INTRODUCTIONMost plants are autotrophs and produce their own carbon compounds through photosynthesis. A parasitic plant, as an angiosperm (flowering plant) that directly attaches to another plant via a haustorium. It is a specialized structure that forms a morphological and physiological link between the parasite and host (Kuijt 1969, Yoshida et al. 2016). Parasite is from the Greek word ‘para’ (beside) and ‘sitos’ (grain or food) which literally means “beside the food”.
Parasitic plants can be categorized based on different criteria such as where they attach to the host, the degree of nutritional dependence upon the host, or whether they require a host to complete their life cycle. In terms of location on the host, two basic types can be distinguished: stem parasites and root parasites. Stem parasites occur in several families, and pathogenic members include some mistletoe and dodder (Cuscuta and Cassytha). Root parasites are more common and occur in diverse taxonomic groups. Parasitic plants may also be classified as hemiparasites or holoparasites.
Hemiparasites contain chlorophyll when mature (hence are photosynthetic) and obtain water, with its dissolved nutrients, by connecting to the host xylem via the haustorium. Holoparasites lack chlorophyll (and are thus nonphotosynthetic) and must rely totally on the contents of the host xylem and phloem. Root parasitism is well-known from species in the families like Scrophulariaceae, Orobanchaceae, Balanophoraceae, etc. These are holoparasites, achlorotic in nature and completely depend on their host for nutrients whereas hemiparasites (aerial parasites) are green and partially depend on their host for nutrients and water. The sandalwood order (Santalales) is the most morphologically and physiologically diverse group of parasitic plants.
The largest family in the sandalwood order is Loranthaceae which contains stem parasitic plants commonly known as mistletoes.Both holo and hemiparasites are connected to their host by a specialised organ called haustorium, which forms on anatomical and physiological bridge between the parasite and host (Kuijt 1969). In all haustoria were studied, xylem is continuous between the host and parasite. Phloem is sometimes observed in older haustoria, but no host-parasite connection of sieve tube members was observed.
The haustorial organ is composed of two distinct regions, viz. the upper haustorium which extends from the parental to the point of contact with the host and the endophyte which penetrates and invades the host tissue (Shanavaskhan and Sivadasan 2009).LoranthaceaeAll members of the family Loranthaceae are parasites, among them majority are aerial parasites, except a few root parasites. De Candolle (1830) divided the family Loranthaceae into two groups, which are generally recognised as two subfamilies: Loranthoideae and Viscoideae. Recent finding indicate that they should be raised to the rank of independent families and designated as Loranthaceae and Viscaceae (Maheswari et al. 1957, Barlow 1964).
Loranthus L.The genus Loranthus L. is now known as Dendrophthoe falcata (L.
f.) Ettingsh. belongs to the family Loranthaceae of the order Santalales. The order contains 158 genera and 224 species that are distributed worldwide, but the greatest diversity occurs in the tropics. Dendrophthoë falcata (L.f.) Ettingsh.
– General InformationLoranthus longiflorus Desr. is the synonym of Dendrophthoe falcata (DF). It is a hemiparasite and glabrous shrub, commonly known as mistletoe, grows up to 2 m tall, on variety of trees and shrubs. Stem is thick, erect with cluster of branches and flattened at the nodes.
It develops haustorium (tumor like growth) at the point where the parasite penetrates into the tissues of host tree and absorbs nutrients from it.Leaves are simple, subopposite-opposite, rarely whorled, with short petiole, 1-12mm or sessile, exstipulate, falcate, ovate-oblong, lanceolate-elliptic, 4.5–18 x 2–10cm, thick, leathery, brittle, cordate-amplexicaule or cuneate at base, obtuse-subacute at apex, curvipinnately, rectipinnately or rarely palmatipinnately nerved, 3-6 pairs, margin entire and undulate along margins.
Inflorescence axillary or terminal, sometimes ramiflorous, simple pseudoraceme or umbellate, sometimes in spike, 2-8 cm long; pedicels 4-5mm long; bracts broadly ovate. Flowers 10-25(-50) flowered, 5-7cm long, with green clavate upper portion, generally bisexual or rarely unisexual, zygomorphic, 4-6 merous, yellow-scarlet. Calyx absent or forming a reduced epigynous rim, green, rarely 4-6 toothed. Corolla yellow or red, gamopetalous, valvate, lobes 5, linear-elliptic, shorter than tube, unilaterally reflexed, 9-12 mm long, ca 1mm wide, green.
Stamens 5, filaments adnate to corolla, bright red, anthers oblong or linear, 3-5mm long, basifixed; disc present. Ovary inferior, unilocular, glabrous or hairy, occasionally rugose or muricate; style 1, simple, green, exerted, stigma capitate, dark red. Fruits ellipsoid-ovoid to oblong, dark pink or orange in colour, a pseudocarp, berry, drupe, glabrous, ovary got fused with receptacular cup developing a berry like fruit. Seed single, often sticky. Clifford (1895) clearly remarked about the dispersal of seed mostly by birds, the chief distribution being the species of Dicacum.
The seeds do not require a host germination stimulant and will germinate spontaneously; however, establishment only occurs on living hosts (Mathur 1949).Taxonomic hierarchyKingdom: PlantaeSubkingdom: ViridaeplantaePhylum: TracheophytaSubphyllum: EuphyllophytinaClass: MagnoliopsidaSubclass: RosidaeSuperorder: SantalanaeOrder: SantalalesFamily: LoranthaceaeGenus: DendrophthoeSpecies: falcataBasionyms: Loranthus falcatus L.f.Vernacular NamesEnglish: MistletoeTamil: Baadanikaa, JidduTelugu: JeevakamuMalayalam: Baandagul, BandaSanskrit: Bandaka, Samharsha, Vrikshadani, VrikharuhaBengali: Maandaa, Bandha, PharullaGujrati: BaandoHindi: BandaaKashmiri: Ittikkanni, ItilMarathi: VrudhongoPunjabi: PulluriDistributionIndia (tropical and subtropical regions, including Andaman & Nicobar Islands, on waste lands and forest trees up to 2500 m altitude), Sri Lanka, Nepal, Bhutan, Bangladesh, Myanmar, Indo-China, Thailand, Malaysia and Australia.
UsesWhole plant used for treating various ailments. Bark astringent, narcotic, treating wounds and menstrual troubles. Leaves used to cure asthma and ear-ache. Wood is useful in tannery industry and the ashes used to wash clothes.Chemical ConstituentsFlavonoid, quercetin, kempferol, rutin, tannins, ?-sitosterol, stigmasterol, ?-amyrin, oleanolic acid.Life cycle of DendrophthoeThe seeds are swallowed by the birds and excreted with faeces. These seeds enclosed by the sticky viscin either fall. The viscin around the seeds play an important role, not only in getting attachment, but also providing moisture for germination.
The seeds of several Loranthus members do not require any special stimulant from the substratum and germinate even on dead objects (Okubamichael et al. 2016). Two Javanese species germinate even during suspension in air (Van Leeuwen 1954).
Mc Lueckie (1923) observed germination on iron wire, wooden gates, trunks of trees, branches and leaves.Impact of Dendrophthoe falcataMistletoes are the predominant groups of angiosperm shoot parasites (Nickrent 2002), found in wide range of ecosystems including boreal forests, tropical rain forests, and arid woodlands which are capable of destroying the trees and shrubs of economic and aesthetic values (Hosseini 2008). It attacks a great number of native as well as introduced trees in different habitats such as saline and non-saline environments. However, the distribution on a landscape scale is not well understood, but it is mostly predicted that the mistletoe infection is positively related to tree size, water and nutrient status, canopy cover and the host- parasite interactive responses are not well understood (Phonenix 2005). In addition, the relationship between parasitic angiosperms and their hosts is variable and this variation creates a significant challenge to understand how hemiparasites interact with their hosts and their environment (Arumugam et al.
