Effect of storage temperatures on the viability and oxidative stress of Paeonia lactiflora pollen

Pollen typically carries all the male genetic information of the plant, but it is difficult to maintain its viability after isolation, so the appropriate preservation temperature is very crucial to preserve pollen viability. In this study, two cultivars of Paeonia lactiflora pollen were used as materials to study the changes in viability and physiological indexes of five preservation temperatures (4 degrees C, -20 degrees C, -40 degrees C, -80 degrees C and - 196 degrees C), to investigate the effect of preservation temperature on pollen. P. lactiflora 'Da Ban Hong' pollen exhibited significantly higher viability than fresh pollen after being preserved at -80 degrees C and - 196 degrees C, while 'Feng Yu Nu' pollen viability was maintained in a relatively stable state after storage at -80 degrees C and - 196 degrees C. Pollen viability of both cultivars was not significantly different from fresh pollen after preservation at -20 degrees C and - 40 degrees C, and the viability of both pollen cultivars was significantly lower than that of fresh pollen after preservation at 4 degrees C. The malondialdehyde (MDA) content of both cultivars pollen was significantly higher than that of fresh pollen after storage at 4 degrees C, and the protein carbonyl (PCO) content of 'Da Ban Hong' pollen after storage at 4 degrees C was also higher than that of fresh pollen MDA and PCO levels reduced to a similar level after storage at -20 degrees C, -40 degrees C, -80 degrees C and - 196 degrees C, and were negatively correlated with the content of superoxide anions (O2<middle dot>-) and viability, but positively correlated with the content of hydrogen peroxide (H2O2). The superoxide dismutase (SOD) activity, ascorbic acid (AsA) content, glutathione (GSH) content, dehydroascorbate reductase activity (DHAR) and monodehydroascorbate reductase (MDHAR) activity of pollen were enhanced after storage at -20 degrees C, -40 degrees C, -80 degrees C and - 196 degrees C. Furthermore, SOD activity, AsA content, GSH content and MDHAR activity were negatively correlated with hydroxyl radical (<middle dot>OH), and DHAR activity was negatively correlated with H2O2 content. These results indicated that increased ROS-induced oxidative damage to membrane lipids and proteins was one of the reasons for the decrease in pollen viability at 4 degrees C, while the oxidative metabolism was less after preservation at -20 degrees C or below, thus alleviating ROS-induced oxidative damage and maintaining or enhancing pollen viability after preservation.