International Research Journal of Biological Sciences ___________________________________ ISSN 2278-3202Vol. 4(7), 73-78, July (2015) Int. Res. J. Biological Sci. International Science Congress Association 73 Natural Mycorrhizal Colonization of Plant Species growing in a Limestone Mine Spoil: Case Study from ACC, Coimbatore, IndiaLogaprabha V. and Tamilselvi K.S. Department of Botany, PSGR Krishnammal College for Women, Peelamedu, Coimbatore, Tamil Nadu – 641004, INDIA Available online at: www.isca.in, www.isca.me Received 25th April 2015, revised 19th May 2015, accepted 30th June 2015 Abstract In the present study we examined the Arbuscular mycorrhizal association in forty seven angiospermic plants of the limestone mine spoils of Coimbatore, India. Forty one plants were colonized by AM fungi while Achyranthes aspera, Aerva lanata, Amaranthus viridis, Alternanthera pungens, (Amarantaceae), Carex speciosa (Cyperaceae)and Argemone mexicana (Papavaraceae) did not possess mycorrhizal association. Some of the common non-mycorrhizal plants, viz., Boerhaavia diffusa, Commelina bhengalensis and Trianthema portulacastrum were found to be associated with AM fungi. The soils of the study area were calcareous, sandy loam with a slight alkaline pH and low in available nutrients. A total of ten AMF spores were identified, which included the genus Acaulospora, Gigaspora and Glomus. Glomus was the most frequent genus observed in the study area. Keywords: Mine spoils, limestone, ACC, Madukkarai, rhizosphere.Introduction Mine spoils are the overburden dumps of waste rocks removed by opencast mining operations. Mine spoils are unstable, physically, chemically and biologically disturbed ecosystems. The soil profile, microbial biota and nutritional aspects are greatly altered and hence vegetation in mine spoils is almost nil. The establishment of a stable nutrient cycle from plant growth and microbial processes is the most important step required in the long term mine spoil reclamation1-3. Arbuscular mycorrhizal fungi had been reported to be the effective micro-organism in mine reclamation4-6. They are obligate symbionts, which improves the plant to access the limited soil minerals like nitrogen, phosphorus and potassium in exchange for the photosynthetic products. Mycorrhiza can promote plant growth, enhance the soil structure, and thereby maintain the stability of the ecosystem. The present study reveals the mycorrhizal status of the plants found in a naturally revegetated limestone mine spoils of Coimbatore, India. Material and Methods Study site: The experimental site is the different aged limestone mine spoil dumps located around the Associated Cement Carriers factory, at Madukkarai, Coimbatore. The study area, limestone mine spoil dumps at Madukkarai is located 2.5 km around ACC Ltd., which lies about 10 km from Coimbatore, on NH 47 connecting Cochin and Salem. Sampling: Sampling was done for a period of two years from September 2011 to August 2013. The study area was surveyed periodically every month, for the availability of plants in the different aged mine spoils. The rhizosphere soil was collected at a depth of 3-30 cm, where most root proliferation occurs. The soil was brought to the laboratory in clean polythene bags, shade dried and stored at 2 - 5°C until further analysis. Roots from the plants were collected by digging out the soil and carefully removing the roots without damaging them. Soil analysis: The physico-chemical properties of the soil such as texture, pH, EC, available nitrogen (Kjeldahl method)10, available phosphorus (Bray I method)10 and available potassium11 were analysed. Mycorrhizal Colonization: The fine roots were carefully removed, washed free of soil in running tap water without damaging the external mycelium and cut into 1-2 cm long segments. The root bits were preserved in FAA (Formalin Acetic acid Alcohol – Formaldehyde, Glacial Acetic Acid and Ethanol in the ratio 1:1:18, respectively) immediately after collection. Percent root