Ex situ conservation is the conservation and maintenance of samples of living organisms outside their natural habitat, in the form of whole plants, seed, pollen, vegetative propagules, tissue or cell cultures.
In vitro techniques have been increasingly used for plants in the last 40-50 years. Conservation of genebank accessions is only one of several uses for the techniques. The basic procedure consists of conserving parts of plants in flasks or tubes in artificial media, under controlled environments, normally in sterile conditions. A prerequisite of successful in vitro conservation is that the plants or plant parts can be regenerated into complete plants for growth and use in any of the ways that genetic resources are used.
Cryopreservation or cryoconservation is a process, where cells, whole tissues, or any other substances susceptible to damage caused by chemical reactivity or time are preserved by cooling to sub-zero temperatures.
All these methods could be used to conserve vegetatively propagating crops.