中文摘要：

通过盆栽实验,混合2种中性盐（NaCl∶Na2SO4=9∶1）和2种碱性盐（NaHCO3∶Na2CO3=9∶1）分别模拟不同强度的盐碱条件,处理35d的羊草幼苗,研究2种胁迫对羊草各营养器官生长和盐离子分布的影响及其适应机制。结果表明,随着盐和碱胁迫浓度的增加,羊草营养器官生物量、克隆生长性状（根茎子株、分蘖子株等）、光合作用、K^＋含量等均显著降低,Na^＋含量和Na^＋/K^＋均显著增加。在高胁迫强度下（200mmol/L）碱胁迫引起的各项指标增减均显著高于盐胁迫。在2种胁迫下,根茎生物量的降低幅度最大,根茎子株的降低量高于分蘖子株。在盐胁迫和低浓度碱胁迫下,根和根茎内Na^＋、K^＋含量和Na^＋/K^＋的增减均高于茎叶,在高浓度碱胁迫下（200mmol/L）茎和叶内Na^＋含量显著增加。这表明在相同强度胁迫下,尤其在高浓度胁迫下,羊草耐盐而不耐碱,在盐胁迫和低浓度的碱胁迫下,羊草具有相似的生长适应策略及Na^＋、K^＋代谢响应,主要表现在减少向根茎的能量输出及子株产生,维持羊草的原位生长策略,同时将Na^＋向根茎和根区划,避免茎叶生长受损。但在高碱胁迫下,pH造成的胁迫超出羊草根与根茎的承载力,使其失去拦截Na^＋的功能而导致大量Na^＋涌入茎叶,进而影响其光合作用,使其生长严重受损。无论在生长适应或者Na^＋、K^＋代谢中,根茎的存在均起到一定的保护作用,缓解了盐碱胁迫对其他器官生长的伤害。

英文摘要：

Two neutral salts（NaCl∶Na2SO4=9∶1） and two alkaline salts（NaHCO3∶Na2CO3=9∶1） were used to simulate different salt and alkali stresses on organ growth and ion metabolism and their adaptation strategies in 35 d old potted seedlings of Leymus chinensis.The dry weight of all organs,clonal growth（rhizome daughter and tiller daughter shoots）,photosynthesis and K^＋ contents decreased significantly while Na^＋ content and Na^＋/K^＋ ratio increased significantly,with increased salinity and alkalinity.Under a high concentration of 200 mmol/L,the change of all variables was higher under alkali than under salt stress.Under the two stresses,the biomass reduction of rhizomes was the largest and that of daughter shoots from rhizomes were higher than those from tillers.Under salt and lower alkali stresses,the changes of Na^＋,K^＋ contents and Na^＋/K^＋ ratio in rhizomes and roots were greater than those in stems and leaves.Under higher alkali stress,the Na^＋ content increased significantly in stems and leaves.In conclusion,L.chinensis was resistant to salt but not to alkali at the same concentration,especially at the higher concentration.Under salt and lower alkali stresses,L.chinensis had similar strategies of growth adaptation and Na^＋,K^＋ metabolism.Rhizome growth and daughter shoots were reduced to maintain development in situ and to compartmentalize the Na^＋ into rhizome and root to avoid stem and leaf growth damage.However,the high pH stress exceeded the carrying capacity of rhizome and root,leading to much Na^＋ transportation to stem and leaves,where it influenced photosynthesis and restrained growth.Either in growth adaptation or in Na^＋,K^＋ metabolism,the existence of rhizomes played a protective role to mitigate the harmful effects of salt or alkali stress on the other organs.