NO可能作为Ca^2＋的下游信号介导乙烯诱导的蚕豆气孔关闭

以蚕豆（Vicia faba L．）为材料,利用药理学实验,结合激光共聚焦显微技术和分光光度法．探讨Ca^2＋和一氧化氮（nitric oxide,NO）在乙烯（ethylene,Eth）调控气孔运动信号转导中的作用。结果表明．光下乙烯利（0．004％,0．04％,0．4％）可诱导蚕豆叶片气孔关闭,且具有时间和剂量效应：NO清除剂cPTIO、硝酸还原酶（nitrate reductase,NR）抑制剂NaN3及胞外Ca^2＋螯合剂EGTA可部分逆转乙烯诱导的气孔关闭;乙烯能够明显增加气孔保卫细胞NO水平;提高蚕豆叶片NO含量和NR活性．并且NO的含量变化与NR活性的变化趋势基本一致;NR抑制剂NaN3可抑制乙烯诱导的气孔保卫细胞和叶片NO含量的增加;清除胞外Ca^2＋可减弱乙烯对NO含量和NR活性的诱导效应。说明Ca^2＋和NO均参与乙烯诱导的蚕豆气孔关闭,且NO（主要由NR途径合成）可能位于Ca^2＋下游参与调控这一信号转导过程。     

乙烯产生抑制剂对高温胁迫下蚕豆幼苗叶片的保护作用

该文报道了乙烯产生抑制剂氯化钴(CoCl₂)及氨基乙基乙烯基甘氨酸(Aminoethoxyvinylglycine, AVG)对高温胁迫下蚕豆(Vicia faba)幼苗叶片保护作用的现象及机制。研究结果表明,用CoCl₂和AVG溶液处理,在高温胁迫前及胁迫12 h时皆显著抑制乙烯产生。20 μmol·L ^-1 CoCl₂浇灌处理在高温胁迫前可以显著提高叶片抗氧化酶SOD、CAT、APX的酶活力,而20 μmol·L ^-1 AVG处理对这些抗氧化酶活力无显著影响。20 μmol·L ^-1 CoCl₂ 与20 μmol·L ^-1 AVG溶液浇灌处理在高温胁迫前对腐胺(Put)、亚精胺(Spd)、精胺(Spm)、叶绿素含量、活性氧(ROS)产生速率和脂质过氧化程度无显著影响。但经45 ℃高温胁迫12 h后,20 μmol·L ^-1 CoCl₂ 与20 μmol·L ^-1 AVG溶液处理显著提高了上述3种多胺的含量,减缓了抗氧化酶活性的下降,对活性氧水平及脂质过氧化水平的增加也起到了有效的抑制作用,这些改变可能对叶绿素降解的减少及膜稳定指数下降的减轻发挥着重要的作用。可见,通过抑制乙烯产生,相对提高多胺含量和抗氧化酶活性,以及抑制活性氧水平的提高和抑制细胞膜稳定指数的下降,CoCl₂和AVG对高温胁迫下的蚕豆幼苗叶片产生了一定的保护作用。     

Modulation of photosynthesis and respiration in guard and mesophyll cell protoplasts by oxygen concentration

Stomatal movement is an energetic oxygen-requiring process. In the present study, the effect of oxygen concentration on mitochondrial respiratory activity and red-light-dependent photosynthetic oxygen evolution by Vicia faba and Brassica napus guard cell protoplasts was examined. Comparative measurements were made with mesophyll cell protoplasts isolated from the same species. At air saturated levels of dissolved oxygen in the protoplast suspension media, respiration rates by mesophyll protoplasts ranged from 6 to 10μmoles O₂ mg^?1 chl h^?1, while guard cell protoplasts respired at rates of 200–300 μmoles O₂ mg chl^?1 h^?1, depending on the species. Lowering the oxygen concentration below 50–60 mmol m^?3 resulted in a decrease in guard cell respiration rates, while rates by mesophyll cell protoplasts were reduced only at much lower concentrations of dissolved oxygen. Rates of photosynthesis in mesophyll cell protoplasts isolated from both species showed only a minor reduction in activity at low oxygen concentrations. In contrast, photosynthesis by guard cell protoplasts isolated from V. faba and B. napus decreased concomitantly with respiration. Oligomycin, an inhibitor of oxidative phos-phorylation, reduced photosynthesis in mesophyll cell protoplasts by 27–46% and in guard cell protoplasts by 51–58%. The reduction in both guard cell photosynthesis and respiration following exposure to low oxygen concentrations suggest close metabolic coupling between the two activities, possibly mediated by the availability of substrate for respiration associated with photosynthetic electron transport activity and subsequent export of redox equivalents.     

蚕豆叶片SOD活性监测大气SO2污染的可行性研究

 本文从实验室熏气和野外大气暴露两方面对利用蚕豆叶片SOD活性评价和监测大气SO2污染的可行性进行了研究。低浓度SO2(0.1312、0.2601mg·m-3)处理,引起叶片SOD活性升高,一定时间后,SOD活性趋于稳定,且0.2601mg·m-3SO2处理时,SOD活性较高,表现出SOD活性增量与SO2浓度相关,为利用SOD活性监测和评价SO2污染提供了可能性。大气暴露试验结果表明SOD活性与大气硫酸盐化速率存在极显著的相关性。利用SOD活性和大气硫酸盐化速率分别对大气SO2污染程度进行了评价,结果基本一致,并根据SOD活性估测了大气硫酸盐化速率,符合程度较高,置信分析表明估测结果可信。以上结果表明,利用蚕豆叶片SOD活性监测和评价大气SO2污染是可行的。