colonization of AM fungi was measured according to the root clearing and staining technique12. Fixed roots were thoroughly washed and cleared in 2.5% KOH13, acidified with 5N HCl and stained with trypan blue (0.05% in lactophenol). Darkly stained roots were bleached using 3% . The roots were left overnight in the dye for staining and the excess stain was removed in clear lactophenol. The root segments were mounted on slides using polyvinyl lactoglycerol as a mounting medium and examined under compound microscope for the vesicles, arbuscules and hyphae. The slides were made semi-permanent by sealing the edges of the cover slip with DPX mountant. Isolation of AM spores: The AM spores were isolated from the soil sample by following the wet-sieving and decanting Research Journal of Biological Sciences ___________________________________________________________ ISSN 2278-3202 Vol. 4(7), 73-78, July (2015) Int. Res. J. Biological Sci. International Science Congress Association 74 technique developed by Gerdemann and Nicolson14. One hundred grams of the soil sample were suspended in a litre of water. Heavier soil particles were allowed to settle down gradually and the liquid was decanted through nested sieves of 37µm to 710µm. The residues from the sieves were washed into separate beakers and collected over a filter paper. Each filter paper was spread over a glass plate and the spores were counted under an appropriate magnification (x100) of a stereo microscope. The spore population was expressed as the number of spores 100 gram-1 of soil. Intact spores were mounted using polyvinyl lacto glycerol and identified using Schenck and Perez manual15 and Trappe16. Spores were identified based on spore morphology and sub cellular characters and compared with original descriptions17. Spore morphology was also compared with the culture database established by INVAM Results and Discussion Physico-chemical properties of the study area: The soils in the study sites were calcareous, sandy loam with a slight alkaline pH and low in available nutrients (table-1). The pH varied between 7.88 and 8.81. Electrical conductivity ranged from 0.41 to 3.07 dSm-1. The amount of available N, P and K ranged from 108 to 179 kg/ha, 7 to 18 kg/ha and 102 to 1552 kg/ha respectively. Occurrence of mycorrhiza: In the present study, 47 plants were collected, of which the major families were Amarantaceae, Asteraceae and Euphorbiaceae. Among the 47 plant species, 41 were colonized by AM fungi (Table 2). AM fungal colonization was absent in Achyranthes aspera, Aerva lanata, Amaranthus viridis, Alternanthera pungens, (Amarantaceae), Carex speciosa(Cyperaceae) and Argemone mexicana (Papavaraceae). Majority of the plants under study were herbs (38), few were shrubs (7) and only 2 trees. Vesicular colonization was noticed in 37 species, viz.,Ruellia tuberosa, Peristrophe bicalyculata(Acanthaceae), Catharanthus roseus (Apocynaceae), Pergularia daemia (Asclepediaceae), Conyza bonariensis, Eclipta prostrata, Eupatorium odoratum, Parthenium hysterophorus, Taraxacum officianale, Tridax procumbens, Vernonia cinerea (Asteraceae), Tecoma stans (Bignoniaceae), Cassis occidentalis(Caesalpiniaceae), Commelina bhenghalensis (Commelinaceae), Ipomoea indica, I. obscura (Convolvulaceae), Coccinia grandis (Cucurbitaceae), Acalypha indica, Croton bonplandianum, Euphorbia hirta, E. hypericifolia, E. prostrata, Phyllanthus niruri (Euphorbiaceae), Abutilon indicum (Malvaceae), Tinospora cordifolia (Menispermaceae), Prosopis juliflora (Mimosaceae), Muntingia calabura (Muntingiaceae), Boerhaavia diffusa (Nyctaginaceae), Passiflora foetida (Passifloraceae), Plumbago zeylanica (Plumbaginaceae), Chloris barbata, Cynodon dactylon, (Poaceae), Santalum album (Santalaceae), Scoparia dulcis (Scrophulariaceae), Datura metel, Solanum nigrum (Solanaceae), Lantana camara (Verbenaceae). Arbuscular colonization was observed only in 16 plant species out of the 47 studied. They were Catharanthus roseus(Apocynaceae), Eupatorium odoratum, Taraxacum