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Investigation of Allelopathic Potentiality of the Himalyan Lichen Parmelia Reticulata Tayl. Against Phalaris Minor Retz.
Available online at www.sciencedirect.com
ScienceDirect APCBEE Procedia 9 (2014) 140 – 144
2013 5th International Conference on Chemical, Biological and Environmental Engineering (ICBEE 2013) 2013 2nd International Conference on Civil Engineering (ICCEN 2013)
Investigation of Allelopathic Potentiality of the Himalyan Lichen Parmelia reticulata Tayl. against Phalaris minor retz. Mayurika Goela, Archna Ranib , P. Durejaa and P. Uniyalc a
b
Division of Agricultural Chemicals, Indian Agricultural Research Institute, New Delhi, India Department of Applied Chemistry, Delhi Technological University, (Delhi College of Engineering), New Delhi, India c Department of Botany, University of Delhi, Delhi, India
Abstract Allelopathic potentiality of hexane , ethyl acetate and methanol extracts of the Himalyan lichen, Parmelia reticulate Taylor, at different concentrations (50, 25 and 12.5μg ml-1) was studied on germination and early seedling growth of highly devastating weed Phalaris minor. The experiments were carried out in portray maintained in natural environment. Current investigation has revealed concentration dependent allelopathic phenomenon of the lichen extracts on P. minor. Hexane and ethyl acetate extracts at 50 μg ml-1 exhibited maximum detrimental effect on seed germination (56 % as compared to control i.e. 90%). Hexane extract at 50 μg ml-1 showed maximum inhibition of early seedling growths, determined in terms of shoot and root lengths of the test weed. It reduced shoot and root lengths to 2.5cm (control 10.7 cm) and 0.9 cm (control 3.4cm) respectively, indicating semipolar nature of constituents responsible for bioactivity.
© 2014 2013Archna Published by Elsevier B.V. Selection and/or peer review under responsibility of Asia-Pacific © Rani. Published by Elsevier B.V. Selection andBiological peer review & under responsibility of Asia-Pacific Chemical, Chemical, Environmental Engineering Society Biological & Environmental Engineering Society Keywords: Allelopathic, Parmelia reticulate Taylor, Phalaris minor
1.
Introduction
After severe setback arising from the detrimental effects associated with the use of conventional synthetic crop protectants, efforts to explore allelochemicals have gained momentum. Because of natural origin, these products can be relatively broad spectrum, bioefficacious, biodegradable and environmentally safe [1].
Corresponding author, fax: +91-11-27871023. E-mail address: [email protected]
2212-6708 © 2014 Archna Rani. Published by Elsevier B.V. Selection and peer review under responsibility of Asia-Pacific Chemical, Biological & Environmental Engineering Society doi:10.1016/j.apcbee.2014.01.025
Mayurika Goel et al. / APCBEE Procedia 9 (2014) 140 – 144
141
Lichens, in this context, are catching the attention of scientists worldwide as new significant sources of bioactive substances [2-5]. Lichens are symbiotic organisms composed of a fungal partner (mycobiont) in association with one or more photosynthetic partners (photobiont) [6]. They commonly grow on rock surfaces, poorly developed soils such as those found in arid lands and boreal arctic regions and as epiphytes on trees and shrubs [7]. The lichen-forming fungi produce antibiotic secondary metabolites and provide protection from animals and pathogenic microorganisms [8]. Their metabolites are structurally unique and highly active in comparison to plant metabolites [8]. The distribution pattern of secondary metabolites is greatly affected by varying conditions of climate, availability of nutrients, substrates, pH, temperature, light, humidity, stress, topography and varied altitude of the area [9-14]. Lichen metabolites have been shown to be toxic and feeding deterrent to insect larvae [15]. Several lichen extracts have been used for various remedies in folk medicine, and screening tests with lichens have shown the frequent occurrence of metabolites with antibiotic, antimycobacterial, antiviral, antitumor, analgesic and antipyretic properties [16, 17]. In spite of possessing remarkable bioactivity the agrochemical potential of lichens have not been explored to its fullest. In accordance with these facts, a comprehensive investigation has been initiated aiming at the survey, collection and chemical and biological screening of lichens from the under collected habitats of Kilberi forest ranges (Northern Himalayas) in the Uttaranchal State (Uttarakhand) [18, 19]. In this paper we report herbicidal activity of solvent extracts of P. reticulata Tayl. in vitro against Phalaris minor. 2.
