: Basic and applied aspects. Chapman and Hall, London. Schmidt S.K., Ley R., Microbial competition and soil structure limit the expression of allelochemicals in nature. In: Inderjit., Dakshini K.M.M., Foy C.L. (Eds.), Principles and practices in plant ecology: allelochemical interactions. CRC, Boca Raton, Fla Sankhla N., Baxi, M.D., Chatterji, U.N., Ecophysiological studies on arid zone plants. I. Phytotoxic effects of aqueous extract of mesquite, Prosopis juliflora DC. Curr. Sci. 21: Sen D.N., Chawan D.D., Ecology of desert plant and observation on their seedlings: III: The influence of aqueous extracts of Prosopis juliflora DC on Euphorbia cardifolia Haines. Vegetatio. 21: Volume 2; Issue 12; December, 2014 Int.J.Curr.Biotechnol. 28