ECONOMIC AND MEDICINAL IMPORTANCE OF PTERIDOPHYTES

Humans have been dependent upon the plants as an important source of medicine since ancient times. Even today, many tribal communities and rural populations are dependent heavily upon the natural resources obtained from the surrounding forest regions for treatment of various ailments and diseases. The Indian traditional medicine is based on different systems such as Ayurveda, Siddha and Unani used by various tribal communities (Gadgil, 1996). Though, lot of studies focusing on the medicinal properties of plants, especially on angiosperms, are available, unfortunately limited amount of studies have been done to explore the medicinal potentialities of the pteridophytes. The medicinal qualities of ferns are mentioned as early as 300 B.C. by the Greek philosopher Theophrastus (Corne, 1924a) and by his Indian contemporaries Sushrut and Charak. The medicinal uses of some ferns and pteridophytes of India have also been described in some of the recent studies (Caius, 1935; Nair, 1959). The best of the compendium on medicinal uses of 61 different ferns and fern-allies of Western Ghats has been prepared by Benjamin and Manickam, 2007.

The leaf and root decoction of commonly occurring Adiantum lunulatum syn. Adiantum philippense has been found to be very effective in the treatment of chest complaints (Nair, 1959; Rout et al, 2009). The fresh fronds of Blechnum orientale are used as a poultice for boils in Malaya; the rhizome is used as an anthelmintic in China, eaten during scarcity of food in Malaya, as cure for intestinal worms, bladder complaints in India, Polynesia and as diaphoretic, aromatic in Philippines (Dixit and Vohra, 1984). The rhizome and roots of Cheilanthes tenuifolia are used by the tribals as general tonic (Dixit, 1959). In the case of Dicranopteris linearis, the rhizome is used as anthelmintic in Assam while the fronds are used for asthma in Madagascar (Manickam and Irudayaraj, 1992). The rhizome of Drynaria quercifolia is bitter and is used as antibacterial, anti-inflammatory, for treating constipation, diarrhea, ulcers and other inflammations. The decoction of plant is used in typhoid fever and fronds are useful in treating swellings (Dixit and Vohra, 1984; Warrier et al, 1996). The young shoots of Lygodium flexuosum, a common climbing fern species, are used as vegetables whereas the rhizome of the plants is boiled with mustard oil and locally applied in rheumatism, sprains, scabies, ulcers, eczema and cuts (Dixit, 1959; Dixit and Vohra, 1984).

Besides having various medicinal properties, the pteridophytes are also employed for a variety of commercial and environmental purposes. One of the noteworthy aquatic ferns Azolla pinnata has a symbiotic association with nitrogen-fixing, blue-green algae namely – Anabaena azollae Strasburger. Due to this property, the agronomic potential of Azolla as biofertilizer for rice has been recognized in many countries including India, Philippines, USA, Sri Lanka and Thailand (Ahluwalia et al, 2002). It has been also found that by applying Azolla the soil fertility is improved by increasing total nitrogen, available organic carbon, phosphorous and potassium (Mandal et al, 1999; Sharma et al, 1999). Azolla has also been used as food supplement in fresh or dried or silage form for aa variety of animals including pigs, cattle, rabbits, ducks, chicken and fish (Ahluwalia et al, 2002). Other uses of Azolla include hydrogen production, biogas production, as an ingredient in soap production and to certain extent as human food (Ahluwalia et al, 2002).

The ferns have also shown to be having an important role in bioremediation of wastewater. Ma et al. (2001) found the Chinese Bracken fern namely Pteris vittata L. to be a hyperaccumulator of the toxic metal arsenic. Besides producing large biomass, they also found this fern to be efficient in Ar accumulation with the concentrations as high as 2.3% in the aerial portions of the fern. Later on, many researchers provided the reports of the hyperaccumulation properties of Pteris as well as many other ferns also. Tu et al. (2002) suggested that P. vittata could be an excellent model to study arsenic uptake and for phytoremediation of arsenic contaminated soil and water.

Among the ferns known so far, perhaps the bracken fern (Pteridium revolutum syn. P. aquilinum) has the most varied economic and medicinal uses owing to its wide distribution. The rhizome of the plant is astringent, anthelmintic and is useful in diarrhea and inflammation of gastric and intestinal mucous membranes. The decoction of rhizome and fronds is given in chronic disorders of viscera and spleen. In times of scarcity the rhizomes are boiled or roasted and eaten or ground into powder for making bread. The rhizomes mixed with malt are used for brewing a kind of beer and are also employed as a feed for stock, especially pigs. The tender fronds of the fern are used as vegetables and also employed in soups. The dried fronds are employed as packaging materials and have also been tried as a source of paper pulp. The bracken ferns have also served as dye yielding plants across the world. The colonists in Plymouth made an olive green dye out of bracken tops mordanted with alum and copper whereas the boiled roots of the ferns, which turn black, have been used as chief black pattern material by the Washo, Mono and Yokut Indians (Manickam and Irudayaraj, 1992).

Besides having all these wonderful properties, the pteridophytes are also greatly valued as ornamentals. Prior to the discovery of these benefits obtained from this group of plants, ferns were used to enhance the beauty of the landscape and are continued to be used so till now. Nephrolepis cordifolia also commonly known as ‘Sword fern’ is one of the most commonly used ornamental fern species. Other ferns like Asplenium sp., Selaginella sp., Lygodium sp., Pteris sp., etc. are also grown in the gardens or in the pots. Many nurseries grow these ferns and sell them off for a good price and these ferns are then used as ornamentals either as garden plants or during functions to beautify the place.