Experimental
2.1. Materials Samples of Parmelia reticulata Tayl. were collected from bark of trees, shrubs and on rocks of Kilberi forest ranges (Northern Himalayas) in the Uttaranchal State (Uttarakhand), India and air-dried. A specimen was deposited in the herbarium of the Department of Botany, University of Delhi, Delhi, India (voucher number DUH 13531). Laboratory grade reagents were procured locally. The solvents used were of analytical grade (AR). Seeds of P. minor Retz. were collected from Division of Agronomy, Indian Agricultural Research Institute, New Delhi. 2.2. Solvent extraction of lichen material The lichen thalli were washed thoroughly with water to remove dust particles and dried at room temperature. The air-dried mass was powdered with a mortar and pestle. The powdered material (50 g) was subjected to soxhlet extraction using hexane followed by ethyl acetate and finally with methanol (500 ml) 6 h for each. The solvent was evaporated in vacuo, and the dried residues obtained were stored at 40C for further biological screening. 2.3. In vitro Biological screening The effect of different solvent extracts at concentrations 50, 25 and 12.50 μg ml-1 on germination and early seedling growth of P. minor was evaluated. The experiments were carried out in portray maintained in natural environment in the National Phytotron Facility, India Agricultural Research Institute (IARI). The concentrations of each solvent extract were prepared containing 1% Tween 20 and minimum amount of acetone to dissolve the extract and the volume was made up to 5 ml in water. Thirty seeds of equal size were soaked overnight in above solutions of different extracts. These soaked seeds were removed from the aqueous solutions and dried in the air, to give a uniform layer of the extract on the seed coat. These coated seeds were
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Mayurika Goel et al. / APCBEE Procedia 9 (2014) 140 – 144
placed in the portrays maintained in natural environment of growth room at 180C and 12 hours daily light periods. Seeds were considered germinated, if a radical protruded at least 1 mm. Root and shoot lengths of the seedlings were measured after 15 days. Each bioassay was replicated 3 times in a complete randomized design. The control treatments for all sets contained the same quantities of 1% Tween 20 and distilled water. The allelopathic efficacy of lichen extracts was calculated in terms of percentage inhibition of seed germination, and root/shoot lengths as shown in equation (1). Root / shoot length in control (cm) Root / shoot length in treatment (cm) (1) u100 % Inhibtion Root / shoot length in control (cm) 3.
Results and Discussion
The effect of hexane, ethyl acetate and methanol extract of P. reticulata on seed germination, shoot length and root length of P. minor is shown in table 1and figure 1a-c. Table 1. Effect of hexane, ethyl acetate and methanol extracts of P. reticulata on seed germination, shoot length and root length of P. Minor Extract
Hexane
Concentration (μg ml-1)
% Germination (% Inhibition)
Shoot length (cm) (%Inhibition)
Control
90 ± 1.86 (0.00)
10.7 ±0.08 (0.00)
3.4 ± 0.16 (0.00)
56 ± 2.64 (37.77) 57 ± 1.73 (36.66) 79 ± 1.00 (12.22)
2.5 ±0.08 (76.63) 4.7 ±0.11 (56.07) 6.0 ±0.15 (43.92)
0.9±0.14 (73.52) 1.4±0.17 (58.82) 2.6±0.16 (23.52)
56 ± 0.81 (26.66) 63 ± 1.24 (25.55) 77 ± 1.73 (15.55)
4.6 ± 0.09 (57.00) 5.4 ± 0.09 (49.53) 7.4 ± 0.12 (30.84)
1.5 ± 0.12 (55.88) 1.8 ± 0.12 (47.05) 1.9 ± 0.10 (44.11)
50 25 12.5
Ethyl acetate
50 25 12.5
Root length (cm) (%Inhibition)
