Vitrification of cryopreserved mint shoot tips as followed by cryo-SEM and DSC

ALINE S. TEIXEIRA; M. ELENA GONZALEZ-BENITO; ANTONIO D. MOLINA-GARCÍA

Praga

Congreso; 23rd IIR International Congress of Refrigeration; 2011

Several currently successfully applied plant germplasm cryopreservation methods rely on cytoplasm vitrification for storage with almost complete stoppage of both chemical reactions and physical processes and without ice crystal biological damage. These procedures involve a serial of previous steps leading to natural defence induction, water content reduction and overall cytoplasm molecular mobility impairment. A quick cooling step by immersion in liquid nitrogen follows. Mint shoot tips, in different stages of the “droplet” cryopreservation protocol, were studied both by cold-stage scanning electron microscopy (cryo-SEM) and differential scanning calorimetry (DSC). Results show how cells at intermediate treatment steps develop ice crystals during liquid nitrogen cooling, while specimens whose treatment was completed become vitrified, with no evidence of ice formation. These results perfectly agree with the generally observed plant recuperation after cryopreservation and allow some preliminary conclusions to be extracted, concerning the cryopreservation protocol followed.