Anatomical Features of the Transverse Sections of the Leaves of Loranthaceae in Nigeria
Ibrahim J. A1*, Kunle O. F1, Ayodele A. E2
1Department of Medicinal Plant Research and Traditional Medicine National Institute for Pharmaceutical Research and Development, PMB 21, Garki, Abuja. Nigeria
2Department of Botany, University of Ibadan, Ibadan. Nigeria
Available Online: 20th April, 2015
ABSTRACT
The anatomical characteristic of the transverse sections of leaves of the Nigerian parasitic family of Loranthaceae were investigated as a contribution to the taxonomy of the family especially in species identification and delimitation. The study revealed presence of palisade tissues for all the species except Tapinanthus bangwensis and T. globiferus. Second layer of palisade cells of Englerina gabonensis and Phragmanthera capitata with wavy outline. Prismatic crystals were present in most of the species and they were either associated with sclereids only or with sclerieds and xylem fibers. Acicular crystals were diagnostic to only Agelanthus bruneus. The presence of brachysclereids and astrosclereids are diagnostic features in the family. The anatomical features observed from the study could be utilized for taxonomic purposes especially as diagnostic features for easy identification of the species even when leaf material is in fragment. The information could also be used in monograph preparation for these medicinally useful species.
Keywords: Microscopy, Loranthaceae, Nigeria, Monograph
INTRODUCTION
Loranthaceae (mistletoes) is a family of parasitic plants widely known for their destructive nature to the host plants which they parasitized1-6. The brightly coloured inflorescence species are well known for their very high medicinal and cultural values7-13. Recent revision of the family in Nigeria documented fifteen species for the region14.
Information on the anatomy of the Loranthaceae is very meager. Apart from a few anatomical features of Elytranthe tetrapetala (Murray) Engl. and Tupeia Cham. & Schltdl. by Metcalfe and Chalk15, anatomical description of Phoradendron liga (Gill. ex H. et A.) Eichl. and Amazonian mistletoe, Cladocolea micrantha (Eichler) Kuijt was also carried out recently by Varela et al.16 and Guimaraes et al. (2007) respectively. Patel18 did a detailed work on the wood anatomy of six New Zealand species and the presence of silica inclusions was recorded in some species, while its absence was recorded in the remaining species. Also, in search of vegetative characters having potential taxonomic value for the mistletoes, Wilson and Calvin19 undertook a study on cuticular epithelium in the group. Little is known about the comparative anatomical features of the family Loranthaceae in Nigeria except the work of Bako et al.20 on the vegetative anatomy of Tapinanthus dodoneifolius (DC) Danser and that of Ibrahim et al.21, who undertook a study to determined the taxonomic significance of epidermal and phytochemical characters of the leaves of Agelanthus dodoneifolius in relation to their hosts. The significant of leaf epidermal characters in taxonomy of Nigerian species have also been documented22.
Cases of misidentification in the family Loranthaceae are common problem to taxonomists and medicinal plants researchers23,7,14,21. The rate at which wrong specific names are applied in many publications in Nigeria is becoming alarming as it can be found in the work of Mbagwu and Onuoha24, Mbagwu et al.,25 Iwalokun et al.26 and so many others. Many of the species names used do not exist in this part of the world while some put all specimens under Tapinanthus bangwensis, (the most known taxon in the Western part of Nigeria) and Tapinanthus dodoneifolius, the most known species in the northern part of Nigeria14. The misidentification is as a result of lack of sufficient information on the taxonomy of the plants and overlapping of delimitation characters either between the genera or among the species as a result of their similarities in appearance and habit27,7. Several workers have employed different parameters in solving taxonomic problems. One of such parameters is anatomical characters from leaves, stem and wood of plants28,18,19,29.
The present study is a part of series of studies aimed at investigating the extent to which leaf anatomical characters could contribute to the elucidation of relationships in the family Loranthaceae for easy identification and delimitation of the taxa. And this particular study focuses on the transverse sections of the leaves.