66 ± 1.73 6.3 ± 0.11 1.5 ± 0.11 (26.66) (41.12) (55.88) 67 ± 2.64 6.8 ± 0.09 2.7 ± 0.17 25 (30.00) (36.44) (20.58) 76 ± 2.64 7.3 ± 0.11 2.9 ± 0.13 12.5 (14.44) (31.77) (14.70) Mean percentage seed germination, shoot length and root length used for calculation, is an average of three replicates and standard deviation ranged from 0.81 to 2.64, 0.08 to 0.15 and 0.10 to 0.17 respectively. Values given in parentheses indicate % inhibition in terms of seed germination, shoot length and root length as compared to the control. Methanol
50
The above results revealed that the allelopathic efficacy of lichen extracts depends upon i) the solvent used for extraction: In general, hexane extract exhibited maximum allelopathic effect followed by ethyl acetate and methanol extracts and ii) the treatment dose: the detrimental effects of extracts are more prominent at higher
143
Mayurika Goel et al. / APCBEE Procedia 9 (2014) 140 – 144
concentrations. The percentage inhibition of seed germination, shoot and root lengths by hexane, ethyl acetate and methanol extracts at different concentration was observed in the range of 12.22-37.77%, 43.92-76.63%, 23.52-73.52%; 15.55-26.66%, 30.84-57.00, 44.11-55.88% and 14.44-26.66, 31.77-41.12, 14.70-55.88% respectively. Furthermore, at maximum concentration of 50 μg ml-1 the percentage inhibition of seed germination, shoot and root lengths was found to be 37.77, 76.63, 73.52% by hexane extract; 26.66, 57.00, 55.88% by ethyl acetate; and 26.66, 41.12, 55.88% by methanol extract. From comparative analysis of the data it is also evident that the extracts are more effective in reducing the early seedling growth than in suppressing the seed germination. It may be attributed to the hard impermeable seed coat which protects the seeds from outer incompatible environment. It is therefore, the weed is highly competitive and can cause significant yield losses under favourable conditions. 25μg/ml
12.5μg/ml
50μg/ml
25μg/ml
12.5μg/ml
50μg/ml
25μg/ml
12.5μg/ml
12
4 0
Solvent extracts (a)
Root length (cm)
12
8
Shoot length(cm)
Shoot length (cm)
50μg/ml
8 4 0
Solvent extracts (b)
4 2 0
Solvent extracts (c)
Fig. 1. Effect of hexane, ethyl acetate and methanol extract of P. reticulata on (a) seed germination (b) shoot length and (c) root length of P. minor
Thus, the current investigation established that hexane extract at 50 μg ml-1 concentration possesses highest in vitro allelopathic efficacy against P. minor indicating the semipolar nature of constituents responsible for bioactivity. 4.
Conclusions
Weeds are any undesirable plants grown in field along with the main crop plants. After microbial phytopathogens, weeds are the next main agricultural yield limiting factors in most parts of the world. In particular, Phalaris minor Retz has been identified as a serious weed of wheat and barley fields in India, USA, Canada, Africa, Australia, France, Pakistan, Iran, Iraq and Mexico [20, 21]. Furthermore, a rice- wheat crop rotation also stimulated its emergence, growth and development [22]. Due to morphological similarity of P. minor with wheat, manual weeding at early stages is difficult. Synthetic herbicides are the preferred methods for its management due to their efficacy and cost effectiveness, even though, their increased use poses serious environmental hazards and public health concerns [23-25]. It provides a compelling justification for the current investigation aimed to explore newer natural resources of safer crop protectants. The results obtained highlight the potentiality of lichens as a reservoir of future agrochemicals. References [1] Cutler HG, Cutler SJ. Biological active natural products: Agrochemicals, Boca Raton, Florida, USA: CRC Press Inc.; 1999. [2] Kowalski M, Hausner G,Michele D. Piercey-Normore. Bioactivity of secondary metabolites and thallus extracts from lichen fungi. Mycoscience 2011; 52 (6): 413-418.