2014).The effect of mistletoes on their hosts may include reduced vigour and growth rates, poor fruit yield or seed set, malformation of woody tissues, sparse foliage, top dying, predisposition to insect and other disease attack and premature death (Arumugam et al. 2014). This parasite can affect host productivity by extracting water, nutrients, and organic compounds from the host’s vascular resources (Scholes et al. 1999). The extent to which this impacts on host performance depend upon the degree of autotrophy of the parasite. The relative ability of host and parasite sinks to attract resources and the tolerance or resistance to infection of the host species (Rispail et al. 2007)The Indian Mistletoe Dendrophthoe falcata (L.
f.) Ettingsh., is remarkable because of its extremely broad host range. The parasite victimizes a large number of dicotyledonous, some coniferous trees and many shrubs. However, the relationship between parasitic angiosperms and their hosts is variable and this variation creates a significant challenge to understand how hemiparasites interact with their hosts and their environment.The negative effects of the obligate hemiparasitic weeds on host photosynthesis are well documented, there are, however, virtually no such data available for D. falcata reporting the effect of host on parasite photosynthesis (Cameron et al. 2008).
The physiological responses of mistletoes found growing on the halophytes especially mangroves remain largely unknown, however the few studies are available (Arumugam et al. 2015).The so called haustorium is the contact organs formed between the parasite and host, in order to obtain nutrients (Weber 1982). Based on the location of origin the haustorium was categorised into three parasitism viz. root, shoot and leaves (Weber 1980). This may be broadly classified into aerial parasitism and root parasitism.
Root parasitism, haustoria are root initiated and in shoot parasitism the contact organs form the secondary haustoria, (Raugh 1937, Kuijt 1969, Kuijt and Toth 1985).Sometimes after the decay of the parasites, the swollen ruptured tissues of the host assume a somewhat radiate structure and are termed ‘wood flowers’ or ‘holzrosen’ (Tubeuf 1936; Plate 1). They are also known as ‘Rosa de palo’ in Mexico and ‘Rosa de Medera’ in Gautemala (Metcalfe and chalk 1950). REVIEW OF LITERATURELoranthus longiflorus Desr. is now known as Dendrophthoe falcata (L.f.) Ettingsh., as one of the commonest parasite from the family Loranthaceae.
The study on host range have been studied by different authors in India (Fischer 1926, Ezekiel 1935, Sayeeduddin and Salam 1935, Lacy 1936, Sayeeduddin and Waheed 1936, Mathur 1949, Singh 1954, 1956 ; 1959, Ravindranath and Rao 1959, Murthy 1960, Sampathkumar and Kunchithapatham 1968, Ghosh 1969 ; 1970, Das and Ghosh 1999, Selvi and Kadamban 2009, Thriveni et al. 2010, Vijayan et al. 2015, Rothe and Maheswari 2017). Phylogeny and family revisionKuijt (1968) distinguished the two families Loranthaceae and Viscaceae. Most modern floras and systems of classifications by various taxonomists like Thorne (1976), Cronquist (1968 ; 1981) and Dahlgren (1980) were accepted the separation of Viscaceae from Loranthaceae.
“The Biology of Parasitic Flowering Plants” by Kuijt (1969) was the first exhaustive book to cover parasitism as it occurs in vascular plants and remains as an outstanding authority on many aspects of parasitic plants. The book was superbly organized covering taxonomy, evolution and morphology of all groups. Johri and Bhatnagar (1972) published a monograph on Loranthaceae which gives an exhaustive bibliography on the family. The embryology of this family was dealt in detail along with the beautiful illustrations. Based on these data the subfamilies Loranthoideae and Viscoideae has been separated and raised to the family level. Sanjai and Balakrishnan (2006) was revised the Indian Viscaceae and Loranthaceae. They discussed in detail about their systematic position, factors responsible for their distribution, morphology and hyper-parasitism. More recently Rajasekaran (2012) studied the Loranthaceae of India.
Traditional and Medicinal uses This plant is used extensively in indigenous system of medicine as an aphrodisiac, astringent, narcotic, diuretic and for the treatment of asthma, wounds, ulcer and pulmonary tuberculosis (Wealth of India Raw Material 1952, Reddy et al. 2006, Kumar et al. 2012), menstrual disorder, swelling wounds, ulcer, renal and vesicle calculi and violated conditions of kapha and pitta (Warrier et al. 1993).
The crud drug is useful in urinary diseases and it is given to diarrhoea, dysentry, insanity, epilepsy, cardiac troubles, blood diseases, convulsions and nervine complaints (Panday and Vijnana 2004). It is also used in menstrual disorder, prevention of stone in kidney and bladder, haemorrhage, miscarriage and abortion during pregnancy (Kunwar et al. 2005). This parasitic plants used for foetus development in Ayurvedic system of medicine when grows on Ficus fistula of the family Moraceae. It is also used to cure vatta, kapha and pitta related ailments. This plant is used to avoid abortion that generally occurs during pregnancy when the age of embryo is 3 months old (Raut et al. 2009). Leaf paste is used for skin diseases and also treat for abortion (Bhattarai 1991, Siwakoti and Siwakoti 2000).
Stem Anatomy of LoranthaceaeA transverse section of young stem of Dendrophthoe falcata shows a single layered epidermis covered on the outside by a thick cuticle. The epidermal cells are somewhat loosely arranged, more or less isodiametric with small papillae on the outer tangential wall and filled with tannin (Johri and Bhatnagar 1972).The epidermis is followed by a broad zone of cortex which is distinguishable into two zones: An outer zone of 6 or 8 layers of densely tannin filled cells and packed with starchAn inner cortical zone of larger cells some of that contain tannins.Frequently, idioblasts or branched sclereids with simple pitted and striated walls occur in the cortex. The sclereids may be branched and sometimes contain solitary crystals in the lumen (Balle and Halle 1961). The strands of fibers with thick walls have been recorded in the pericycle of some species of Loranthaceae (Metcalfe and Chalk 1950). These strands are opposite to the vascular bundles (Johri and Bhatnagar 1972).
Cortex is a collateral ring, open and endarch vascular bundles. These are separated from each other by one or two layers of radially elongated cells – medullary rays. The pith is usually large and parenchymatous. Most of the cells are filled with tannin, whereas others they are lignified and develop simple pits on their walls. In some species the pith is parenchymatous with starch containing cell (Balle and Halle 1961).
Mucilage canals have been reported in some species of Loranthus. They first appear in the pith, and later in the bast (phloem). The pith contains a central mucilage canal, and peripheral ones are situated opposite to the larger vascular bundles. They do not branch any further, but become considerably swollen here and there. The mucilage canals have an epithelium of several layers and originate lysigenously.The secondary growth is profuse with prominent growth rings. The secondary phloem is much less when compared to xylem. These cells arranged in radial rows, and are frequently associated with phloem parenchyma cells.
The ray cells in this region are rich in crystalliferous sclereids in Globimettula. The secondary xylem consists of large number of vessels. The wood is diffuse, porous, and the vessels exhibit a variable arrangement. They may be present in clusters or multiples or in clusters and short tangential groups or rows as in some species. The vessels are extremely small in some species.