MATERIALS AND METHODS
Sources of material
Specimens of the mistletoes used for the study were collected during field trips to different parts in Nigeria. Samples of well authenticated Herbarium specimens were also used for taxa not collected during the field trips. List of taxa studied is presented in Table 1.
Leaf sectioning
The leaves were first rehydrated by boiling in water for some minutes. These were then transferred to 50% ethanol ready for sectioning. Unripe pawpaw was used as the embedding material, which was to support leaf tissue during sectioning from damage by the microtome knife. A 3cm by 3cm portion of the leaves was cut at the median position; these were put in between the unripe pawpaw and inserted in the sliding microtome for sectioning. The transverse sections of the leaves were made at the 8µ thickness. The sections were removed from the microtome with the use of camel hair brush into a Petri dish containing water. The sections were selected from the Petri dish using dissecting needle and camel hair brush and transferred into storage bottles containing 50% ethanol.
Slide preparation
The transverse sections were later removed from the 50% ethanol and washed in water and cleared in 15% Sodium hypochlorite for 10seconds to 1minute. They were later washed in water and stained in Sudan IV for about 3 to 5 minutes. These were mounted in glycerine on a slide with the edges of the cover slip ringed with nail varnish to preserve them from dehydration. The slides were observed and studied using the light microscope. The slides were observed and studied using the light microscope. Photomicrographs were taken using Olympus microscope Hyper Crystal LCD model No E-330 with Olympus camera CX31 RTSF. Tissues and cells identification were done following the procedure of Ghani30, Metcalfe and Chalk31 and Fahn32.
RESULTS
Leaf Anatomy
Table 2 shows characters of the species of Loranthaceae obtained from transverse sections of leaves. Palisade tissues were one – three layers in the family. There were two layers in Agelanthus bruneus, Englerina gabonensis, Globimetula oreophila, Helixanthera mannii and Phragmanthera capitata (Table 2; Plate 1a-b, 2a-b, 2e-f, 3a-b, 3d-g), one layer in Helixanthera spathulata and Phragmanthera nigritana (Table 2, Plate 3c, 4a-d) and three layers in Agelanthus dodoneifolius, Globimetula braunii, Phragmanthera talbotiorum and Tapinanthus cordifolius (Table 2; Plate 1e-f, 2c-d, 4e-f, 5c-d). Agelanthus heteromorphus has palisade cells on both layers (Table 2; Plate 1e-f). The palisade cells of Agelanthus dodoneifolius were not elongated like the typical palisade cells; they were more or less isodiametric in nature (Plate 1c-d). Englerina gabonensis and Phragmanthera capitata’s second layer of palisade cells was wavy in nature (Plate 2d, 3d). Single layer of epidermal cells was observed in all the specimens and they were elongated or box-like in shape (Plate 1-5). Hypodermal cells were present in only 3 species, Agelanthus heteromorphus on the abaxial surface, Helixanthera spathulata and Phragmanthera nigritana on the adaxial surface (Plate 1e-f, 3c, 4a-d). The midrib was much protruded in some species and not so in others it protruded adaxially and abaxially in Agelanthus bruneus, Agelanthus dodoneifolius and Tapinanthus bangwensis. Different types of trichomes were observed in three species; Agelanthus heteromorphus, Phragmanthera capitata and Phragmanthera nigritana (Table 2; Plate 1e, 3g, 4c). Prismatic crystals were present in most of the species and they were either associated with sclereids only or with sclerieds and xylem fibers (Table 2; Plates 1a-d, 2c-d, 3-5). Acicular crystals were found in Agelanthus bruneus (Table 2; Plate 1b). Oil globules were abundant in some species, scanty in one species and totally absent in others (Table 2; Plate 1d, 2b, 2d, 3e-f, 4b, 4f, 5b, 5c-d, 5e-g). Reticulate and sclariform pit type in xylem vessels were observed in most of the species. Xylem fibers were short in some species compared to other species that had long fibers (Table 2, Plates 1-5). Isodiametric or brachysclereids and irregular or astrosclereids were found in the family (Table 2; Plates 1a-d, 2c-f, 3-5a-b, 5e-g) and druses were observed in Phragmanthera capitata, Phragmanthera nigritana and Tapinanthus cordifolius (Table 2; Plate 3e-f, 4d, 5d).
