Concept of ex-situ Conservation
ex-situ conservation is the technique of conservation of all levels of biological diversity outside their natural habitats through different techniques like zoo, captive breeding, aquarium, botanical garden, and gene bank. It is conservation of selected rare flora/fauna in place outside their natural habitat. Significance of ex situ conservation-
Plants cannot be conserved always inside their natural habitat as there is an ever increasing demand for cropland to feed the raising population. Forests and other natural habitats are required for extending urbanization and industrialization. Natural areas are submerged at large scale as dams are built for prevent flood. supply water for irrigation and generate electricity. This loss of habitat makes ex situ conservation very important method of conservation.
ex-situ conservation is very important for those plants and animals which cannot be conserved in-situ due to different reasons.
There are different methods for conserving biodiversity ex-situ.
Botanical Gardens
Botanical gardens are the institutions or establishments where plants are cultivated and maintain for scientific, educational, and ornamental purposes. Plants from different varieties including ornamental, wild and medicinal from different geographical regions are maintained in botanical gardens. An ideal botanical garden must include green houses, a library, a herbarium, research laboratories, and several miscellaneous resources including photographs, paintings, illustrations, reprints, note-books and specimens of several types.
in-vitro Repositories
ex-situ in vitro repositories conservation refers to of living animal or plant in artificial environment, under cryogenic conditions. In animals this is achieved by cryopreservation of embryos, semen, oocytes or tissue having the potential to reconstitute live animal in future.
This is necessary when there is a critically threat of a breed or species becoming extinct. In-vitro repositories ensure availability of adequate gene pool sustained for future improvement programme.
Cryopreservation
The freezing-storage-thawing cycle is an external procedure consisting of the
following basic stages-
(1) Selection of Materials- Young meristematicsmall cells which are highly cytoplasmic, non-vacuolated and thin walled are good materials to he selected for this purpose.
(ii) Addition of Cryoprotectors / Cryopreservatives- Chemicals which decrease cryodestruction like sugars, glycols, sugar alcohols, alcohols, polyvinylpyrrollidone, polyethylene glycol (PEG), polyethylene oxide (PEO), dextrans, hydroxystarch, glycerine, sucrose, and some amino acids (eg. proline) are used as Cryopreservatives. Bajaj (1987) has advised to use a mixture of two or three cryoprotectants at low concentrations rather than a single cryoprotectant at a high concentration as it could be toxic. During treatment, the cultures should be maintained in ice to avoid deleterious effects.
(iii) Freezing- Freezing should be done in such a way that it does not cause intracellular freezing and crystal formation, as it is possible in sudden freezing. To avoid this problem, regulated rate of cooling or pre-freezing is done.
(iv) Storage in Liquid Nitrogen- If the cells are not stored at sufficiently low temperature, an additional injury to the cultures may be caused. The storage temperature should be such that it stops all metabolic activity and prevents biochemical injury (Bajaj 1987). Prolonged storage of frozen materials is possible only when the temperature is lower than 130°C. This can be simply achieved with the help of liquid nitrogen, which keeps the temperature -196°C.
(v) Thawing-Thawing is the process of releasing the vials containing cultures
from the frozen state to elevate the temperature between 35 and 40°C. It
should be done quickly but without over heating. As soon as the last ice crystals disappear, the vials are transferred into a water bath at 0°C (Popov, 1985)
(vi) Washing and Reculturing- Washing of plant materials is done to remove the toxic cryoprotectants.
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