In some species of Loranthus it is slightly larger than 50 microns. Perforations are simple. Intervascular pitting is alternate with small to large, sometimes coalescent apertures.
The parenchyma shows large and simple pits, similar to intervascular pitting (Johri and Bhatnagar 1972). In DF the secondary xylems are in clusters or in multiples. The vessels have small perforation in the lateral walls and each ray has a single crystal.Phytolith – General informationPhytoliths are produced as a result of biological and physical processes in certain plant groups and deposited as solid silica in intercellular or extracellular locations after absorbing silica in soluble form as monosilicilic acid (H4SiO4). The term “phytolith” was proposed by Ruprecht (1866) and it is composed of two Greek words ‘phyton’ means plant and ‘lithos’ means stone meaning plant stone.
This term has been used to indicate all forms of mineralized substances deposited in higher plants, be siliceous or calcareous in nature. Numerous other terms have also been used for silica bodies found in plants, such as “opal phytolith”, “plant opal” and “opaline silica”. The term ‘opal’ has been used because of the color of the particles in reflected light. Phytoliths, like mineral, opal deposited by geological processes, are not crystalline in structure. They are amorphous (non-crystalline) and have variable water content. Phytoliths are also put under a more generalized term, as “biogenic silica” or simply “bioliths”. These are all inclusive terms for silicon found in plants and animals.
They help to distinguish silica derived from living system, silica of inorganic and mainly pedogenic origin. The plant does not use the silica for any of its metabolic processes and so deposits it as a siliceous gel within cavities in its own structure (Clarkson and Hanson 1980).Silicon is the second most abundant element in the continental crust (Wedepohl 1995). It is present in soil mostly in the form of insoluble oxides or silicates. Soluble silicic acid occurs in the concentration range of 0.1–0.
6mmol L-1 (Hodson et al. 2005). Monomeric silicic acid (Si(OH)4) is absorbed by plant roots along with other elements occurring in soil solution, carried upward via the water conducting tissue, and partially deposited as hydrated amorphous silica (SiO2•nH2O) in a growing plant as opaline silica filling in cell walls, cell interiors, and intercellular spaces. In some cases, extracellular precipitation of silica can occur due to concentration of xylem sap by transpiratory water loss from the shoots, leading to supersaturation of monomeric silicic acid in the apoplasm.
They are usually termed as phytoliths or silica bodies (Kamen?k et al. 2013).Depending upon the species habit, silica is deposited between the cells, within the cell walls, or even sometimes completely infilling the cells themselves. Among vascular plants, silicification is substantial especially in Poales and Equisetales, where hemicellulose in the cell wall serves as a template for silification. The chemical composition of phytoliths may be influenced by several factors, eg., plant taxa, soil substrate composition, climatic conditions. The chemical data on phytoliths are surprisingly limited in literature.
Scanty information on major elements can be found, but the content of trace elements is virtually unknown. According to one of few available papers, phytolith has a mixture of elemental composition (Bartoli and Wilding 1980); phytoliths contain minor to trace quantities of Mg, Ca, Na, K, Mn, Fe, Al and organic carbon. Carnelli et al. (2002) evidenced by a semiquantitative analysis that aluminium is co-deposited with silica in phytoliths of certain, mostly woody species in the form of aluminosilicates. Wust et al. (2002) reported a qualitative analysis of opaline and Al–Si phytoliths recovered from the Holocene peat deposits of tropical Tasek Bera in Peninsular Malaysia. Beside Si and Al as major constituents, the presence of trace amounts of P, Fe, Mg, S, K, Ca, Ti and Mn was also recorded. Hodson et al.
(2008) reported in the study of Si, O, C isotope composition of wheat phytoliths in dry weight about 1.6% of C and 0.04% of N studied in these materials.
Metcalfe (1960) considered the structure of silica bodies as one of the characteristics feature useful in plant identification. Although the elemental analysis of phytoliths paired with their morphology could improve the taxonomic identification of phytoliths and provide further useful information. Phytoliths was extracted from many different plant organs, including leaves, stems, inflorescence (flowers), seeds and roots. Normally it is used to take the shape of readily recognized cells, for example hairs, stomata, bilobate or cross forms (Ernst et al. 1995, Pearsall et al. 2005). Each plant produces an assemblage of phytolith types, which may or may not be taxonomically significant to family, genus or species level (Thorn 2008). Current knowledge suggests that phytoliths are restricted to the vascular plants, basal angiosperms (magnolias), and monocotyledons (particularly the grasses and sedges), eudicots and at family-specific forms occurring in the pteridophytes (tree ferns and horsetails), (Blinnikov et al.
2001 ; 2002, Iriarte 2003).Studies made by Ollendorf et al. (1988) shown that phytolith characters can be used to distinguish Arundo donax from Phragmites communis, are two giant reed grasses difficult to identify from the field. Various studies were distinguished phytoliths in cultivated crops from wild relatives to hybridised crop plants (Piperno1984, Pearlshall et al. 2004, Zheng et al. 2003).
Silica deposits in grasses have been well documented since long (Metcalfe 1960, Ollendorf et al. 1988, Ball et al. 1993, Whang et al.1998, Krishnan 2000). According to Metcalfe and Kaufman et al.
(1960 and 1981) silica deposits in grasses occur primarily in epidermal long cells, trichomes (hairs), specialized silica short cells and as fillings within the bulliform cells of plant leaves. Phytolith shapes are found to be consistent within a species and hence they can provide significant taxonomic information (Piperno 1988, Jones and Handreck 1965, Raven 1983). Silica bodies in the silica cells of grasses assume characteristic forms when the leaf is mature. Phytoliths fulfil some criteria for adaptations because silica accumulation is heritable, solves a problem, enhances fitness in plants, and is derived within land plant clades (Padian 1987, Strömberg 2006). Still, detailed phylogenetic patterns of silica deposition remain unknown because some of the enclosing cell material may be trapped inside the phytolith as it crystallizes (Lentfer and Green 2004, Thorn 2008).
When the plant dies and decays, the phytoliths are released into the soil undergoing erosion, transport and depositional processes as other sedimentary particles (Blackman and Parry 1968, Thorn 2004). Owing to the variety of cell types within a plant, phytoliths are formed in a multitude of shapes and sizes depending on the location of deposition and age of the plant. The differing morphologies of the phytoliths, derived from different plant families and even individual species, offer a potential for palaeobotanical, palaeoecological and archaeological reconstructions (Clarke 2003, Piperno 2006, Raven and Giordano 2009, Blackmann 1971, Rovner 1983, Bartolome et al. 1986, Twiss 1987, Piperno 1988, Fisher et al. 1995, Alexandre et al.
1997, Carter 1999, Carnelli 2004, Gallego 2004, Barboni and Bremond 2009). Distribution in Plant KingdomPhytoliths are wide spread in plant kingdom, occurring in all types of plants and all their different organs and structures, from roots, wood to inflorescences. Evidences are accumulating that a silicon deposition system developed at an early stage of plant evolution. Jones (1964) described Phytoliths from 60 million-year-old sedimentary rocks and Stromberg (2002) recovered copious numbers of phytoliths belonging to a variety of monocotyledons, dicotyledons, conifers and ferns from sediments ranging from late Eocene (about 35 million years) to late Miocene (about 7 million years) age.