DISCUSSION
The results obtained from the transverse sections of the leaves from the present study are very informative and are similar to earlier studies on parasitic plants33,34,17,35. The different types of sclereid and cristarque cells i.e cells containing crystals as they were referred to by Kuijt & Lye 34 on Neotropical Loranthaceae leaves were also found in the leaves of the Loranthaceae in Nigeria. Sclerenchymatous cells were observed in the leaves of Amazonian mistletoes, Cladocolea micrantha17. Sclerenchymatous cells have been described for many angiosperms 36 and Kuijt & Lye34 have also used the information obtained from their study on foliar sclerenchyma to make taxonomic decisions for the plants studied. Likewise, the information obtained from this study on the occurrence of irregular- branched sclereid (astrosclereid) and isodiametric sclereid (brachysclereids) either occurring together or separately in all the species except Agelanthus heteromorphus, Englerina gabonensis and Tapinanthus cordifolius, the cluster of isodiametric sclereids in Globimetula braunii, the peculiar shaped sclereids attached to the epidermal cells or on the palisade cells of Phragmanthera capitata and the association of sclereids with xylem fibers in Phragmanthera nigritana, Phragmanthera talbotiorum Tapinanthus bangwensis and Tapinanthus globuferus are all of taxonomic value and they can be used in conjunction with other characters to delimit the species of Loranthaceae in Nigeria.
The simple and two-armed trichome types in Agelanthus heteromorphus, stellate trichomes in Phragmanthera capitata and the dendritic trichome type in Phragmanthera nigritana are diagnostic for these species and therefore can be used to separate them from the other species in the family. This character was also used by Polhill and Wiens23 as one of the diagnostic features to describe these species. Trichomes are found to be significant at intra-specific level taxonomically37. The taxonomic value of trichomes in angiosperms have been well documented in literature38,31, also it has been reported that leaf surfaces i.e whether glabrous, tomentose or hairy is under strong genetic control and therefore, environmental factors may have little or no effect at all on the appearance of a leaf. Okpon39 and Stace40 stated that types of hairs are usually constant in many species that possess them. Phragmanthera talbotiorum shows the presence of trichome bases but no trichome was observed on the transverse sections of the leaf. This lack of trichomes also confirmed the glabrescent nature of the leaf. Prismatic crystals associated with only sclereids in Agelanthus bruneus, Agelanthus dodoneifolius, Helixanthera spathulata, Phragmanthera nigritana, Phragmanthera talbotiorum and Tapinanthus bangwensis or associated with sclereids, fibers and mesophyll cells in Globimetula braunii and Tapinanthus globiferus or with only fibers in Helixanthera mannii and Phragmanthera capitata are all taxonomically useful. The acicular crystals in the mesophyll cells of Agelanthus bruneus in addition to prismatic crystals found in them are also taxonomically important because it is the only taxon in which this character occurs in the family. Sclereids containing prismatic crystals have also been observed in other species of Loranthaceae34 where they were referred to as cristarque cells. Varela et al.16 observed the presence of oxalate crystals in the center of the mesophyll and fibers surrounding the vascular bundles in Phoradendron liga (Gill. Ex H. et A.) Eichl. Khan et al.35 observed the occurrence of crystals in some species of parasitic plants studied.
CONCLUSION
The anatomical features observed from the transverse section of leaves of loranthaceae could be utilized for taxonomic purposes especially as diagnostic features for the species. And when used in conjunctions with other characters (macromorphology, epidermal morphology etc.) would be helpful in the identification of the species. The diagnostic characters could also be used for plant material in fragments which might subsequently reduce adulteration due to intentional and unintentional substitution since the family is of high medicinal values in Nigeria and beyond.
