Abstract: Developing maize embryos were used to investigate the relationship between developmental changes in desiccation tolerance and antioxidant system . The results indicated that maize embryos acquired germinability at 18 days after pollination(DAP), but were desiccation-sensitive .Maize embryos started to acquire desiccation tolerance at 36 DAP, and the tolerance to dehydration gradually increased with development . With embryo development , the activities of superoxide dismutase (SOD) , ascorbate peroxidase (APX), glutathione reductase (GR) and dehydroascorbate reductase (DHAR) gradually
decreased , while catalase (CAT) activity significantly increased . The ascorbic acid (AsA) contents could not be detected in 16 - 22 DAP embryos, and notably increased in 24- 50 DAP embryos. Reduced glutathione (GSH) contents gradually increased during development of embryos . The activities of SOD, APX and DHAR in dehydrated embryos were lower than those in control ( non-dehydrated embryos), however , the CAT and GR activities were higher in control embryos thanin dehydrated samples during the early stage of development , and were lower during the middle and late stages . Contents of AsA and GSH of dehydrated embryos obviously decreased compared with non-dehydrated embryos. Malondialdehyde (MDA) contents of embryos gradually decreased with development , and those of dehydrated embryos were higher than control. These results showed that the increase in catalase activity and AsA and GSH contents, and decrease in MDA content were closely related to acquisition of desiccation tolerance of maize embryos .

Key words: Antioxidant system