Unicellular organism such as diatoms that evolved long before plants invading land developed mechanisms for the impregnation of solid silica into their structures hundred of million years ago (Armbrust et al. 2004), and primitive land plants such as bryophytes (liverworts, hornworts and mosses) apparently did the same after their ancestors left the oceans (Takahashi and Miyake 1977). Numerous angiosperms, gymnosperms and pteridophytes produce large quantity of phytoliths (Piperno 1998). Among the pteridophytes, the members of Equisetaceae was termed as heavy silicon accumulators (Chen and Lewin 1969). The dicotyledons have traditionally been thought of as plants that absorb relatively small amounts of silica. Scurfield et al. (1974) found silica deposits in 32 woody dicotyledons and Postek (1981) proved deposition to occur in the leaves of Magnolia grandiflora.
Examples of herbaceous dicotledon families in which silica deposits was located include members of Canabaceae (Dayanandan and Kaufman 1976) and Urticaceae (Sowers and Thurston 1979). Despite the above observations it is probably still true to say that monocotyledons generally take up and deposit more silicon than the dicotyledons. According to Dahlgren and Clifford (1982) silica deposition is most common in certain monocotyledonous families, including Arecaceae, Bromeliaceae, Cypraceae, Orchidaceae, Restionaceae and Zingiberaceae. However, Poaceae is the most highly evolved and successful family ecologically, that had heaviest and most characteristic deposits of silica occur (Metcalfe 1960, Parry and Smithson 1964).Distribution in Plant partsLanning and Eleuterius (1981) reported the leaves of herbaceous plants accumulate twice the amount of silica when compared to stems and roots.
Levels of silica were found to be more in grain crops followed by grasses, vegetables, fruit crops and legumes (Thiagalingam et al. 1977, Lanning et al. 1981, Piperno et al. 1988). Comparatively stems of many species have low silicon content in correspondence to the leaves. Studies on reproductive organs of plants have higher phytolith content than in fruits and seeds (Bozarth 1992, Lentfer 2003).
In cereals, the inflorescence bracts enclosing the seeds of wheat, oats, barley, rye, rice and maize known in botanical terms as glumes, lemmas and palaes, very often have higher phytolith content than the leaves. It has been assumed that most roots and other subterranean organs have negligible phytolith content (Piperno 1988). Sangster and Hodson, (1992) found in Marantaceae and Heliconiaceae species of rhizomes and tubers possesses a considerable phytolith content.
Phytolith distribution in trees and shrubs are fewer. These are evidenced from the studies of Lentfer (2003) and Iriarte (2003). In woody plants, not as in herbaceous taxa, production is often restricted to the epidermis of fruit exocarp and mesocarp, where phytoliths probably function as to protect the propagules of plants from their predators.
Silica deposition in grass caryopsis (grain) was little studied, but recent investigations have indicated its presence in Setaria italica (Hodson and Parry 1982). It’s presence on the epicarp hairs of mature caryopsis of the 4 cereals barley, oats, rye and wheat was investigated by Bennett and Parry (1981). In all four cases silicon was found along the whole length of hairs, but it was mostly concentrated at the extreme tips.
Physiological role Arnon and Stout (1939) observed high silicon accumulation in plants but until now it was not yet considered as an essential element for higher plants according to the criteria of essentiality, but it was recognized as a beneficial element for plants growing under biotic and abiotic stresses such as heavy metal, drought, salinity and pathogens. Ma (2004) reported the beneficial effects of silicon was observed on growth, development, yield and disease resistance in wide variety of plant species. Growth and DevelopmentSilicon is an indispensable element for the normal growth and development of some plant species. Examples include horsetails or scouring rushes (Equisetum), rice (Oryza sativa) and beets (Beta vulgaris).
Negative effect was observed from Equisetum, is a heavy silica accumulator (Chen and Lewin 1969), collapsed when grown in a silca-free medium (Postek 1981). Silicon was found to provide structural rigidity to plant parts and hence increasing light interception and energy manufacturer. It allowing more light to reach the lower leaves and substantially increasing the photosynthetic activity (Lanning and Eleuterius 1983). According to “window” hypothesis, presence of epidermal silica bodies facilitates the transmission of light through the epidermis to the photosynthetic mesophyll or to stem cortical tissue, consequently increasing photosynthesis and plant growth (Hutsun and Norrish 1974). Silica deposited in epidermal cells may act to reduce the rate of transpiration in leaves thereby improving water use efficiency (Matsuda et al. 1983).
Silica may help to maintain rigidity in stems and linear leaves, although leaf stiffness may also be related to the degree of lignification. It has shown to improve the lodging resistance in wheat (Shakoor et al. 2015) and it was proved in experiments with solution culture and soil-grown plants. The mechanical strength of plants enabling them to achieve and maintain an erect habitat and light conductive interception was resided in the cell wall. Reviews on the role of silicon in plants were stressed the association of Si in cell walls and discussed the increased rigidity of plants grown under ample available Si in terms of that association. The incorporation of silica into the cell walls has at least two times energetically positive effects. First, the role of silica is analogous to that of lignin in that it is a compression-resistant structural component of cell walls. Raven (1983) was calculated that on a unit weight basis, the energetic cost of incorporating silica is only 3.
7% that of incorporating lignin. For incorporation of silica compared with that of cell-wall carbohydrate, the corresponding value is 6.7%. Silica is thus an energetically inexpensive structural component of cell walls. Second, the erect habit and the disposition of the leaves of plants amply supplied with Si favor light interception and hence for photosynthesis.
Adatia and Besford (1986) experimented with cucumber plants grown in a recirculating nutrient solution and the responses of leaves with high Si plants that elicited by high levels of solar radiation. Although no systematic comparisons made and it was likely that many of the positive effects of Si on plant growth recorded were due to increased total energy capture. Optimization of silicon nutrition results in increased mass and volume of roots, giving increased total and adsorbing surfaces.
As a result of application of silicon fertilizer, the dry weight of barley increased 21% in 20 days and 54% in 30 days of growth due to supplemental silicon. It plays an important role in hull formation in rice and in turns to influence grain quality. The hulls of poor-quality, milky-white grains (kernals) were recorded generally with low silicon content (Savant et al. 1997). Sangster et al. (2001) reported that physiological functions involve the interaction of silica with other processes taking place in a plant or its growing environment.
Silicon dioxide may ameliorate the toxic effects of aluminium and other heavy metals, such as manganese on plant growth. A number of experimental studies indicate that the addition of silicon in growth medium mitigates the damaging effects of aluminium and manganese on plant growth. A co-deposition of solid silica and aluminium in and around plant cells was demonstrated for a wide variety of species and plant organs; hence the mechanism for detoxification might be sequestration of aluminium by silica (Shakoor et al. 2015). All the above debate suggests structural and physiological functions of phytoliths.SCOPE OF THE STUDYIn plants, interaction science has emerged as a major area of research which deals with the mechanism, reasoning for interactions of plant with plant, animals, and/or micro-organism. Among them the plant parasite relation with their host through the haustorium interfaces and draws nutrients from the host conductive tissues to the parasite (Devkota 2005).
Among the parasites, mistletoes are considered as an important component of biodiversity (Watson 2001, Shaw et al. 2004). Many studies have performed and revolving around the parasite DF, especially on the morphology, geographical distribution, in vitro establishment, scientific justification of the ethno-medicinal properties, and various existing possible control strategies. Few important studies among them are? Parker and Westwood (2009) considered as the commonest of all other mistletoes widely occurring in India.? Very variable in floral and leaf characters, haustorial polymorphism, explosive flowering, fruit adhesive pulp etc. (Barlow 1995).? The difficulties of circumscribing the species identity have been pointed out by Danser (1931, 1938).