ACKNOWLEDGEMENT
We are grateful to the following people who render assistance during field trips for specimen collection: Dr. Florence Tarfa, Dr. Theresa Omara-Achong, Oyepeju M.K.O, Baba Nafi of Keji village, Pastor Frank of University of Calabar, Dr. Colman Goji, Muazzam Ibrahim, Tanko Garba, Mrs. Sumbo Wahab and Mr. Owolabi. We are also grateful to Mr. Akinloye of Anatomy Lab, Dept. of Botany, University of Ibadan for assisting with preparation of the transverse sections.
REFERENCES
Room PM. Ecology of the Mistletoe Tapinanthus bangwensis growing on cocoa in Ghana. Ghana Journal of Ecology 1973, 61: 729-742.
Philips EJ. Mistletoe on cocoa in Ghana. Ghana Journal of Agricultural Science 1977, 10: 137-143.
Gill LS, Onyike HI. Mistletoes on rubber trees in Nigeria. Haustorium 1990
Knutson DM. Physiology of mistletoe parasitism and disease responses in the host. The biology of mistletoes. Calder M. Bernhardt, P. Eds. Academic Press, Sydney, 1983, 295-316
Kolb TE. Ecofisiologia del parasitismo en reino vegetal. Plantasparasitias del la PennisulaIberica e Islas Baleares Madrid. Saez-Lopez JA, Catalan P, Saez L. Eds. Mundi-Prensa, 2002, 57-85.
Hawksworth GF, Wiens D. Dwarf Mistletoes: Biology, Pathology, and Systematic. Washington DC, 1996.
Burkill HM. The useful plants of West Tropical Africa. Edn 2, Vol. 3, Royal Botanic Gardens, Kew, 1995, 857.
Irvine FR. Woody plants of Ghana. Oxford University Press, London, 1961.
Kerharo J, Bouquet A. Plantersmedicineles et toxiques de la Codte d’ outré-mer. Office de la Re Cherche Scienctitique Outre-Mer, Paris,
Obatomi DK, Aina VO, Temple VJ. Effects of African mistletoe extract on blood pressure in spontaneously hypersensitive rats. International Journal of Pharmacognosy 1996, 34: 124-127.
Oliver I. Teemohlware – a refreshing bush tea. Veld and Flora 1987, 73: 16
Deeni YY. Plants in Kano Ethnomedicine: Screening for Antimicrobial Activity and Alkaloids. M.Sc. thesis. Bayero University, Kano, Nigeria,
Hussain HSN, Karatela YY. Traditional medicinal plants used by Hausa tribe of Kano State of Nigeria. International Journal of Crude Drug Research 1989, 27, 211-216
Ibrahim JA, Ayodele AE. Taxonomic revision of Loranthaceae in Nigeria. Nigerian Journal of Botany 2011, 24 (1): 153-188.
Metcalfe CR, Chalk L. Anatomy of the Dicotyledons. Vol . 2, Clarendon Press, Oxford, 1950.
Varela BG, Fernandez T, Ricco RA, Zolezzi PC, Hajos SE, Gurni A A, Alvarez E, Wagner ML. Phorandendronliga (Gill. ex H. et A) Eichl. (Viscaceae) used in folk medicine: anatomical, phytochemical and immunochemical studies. Journal of Ethnopharmacology 2004, 94: 109-116.
Guimaraes AC, Kuster RM, Amaral ACF, Ferreira JLP, Sinia AC. Histological study of the leaf and stem of the Amazonian medicinal mistletoe Cladocolea micrantha (Loranthaceae). International Journal of Botany 2007, 3(2): 218-221.
Patel RN. Wood Anatomy of the Dicotyledons indigenous to New Zealand 21. Loranthaceae. New Zealand Journal of Botany 1991, 29: 429-449.
Wilson CA, Calvin CL. Development, taxonomic significance and ecological role of the cuticular epithelium in the Santalales, IAWA Journal 24 (2): 129-138
Bako SP, Bello RA, Bako LSP. Vegetative Anatomy of the Loranthacean Mistletoes (Tapinanthus dodoneifolius(DC) Danser). Nigerian Journal of Botany 2003, 16: 98-104.
