中文摘要：

用不同浓度的Na2CO3以及与之各个浓度分别对应等渗的NaCl处理星星草幼苗7d后，测定幼苗渗透势、pH值、电解质外渗率、超氧化物歧化酶（SOD）、抗坏血酸过氧化物酶（APX）、谷胱甘肽转移酶（GST）、O2^-·产生速率和丙二醛（MDA）含量。当基质渗透势相等时，Na2CO3的碱性盐浓度明显比NaCl的低，而pH值要高的多。与NaCl处理相比．Na2CO3胁迫使星星草幼苗渗透势、叶绿素含量下降幅度更明显。当培养基质渗透势较高时，NaCl和Na2CO3胁迫下的星星草幼苗叶绿体SOD和APX活性都呈上升趋势。随着基质渗透势的降低。酶活性也下降．但NaCl胁迫下星星草幼苗叶绿体保护酶活性比Na2CO3胁迫下的强。而Na2CO3胁迫下的相对电导率、O2^-·产生速率和MDA含量高于NaCl胁迫的。这可能与Na2CO3胁迫的pH值较高．渗透调节能力较低．保护酶活性较弱，活性氧清除能力降低有关。

英文摘要：

P. tenuiflora was treated under iso-osmotic Na2CO3 and NaCl solution for 7 d, and the effects of the salt and alkali on osmotic potential of leaves, relative electric conductance, superoxide dismutase （SOD）, ascorbate peroxidase （APX）, glutathione transferase （GST）, O2^- · producing rates and MDA content were studied. Compared with NaCl culture under isotonic stress, there was a significantly higher pH value and lower concentration of salt in Na2CO3 culture. The osmotic potential and SPAD of seedling leaves of P. tenuiflora significantly decreased more under Na2CO3 stress than under NaCl stress. Activities of APX and SOD showed a similar trend of increase （more than -3.40 ×10^5 Pa） then decreased as the osmotic potential of the culture solution decreased. However, there was no obvious change in GST activity under Na2CO3 stress. APX,GST and SOD activities under NaCl stress were higher than those under Na2CO3 stress, and the higher activities of antioxidant enzymes in chloroplasts was accompanied by lower relative electric conductance, O2^- ·producing rates and MDA content under NaCl stress. All the above results showed that P. tenuiflora resistance to Na2CO3 stress was less than that to NaCl. This was probably due to a decrease of buffering pH value in cells, lower osmotic potential and lower ability of scavenging reactive oxygen species （ROS）, because of the weak SOD, APX and GST activities.