? Their miraculous medicinal values especially to take down the abnormal tissue growth of cancer (Kunwar et al. 2005).? Higher nutrient tier than their host (Lamont 1983; Karunaichamy et al. 1999).
? Three different haustorial connections of aerial parasite (Calvin and Wilson 1998).? Extraordinary internal and external treatment of ethnobotanical values of DF (Oudhia 2008).? Parasitic plants mimicking the host (Pannell and Farmer 2016).? Physiological and metabolic perturbations induced by the parasite on host leaf area, leaf number, and growth performance of the host.QuestionsCollectively, based on the above statements or studies we arrives this question. How the parasites are related with their host?The Present PerspectivesTo overcome the above questions, this study is approaching through anatomical and phytolith components to understand the exact relationship (positive and/ or negative) between the host and parasite.
MATERIALS AND METHODSSpecies selectionBalachandran (2016) recorded four parasites viz. Cassytha filiformis of Lauraceae, Cuscutta chinensis and C. reflexa of Convolvulaceae and Dendrophthoe falcata (DF) of Loranthaceae from the Coromandel Coast of north Tamil Nadu and Pondicherry.
In which the first three species are herbaceous and wiry in nature. The other mistletoes, Taxillus bracteatus of Loranthaceae and Viscum orientale of Viscaceae also recorded from region but it has very limited host range when compared to D. falcata. So as the parasite DF was selected for this study. It is woody in nature and has wide range of host (Plate 2).
Intraspecific variations are also recorded at habit, leaf and flower. Flower differ from host to host and place to place (IBP 2016).Study Area (Figure 1)Three manmade forests viz. Aranya, Merve, Shakti and Puthupet, a sacred grove was selected and studied. Of which ‘Aranya’ and ‘Shakti’ are belonging to Auroville whereas ‘Merve’ is attached with Sri Aurobindo Ashram Education Trust.Aranya (Figure 2)’Aranya forest and Sanctuary’ is located at north-east of Oussdu Lake, south-west of Auroville, belongs to the international city, Auroville. It spreads over 40 hectares and harbours more than 600 native species, special attention to Tropical Dry Evergreen Forest (TDEF) elements that distributed along the Coromandel Coast, east coast of Peninsular India. Initially it was a severely eroded barren waste land, and was used mainly by the local villagers for pebbles mining.
Restoration work was begun in 1997, funded by IDRC (International Development Research Centre) is ongoing to till date and taken care of conserving the indigenous dry evergreen species in cooperation with the local inhabitants. Two magnificent canyons cut across Aranya, harbouring rare and endangered flora and fauna comes back naturally, though it is a manmade forest. The natural landscape, manmade contours, check dams and ponds created room for rainwater conservation and it favours the growth and natural regeneration of the TDEF species. This vegetation have attracted avifauna, reptiles, amphibians and arthropods. So as it is of interest to many groups of people, botanists, zoologists, ornithologists, geologists and environmentalists visit Aranya as part of their professional engagements, often staying for extended periods of time to complete their research. Students from school to the post-graduate level found Aranya as an ideal study site and are encouraged in their endeavours. Children from Eco-clubs spend hours enjoying nature in idyllic surroundings. Merve (Figure 3)This study site also called as Lake Estate, is situated 10km west of Puducherry town (11º 57′ 8.
3″N, 79º 45′ 57.2″ E and 40m asl). It spreads over 160ha of which 40ha have been afforested through eco-restoration from a barren eroded gulley landscape with red ferralitic soil over a period of more than 35 years by the involvement of Sri Aurobindo International Centre of Education.
Eco-restoration comprised active human intervention through the introduction of drought tolerant soil nitrogen fixing species and Tropical Dry Evergreen Forest (TDEF) elements. Check dams were constructed along the gullies to prevent the soil erosion and through rainwater conservation the soil fertility and ground water level was increased helped to increase the diversity and richness of vegetation. As a result, the introduced TDEF species was established themselves and are naturally regenerated along the thickets in the past thirty years. Lowland herbaceous species was also established themselves as a green cover and soil texture has been transformed and the fertility too increased. Puthupet (Figure 4)A sacred grove located at Puthupet, Vanur Taluk, Villupuram district, 15km north of Pondicherry, on the way to Marakkanam. This grove is dedicated to Manjaneeswara Ayyanar. The name of the village is Puthupet Chavadi, but is commonly referred to as Puthupet. The name is derived from the Tamil word ‘puthu’ which means white anthill occupied by a snake.
There is a large anthill in the grove, with two horses dedicated to the Ayyanar. The sacred puthu (termite mound) is suitated under the Memecylon umbellatum tree, on which numerous cradles are tied with cloth. Meher-Homji (1986) very neatly stated how a sacred grove was conserved through faith and belief system on behalf of “a sacred termite mound or puthu”. Many floristic, ecological and sociocultural studies were carried out and disseminated scientific publications by different academic, research and natural lovers from that 30 acre natural vegetation, protected since ages. It is one of the natural gene banks of TDEF elements to till date, for the collection of seeds, to raise seedlings and do plantation in many afforestation programs in and around Auroville.Sakthi, Auroville (Figure 5)It is one of the many afforested communities in Auroville, located at 11° 59’15’ N 79° 50′ 19′ E at an altitude of 35m, in Vanur taluk, Vilupuram district of Tamil Nadu. Sakthi was created during 1983 by Walter F.
Gastmans and his wife Christina. Initially the land was barren without a single tree in sight and had few canyons. To makes the community green, afforestion was taken in the same year, with very dense planting of exotic species, (Acacia auriculiformis of Mimosaceae), in order to create a natural environment, to stop the dust storms and check soil erosion. Through seed exchange programme from more than 500 Botanical gardens around the world many exotic species was introduced in Sakthi and to other Auroville communities.
The area is about 35 acres of manmade forest and the plant diversity is about 400, including many indigenous and exotic herbs, shrubs, climbers and trees. More than 180 Tropical dry Evergreen arborescent species and 125 exotic species were planted for the last 34 years. With financial support of “Foundation for Revitalisation of Local Health Traditions” (FRLHT), placed at Bangalore, propagated “Tropical Dry Evergreen forest” seedlings and constructed AURO herbarium that exclusively meant for the collection of TDEF species from Tamil Nadu, Pondicherry and Andhra Pradesh. The Herbarium is at present serves as a study and reference centre for many universities, research scholars and students. At present nearly 13000 herbarium collections from 3650 species were preserved.
Physiographical featuresGeologically, these four sites belong to Cuddlaore sandstone intrinsic formation during Miocene period. The soil and geology of this region was described in detail by Meher-Homji (1970). Generally, the soil along the coast is sandy loam or red ferralitic and sometimes covered with alluvial deposits. It becomes clayey in the interiors (Meher-Homji 1974, 1984).
The natural vegetation is mostly found on the less fertile and red ferrallitic soil whereas black clay and alluvial, are mostly under cultivation. From the published sources ampole (Marlange and Meher-Homji 1965, Visalakshi 1995, Parthasarathy and Karthikeyan 1997, Parthasarathy and Sethi 1997) informations were available about the soil type, pH ranges (between 5 and 9.5) macro and micro nutrients of temple groves of Cuddalore and Villupuram.
