The role of reactive oxygen species and antioxidants during precooling stages of axis cryopreservation in recalcitrant Trichilia dregeana

摘要

Cryopreservation is currently the only feasible method for long-term conservation of non-orthodox germplasm. Previous attempts to cryopreserve embryonic axes of Trichilia dregeana Sond. indicated that the inability to produce shoots, suggestedly associated with a wound-induced burst of reactive oxygen species (ROS) accompanied by declining antioxidant potential, consistently accompanied procedures necessary for cryopreservation. This study involved the provision of cathodic protection, both in the aqueous phase (electrolysis of a solution containing dilute electrolytes) and dry state (rapid drying of axes on a grid on which a static field is generated via the cathode of a power-pack) with the addition of other antioxidants, i.e., ascorbic acid and DMSO, to counteract uncontrolled ROS activity. The production of superoxide (center dot O-2(-)), hydrogen peroxide (H2O2), and hydroxyl radical (center dot OH) in conjunction with the corresponding total aqueous antioxidant activity and viability was quantitatively assessed after each stage of the cryoprocedure, with or without cathodic protection and (or) antioxidants. No shoot production occurred in the treatments without cathodic protection and (or) antioxidants. In contrast, 80% of axes produced seedlings after excision, 40% after cryoprotection, and 40% after flash (rapid) drying, when the treatments included a form of cathodic protection.