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Mayurika Goel et al. / APCBEE Procedia 9 (2014) 140 – 144
[3] Eisenreich W, Knispel N, Beck A. Advanced methods for the study of the chemistry and the metabolism of lichens. Phytochemistry Reviews 2011; 10 (3): 445-456. [4] Shukla V, Joshi GP, Rawat M S M. Lichens as a potential natural source of bioactive compounds: a review. Phytochemistry Reviews 2010; 9:303- 314. [5] Boustie J, Tomasi S, Grube M. Bioactive lichen metabolites: alpine habitats as an untapped source. Phytochemistry Reviews 2011; 10( 3): 287-307 [6] Nash TH. Lichen Biology, Cambridge: Cambridge University Press, 1996 [7] Taylor TN, Hass H, Wand R, Kerp H. The oldest fossil lichen. Nature 1995; 378: 244. [8] (a) Lawrey, JD. Biological Role of Lichen Substances. The Bryologist 1986; 89(2): 111-122. (b) Lawrey J D. Lichen secondary compounds: evidence for a correspondence between antiherbivore and antimicrobial function. The Bryologist 1989; 92:326-328. [9] Bjerke JW, Lerfall K, Elvebakk A. Effects of ultraviolet radiation and PAR on the content of usnic and divaricatic acids in two arctic-alpine lichens. Photochem Photobiol Sci 2002; 1 (9): 678-85. [10] Bjerke JW, Joly D, Nilsen L, Brossard T. Spatial trends in usnic acid concentrations of the lichen Flavocetraria nivalis along local climatic gradients in the Arctic (Kongsfjorden, Svalbard). Polar Biology 2004; 27(7): 409-417. [11] Bjerke JW, Elvebakk A, Domínguez E, Dahlback. A Seasonal trends in usnic acid concentrations of Arctic, alpine and Patagonian populations of the lichen Flavocetraria nivalis. Phytochemistry 2005; 66(3):337-44 [12] Rubio C, Fernández E, Hidalgo ME, and Quilhot W. Effects of solar UV-B radiation in the accumulatio of rhizocarpic acid in a lichen species from alpine zones of Chile. Bol. Soc. Chil. Quím 2002; 47(1): 67-72. [13] Vicente C, Ruiz JL, Estevez M.P. Mobilization of usnic acid in Evernia prunastri under critical conditions of nutrient availability. Phyton: international journal of experimental botany 1980; 39: 15-20. [14] Hager A, Brunauer G, Türk R, Stocker-Wörgötter E. Production and Bioactivity of Common Lichen Metabolites as Exemplified byHeterodea muelleri (Hampe) Nyl. Journal of Chemical Ecology 2008; 34( 2): 113-120 [15] Emmerich, R., Giez, I., Lange, OL, Proksch, P. Toxicity and antifeedant activity of lichen compounds against the polyphagous herbivorous insect Spodoptera littoralis. Phytochemistry1993; 33: 1389-1394. [16] (a)Podterob A P. Chemical composition of lichens and their medical applications. Pharmaceutical Chemistry Journal 2008; 42(10): 582-588; (b)Huneck S. The significance of lichens and their metabolites. Naturwissenschaften , 1999; 86(12): 559-570, [17] (a) Kosanić M, Ranković B, Vukojević J. Antioxidant properties of some lichen species. Journal of Food Science and Technology 2011; 48(5): 584-590. (b) Shrestha G, Larry L. St. Clair. Lichens: a promising source of antibiotic and anticancer drugs. Phytochemistry Reviews 2013; 12(1): 229-244. [18] Goel M, Dureja P, Rani A, Uniyal P L, Laatsch H. Isolation, characterization and antifungal activity of major constituents of the Himalayan Lichen Parmelia reticulata Tayl. J. Agric. Food Chem 2011; 59 (6): 2299-2307. [19] Goel M, SharmaP K, Dureja P, Rani A, Uniyal P L.Antifungal activity of extracts of the lichens Parmelia reticulata, Ramalina roesleri, Usnea longissima and Stereocaulon himalayense. Arch Phytopathology Plant Protect. 2011; 44(13): 1300-1311. [20] Holm L,Pacho JV, Herberger JP, Plucknett DL. A geographical atlas of world weeds, New York:Wiley 1979. [21] Shad R, Siddiqui S, Problems Associated with Phalaris minor and Other Grass Weeds in India and Pakistan. Experimental agriculture 1996; 32: 151-160. [22] Chhokar RS, Sharma RK, Singh RK and Gill SC. Herbicide resistance in littleseed canarygrass (Phalaris minor) and its management. Global Issues. Paddock Action." Edited by Unkovich M. Proceedings of 14th Agronomy Conference, Adelaide, South Australia, September 2008, 21-25. [23] Gupta PK, Herbicides and fungicides chapter 39 in Reproductive and Developmental Toxicology (editor Gupta RC) : Academic Press; 2011; 503-521 [24] Bradberry SM, Watt BE, Proudfoot AT, Vale JA. Mechanisms of toxicity, clinical features, and management of acute chlorophenoxy herbicide poisoning: a review. J Toxicol Clin Toxicol. 2000; 38(2):111-22. [25] Aktar W, Sengupta D, and Chowdhury A. Impact of pesticides use in agriculture: their benefits and hazards. Interdiscip Toxicol. 2009; 2(1): 1–12.