EnvironmentA typical maritime tropical climate with dissymmetric rainfall regime prevails in the study area. The weather is generally hot and humid for most part of the year with minor variations between Cuddalore and Puducherry, are provided by the Regional Meterological Centre, Chennai. The advancing South-West monsoon contributes 18 to 23% of total annual rainfall during June-August months. September-December months constitute the principal rainy season accounting for 60 to 95% of precipitation during North-East monsoon in which 40 to 70% of annual rainfall is attributed to depressions and cyclonic storms originating in the Bay of Bengal (Meher-Homji 1975). The mean annual rainfall was 1256mm with mean rainy days of 56 per year prevails in this study area. The minimum temperature 17.7 °C is in January, the maximum record 40.
5 °C in May and the mean is 28.5 °C. The average relative humidity is 76%. The weather is generally cool during December to January with the late nights dewy. Dry weather prevails during April to June. Wind speed ranges from 5.0km/hour in June to July and 9km/hour from August to September but extremely higher during the cyclonic days.Field SurveyRegular field visit, two days in a week between the month of December (2017) and January (2018) was made in all the four sites.
During the survey, the parasite: Dendrophthoe falcata infected plants were enumerated, collected voucher samples, prepared herbarium and deposited at Herbarium, French Institute of Pondicherry (HIFP). Leaf, stem and haustorium samples both from host and parasite were collected to study the anatomical, phytolith relationship between them. Anatomical StudyDuring the survey stem pieces with pencil thickness and 2cm long was collected from both host Albizia lebbeck of Leguminosae, Casuarina equisetifolia of Causarinaceae, Dolichandrone falcata of Bignoniaceae, Gmelina arborea of Verbenaceae, Hardwickia binata of Leguminosae, Morinda coreia of Rubiaceae and Strychnons nux-vomica of Loganiaceae, and their parasite Dendrophthoe falcata samples were collected and fixed in FAA (Formalin 20 ml + Acetic acid 7.5 ml + Alcohol (Ethanol) 300 ml) for two days.
Using Microtome apparatus (MIKROT L WSL lightweight G.S.L.-1 microtome) at 2-3 microns thickness, CS (cross section) and MLS (median longitudinal section) of the stem sections were taken.
The samples felt hard then it was subjected to treat with Glycerol or 5% NaOH for softening. Then these sections were stained with Safranin or TBO (Toluene Blue O) and in some specimens stained with a mixture of both. These stained sections were mounted on the slides by using Glycerin as a medium. Similarities of cell components between the host and parasite; differences among the parasitic stem was studied and those were photographed.PhytolithNow a day, phytolith is used as a taxonomic tool for the identification of angiospermic plants. To know the relationship between the host and parasite, the leaves from six hosts trees such as Acacia colei, Casuarina equisetifolia, Chloroxylon swietenia, Dolichandrone falcata, Ficus benghalensis, Hardwickia binata and their parasite (Dendrophthoe falcata) leaves were chosen for this study. Wet oxidation method (Piperno 2006) was followed to extract the phytolith from these leaves. The Modern Plant Phytolith (MPP) reference slides were made and they were deposited at Palynology Lab, French Institute of Pondicherry with the accession number in between 625 and 636.
Step 1: The dried leaves were soaked in 1% alconox solution for few hours and then washed thoroughly with water for several times to clean the dust particles.Step 2: The leaves was soaked in 10% HCl for few hours and then washed with water for several times. Step 3: The samples were allowed to dry at 60-70°C. Step 4: About one g of dry leaf taken for phytolith extraction.Step 5: Add 10ml of Con.H2SO4 directly to the samples and placed on hot water bath.
The heating continued until complete dissolution.Step 6: After cooling 10ml of 30% H2O2 slowly added to the samples and placed on a hot plate. The heating continued by adding sufficient amount of H2O2until the sample become colourless.
Step 7: The digested solution allowed cooling and adding distilled water.Step 8: The residue containing phytolith, also called as AIF (Acid Insoluble Fraction) was transferred to the 15ml Polypropylene (PP) narrow bottom centrifuge tubes.Step 9: The residue washed with distilled water by centrifugation.Step 10: The residue allowed to dry.
Step 11: The dry weight of AIF measured.Step 12: A known weight of AIF mounted on glass slides using Canada Balsam (CB). Step 13: The percentage of AIF calculated. OBSERVATION AND RESULTSThe parasitic taxon Dendrophthoe falcata belong to the family Loranthaceae was selected for the study to know the relationship between the host and parasite. Three manmade vegetation viz. Aranya forest and sanctuary, Sakthi Auroville, Merve and one natural sacred grove – Puthupet was selected for the study. The field survey was carried out from these four different places during the months of December 2017 and January 2018. The DF infected host species were enumerated and recorded.
A total of 64 species recorded, among these four sites Aranya forest and sanctuary recorded with maximum number (34) of host species followed by Shakti (27), Merve (26), and minimum number (5) was recorded at Puthupet. Out of 64 species 27 are recorded for the first time as host of DF (Table 1). These 64 species were represented from 51 genera and 25 families. Maximum number of DF infection was found in the family Leguminosae (18 species) followed by Rutaceae and Sapotaceae had 5 species each and 4 from Rubiaceae. Most affected genus is Acacia (5 species) and 3 species each was noticed on Albizia and Dalbergia. From this study Combretaceae, Cordiaceae, Loganiaceae and Sapindaceae are the new family host range recorded for the first time. Out of 64 species recorded 42 are belonging to native and 22 exotic category.The study was observed two types of growth pattern in DF, erect and pendulus.
Well established growth was noticed in the species Albizia lebbeck, A. saman, A. quachepalae, Casuarina equisetifolia, Lepisanthes tetraphylla, Morinda coreia, Pongamia pinnata and others. These group of plants have both erect and pendulous growth pattern in DF whereas erect and stunted pattern of growth was noticed in Cordia subcordata, Dolichandrone falcata, Gmelina arborea, Hardwickia binata, Memecylon umbellatum, Strychnos nux-vomica and others. (Plate 3). Albizia lebbeck is the only native species recorded in all the four sites and Acacia auriculiformis is the only exotic species recorded in all three man made vegetation with DF. From the survey A. lebbeck and Morinda coreia was heavily infected in all three manmade forest.
The DF was affected at few branches of A. lebbeck, Casuarina equisetifolia, Gmelina arborea and Pongamia pinnata of which A. lebbeck has more susceptible and leads to death (Plate 4). Aegle marmelos is a sacred tree infected by DF at Puthupet sacred grove as well as at Shakti, Auroville.
Anatomical ralations – stem anatomyThe FAA fixed stem samples from 3 hosts and their respective DFs were undergone microtome sections by 2-3 micron thickness. Both cross section (CS) and longitudinal sections (LS) were taken where ever possible from the stems of Hardwickia binata, Morinda coreia and Strychnos nux-vomica and from all DF stems. In addition the DF stem samples from the host of Albizia lebbeck, Dolichandrone falcata and Gmelina arborea also were sectioned and studied anatomical similarities and differences among the samples. Hardwickia and DF (Plate 5)General features – comparatively, both host and parasite have distinct sap and heart wood (plate a).Anatomical features – growth ring was distinct in both the species but the parasite was distinguished with the deposition of starch and tannins at the summer wood.Vessels – primary and secondary xylems especially in arrangement of vessels are similar in both host and parasite.
Summer and spring woods are also prominent in both but comparatively the numbers of vessels are less in parasite. Summer wood of parasite that is the tracheids and ray parenchyma cells filled with starch and tannins. Fibres – thick walled, non-septate, xylem and phloem fibres were also common between the parasite and host. Tracheids – also arranged well with vessels whereas the sclereids were found at pith and cortex regions of the DF. Gum ducts – were found scattered in pith, vascular and cortical regions of the DF.
