plant genetic material in gene-bank is preserved at 196 c in liquid nitrogen as mature seed ( dry ).
plant genetic material in gene-bank is preserved at 196 c in liquid nitrogen as mature seed ( dry ).
plant genetic material in gene-bank is preserved at 196 c in liquid nitrogen as?
mature seed ( dry )
gene bank









































gene banks are a type of biorepository which preserve genetic material. for plants, this could be by in vitro storage, freezing cuttings from the plant, or stocking the seeds (e.g. in a seedbank). for animals, this is the freezing of sperm and eggs in zoological freezers until further need. with corals, fragments are taken which are stored in water tanks under controlled conditions. plant genetic material in a 'gene bank' is preserved at -196° celsius in liquid nitrogen as mature seed (dry) or tissue (meristems).
gene bank
in practice, it is very difficult to achieve high enough cooling rates to produce amorphous ice in specimens more than a few micrometres in thickness. for this purpose, plunging a specimen into liquid nitrogen at its boiling point (−196 °c) does not always freeze the specimen fast enough, for several reasons. first, the liquid nitrogen boils rapidly around the specimen forming a film of insulating gas that slows heat transfer to the cryogenic liquid, known as the leidenfrost effect. cooling rates can be improved by pumping the liquid nitrogen with a rotary vane vacuum pump for a few tens of seconds before plunging the specimen into it. this lowers the temperature of the liquid nitrogen below its boiling point, so that when the specimen is plunged into it, it envelops the specimen closely for a brief period of time and extracts heat from it more efficiently. even faster cooling can be obtained by plunging specimens into liquid propane or ethane (ethane has been found to be more efficient) cooled very close to their melting points using liquid nitrogen or by slamming the specimen against highly polished liquid nitrogen-cooled metal surfaces made of copper or silver. secondly, two properties of water itself prevent rapid cryofixation in large specimens. the thermal conductivity of ice is very low compared with that of metals, and water releases of latent heat of fusion as it freezes, defeating rapid cooldown in specimens more than a few micrometres thick.
cryofixation