Enzymatic and nonenzymatic antioxidant systems impact the viability of cryopreserved Paeonia suffruticosa pollen

Abstract

Antioxidant systems are important defense systems in plants, and studying their response to environmental stress helps reveal the mechanisms underlying plant stress tolerance. Pollen from three Paeonia suffruticosa cultivars with significant differences in viability after cryopreservation was used to study the relationship between pollen viability and the enzymatic and nonenzymatic antioxidant systems. The pollen viabilities of one cultivar decreased after cryopreservation, one was stable and one increased. The reactive oxygen species (ROS) contents were significantly different in the three cultivars. ROS in the cultivar with increased viability was significantly lower than in the other two cultivars. The oxidative damage indices of the malondialdehyde (MDA) and protein carbonyl (PCO) contents were significantly lower in the cultivar with increased viability than the other two cultivars while the superoxide dismutase (SOD) activity was higher. The difference in the peroxidase (POD), catalase (CAT), ascorbic acid peroxidase (APX), and glutamate reductase (GR) activities was not significant. SOD activity was significantly correlated with the MDA and POD contents. In the cultivar with increased viability, ascorbic acid (AsA) was lower than in the other two cultivars and glutathione (GSH) was higher. AsA was significantly positively correlated with the MDA and PCO contents, while GSH was significantly negatively correlated. This indicated that the membrane lipid and protein oxidative damage caused by ROS was a major cause of the decrease in pollen viability after cryopreservation. SOD, AsA and GSH effectively maintained the internal balance of oxidative metabolism and reduced the levels of oxidative damage, thus ensuring pollen viability. After cryopreservation, pollen viability showed different changes, enzymatic and non-enzymatic antioxidant systems plays an important in viability difference through effect on the ROS.