ScienceDirect APCBEE Procedia 9 (2014) 140 – 144
2013 5th International Conference on Chemical, Biological and Environmental Engineering (ICBEE 2013) 2013 2nd International Conference on Civil Engineering (ICCEN 2013)
Investigation of Allelopathic Potentiality of the Himalyan Lichen Parmelia reticulata Tayl. against Phalaris minor retz. Mayurika Goela, Archna Ranib , P. Durejaa and P. Uniyalc a
b
Division of Agricultural Chemicals, Indian Agricultural Research Institute, New Delhi, India Department of Applied Chemistry, Delhi Technological University, (Delhi College of Engineering), New Delhi, India c Department of Botany, University of Delhi, Delhi, India
Abstract Allelopathic potentiality of hexane , ethyl acetate and methanol extracts of the Himalyan lichen, Parmelia reticulate Taylor, at different concentrations (50, 25 and 12.5μg ml-1) was studied on germination and early seedling growth of highly devastating weed Phalaris minor. The experiments were carried out in portray maintained in natural environment. Current investigation has revealed concentration dependent allelopathic phenomenon of the lichen extracts on P. minor. Hexane and ethyl acetate extracts at 50 μg ml-1 exhibited maximum detrimental effect on seed germination (56 % as compared to control i.e. 90%). Hexane extract at 50 μg ml-1 showed maximum inhibition of early seedling growths, determined in terms of shoot and root lengths of the test weed. It reduced shoot and root lengths to 2.5cm (control 10.7 cm) and 0.9 cm (control 3.4cm) respectively, indicating semipolar nature of constituents responsible for bioactivity.
© 2014 2013Archna Published by Elsevier B.V. Selection and/or peer review under responsibility of Asia-Pacific © Rani. Published by Elsevier B.V. Selection andBiological peer review & under responsibility of Asia-Pacific Chemical, Chemical, Environmental Engineering Society Biological & Environmental Engineering Society Keywords: Allelopathic, Parmelia reticulate Taylor, Phalaris minor
1.
Introduction
After severe setback arising from the detrimental effects associated with the use of conventional synthetic crop protectants, efforts to explore allelochemicals have gained momentum. Because of natural origin, these products can be relatively broad spectrum, bioefficacious, biodegradable and environmentally safe [1].
Corresponding author, fax: +91-11-27871023. E-mail address: [email protected]
2212-6708 © 2014 Archna Rani. Published by Elsevier B.V. Selection and peer review under responsibility of Asia-Pacific Chemical, Biological & Environmental Engineering Society doi:10.1016/j.apcbee.2014.01.025
Mayurika Goel et al. / APCBEE Procedia 9 (2014) 140 – 144
141
Lichens, in this context, are catching the attention of scientists worldwide as new significant sources of bioactive substances [2-5]. Lichens are symbiotic organisms composed of a fungal partner (mycobiont) in association with one or more photosynthetic partners (photobiont) [6]. They commonly grow on rock surfaces, poorly developed soils such as those found in arid lands and boreal arctic regions and as epiphytes on trees and shrubs [7]. The lichen-forming fungi produce antibiotic secondary metabolites and provide protection from animals and pathogenic microorganisms [8]. Their metabolites are structurally unique and highly active in comparison to plant metabolites [8]. The distribution pattern of secondary metabolites is greatly affected by varying conditions of climate, availability of nutrients, substrates, pH, temperature, light, humidity, stress, topography and varied altitude of the area [9-14]. Lichen metabolites have been shown to be toxic and feeding deterrent to insect larvae [15]. Several lichen extracts have been used for various remedies in folk medicine, and screening tests with lichens have shown the frequent occurrence of metabolites with antibiotic, antimycobacterial, antiviral, antitumor, analgesic and antipyretic properties [16, 17]. In spite of possessing remarkable bioactivity the agrochemical potential of lichens have not been explored to its fullest. In accordance with these facts, a comprehensive investigation has been initiated aiming at the survey, collection and chemical and biological screening of lichens from the under collected habitats of Kilberi forest ranges (Northern Himalayas) in the Uttaranchal State (Uttarakhand) [18, 19]. In this paper we report herbicidal activity of solvent extracts of P. reticulata Tayl. in vitro against Phalaris minor. 2.
