Vitrification-cryopreservation procedure causes physiological and histology injuries to dormant buds of Codonopsis pilosula (Franch.) Nannf. while all maintain genetic integrity in cryo-derived plantlets

Vitrification-based cryopreservation exhibits considerable potential for the large-scale preservation of plant genetic resources. This study investigated the physiological and histological alterations in dormant buds of Codonopsis pilosula (Franch.) Nannf. during cryopreservation. At the loading stage, superoxide dismutase (SOD) activity and proline content were significantly elevated, whereas catalase (CAT) activity, peroxidase (POD) activity, ascorbate (ASA) content, and reduced glutathione (GSH) content were markedly reduced. Treatment with Plant Vitrification Solution 2 (PVS2) and freeze-thawing resulted in decreased SOD activity but exerted minimal effects on other aforementioned indicators. Plasmolysis was observed following the loading treatment and was further exacerbated after PVS2 exposure. Surviving cells were primarily localized in the apical meristem, leaf primordia, and upper region of the bud axis. Cooling in liquid nitrogen (LN) and subsequent freeze-thawing caused extensive damage to cells in the outer and lower regions of the bud axis.Cryopreserved shoot tips exhibited a high survival rate without detectable phenotypic or genetic variations. These findings enhance the understanding of the mechanisms underlying dormant bud cryopreservation and provide a basis for optimizing plant cryopreservation protocols.