Ultrastructural effects of early imbibition and cryostorage on Zea mays L-root meristems

In order to achieve successful cryopreservation of a hybrid maize variety i t was necessary to isolate the embryonic axes from the caryopses. To facili tate the isolation of the axes without physical injury, the seeds were firs t imbibed thereby softening the testa. The effects of imbibition and subseq uent cryostorage on vigour, viability and on the root meristem ultrastructu re were followed for a range of imbibition periods. Imbibition for more tha n 4.5 h resulted in extensive subcellular damage post cryostorage and this was associated with a loss in vigour and quality of regenerative growth. Ma terial imbibed for shorter periods prior to cryostorage exhibited less dama ge to the cells of the meristem and this was linked to the low level of cel lular metabolism as indicated by the ultrastructure.