Experimental
2.1. Materials Samples of Parmelia reticulata Tayl. were collected from bark of trees, shrubs and on rocks of Kilberi forest ranges (Northern Himalayas) in the Uttaranchal State (Uttarakhand), India and air-dried. A specimen was deposited in the herbarium of the Department of Botany, University of Delhi, Delhi, India (voucher number DUH 13531). Laboratory grade reagents were procured locally. The solvents used were of analytical grade (AR). Seeds of P. minor Retz. were collected from Division of Agronomy, Indian Agricultural Research Institute, New Delhi. 2.2. Solvent extraction of lichen material The lichen thalli were washed thoroughly with water to remove dust particles and dried at room temperature. The air-dried mass was powdered with a mortar and pestle. The powdered material (50 g) was subjected to soxhlet extraction using hexane followed by ethyl acetate and finally with methanol (500 ml) 6 h for each. The solvent was evaporated in vacuo, and the dried residues obtained were stored at 40C for further biological screening. 2.3. In vitro Biological screening The effect of different solvent extracts at concentrations 50, 25 and 12.50 μg ml-1 on germination and early seedling growth of P. minor was evaluated. The experiments were carried out in portray maintained in natural environment in the National Phytotron Facility, India Agricultural Research Institute (IARI). The concentrations of each solvent extract were prepared containing 1% Tween 20 and minimum amount of acetone to dissolve the extract and the volume was made up to 5 ml in water. Thirty seeds of equal size were soaked overnight in above solutions of different extracts. These soaked seeds were removed from the aqueous solutions and dried in the air, to give a uniform layer of the extract on the seed coat. These coated seeds were
142
Mayurika Goel et al. / APCBEE Procedia 9 (2014) 140 – 144
placed in the portrays maintained in natural environment of growth room at 180C and 12 hours daily light periods. Seeds were considered germinated, if a radical protruded at least 1 mm. Root and shoot lengths of the seedlings were measured after 15 days. Each bioassay was replicated 3 times in a complete randomized design. The control treatments for all sets contained the same quantities of 1% Tween 20 and distilled water. The allelopathic efficacy of lichen extracts was calculated in terms of percentage inhibition of seed germination, and root/shoot lengths as shown in equation (1). Root / shoot length in control (cm) Root / shoot length in treatment (cm) (1) u100 % Inhibtion Root / shoot length in control (cm) 3.