officianale, Tridax procumbens (Asteraceae), Tecoma stans (Bignoniaceae), Ipomoea obscura (Convolvulaceae), Melothriamadaraspatana (Cucurbitaceae), Acalypha indica, Croton bonplandianum, Euphorbia hirta, E. prostrata, Phyllanthus niruri (Euphorbiaceae), Passiflora foetida (Passifloraceae), Scoparia dulcis (Scrophulariaceae), Datura metel, Solanum nigrum (Solanaceae). The extent of colonization ranged from 15% (Trianthema portulacastrum) to 92% (Euphorbia hirta) in herbs, 10% Lantana camara) to 64% (Abutilon indicum) in shrubs and 49% (Muntingia calabura) to 64% (Santalum album) in trees. The entry of fungal hyphae into the roots was characterized by the presence of an appressorium (figure-1.b). The different AM fungal structures viz., hyphal coils, intra-radical hyphae, inter or intra cellular vesicles and micro-sclerotia were observed (figure-1). AM Fungal Diversity: A total of ten AM fungal spore morphotypes were identified based on their spore morphology. They included two species in Acaulospora Acaulospora leaves and A. scrobiculata), one species in Gigaspora Gigaspora gigantea) and seven species in Glomus Glomus aggregatum, G. diaphanum, G. etunicatum, G. fasciculatum, G. geosporum, G. intraradices and G. microaggregatum) (figure-2). Table-1 Physico-chemical characteristics of the 5 different limestone mine spoils of ACC, Madukkarai, Coimbatore Soil No. Lime Status Texture pH EC dSm-1N kg ha-1P kg ha-1K kg ha-1 1 Calcareous Sandy loam 7.88 1.78 179 15.0 977 2 Calcareous Sandy loam 8.81 0.41 109 17.0 102 3 Calcareous Clay loam 7.96 0.75 132 18.0 1552 4 Non Calcareous Sandy loam 8.30 3.07 108 7.0 1016 5 Calcareous Sandy loam 8.09 0.50 140 13.0 1106 Samples taken in triplicate; EC- Electrical Conductivity; N- Available Nitrogen; P- Available Phosphorus; K- Available Potassium. Research Journal of Biological Sciences ___________________________________________________________ ISSN 2278-3202 Vol. 4(7), 73-78, July (2015) Int. Res. J. Biological Sci. International Science Congress Association 75 (a) intercellular hyphae in Eclipta prostrata; (b) appressorium in Conyzabonariensis; (c) hyphal coils and intra-radical spore in Conyza bonariensis; (d) vesicles in Eupatorium odoratum; (e) arbuscules in Ipomoea indica; (f) micro sclerotia in Pergularia daemia . ih, intercellular hyphae; ap, appressorium; hc, hyphal coils; is, intra-radical spore; v, vesicle; a, arbuscule; ms, micro sclerotia.Figure-1 AM colonisation in the roots of the plants in the study areaDiscussion: The limestone mine spoils generally supported several plant species. Majority of the primary colonizers of the mine spoils were associated with AM fungi. The level of AM infection markedly differed among various plants. Heavy root infection was recorded in Croton bonplandianum (92%) and Ipomoea indica (91%). Some of the plants which were previously reported to be non-mycorrhizal, were found to possess mycorrhizal association. Plants belonging to the family Aizoaceae (Trianthema portulacastrum), Commelinaceae (Commelina bhengalensis) and Nyctaginacea (Boerhaavia diffusa), believed to be non-mycorrhizal plants were found to be associated with AM fungi. The extent of colonization was 15% in Trianthema portulacastrum; 26% in Commelina bhengalensis and 28% in Boerhaavia diffusa. AM colonisation has also been reported in Boerhaavia diffusa and Commelina bhengalensis18,19. Arbuscular colonization was not present in any of the three plant species, whereas vesicles were present in Commelina bhengalensis (less than 1 %) and Boerhaavia diffusa (3%). Glomus was the dominant genus followed by Acaulospora. This is in accordance with the previous results of many researchers20-22. Pattern of spore population of Glomus might cause the dominancy of this genus23. Spores of Glomus are borne in clusters and hence they sporulate more frequently while the others like Gigaspora and Scutellospora sporulate singly24. Research Journal of Biological Sciences ___________________________________________________________ ISSN 2278-3202 Vol. 4(7), 73-78, July (2015) Int. Res. J. Biological Sci. International Science Congress Association 76 Table-2 Arbuscular mycorrhizal association in the angiospermic plants of the study area Family name Plant name Habit Life cycle AMF Colonization (%) HC VC AC Acanthaceae Ruellia tuberosa H A/B 34.0±12.27 3.88±4.0 0.00 Peristrophe bicalyculata H A/B 62.26±8.13 41.12±9.08 0.00 Aizoaceae Trianthema portulacastrum H A 14.72±4.16 0.00 0.00 Amarantaceae Achyranthes aspera H A 0.00 0.00 0.00 Aerva lanata H A 0.00 0.00 0.00 Amaranthus viridis H A 0.00 0.00 0.00 Alternanthera pungens H A 0.00 0.00 0.00 Apocynaceae Vinca rosea H A/B 53.89±5.45 20.83±5.47 3.06±2.51 Asclepediaceae Pergularia daemia TH A/B 51.11±5.22 24.45±3.99 0.00 Asteraceae Conyza bonariensis H A 41.95±9.24 6.11±7.73 0.00 Eclipta prostrata H A 41.28±10.43 8.43±7.13 0.00 Eupatorium odoratum S A 78.89±9.61 42.78±13.95 9.17±5.19 Parthenium hysterophorus H A 57.78±6.79 20.55±7.23 0.00 Taraxacum officianale H A 45.83±3.23 14.17±11.61 11.94±11.85 Tridax procumbens H A 56.95±5.27 16.11±5.64 13.06±8.17 Vernonia cinerea H A 49.72±9.07 7.50±6.12 0.00 Bignoniaceae Tecoma stans S P 79.44±8.02 43.61±11.25 26.95±10.78 Boraginaceae Trichodesma indicum H A 37.22±10.25 0.00 0.00 Caesalpiniaceae Cassis occidentalis S P 68.33±3.62 10.28±4.37 0.00 Commelinaceae Commelina bhenghalensis H A 25.56±10.86 0.56±0.56 0.00 Convolvulaceae Ipomoea indica TH A 91.39±3.79 34.72±7.66 0.00 I. obscura TH A 60.28±5.97 32.50±13.51 2.50±2.89 Cucurbitaceae Coccinia indica C A 37.22±10.70 20.56±9.71 0.00 Melothria madaraspatana C A 35.28±9.06 0.00 10.0±6.12 Cyperaceae Carex speciosa H A 0.00 0.00 0.00 Euphorbiaceae Acalypha indica H A 78.33±7.41 28.61±8.02 16.67±8.55 Croton bonplandianum H A 91.94±2.88 9.44±4.82 4.20±2.17 Euphorbia hirta H A 75.0±0.0 13.06±5.59 46.67±11.48 E. hypericifolia H A 78.06±8.07 5.83±4.03 0.00 E. prostrata H A 75.0±0 19.45±4.38 56.11±14.03 Phyllanthus niruri H A 83.88±2.07 25.25±6.18 7.13±4.29 Malvaceae Abutilon indica S A 63.88±3.24 39.50±3.06 0.00 Menispermaceae Tinospora cordifolia C P 65.0±7.66 29.72±10.65 0.00 Mimosaceae Prosopis juliflora S P 28.71±13.15 15.74±8.80 0.00 Muntingiaceae Muntingia calabura T P 48.89±8.10 26.39±12.49 0.00 Nyctaginaceae Boerhaavia diffusa H A 27.50±8.18 2.78±1.92 0.00 Papavaraceae Argemone mexicana H A 0.00 0.00 0.00 Papilionaceae Crotolaria verrucosa S P 25.0±0 0.00 0.00 Passifloraceae Passiflora foetida C A 41.39±13.65 6.11±4.73 2.22±2.81 Plumbaginaceae Plumbago zeylanica H A 16.03±4.56 1.50±3.0 0.00 Poaceae Chloris barbata H A 68.79±7.11 5.46±2.71 0.00 Cynodon dactylon H A 61.46±9.14 27.47±10.29 0.00 Santalaceae Santalum album T P 63.61±5.63 10.0±3.69 0.00 Scrophulariaceae Scoparia dulcis H A/B 53.89±10.89 33.89±15.86 3.89±3.01 Solanaceae Datura metel H A 85.88±7.98 37.50±8.06 12.25±4.95 Solanum nigrum H A 79.13±4.98 15.50±6.41 7.50±2.78 Verbenaceae Lantana camara S P 10.35±20.41 8.33±4.45 0.00 Abbreviations used: H, herb; S, shrub; T, tree; TH, twining herb; C, climber; A, annual; B, biennial; A/B, annual or biennial; HC, hyphal colonisation; VC, vesicular colonisation; AC, arbuscular colonisation. Research Journal of Biological Sciences ___________________________________________________________ ISSN 2278-3202 Vol. 4(7), 73-78, July (2015) Int. Res. J. Biological Sci. International Science Congress Association 77 (a) Acaulospora laevis; (b) Gigaspora gigantea; (c) Glomus fasciculatum; (d) G. microaggregatum; (e) G. diaphanum; (f) G. intraradices; (g) G. etunicatum; (h) A. scrobiculata; (i) G. aggregatum; (j) G. geosporumFigure-2 AM fungal spores isolated from the rhizosphere soils of the study areaConclusion From the study, it can be concluded that most of the plants in the limestone mine spoils survive due to the AM fungal associations. Glomus was the dominant genus found in the limestone mine spoils. AcknowledgementWe thank the University Grants Commission, New Delhi, for the financial support. 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