Ex- Situ Conservation of Biodiversity
Ex-Situ conservation means ‘out of site conservation’. It is the conservation of rare plants/ animals in places outside their natural habitat. Examples of ex-situ conservation are zoos, botanical gardens, culture collection, etc. Besides these, seed banks, germplasm bank, semen, ova and embryo banks are also examples of ex-situ conservation.
Zoological parks are areas which provide animals with conditions as close as possible to the natural habitats. There are 275 zoos, deer parks, safari parks, aquaria etc. Government of India has set up a Central Zoo Authority to secure better management of zoos. The zoological parks are centres of education and recreation, they also play an important role in the conservation of species such as Manipur Thamin deer and the white winged wood duck. Successful breeding has also been achieved in captive breeding of some endangered animal species like Gangetic gharial, crocodiles, turtles and white tiger.
Botanical gardens are the centres of collection, introduction, cultivation and preservation of known as well as new plants of economic and scientific importance. There are 33 botanical gardens. The central and state government of India together manage these botanical gardens. Universities have their own botanical gardens. These gardens get financial assistance for ex-situ conservation of threatened and endangered species of their respective areas. They also maintain germplasm collection of selected economic, ornamental and medicinal plants and their wild progenitors. Botanical gardens also undertake research on propagation of rare and threatened species for afforestation and energy.
Arboretum and Aquaria
An arboretum is a place or a plot of land which has a collection of rare trees or shrubs for scientific and educational purposes.
Aquaria are glass tanks or artificial ponds for keeping living aquatic animals or plants.
Plant breeders need a collection of large varieties of plants with useful characters for the building programmes. Therefore it is desirable to collect and suitably store the plants with distinctive characters. Gene banks preserve such plants/ animal material. Gene banks are institutes that maintain stocks of viable seeds (i.e., seed banks), live growing plants (orchards), tissue culture and frozen germplasm with the whole range of genetic variability.
Seeds are of two types orthodox seeds and recalcitrant. Orthodox seeds are those which can tolerate reduction in moisture content, aerobic conditions and low temperature for prolonged period. For example, cereals, legumes etc. At intervals the seeds germinate, form plants and develop fresh seeds for storage.
Recalcitrant seeds are those seeds which on reduction of moisture and exposure to low temperatures die. For example, tea, cocoa, jack fruit, coconut. Storing of the seeds for shorter duration requires treatment with fungicides in rooms having humid air and normal oxygen.
Seed gene banks are the easiest way of maintaining germplasm. Collection and preservation of genetic resources for wild relatives of crop plants is done through National Bureau of plant Genetic Resources (NBPGR) New Delhi. Similarly there is National Bureau of Animal Genetic Resources (NBAGR) at karnal for domesticated animals and the National Bureau of Fish Genetic Resources (NBFGR) at Lucknow for economically valuable fish species. In addition, three gene banks have been established for medicinal and aromatic plants at Central Institute for Medicinal and Aromatic Plants(CIMAP) in Lucknow. NBPGR at New Delhi and Tropical Botanical Garden and Research Institute (TBGRI) in Trivandrum.
Orchards contains plants with recalcitrant seeds. It has a collection of all possible strains and varieties . For example, litchi, oil palm, rubber tree, etc.
It is carried out through callus formation, embryoids, pollen grain culture and shoot tip culture for those plants which are either seedless, have recalcitrant seeds, variable seed progeny or where clone is to be maintained.
The method is useful in maintaining a large number of genotypes in small area, rapid multiplication of even endangered species and for hybrid rescue. Shoot tip culture maintains virus free plants. It is used for international exchange of germplasm in vegetatively multiplied cultivars, for example,banana, potato etc.
Cryopreservation is the storage of material at -196 degree centigrade. It is a useful method for long term storage of a wide variety of plants such as buds, seeds, seed parts,twigs, tissue cultures, cells, DNA, etc., and animal germplasm such as living sperm, ova, embryo.
Seeds of several plants deteriorate very quickly using traditional storage methods. Cryopreservation has been very useful in storing such seeds and other types of germplasm for long periods.
Cryopreservation is done at -196 degree centigrade in liquid nitrogen. Two important factors which determine survival of the germplasm at such a low temperature are pre-treatment of the material and rate of cooling. Pre-treatment requires cryoprotectants such as sucrose. Cooling usually requires two steps. In the first step cooling of material at -40°C takes place for 2-3 hours before placing it directly in liquid nitrogen at -196°C. At very low temperature the material dehydrates as water moves outside from the cell. On warming the material, water moves back into the cell restoring the cellular metabolism. Zoological Society of San Diego has “Frozen Zoo” to store samples of more than 350 animals, including mammals, reptiles and birds.
Pollen and spore banks
Preservation of pollen and spores is a significant value for conservation of biodiversity of important flowering and spore bearing plants. Cryogenic technique is useful in preserving pollen from flowering or cone bearing plants and spores from non flowering plants such as ferns and mosses. Pollen are so tiny that thousands and even millions can be stored in a very small vial. Preservation of pollen is thus advantageous over seed preservation, as it gives opportunity to preserve the full range of variation within the population in a very simple manner.
Fresh spores which are similar in size to pollen can be treated just like pollen. Germination occurs even in the spores of tropical ferns such as Staghorn and Platycerium species after drying and freezing.