Results and Discussion
The effect of hexane, ethyl acetate and methanol extract of P. reticulata on seed germination, shoot length and root length of P. minor is shown in table 1and figure 1a-c. Table 1. Effect of hexane, ethyl acetate and methanol extracts of P. reticulata on seed germination, shoot length and root length of P. Minor Extract
Hexane
Concentration (μg ml-1)
% Germination (% Inhibition)
Shoot length (cm) (%Inhibition)
Control
90 ± 1.86 (0.00)
10.7 ±0.08 (0.00)
3.4 ± 0.16 (0.00)
56 ± 2.64 (37.77) 57 ± 1.73 (36.66) 79 ± 1.00 (12.22)
2.5 ±0.08 (76.63) 4.7 ±0.11 (56.07) 6.0 ±0.15 (43.92)
0.9±0.14 (73.52) 1.4±0.17 (58.82) 2.6±0.16 (23.52)
56 ± 0.81 (26.66) 63 ± 1.24 (25.55) 77 ± 1.73 (15.55)
4.6 ± 0.09 (57.00) 5.4 ± 0.09 (49.53) 7.4 ± 0.12 (30.84)
1.5 ± 0.12 (55.88) 1.8 ± 0.12 (47.05) 1.9 ± 0.10 (44.11)
50 25 12.5
Ethyl acetate
50 25 12.5
Root length (cm) (%Inhibition)
66 ± 1.73 6.3 ± 0.11 1.5 ± 0.11 (26.66) (41.12) (55.88) 67 ± 2.64 6.8 ± 0.09 2.7 ± 0.17 25 (30.00) (36.44) (20.58) 76 ± 2.64 7.3 ± 0.11 2.9 ± 0.13 12.5 (14.44) (31.77) (14.70) Mean percentage seed germination, shoot length and root length used for calculation, is an average of three replicates and standard deviation ranged from 0.81 to 2.64, 0.08 to 0.15 and 0.10 to 0.17 respectively. Values given in parentheses indicate % inhibition in terms of seed germination, shoot length and root length as compared to the control. Methanol
50
The above results revealed that the allelopathic efficacy of lichen extracts depends upon i) the solvent used for extraction: In general, hexane extract exhibited maximum allelopathic effect followed by ethyl acetate and methanol extracts and ii) the treatment dose: the detrimental effects of extracts are more prominent at higher
143
Mayurika Goel et al. / APCBEE Procedia 9 (2014) 140 – 144
concentrations. The percentage inhibition of seed germination, shoot and root lengths by hexane, ethyl acetate and methanol extracts at different concentration was observed in the range of 12.22-37.77%, 43.92-76.63%, 23.52-73.52%; 15.55-26.66%, 30.84-57.00, 44.11-55.88% and 14.44-26.66, 31.77-41.12, 14.70-55.88% respectively. Furthermore, at maximum concentration of 50 μg ml-1 the percentage inhibition of seed germination, shoot and root lengths was found to be 37.77, 76.63, 73.52% by hexane extract; 26.66, 57.00, 55.88% by ethyl acetate; and 26.66, 41.12, 55.88% by methanol extract. From comparative analysis of the data it is also evident that the extracts are more effective in reducing the early seedling growth than in suppressing the seed germination. It may be attributed to the hard impermeable seed coat which protects the seeds from outer incompatible environment. It is therefore, the weed is highly competitive and can cause significant yield losses under favourable conditions. 25μg/ml
12.5μg/ml
50μg/ml
25μg/ml
12.5μg/ml
50μg/ml
25μg/ml
12.5μg/ml
12
4 0
Solvent extracts (a)
Root length (cm)
12
8
Shoot length(cm)
Shoot length (cm)
50μg/ml
8 4 0
Solvent extracts (b)
4 2 0
Solvent extracts (c)
Fig. 1. Effect of hexane, ethyl acetate and methanol extract of P. reticulata on (a) seed germination (b) shoot length and (c) root length of P. minor
Thus, the current investigation established that hexane extract at 50 μg ml-1 concentration possesses highest in vitro allelopathic efficacy against P. minor indicating the semipolar nature of constituents responsible for bioactivity. 4.
Conclusions
Weeds are any undesirable plants grown in field along with the main crop plants. After microbial phytopathogens, weeds are the next main agricultural yield limiting factors in most parts of the world. In particular, Phalaris minor Retz has been identified as a serious weed of wheat and barley fields in India, USA, Canada, Africa, Australia, France, Pakistan, Iran, Iraq and Mexico [20, 21]. Furthermore, a rice- wheat crop rotation also stimulated its emergence, growth and development [22]. Due to morphological similarity of P. minor with wheat, manual weeding at early stages is difficult. Synthetic herbicides are the preferred methods for its management due to their efficacy and cost effectiveness, even though, their increased use poses serious environmental hazards and public health concerns [23-25]. It provides a compelling justification for the current investigation aimed to explore newer natural resources of safer crop protectants. The results obtained highlight the potentiality of lichens as a reservoir of future agrochemicals. References [1] Cutler HG, Cutler SJ. Biological active natural products: Agrochemicals, Boca Raton, Florida, USA: CRC Press Inc.; 1999. [2] Kowalski M, Hausner G,Michele D. Piercey-Normore. Bioactivity of secondary metabolites and thallus extracts from lichen fungi. Mycoscience 2011; 52 (6): 413-418.
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