中文摘要：

为探究植物抗盐、碱生理机制的异同，根据东北地区盐碱化草原土壤可溶性盐分的组成特点，模拟0～240mmol／L的盐胁迫和碱胁迫条件，对苗龄8周的星星草（Puccinelliatenuiflora）幼苗进行了胁迫处理，分析了两种胁迫下植株体内外有机酸组分及其含量的变化．结果表明：在盐胁迫和碱胁迫条件下，星星草茎叶中所含的有机酸均以苹果酸、草酸、柠檬酸和琥珀酸为主，但有机酸总量和比例显著不同．星星草茎叶中的有机酸总量随着碱胁迫强度的增大而急剧上升，但随着盐胁迫强度的增大而略有下降．在4种有机酸中，碱胁迫对柠檬酸含量的影响差异最大，使其构成了碱胁迫下有机酸积累的主体．对于盐、碱胁迫下星星草根系分泌物的研究表明：只有在碱胁迫条件下，星星草根系才分泌有机酸而且柠檬酸是唯一可检测出的成分．说明体内大量积累和根系分泌以柠檬酸为主的有机酸是抗碱盐植物星星草对碱胁珀的关键生理响应．

英文摘要：

The stresses triggered by the soluble salts and alkali salts of the salt-alkaline grasslands of north-eastern China were simulated. Eight-week old Puccinellia tenuiflora seedlings were treated with either of these salts to study the differences of physiological mechanism by plants. The treatments included salt concentrations ranging from 0 to 240 mmol/L. The differences in the effects of salt stress and alkali stress were analyzed and compared by determining the changes in the quantities and compo- sitions of organic acids in P. tenuiflora in response to salt or alkali stress. The result shows that the constituent organic acids in the shoots of P. tenuiflora were included predominantly malic acid,oxalic acid,citric acid,and succinic acid under salt stress and alkali stress. However,these two stressors led to differences in the total quantities of organic acids and the proportion of each organic acid in the total. The total content of organic acids in the shoots of P. tenuiflora increased rapidly with increased alkali- induced stress, but did not increase or even decreased slightly with increased salt stress. Of these four organic acids, the difference in the citric acid content was the most striking between salt-stressed and alkali-stressed plants,in that citric acid became the dominant component under alkali stress. The roots did not secrete any organic acid, when stress free or under salt stress, but did so under alkali stress, when citric acid was the only detectable component. Based on these results, propose that the key physi- ological responses of P. tenuiflora to alkali stress are the accumulation of large quantities of organic acids in its shoots and their secretion from its roots,with citric acid the dominant component.