Changes in Desiccation Tolerance of Maize Embryos during It's Development

Changes in desiccation tolerance of isolated maize embryos and effect of drying rate on embryo desiccation tolerance were discussed in this paper.The maize embryos could tolerate a slight dehydration after they were pollinated for 16 days.When water content descended from 1.45 to 0.28?g H_2O g -1 DW,embryo germination was 100%,whereas embryos died when their water content were less than 0.1?g H_2O g -1 DW.The embryo desiccation tolerance increased gradually in accordance with its development,which presented as the electrolyte leakage decreasing and the germination and dry weight of seedlings increasing.At 20 days after pollination (DAP),the superoxide dismutase (SOD) and the ascorbate peroxidase (APX) were relatively more active than that of 24 DAP,which was opposite to catalase (CAT).The malonylaldehyde (MDA) content showed a tendency of declining in the course of seed development.Different drying rate had an obvious influence on desiccation tolerance.When water content decreased to 0.1-0.18?g H_2O g -1 DW at a slow speed of dehydration,embryo germination and dry weight of seedlings were higher than that of rapid dehydration,but electrolyte leakage was lower.The SOD,APX activities and MDA content in the condition of rapid dehydration were higher than that of slow dehydration.The changes of CAT activities are not evident.