烟草幼苗根系抗氧化系统对渗透胁迫的生理响应

用不同渗透势的PEG-6000对2个烟草品种幼苗根系进行渗透胁迫处理，研究了根系质膜透性，MDA含量和抗氧化系统的变化情况。结果表明，根系质膜透性随渗透胁迫强度的加强而增大，根中MDA含量和H2O2含量增加。渗透胁迫期间几种保护酶活性变化不同，SOD和CAT活性呈先升后降的变化趋势，POD活性上升，而抗坏血酸过氧化物酶(ASP)活性下降。根中抗氧化物质(ASA和GSH)在低渗透胁迫下含量增加，高渗透胁迫下含量下降。渗透胁迫期间根系抗氧化酶和抗氧化物质含量与膜脂过氧化水平及膜透性呈一定的负相关性。2个供试品种的抗氧化系统对PEG-6000渗透胁迫的反应存在一定差异。

PHYSIOLOGICAL RESPONSES OF THE ANTIOXIDANT SYSTEM IN THE ROOTS OF TOBACCO SEEDLINGS UNDER OSMOTIC STRESS

Two tobacco cultjvars (Hongda and NC 89) were exposed to different levels of osmotic stress created by PEG-6000 and the changes in the relative permeability of the plasma membrane, MDA content and the antioxidant system in the roots were studied. The permeability of the plasma membrane, and MDA and H2O2 contents increased with osmotic stress. During osmotic stress, SOD and CAT activities in tobacco roots showed a rise, followed by a drop, POD activity kept rising and ASP activity dropped. The contents of the antioxidants (AsA and GSH) increased under low osmotic stress and decreased under high osmotic stress. A negative correlation was present between antioxidant enzyme activity and antioxidant content in the roots, on the one hand, and the level of membrane-lipid peroxidation and the permeability of plasma membrane, on the other. A certain difference existed between the two cultivars tested in the response of their antioxidant system to the osmotic stress.