USES, THREATS AND CONSERVATION OF LICHENS
Sharath K P
Guest Faculty-Dept of Botany
GFGC Tumkur
Email: sharu5121@gmail.com
Ph: 8722033594
INTRODUCTION
The word ‘lichen' has a Greek origin, which denotes the superficial growth on the bark of olive trees. Theophrastus, the father of botany, introduced the term ‘lichen' and this group of plants to the world which is a combination of two organisms, an alga and a fungus, living together in symbiotic association. The algal component in the lichen is called phycobiont or photobiont while fungus as mycobiont. The phycobiont and the mycobiont loose their original identity during the association and the resulting entity (lichen) behave as a single organism, both morphologically and physiologically. Hence the lichen is called as a composite organism.
In lichen thallus (body) phycobiont constantly supply photosynthetically produced carbohydrates, the mycobiontensures the protection from desiccation by sheltering the delicate thalli of the alga, the fungal partner predominates with 90% of the thallus volume and provides shape, structure and colour to the lichen with partial contribution from algae. Whatever visible from outside in a lichen thallus is fungal part, which holds algal cell inside. Hence the lichens are placed in the Kingdom – Mycota (Fungi). The fungi present in lichens are called as lichenized fungi. Among the 20,000 lichen species known in the world 95% belongs to the Ascomycetes group of fungi while Bacidiomycetes and Deuteriomycetes groups are represented by only 3% and 2% of species respectively.
These obiquotes group dominating as much as 10% of the earth’s surface, they are estimated about 20,000 species present throughout the world and in India the estimated record is 2,303 species, which represents 14% of world lichen population. They grow on a wide range of substances, both natural and man-made, on the basis of their substrate preference lichens are classified as corticolous (bark inhabiting), saxicolous (rock inhabing) terricolous (soil inhabiting), lichenicolous (lichen inhabiting), muscicolous (moss inhabiting) etc. They obtained their required nutrients and water directly from the atmosphere and have evolved efficient mechanismsfor accumulating nutrients from the environment in which the live. They adsorb metal ions such as Ca2+ via an ion exchange mechanism and can trap tiny particles of rock, soil or any other heavy metal pollutants within their structure. This ability of lichens can be efficiently used for monitoring the pollution levels and chemical analysis of lichen samples can be used to determine the extent and type of pollutant emissions around a particular industrial installation. Thus lichens are considered as Bioindicators of environmental pollution.
USES OF LICHENS
Lichens and lichen products have been used in traditional medicines for centuries and still hold considerable interest as alternative treatments in various parts of the world. In various systems of medicine across the world including the Indian system, lichen species are said to effectively cure dyspepsia, bleeding piles, bronchitis, scabies, stomach disorders, and many disorders of blood and hear . Lichen substances exhibit a great diversity of biological effects, including antimicrobial, anti-inflammatory, analgesic, antipyretic, and anti-proliferative and cytotoxic activities, and there has been a growing interest in the pharmaceutical properties of compound derived from lichens. In India, species of Parmelia are used extensively in traditional medicines and are also being collected extensively. Although many natural lichens and cultured lichens have been screened for their biological activities and several novel compounds have been isolated and identified, lichens have been essentially ignored by the modern pharmaceutical industry because of their slow growth in nature.
The lichen was soaked to leach out any bitter principles, cooked over steaming rocks dried and cut into compact loaves. In Japan the foliose rock type’s umbilicaria are collected in mountain areas and eaten in salads or even deep fried in fat.The lichens have been household items of Indians since ancient times as medicines and in various cultural events. The common condiments used in food dishes called ‘Garam Masala', ‘Meat Masala', ‘Sambar Masala' also contains lichen powder or whole plants as a major ingredient. Parmotrematinctorum is used as spice and flavoring agent. Lichens are important as a food source for reindeer and caribou in the tundra and subarctic forests. The reindeer mosses (Cladinas, Cladonias, and Cetrarias) are most commonly grazed by these animals. Sheep in Libya graze on Aspiliciaesculenta in the desert. Some of the lichens, including species of Umbilicaria and Usnea, are well known to serve as a staple diet for the Alaskan reindeer and the Himalayan musk deer.
Lichens have been used as a source of dyestuffs since classical Greek times. Roccella, fruticose lichen is primary source of purple dye. Ochrolechia, Parmotrematinctorum which contain simple depsides are soaked in a solution of ammonia to extract a deep purple principle called orchil. Lichens are also used in preparation of perfumes and cosmetics. Pseudeverniafurfuracea (Tree moss) and Everniaprunastri (oak moss) are widely used in the manufacture of perfumes.
THREATS AND CONSERVATION
Lichens are very sensitive organisms and their response to the environmental changes may include changes in their diversity, abundance, morphology, physiology, accumulation of pollutants etc. The main threats that apply to biodiversity in general are also true for lichens, e.g. habitat degradation and loss, habitat fragmentation, overexploitation, air pollution, and climate change. The fast pace of urbanization and industrialization in recent years is responsible for a perceptible decline in the vast ranges of forest areas in different parts of the world. The various activities such as agriculture, mineral extraction, tourism, hydroelectric and road building projects leads to the rapid extinction of lichens. Factors such as Environmental pollution, urbanization, forest fires and deforestation have been identified as the major threats to the lichen flora. Overgrazing by animals like reindeer also leads to extinction of lichens. There has been a sharp increase for the demand of herbal products, spices, condiments, non-timber forest products, etc. from the forests and hence, the unregulated harvesting of lichens has become a serious hazard to biodiversity in Himalayas and Western Ghats. Lichens are slow growing organisms and thus, if once removed from their habitat, they will take several years to reestablish. Air pollution is yet another major threat to the lichens as they are sensitive to different levels of pollution. Loss of the lichen diversity and change in their community due to air pollution, urbanization and changed climate was clearly witnessed in Bangalore) and Kolkata cities.
The present estimate of the lichen populations in Western Ghats is based on the survey of some limited localities and hence, this estimate is very poor. The Western Ghats possess many protected areas in form of National Parks, Wildlife Sanctuaries, Biosphere Reserves and Reserve Forests. Conservation of their habitat is very important to prevent the extinction of lichens. It can be done by developing strategies for insitu and exsitu conservation. The overexploitation of natural resources should be reduced and conservation areas must be prioritized. It is important to create awareness among peoples about the importance and conservation of lichens. Declaring lichen-rich areas as ‘lichen sanctuaries’, enriching the existing botanical gardens with lichens and creating lichen gardens would be effective methods to conserve them in their natural habitats. Such sanctuaries and gardens would be unique in the world; apart from conservation, they also serve as educational and recreational sites. The illegal harvesting of lichens for commercial purposes should be prohibited. The developmental projects affecting the protected areas should be reviewed before it is implemented. More research activities should be encouraged on lichens.