【作者】 张云霞；

【导师】 陈少良；

【作者基本信息】 北京林业大学 ， 植物学， 2008， 硕士

【摘要】 本文以典型的耐盐树木胡杨（Populus euphratica Oliv.）和不耐盐的群众杨（Populus‘pupularis 35-44’,P.popularis）为实验材料,比较研究了两种杨树的盐胁迫响应机制。实验结果表明,胡杨对初始盐胁迫的灵敏响应与其抗盐性密切相关,而且发现在初始盐胁迫诱导胡杨气孔关闭的过程中,是由ABA和CaM共同参与的。具体实验结果如下;1、长期盐胁迫（盐处理19天,土壤NaCl浓度从111.8 mmol/L提高到250.0mmol/L）（1）胡杨叶片气体交换盐胁迫开始阶段就明显下降,群众杨反应明显滞后于胡杨,在第6天才显著降低,说明胡杨感知土壤盐分敏感于群众杨。而且,在整个盐胁迫过程中,胡杨始终保持较高的气孔导度（Gs）、蒸腾速率（EVAP）和净光合速率（Pn）,而群众杨在盐处理13天后,叶片气体交换就剧烈下降,而且出现明显的盐害症状。（2）在盐处理伊始,胡杨叶片ABA,CaM含量就迅速增加,且在整个高盐胁迫过程中,都保持了相对较高的ABA和CaM浓度,即使在第19天高盐胁迫下,仍分别为对照的1.2倍和1.9倍。而群众杨则仅为对照的52%和55%。因此,在长期盐胁迫条件下,胡杨有相对较强的合成胁迫信使—ABA和CaM的能力,而且我们推断在盐胁迫诱导胡杨气孔关闭的过程中,需要ABA和CaM的共同参与。2、初始低盐胁迫（50 mmol/L NaCl,4h）在初始盐胁迫下,胡杨叶片ABA和CaM水平提高,叶片气孔导度、蒸腾速率和净光合速率相应迅速下降,表明ABA和Ca²⁺/CaM参与了胡杨盐诱导的气孔关闭。5mmol/L钨酸钠（ABA合成抑制剂）、10mmol/L EGTA(胞外Ca²⁺螯合剂)和5mmol/L LaCl₃(Ca²⁺通道抑制剂)处理胡杨根部24h,对照苗木叶片的EVAP、Gs和Pn未受到影响,却提高了盐处理苗木（50 mmol/L NaCl,4h）的气体交换。结果显示,盐诱导内源ABA和CaM水平的提高导致了胡杨叶片的气孔关闭,这是因为;（1）钨酸钠处理降低了盐处理苗木的ABA水平,增加了CaM的含量;（2）EGTA或LaCl₃处理显著降低了胡杨的CaM水平,但ABA水平显著升高。3、外源ABA导入通过导入外源ABA来模拟盐诱导内源ABA水平的提高,发现茎部导入的ABA（10μmol/L 4h和8h）能使胡杨叶片ABA和CaM水平迅速升高,叶片Gs、EVAP和Pn相应迅速下降,而先ABA导入的5 mmol/L LaCl₃或5 mmol/L EGTA虽然提高了ABA的水平,但却显著降低了CaM水平,ABA（10μmol/L,4h和8h）诱导胡杨的气孔关闭也受到明显抑制。此外,本文还比较研究了胡杨叶片对外源ABA导入浓度（10μmol/L和100μmol/L）的不同响应。以上研究结果显示,钨酸钠、EGTA和LaCl₃的使用,都能抑制盐诱导胡杨的气孔关闭,因此,在初始盐胁迫诱导胡杨气孔关闭的过程中,ABA和CaM很可能是共同作用;即诱导细胞内Ca²⁺水平的提高,激活外向的K⁺通道和Cl^-通道,诱导气孔关闭,从而降低经由蒸腾流进行的根冠盐离子运输。总之,胡杨对初始盐胁迫的灵敏响应对其适应长期盐胁迫具有重要意义。更多还原

