NaCl胁迫对4种豆科树种幼苗生长和K^+、Na^+含量的影响

Effects of NaCl stress on the seedling growth and K^+ -and Na^+ -allocation of four leguminous tree species

以合欢、刺槐、国槐和皂荚4种豆科树种盆栽实生幼苗为试验材料,研究了NaCl胁迫下4个树种幼苗的生长、耐盐临界浓度和Na+、K+含量的变化,并对其耐盐性进行了比较.结果表明:NaCl胁迫抑制了4个树种幼苗的生长,苗木的干物质积累量减小、根冠比增大,尤其对合欢和皂荚的影响较大;以相对干质量降至对照组50%时的NaCl浓度作为生长临界NaCl浓度(C50)指标,4个树种的耐盐强弱顺序为:刺槐(5.0‰)>国槐(4.5‰)>皂荚(3.9‰)>合欢(3.0‰);随NaCl浓度的增加,各树种幼苗根、茎、叶中Na+含量逐渐增加,K+含量先增加后减小(合欢根除外),而K+/Na+差异较大.相同浓度NaCl胁迫下,幼苗器官的Na+分布为根>茎>叶,K+因树种和NaCl浓度不同而各异,以叶片中较多,K+/Na+为叶>茎>根.NaCl胁迫下,刺槐的K+含量和K+/Na+较高,地上部分Na+含量较低,幼苗干物质量大,耐盐性较强;而合欢的K+/Na+较小,高浓度NaCl胁迫下地上部分的Na+含量较高,幼苗干物质量小,耐盐性较差.苗木地上部分对K+的积累和根部对Na+的滞留是影响豆科树种耐盐性能的主要因素.

Taking the pot-cultured seedlings of four leguminous tree species（Albizia julibrissin,Robinia pseudoacacia,Sophora japonica,and Gleditsia sinensis） as test materials,this paper studied their growth indices,critical salt concentration（C50）,and K＋ and Na＋ allocation under different levels of NaCl stress,aimed to understand the difference of test tree species in salt tolerance.NaCl stress inhibited the seedling growth of the tree species.Under NaCl stress,the dry matter accumulation decreased,while the root/shoot ratio increased,especially for A.julibrissin and G.sinensis.Quadratic regression analysis showed that the C50 of A.julibrissin,R.pseudoacacia,S.japonica,and G.sinensis was 3.0‰,5.0‰,4.5‰,and 3.9‰,respectively,i.e.,the salt tolerance of the four tree species was in the order of R.pseudoacacia S.japonica G.sinensis A.julibrissin.In the root,stem,and leaf of the four tree species seedlings,the Na＋ content increased with the increase of NaCl stress,while the K＋ content（except in the root of A.julibrissin） decreased after an initial increase,resulting in a larger difference in the K＋/Na＋ ratio in the organs.Under the same NaCl stress,the allocation of Na＋ in different organs of the four tree species seedlings decreased in the order of root stem leaf,while that of K＋ differed with tree species and NaCl stress,and leaf was the main storage organ for K＋.The K＋/Na＋ ratio in different organs decreased in the sequence of leaf stem root.R.pseudoacacia under NaCl stress accumulated more K＋ and less Na＋ in stem and leaf,and had higher K＋/Na＋ ratio in all organs and higher dry mass,being assessed to be more salt-tolerant.In contrast,A.julibrissin under high NaCl stress accumulated more Na＋ in stem and leaf,and had a lower K＋/Na＋ ratio in all organs and lower dry mass,being evaluated to be lesser salt-tolerant.The K＋ accumulation in seedling stem and leaf and the Na＋ retention in seedling root could be the main reasons for the salt tolerance of leguminous tree species under NaCl stress.