Water content significantly influences post-cryopreservation survival of air-desiccated oil palm (Elaeis guineensis Jacq.) zygotic embryos: A thermal and ultrastructural study

The present study outlines the influence of free water content in oil palm (Elaeis guineensis Jacq.) zygotic embryos after desiccation on survival post-cryopreservation. Aseptically isolated zygotic embryos were analysed for water content and resurgence ability after air-desiccation and freezing (in liquid nitrogen). The results indicated that the desiccated zygotic embryos with water content of below 0.24 and above 0.16 g H2O /g dry weight (dw) exhibited survival after freezing. The survival was maximum (80%) when the desiccated zygotic embryos contained 0.16 g H2O /g dw of water content. This optimal water content not only helped oil palm zygotic embryos to sustain their cellular integrity but also assisted to retain their regeneration potential following cryopreservation. On the contrary, the zygotic embryos with water content above 0.24 g H2O /g dw or below 0.16 g H2O /g dw lost their viability as well as their cellular integrity attributable to either excess water content or excessive loss of water, after desiccation and successive freezing. Differential scanning calorimetric analysis revealed characteristic sharp peak for zygotic embryos with high water content and reduced peaks with successively lower water content. Scanning electron microscopic and transmission electron micrographic studies also confirmed that there was no noteworthy distinction in morphology of epidermal layer and cellular integrity between zygotic embryos with different water content before and after desiccation as well as their successive freezing. The parallel trend was reflected in their revival also. •Desiccated zygotic embryo with 0.16 g H2O/g dry weight survived freezing.•Maximum survival (80%) of zygotic embryos was obtained with 0.16 g H2O/g dry weight.•Differential scanning calorimetry showed distinct peaks at high free water that declined with desiccation.•Optimal free water ensured cellular integrity and post-freezing regeneration.•Post-desiccation and -freezing cellular ultrastructural features revealed via electron microscopy.