Pith – the DF representing parenchyma cells and it was interrupted by thick walled sclereids. These parenchyma cells were always filled with starch and tannin. The ray cells of Hardwickia 1-2 thickness of ray cells throughout the wood, whereas the parasite has 1-2 at primary wood and 3-6 cells thickness at secondary wood.
Same as the host Hardwickia, the parasite was also recorded with uneven size of vessels, 2-4 in clusters and round to oval shape all along the section.Morinda and DF (Plate 6)General features – comparatively, both host and parasite have no distinct sap and heart wood.Anatomical features – both host and parasite has devoid of distinct growth ringsRay cells – both DF and Morinda have 1-3 thickness of rays at primary region, 3-7 at secondary regions. Interestingly sclereids were recorded at the wider portion of rays in secondary wood of DF.Pith – only parenchyma cells found in host whereas the pith of DF, the parenchyma disrupted by sclereids. Raphids are distributed scatteredly at pith and cortex regions of Morinda but it was absent in their DF.
In DF, parenchyma cells stuffed with starch, tannins and scattered gum ducts also found in pith.Xylem – the vessels of primary xylem from both host and parasite was uniformly arranged one above other but at secondary wood region was found 1-3 medium (but uneven) sized vessels. The pits are simple and circular. Tracheids and fibres are also found as common in both species. In DF secondary phloem mixed with sclereids is the additional features.
These fibres and tracheids of DF rarely filled with starch and tannins. Interestingly from the cross and longitudinal sections of vessels of DF recorded with tannin content.Cortex – a mixture of parenchyma, sclerenchyma and ellipsoid thick walled oil ducts are present in DF. This feature is differing from the host. Strychnos and DF (Plate 7)General features – comparatively, both host and parasite have distinct sap and heart wood.Anatomical features – distinct partition of primary and secondary growth rings.Xylem – both host and parasitic vessels are very variable in size and number (1-4).
However the vessel pits are simple and similar in both species. Tracheids were intermixed along with vessels in both host and parasite.Phloem – radial strands of phloem in both host and parasite was found but the DFs secondary phloem inter mixed with sclereids.Ray cells – from LS study, the ray cells are 3-12 cells wide and intermixed with sclereids in both host and parasite.Fibres – are simple, medium sized and clustered. Additional DF stem studies (Plate 8)The anatomical similarity (CS ; LS) between the host and DF, differences among the DF was studied. In which the CS and LS of DF stem from the host Albizia lebbeck, Gmelina arborea and Morinda coreia was compared. The DF stem from Albizia, Hardwickia and Strychnos ray cells have thick walled sclerenchyma with scattered rhomboidal crystals found where as other species have no such formation.
The starch grains were found at the summer wood of Albizia also recorded in the DF of Hardwickia too.LS of DF from the host Albizia, Casuarina, Gmelina and Morinda were also studied. The vessels length of Casuarina and Gmelina DF has longer than other species here studied, Hardwickia, Morinda and Stychnos. The conduction of tannins through vessels was recorded in CS/LS of DF stem from Albizia, Dolichandrone, Gmelina, Hardwickia and Morinda.
These vessels were recorded from the primary and secondary wood as well as special, thick walled and ellipsoid shaped ducts in the cortical regions. Presence of sclereids in the ray cell has another major difference among the DF stems. This was recorded in Albizia, Casuarina, Hardwickia, Morinda and Strychnos. In addition, vessels filled with starch grains were recorded in the DF of Morinda. PhytolithThe leaves selected for the plant phytolith studies are Acacia colei, Casuarina equisetifolia, Chloroxylon swietenia, Dolichandrone falcata, Ficus benghalensis and Hardwickia binata with their corresponding parasite, Dendrophthoe falcata.
Among the six hosts, Ficus benghalensis shows the maximum quantity of phytolith which is 8.134% and Hardwickia binata shows the minimum quantity which is 0.037% also the DF from Ficus benghalensis shows the maximum yield which is 6.741% and DF from Hardwickia binata shows the minimal yield of phytolith which is 0.032% (Table 2).
In Casuarina equisetifolia, Blocky Facetate, Ecinate, Blocky psilate to granular surface, Blocky rhomboidal, Blocky psilate, Facetate spine, Tabular psilate and Trachieds were recorded where as only two morphotypes viz. Facetate and Trichome was found from the DF growing on C. equisetifolia.From Chloroxylon swietenia, Epidermal, Facetate, Globular spinulose, Globular psilate, Tabular pailate, Tabular psilate and Trachieds were represented but from their parasite Blocky facetate, Facetate, Tabular like facetate, Trichome, Tubular like facetate were observed.
The phytolith morphotypes observed in Dolichandrone falcata were Elongate wavy, Epidermal cells, Facetate, Globular verrucate phytolith, Silicified Collenchym and Trichomes. From their DF Bulliform, Facetate, Tubular like facetate, Silicified Guard Cells and with granulate were found.The observation from Ficus benghalensis are Blocky spinulose, Blocky psilate, Elongate echinate, Epidermal grany surface with spine base, Epidermal and Tabular trapizoids. The morphotypes observed in the DF of Ficus benghalensis were Blocky Ecinate, blocky facetate, Blocky Psilate, Tubular Psilate, Facetate, Facetate Elliptical, Rectangle echinate, Facetate Psliate, Mesophyll phytolith, Tabular granular surace and Trichomes.
Only two mophotypes viz. Elliptical spine body and Trachieds are found both in the host and its DF. Trace amount of Acid Insoluble Fraction (AIF) or phytolith was found in Acacia colei, Hardwickia binata and their DF, but Epidermal, Trachids and Facetate was recorded from both taxa.Totally 35 morphotypes were recorded in this study.
Out of 35, 17 different shapes of phytoliths were observed from DF (Plate 9, 10) and 21 from six host (Plate 11, 12). In which Ficus benghalensis-DF (19) and Chloroxylon swietenia-DF (11) contributed maximum number of phytolith shapes. From the 12 samples, 6 host and 6 DF, ‘Facetate’ is one of the morphotype found as common in all DF. Blocky Facetate, Epidermal cells, Mesophylls and Trichomes are the other generally noticed acid insoluble fractions both in host as well as the parasite.DISCUSSIONDendropthoe falcata (L.f.) Ettingsh.
of the family Loranthaceae, is one of the commonest and non host specific hemiparasitic plant in India. It causes considerable damage to forest trees but also have important medicinal values. Despite the profound effects on the plant communities in which they occur, they are still often ignored in community theory (Pennings and Callaway 2002).
Since Danser (1933) to till date the studies are coming up on DF in different aspects. However there was no single study available about the exact relationship between the host and DF. To know this, the stem parasite (DF) was selected based on Balachandran (2016) study from TDEF along the Coromandel coast of Tamil Nadu. The host by DF attachment was studied in three man made forest viz, Aranya Forest and Sanctuary, Sakthi-Auroville, Merve and one sacred grove named as Puthupet. There were 64 species infected with DF and they were represented from 51 Genera and 25 Families. Interestingly this study was recorded with four new families Combretaceae, Cordiaceae, Loganiaceae and Sapindaceae and 27 new host species. It is highly significant than the study of Singh (1962), Johri and Bhatnagar (1972), Selvi (2006), Thriveni et al. (2010), Vijayan et al.
