New techniques in plant tissue culture and plant biotechnology led to the formation of new varieties of plants. These plants can be cultivated naturally only in some parts of the world. Unfortunately as more and more new forms of plants are produced, wild variety of same plant faces the danger of extinction due to the neglected behaviour of human and also deliberate destruction for human development.
Cryopreservation is a technique used to preserve the reservoirs of genetic diversity, their by overcoming the treat of extinction of wild variety of plants. Cryopreservation is a technique used to preserve cell or tissue using liquid nitrogen. Temperature is maintained as low as 77K, at this temperature all the biological activity of a cell or tissue is stopped. When these cells are removed from cryopreservation, all the biological activity is resumed by the cell or tissue. That is cryopreservation is a technique where cells or tissues can be preserved for any number of years.
1. Cryoprotective agents are added to cells or tissues of the plant before cooling.
2. Cells are then cooled slowly to the temperature at which they are stored
3. Warming the cells or tissues.
4. Cryoprotetive agent are removed from the cell or tissues after thawing
5. Plant materials such as pollen, seeds, embryo, cells in plant tissue culture, tissues from early stages of development, buds, twigs, meristematic tissue (growing point of the plant) can be preserved using this technique.
1. Cryopreservation techniques are used to preserve the genetic materials of plants which are on the verge of extinction. These preserved plant material can be used after many years to obtain same variety of plants, therefore this technique can be used to prevent the extinction of plant varieties. This method used to preserve tropical plants, to preserve seeds of forest trees, and fruiting plants. More than 40 tropical species have been preserved using this technique.
2. Cryopreservation technique is also used to maintain biosynthetic properties of plants. This technique can be used to preserve plant genetic material for a long time, since under these condition all the biological, biochemical and also physiological process are completly stopped, therefor plant material can be stored for unlimited periods. Specific plant tissue features can be conserved in cryopreservation method, but these features can be lost during normal in-vitro maintenance. Medicinally important plants which produces alkolioids are cultured and cell lines, hairy root cultures can also be preserved using this technique. For example rice, maize, coffee, banana, Papaver somniferum , Chrysanthemum cinerariaefolium and much more are preserved.
3. Cryopreservation technique makes it easy to collect, coordinate and manage all categories of crop genetic material throughout the world. Cryopreservation helps international exchange of germplasm, since the size of the sample material is dramatically reduced and can be shipped in sterilized condition anywhere in the world.
4. Cryopreservation reduces the risk of contamination, disease and mutations, as external disease attack, storms or natural calamities like earthquake will not destroy plant variety. Cryopreservation is performed and preserved in aseptic condition therefore contamination with fungi, bacteria or viruses is also avoided.
5. Cryopreservation technique is used in the construction of gene bank or seed bank
6. Cryopreservation is very important in forestry breeding programme, also support crop plant conservation.
7. No clear evidence is present for morphological, cytological or genetic alterations due to cryopreservation has been produces.
Even though cryopreservation technique is simple, limited knowledge on cryogenics makes this technique highly complex. Efficient cryopreservation protocols for many plant species are unavailable, therefore research is being conducted to simplify and standardize the procedure so that this technique can be used in wide variety of plant species.
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