Dendrophthoe falcata
Dendrophthoe falcata is one of the hemiparasitic plants that belong to the mistletoe family Loranthaceae. It is the most common of all the mistletoes that occur in India. At the moment reports say that it has around 401 plant hosts. The genus Dendrophthoe comprises about 31 species spread across tropical Africa, Asia, and Australia among which 7 species are found in India.
D.falcata bears grey bark, thick coriaceous leaves variable in shape with stout flowers. The inflorescence of D.falcata was described formerly as axillary or as developing from the scars of fallen leaves, but Y.P.S Pundir determined it to be of strictly cauliflorous nature and noted also that it bears a certain similarity to those of the fig species Ficus glomerata, F. pomifera and F. hispida. Two of its varieties are widespread in India namely, var. falcata and var. coccinea distinguishable by their bearing white and red flowers respectively.. To date, D.falcata bears the distinction of being the mistletoe species with the largest global host range - a range which is continuously and rapidly widening to include more and more host species.
Host-parasite interface
Among angiosperms, parasitic relationship through the formation of haustorial linkages is known to be widespread. In general, haustorial connections among 72 aerial parasitic genera may belong to either of the four types viz., epicortical roots, clasping unions, wood roses, and bark strands. ERs may run along the host branches in either direction forming haustorial structures at variable intervals while “unions” occur as single points of attachment of individual parasites hence pronounced as solitary. In D.falcata on different hosts two of the haustorial kinds have been observed viz., solitary unions as on Sugar apple, and epicortical roots as on Sapota, guava, pomegranate have been known. It is unknown about what factors decide formation of different haustorial types by the leafy mistletoe on different hosts.The host branches infected with D.falcata show a gradual reduction in growth and diameter as compared to other healthy uninfected branches. This mistletoe does not have an indigenous rooting system and is dependent on the host for water and minerals. Nutrient dynamics have shown that a higher titre of N, P, K, Mg and Na in the leaves of mistletoe than the leaves of uninfected and infected hosts which may be due to differential translocation of elements within the host phloem. The haustorial connections of the parasite with the plant are devoid of any efficient retranslocation system.
Seed dispersal and pollination
Seed dispersal and pollination are usually mediated by the birds that thrive on fruits from the parasite and/or host. Particularly in southern India, Tickel’s flowerpecker is reported to facilitate seed dispersal of D. falcata among Neem through fecal excretions or regurgitations. Studies conducted at the higher altitudes of the Western Ghats, which parallel the western coast of India infer that the flowerpecker pollinated mistletoes have particularly developed features specialized to attract a unique vector both to facilitate pollination and seed dispersal: the fruit and flowers have similar resemblance and more significantly, the fruiting time overlap with the next flowering season. The hair-crested drongo and sunbirds are also known to feed on the nectar from the D.falcata flowers adding to the list of pollinators to this mistletoe.Medicinal uses
Dendrophthoe falcata is used as traditional medicine through South and Central Asia. It possesses remarkable potential as a medicinal plant, as is evident from the wound healing, anti-microbial, anti-oxidant and antinociceptive properties of its ethanolic extracts. Medicinal properties of this hemiparasite may vary in effects respective to different hosts it establishes a relation with.The whole plant is used in indigenous system of medicine as cooling, bitter, astringent, aphrodisiac, narcotic and diuretic and is useful in treating pulmonary tuberculosis, asthma, menstrual disorders, swelling wounds, ulcers, renal and vesical calculi and vitiated conditions of kapha and pitta. Also, the decoction of plant used by women as an anti-fertility agent has been evidenced to possess anticancer activity. The leaf ethanolic extract significantly and dose dependently inhibits the acetic acid induced writhing in mice and has indicated a low level toxicity in the brine shrimp lethality assays. Besides, a more recent work by Pattanayak et al. shows significant tumor reduction in induced mammary carcinogenesis in Wistar female rats when fed with hydroalcoholic extracts of D. falcata.
Diseases
Dendrophthoe falcata is susceptible to diseases such as leaf blight caused by Colletotrichum stage of Glomerella cingulata.Hyper-parasitism
Dendrophthoe falcata can be parasitised by Scurrula cordifolia . Similarly, Viscum orientale has also been reported to grow on D. falcata. In another instance Cuscuta reflexa has been shown to act as a rival to the leafy mistletoe.From a conservation biologists’ viewpoint mistletoes are considered as a keystone resource of biodiversity and from that of an ethnobiologist’s and/or pharmacologist’s, they possess numerous ethnomedicinal assets with prospects extending to promises even for use as an anti-tumor agent. Besides, a farmer’s perspective entails that they are notorious and devastating parasitic plants. Being backed by easy seed dispersal mediated by frugivorous birds, they continue to pose serious losses to economically valuable fruit trees, flowering plants and those with medicinal properties whether growing in forests, orchards or gardens.