Abstract
This thesis discussed how to cryopreserve blue waterlily (Nymphaea caerulea) seeds. Due to lack of desiccation and low-temperature tolerance, N. caerulea is considered as recalcitrant, which hard to long-term storage by conventional method. Cryopreservation is an effective and economical method to recalcitrant seeds preservation. Seeds need to be vitrified using the plant vitrification solution (PVS) before cryopreservation. PVS3, a widely used PVS, was not effective in N. caerulea seeds cryopreservation. I hypothesized two reasons that caused PVS3 inefficiency, ice crystals forming and reactive oxygen species (ROS) - related programmed cell death (PCD). Ice crystals form at temperature from below 0℃ to glass transition temperature (Tg). Therefore, developing a PVS with higher Tg can narrow the temperature range, therefore producing less ice crystals forming. Germination rate of seeds treated with higher Tg PVSs were not increased to the normal level. However, PVS+, a glutathione (GSH) adding PVS, decreased ROS accumulation induced by cryopreservation and increased the germination rate to normal level. Previous consensus asuggested that ice crystals forming may be the main reason for cryopreservation inefficiency but my findings indicated that this consensus is oversimplified. It also suggested that ROS accumulation harmed seeds after cryopreservation and antioxidants may prevent the damage.