Ibrahim JA, Ayodele AE, Okhale SE, Jegede AI, Kunle OF. The taxonomic significance of Agelanthus dodoneifolius(DC.) Polh. & Wiens in relation to its hosts. Nigerian Journal of Botany 22 (1) 89-101.
Ibrahim JA, Ayodele AE. Taxonomic significance of leaf epidermal characters of the family Loranthaceae in Nigeria. World Applied Sciences Journal 2013, 24 (9): 1172 – 1179
Polhill RM, Wiens D. Mistletoes of Africa. The Royal Botanic Gardens, Kew, 1998, 370
Mbagwu FN, Onuoha K. Observations on the floral and vegetative morphology of five variants of the genus Viscum (Loranthaceae). Journal of American Science 2007, 3(3): 17– 21.
Mbagwu FN, Unamba CIN, Ezeibekwe IO. Leaf anatomical characteristic of five variants of the genus Viscum (Loranthaceae). Academia Arena 2009, 1 (5): 1 – 4.
Iwalokun BA, Oyenuga AO, Saibu GM, Ayorinde J). Analyses of Cytotoxic and Genotoxic of Loranthus micranthus using the Allium cepa Current Research Journal of Biological Sciences 2011, 3(5): 459 – 467.
Hutchinson J, Dalziel JM. Flora of West Tropical Africa. Grown Agents for Overseas Government and Administration. London. Vol. 1, 1954.
Stace AC. The taxonomic importance of the leaf surface. Current concepts in plant taxonomy. Eds. Heywood VH, Moore DM, Academic Press, London and Orlando. Systematic Association Special Vol. 25, 1984, 67-93
Ibrahim JA, Ayodele AE, Jegede AI, Kunle YF. Comparative Studies on Khaya Juss. (Meliaceae) in Nigeria. African Journal of Biotechnology 2006, 5(11): 1154-1160.
Ghani A. Introduction to Pharmacognosy. Ahmadu Bello University Press, Zaria, Nigeria, 1990, 250
Metcalfe CR, Chalk L. Anatomy of the Dicotyledons. Edn 2 ed. Vol. 1, Oxford University Press, Oxford, 1979, 276.
Fahn A. Plant Anatomy. Edn 2, Pergamon Press, Oxford, New York, Toronto, Sydney, Paris, Frankfurt, 1977, 61
Sanchez-Areola E, Maiti RK, Trujillo-Perez B. Morpho-anatomical characters and secondary metabolites from Psittacanthus calyculatus (Loranthaceae). International Journal of Experimental Botany 2004. 53: 119-121.
Kuijt J, Lye D. Gross xylem structure of the interface of Psittacanthus ramiflorus (Loranthaceae) with its hosts and with a hyperparasite. Botanical Journal of the Linnaean Society 2005, 147: 197-201.
Khan MA, Sharif T, Ahmad M, Zafar M, Tareen RB. Anatomical characterization of Parasitic Plants of Pakistan. Pakistan Journal of Botany 2009, 41(6): 2661-2669.
Rao TA. Compendium of foliar sclereids in Angiosperms: morphology and taxonomy. Wiley Eastern, New Delhi, 1991.
Olowokudejo JD, Ayodele AE. The diversity of leaf epidermal features in the genus Hyptis (Labiatae). West Africa. Bio-Science Research Bulletin, 2007, 23(2): 141-158.
Theobald WL, Krauhulk JL, Collins RC. Trichome description and classification. Anatomy of the Dicotyledons. Metcalfe CR, Chalk. Eds. Clarendron Press, Oxford. Edn 2, 1929, 40-53.
Okpon ENU. Morphological notes on the genus Cassia. Notes from the Royal Botanic Garden Edinburgh, 1969, 29: 185-196.
Stace AC. Cuticular studies as an aid to plant taxonomy. The Bulletin of the Museum (Natural History). Botany Series. Trustees of the British Museum (Natural History). Vol. 4, No. 1, 1965.
Submit Manuscript | Contact IJPPR | Join Editorial | Accepted Manuscripts | Home
The post Volume7,Issue3,Article18 appeared first on International Journal of Pharmacognosy and Phytochemical Research.