【Abstract】 Using a salt-resistant woody species,Populus euphratica Oliv.and a salt-sensitive woody species, Populus ’pupularis 35-44’（P.popularis）,we investigated the genotypic difference in the response to salt stress.Results showed that P.euphratica seedlings were sensitive to the initial salinity,which contributing to the salt tolerance in a longer-term of stress.Furthermore,we found that the initial salinity-induced stomatal closure was the result of increased endogenous abscisic acid（ABA）and calmodulin（CAM）.1.A longer-term of increasing salinity（19 days,NaCl increased from 111.8 mmol/L to 250.0 mmol/L）（1）Leaf stomatal conductance（Gs）,unit transpiration rate（EVAP）and net photosynthetic rate （Pn）markedly decreased in P.euphratica after the onset of NaCl treatment.The salt-induced decline of gas exchange in P.popularis took place on day 6,indicating that P.popularis leaves were less sensitive to the initial soil salinity.Moreover,P.euphratica maintained higher Gs,EVAP and Pn throughout the duration of salt stress.However,leaf gas exchange were severely restricted in P.popularis after day 13, Meanwhile,symptom of salt damage was clearly seen in P.popularis leaves.（2）Endogenous leaf ABA and CaM contents in P.euphratica significantly increased at the beginning of treatment,and P.euphratica maintained higher leaf ABA and CaM during the period of salinity,e.g.ABA and CaM content was 1.2 times and 1.9 times of that in controls after 19 days of salt stress.However,leaf ABA and CaM in P.popularis was markedly reduced by salt stress,which were 52% and 55% of that in controls at the end of experiment.Results suggest that P.euphratica had a higher capacity to synthesize stress signal—ABA and CaM under a longer-term of increasing salinity. Moreover,the increased endogenous ABA and CaM may contribute to the salt-induced stomatal closure.2.A short-term of salinity（50 mmol/L NaCl,4h） Endogenous abscisic acid（ABA）and calmodulin（CAM）in P.euphratica leaves significantly increased after the onset of NaCl treatment（50 mmol/L NaCl,4h）,stomatal conductance,unit transpiration rate and net photosynthetic rate markedly declined correspondingly,suggesting that the increased concentrations of ABA and CaM both contribute to the salt-induced stomatal closure.Gs,EVAP and Pn in control plants were not changed after plants subjected to 24 hours of 5 mmol/L tungstate（sodium form）（ABA synthesis inhibitor）,10mmol/L EGTA（extracellular calcium chelator）or 5mmol /L LaCl₃（calcium channel inhibitor）treatment,but leaf gas exchange of NaCl-stressed plants（50 mmol/L NaCl,4h）was significantly elevated.Results showed that tungstate （sodium form）application decreased ABA synthesis but increased CaM levels in salt-stressed plants,in contrast,EGTA or LaCl₃ treatment decreased CaM levels but increased ABA synthesis in stressed P. euphratica.Accordingly,application of tungstate（sodium form）,EGTA or LaCl₃ exhibits an inhibitory effect on salt-induced stomatal closure.3.Extraneous ABA introductionExtraneous ABA was applied via xylem feeding to mimic the salt-induced elevation of ABA in P. euphratica leaves.Endogenous abscisic acid（ABA）and calmodulin（CAM）in P.euphratica leaves significantly increased after ABA application（10μmol/L,4h,8h）,and Gs,EVAP and Pn correspondingly declined.The introduction of 5mmol/L EGTA or 5mmol/L LaCl₃ prior to ABA-feeding decreased CaM levels and the inhibitory effect of ABA on leaf gas exchange was significantly reduced although ABA levels were increased by EGTA or LaCl₃ application.Moreover,we examined the concentration effect of ABA（10μmol/L and 100μmol/L）on leaf gas exchange in P.euphratica.Collectively,application of tungstate（sodium form）,EGTA or LaCl₃ exhibits an inhibitory effect on ABA-induced stomatal closure,suggesting that ABA and CaM both participate in the process of salt-induced stomatal closure,which induces the increase of cytosol Ca²⁺concentration and activates the outward K⁺ and Cl^- channels,causing stomatal closure and subsequently reduces the root-to-shoot salt transport via transpiration stream.更多还原