The role of hydrogen peroxide in cryopreservation of cockscomb (Celosia plumosa) seedlings

Recently, many researches showed that oxidative stress is a potential cause of damage in plant cells during cryopreservation, and hydrogen peroxide (H(2)O(2)) may be the leading reactive oxygen species (ROS) components. However, H(2)O(2) is not only being a toxic by product causing oxidative damage to membrane lipids, protein and DNA at high concentrations, but also involving in signal transduction pathways leading to activate the plant defense against biotic and abiotic stresses at low concentrations. The effects of H(2)O(2) in cryopreservation were investigated in the present study by adding H(2)O(2) or CAT in each step of cryopreservation, detected the dynamic changes in antioxidant systems during cryopreservation of cockscomb seedlings. The results showed that: 1) the process of cryopreservation resulted in the rise of H(2)O(2), and it reached the peak after unloading; 2) addition of either low concentration of H(2)O(2) or CAT can improve the regeneration rate of cryopreserved cockscomb seedlings, while sthe addition stages were different. Adding 4 µmol L(-1)H(2)O(2) in loading stage got 73.33±3.52% regeneration rate, and adding 200 U mL(-1) CAT during the unloading process resulted in 76.67±4.17% regeneration rate; and 3) the addition of H(2)O(2) in loading phase increased the activity of CAT in the seedlings, resulting a sharp drop of H(2)O(2) content at PVS2 stage and the continuous decline of MDA content after freezing. Therefore, we conclude that adding low concentration of H(2)O(2) at early cryopreservation steps improves cockscomb seedlings' cryo-tolerance by enhancing the antioxidant capacity, which prevents ROS accumulation.