(2015) and Rothe and Maheshwari (2017). Downey (1998) stated that ‘several mistletoe species opportunistically parasitised exotic species as well as native species, the significance of which is poorly understood’. This study also has record of 26 exotic and 38 native species out of 64 hosts.
Of which 18 species represented from the family Leguminosae has scored high number and the genus Acacia was highly infected with 5 species. Meanwhile Albizia lebbeck is the only native species and Acacia auriculiformis is an exotic species recorded with DF from all the three man made forests and the first species was heavily infected and leading to death. It proves the statement of Aukema (2003) that “in the most extreme cases, such as heavy mistletoe infestation may result in host death” (Table 1).This study was observed two types of growth pattern for the first time from the DF that is erect and pendulous. Distinctly, 7 species was observed with erect growth pattern, 5 species with erect and pendulous growth pattern and the remaining 8 out of 20 species has no distinct growth pattern that is growing along with the host branches.
However, well established growth of DF, up to 2m long was found in 7 species. This report strengthens the conclusion of Downey (1998) study on aerial mistletoe species of Australia (Plate 3). Downey (1998) stressed to study on the relationship between mistletoe distribution and host species. To till date no such study was made, instead the present work focused on anatomical and phytolith relations between the host and DF. AnatomyThe anatomical relationship between Dendrophthoe falcata and their host was studied here for the first time. Three pair’s viz.
Hardwickia binata-DF, Morinda coreia-DF and Strychnos nux-vomica-DF of stems were collected and sectioned (CS and LS). General and anatomical features were similar in these three pairs that is the presence or absence of sap and heart wood and growth rings. In regard to vessel the size (small to moderately large), number (1 to 4) and their arrangement at primary and secondary xylem regions are almost similar between the host and parasite.
The number and shape of ray cells in between the host and parasite in summer and spring woods are also same except secondary wood of DF stem from Morinda, have 3-7 cell thickness. Tracheids and fibres, as usual arranged along with the xylem and phloem region, whereas sclereids scattered in pith and secondary cortical portion along with parenchyma cells in all the DF stems but it was not found from the hosts. Like sclerieds, Morinda has acicular raphids (calcium oxalate crystals), an important character of Rubiaceae, found at pith and cortical portion but it was absent in DF sections. Presence of tracheids, deposition of starch grains and tannins in primary and secondary wood region of DFs are the unique characters of Loranthaceae. Meanwhile the presence of gum ducts found in Albizia-DF, Hardwickia-DF and Morinda-DF pairs implies the strong anatomical relation between the two (Plate 5, 6, 7, 8). This piece of work was strengthened the study of Balle and Halle (1961) and Metcalfe and chalk (1957), (ie. the presence of parenchymatous cells in the pith were filled with starch and tannin in Loranthaceae). Chauhan and Rao (2003) are stated that the vessels of Hardwickia binata were filled with gummy deposition and this study also found the same in Hardwickia and its DF too.Occurrence of rhomboidal crystals in sclerenchyma or sclerieds found at pith, cortical and ray cells of Albizia and Hardwickia (Chauhan and Rao 2003) and Morinda, Strychnos (Metcalfe and Chalk 1957) were already recorded. Surprisingly the occurrence of these rhomboidal crystals at the same regions of DF stems that growing on these hosts was recorded here for the first time, is once again proved that the host and parasite has promising relation.Phytolith Phytoliths are inorganic, rigid, microscopic structure made of silica, found in plant tissues and persisting in the soil after the decay of plants. Based on this Palaeobotanical, palaeoecological and archaeological reconstruction studies were available extensively (Blackman 1968, Rovner 1983, Bartolome 1986, Twiss 1986, Piperno 1988, Alexandre 1995, Carter 1999, Clarke 2003, Carnelli 2004, Gallego 2004, Thorn 2004, Piperno 2006, Barboni 2009, Raven and Giordano 2009). Less numbers of studies are available on modern plant phytolith, especially on woody plants. The work related to phytoliths or AIF were found more on grass species (Shakoor et al. 2015, Sangster et al. (2001), Shakoor et al. (2015). The present study is new to the parasite family, Loranthaceae and it was made for the first time to know relationship between the host and parasite. Totally 6 host viz. Acacia colei, Casuarina equisetifolia, Chloroxylon swietenia, Dolichandrone falcata, Ficus benghalensis and Hardwickia binata and the DF growing on it was selected for this project. Among them, Ficus benghalensis and its DF recorded with maximum amount of phytolith which is 8.134% and 6.741% respectively and Hardwickia binata and its DF shows the minimum deposition which is 0.037% and 0.032% (Table 2). There are 35 morphotypes observed in this study, of which 17 are from DF and 21 from the hosts. Only one morphotype named as ‘facetate’ is common in all the DFs whereas ellipitical spine body and tracheids were found in Ficus benghalensis and its DF. Almost equal amount of morphotypes were found between the host and parasite, however the size and shape was varied. This study was strongly proved the conduction of nutrients from host to parasite. In other words, it emphasizing the uptake of silicon through the host and it get deposited in the plant tissues of DF too (Plate 11, 12). In all, to understand the relationship between the host and DF, anatomical and phytolith studies were made. In which all the studies were recorded with more positive and less negative correlation. Further, to conclude the relation, more samples needs to be analysed and comparisons are also to be viewed from molecular and genetical sides.SUMMARYDendropthoe falcata (L.f.) Ettingsh. of Loranthaceae, is a non-host specific, stem parasite found as common along the Coromandel coast of Tamil Nadu. To know the relationship between the host and parasite, three man made forest viz. Aranya Forest and Sanctuary, Sakthi-Auroville, Merve and one sacred grove named as Puthupet was selected. Among the four sites Aranya forest and sanctuary recorded with maximum number (34) of host species followed by Shakti (27), Merve (26), and the least number (5) recorded at Puthupet. There were 64 species infected with D. falcata, represented from 51 genera and 25 families, of which four are new family and 27 new host records. The DF infected dominant family is Leguminosae (18 species) and the genus is Acacia (5 species). Albizia lebbeck is recorded as the most susceptible species. Out of 64 species 42 were belonged to native and 22 under exotic category. This study in DF was observed two pattern of growth viz. erect and pendulous. The anatomical relationship between Dendrophthoe falcata and their host was studied here for the first time. Three pair’s viz. Hardwickia binata-DF, Morinda coreia-DF and Strychnos nux-vomica-DF of stems were sectioned (CS and LS). Over all, general (sap and heart wood, growth rings) and anatomical features (vessel size, number, arrangement at primary and secondary xylem, fibres, gum ducts, ray parenchyma) were found similar from the sections in these three pairs. However the presence of tracheids, deposition of starch and tannins in pith, cortex, sometimes in the primary or secondary woods of DF stems sections was representing the characters of Loranthaceae. Occurrence of rhomboidal crystals in sclerenchyma or sclerieds and gum ducts from the two stem sections is another proof for the positive relationship.The phytolith study is entirely new to the parasite family, Loranthaceae and it was made for the first time to know relationship between the host and parasite. Leaves from 6 host viz. Acacia colei, Casuarina equisetifolia, Chloroxylon swietenia, Dolichandrone falcata, Ficus benghalensis and Hardwickia binata and their DF was studied. Among them, Ficus benghalensis-DF pair was recorded with maximum amount of phytolith or AIF and trace amount found in Hardwickia binata-DF. There are 35 morphotypes observed in this study, of which 17 are from DF and 21 from the host. Only one morphotype named as ‘facetate’ is common in all the DFs. 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