Storing of seeds at freezing temperature is

Storing seeds at freezing temperature is Ex-situ conservation.
Ex situ conservation means, "off-site conservation". It is the process of protecting an endangered species, variety, or breed, of plant or animal outside its natural habitat.
Seeds were stored in paper bags and either kept in a cold chamber (7 ± 2°C) in the dark (ex situ conservation) or buried in the soil to a depth of 5 cm in an area of the natural occurrence of the species (in situ conservation).
Ex situ conservation is the most efficient way to maintain the viability of the seeds of this endangered species.