玉米胚发育过程中脱水耐性的变化

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

对离体玉米胚脱水耐性的变化以及不同脱水速率对其脱水耐性的影响进行了研究.授粉后16 d的玉米胚能耐轻微脱水,含水量从1.45降低到0.28g H2O g-1 DW时胚的萌发率为100%,但含水量低于0.1 g H2O g-1 DW时胚死亡.胚的脱水耐性随着发育逐渐加强,表现为电解质渗漏速率逐渐降低,萌发率和幼苗干重逐渐增加.授粉后20 d胚内超氧化物歧化酶(SOD)和抗坏血酸过氧化物酶(APX)活性较高,过氧化氢酶(CAT)活性较低;授粉后24 d,这些酶的活性与授粉后20 d的正好相反.脂质过氧化产物丙二醛(MDA)在种子发育过程中呈下降趋势.不同脱水速率明显地影响胚的脱水耐性:在慢速脱水到含水量0.1～0.18 g H2O g-1 DW时,胚的萌发率和幼苗干重比快速脱水高,电解质渗漏速率比快速脱水低;在快速脱水条件下胚中的SOD、APX活性和MDA含量也比慢速脱水高;CAT活性的变化不明显.

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.