KMS XINJIANG INSTITUTE OF ECOLOGY AND GEOGRAPHY，CAS
| 重金属对拟南芥光系统的影响 | |
| 王淑智 | |
| Subtype | 博士 |
| Thesis Advisor | 潘响亮 |
| 2016 | |
| Degree Grantor | 中国科学院大学 |
| Place of Conferral | 北京 |
| Degree Discipline | 生态学 |
| Keyword | 拟南芥 重金属 毒性 光系统i 光系统ii |
| Abstract | 以水培模式植物拟南芥为实验材料，研究了镉（Cd）、铜（Cu）、汞（Hg）、镍（Ni）、铅（Pb）、锌（Zn）为代表的二价金属阳离子对拟南芥幼苗的生长、表观形态等毒性的差异，着重研究了各种重金属离子对拟南芥光合作用方面的毒害作用，如对叶绿素含量、叶片的光合放氧速率、光合系统的反应中心活性、供受体侧及电子传递的影响。比较了不同重金属对光系统的毒害程度，同时研究了重金属对光系统I（PSI）和光系统II（PSII）的毒性差异。采用了电子阻断剂和拟南芥突变体来研究重金属对光合电子传递中围绕PSI的环式电子传递的影响，及环式电子传递在光合器官在重金属胁迫下保护机制中所起的生理作用。研究了重金属离子和离体光系统颗粒的结合能力，以解释重金属毒性差异结果。 主要结果如下： 1.汞和铜对拟南芥幼苗的生长抑制作用最明显，毒害作用最强。之后毒性较强的是镉。镍、铅、锌对整株植物的毒害作用较小，镍的毒害作用最小。 2. 在不同重金属对光合放氧速率和叶片最大光化学效率Fv/Fm的对比中发现，镉、铜和汞的毒性均较强。与上述三种重金属相比，重金属锌的毒性作用较弱，对拟南芥植株生长毒性最小的铅和镍对光合放氧和Fv/Fm没有显著影响。 3. 汞是对拟南芥离体叶片的PSI和PSII均具有最强毒性的重金属。铜对PSII的电子传递(ETR)具有高毒性，然而铜对PSI的电子传递没有抑制作用。镉对PSII电子传递速率的光响应曲线造成的影响大于对PSI的。高浓度铅对于PSII和PSI的电子传递均有毒性作用。在重金属对PSI电子传递的毒害对比中铅的毒害作用与汞一样突出。锌处理对PSII电子传递有抑制作用，而对PSI的电子传递则没有体现抑制作用。各种重金属对PSI和PSII电子传递的影响中，镍的抑制作用最小，对PSI电子传递在一定浓度下有促进作用。对PSII电子传递速率的光响应曲线的抑制作用而言，不同重金属的抑制作用从强到弱次序为：汞>铜>镉≈锌>铅>镍。对PSI而言，汞有最强的毒性，铅也有抑制作用，镉、锌和镍作用不显著，而铜有促进作用。 4. 在各种重金属的胁迫处理下，野生型拟南芥离体叶片的CEF均有一定的激发，起到保护作用。和NDH途径相比，PGR5途径的缺失对环式电子传递的激发及其保护作用造成的影响较大。在镉胁迫处理下，CEF可以很好的激发，来保护PSI。相比于镉的处理，铜对环式电子传递有更加明显的促进作用。汞降低PSII和PSI的活力，降低整个电子传递链的活性。镍对电子传递的抑制作用小，CEF不需很高的激发即起到保护作用。高浓度铅的处理对PSI的电子传递造成影响，CEF没有激发来起到保护作用。锌和汞处理会对CEF中NDH途径造成抑制，使得pgr5突变体受到高浓度锌或汞处理后，两条CEF途径均无法起到作用。 5. 通过提取出类囊体膜进行77K低温荧光光谱研究发现，镉、铜和锌对PSII的影响更明显。汞对PSII的毒性作用也要强于对PSI的毒性，但是高浓度汞对PSI和PSII均有抑制作用。铅处理下PSII相对于PSI受到的抑制较重，但是不如镉、铜、汞和锌作用下的毒性作用大。几种重金属中毒性最小的镍对两个光系统的影响均较小。Hg和光系统颗粒的结合能力最强，可以解释Hg对光系统和光合作用器官的高毒性。Cd和Zn更易于与PSII结合，因此解释了Cd和Zn对PSII毒性强的原因。重金属Pb和其他重金属相比，与两个光系统的结合能力较弱，解释了Pb毒性较弱的原因。 |
| Other Abstract | The model plant Arabidopsis thaliana was used in the present study to investigate toxic effects of heavy metals, like cadmium (Cd), copper (Cu), mercury (Hg), nickel (Ni), lead (Pb), zinc (Zn), on the growth, appearance symptom, and especially photosynthetic performance of plants. The toxic effects of heavy metals on chlorophyll content, photosynthetic oxygen evolution, the activities of photosystems were tested. The difference between their toxic effects was compared to each other. The different effects of these heavy metals on photosystem I (PSI) and II (PSII) were analyzed. Electron transfer inhibitor was also used to investigate the response of cyclic electron flow (CEF) around PSI to different heavy metals treatments. Two strains of cyclic electron transport mutan were studied together with the wild type.We tested the binding ability of heavy metals and photosystems to detect the cause of the different toxic effects of these heavy metals. The main conclusions were as follows: (1) Among these heavy metals, Hg and Cu showed most obvious inhibition on growth of the plants. And their toxic effects were strongest. Cd showed less toxic effect than Hg and Cu. Ni, Pb and Zn showed less toxic effects on the whole plant than above heavy metals.The toxic effect of Ni was the weakest. (2) The toxic effects of heavy metals on A. thaliana were also tested by photosynthetic oxygen evolution rate and maximal photochemical efficiency (Fv/Fm). Similar to the inhibition on growth, Hg, Cu and Cd seriously decreased oxygen evolution rate and Fv/Fm. The toxic effect of Zn was less than above heavy metals. Ni and Pb almost caused no significant inhibition on oxygen evolution and Fv/Fm. (3) Hg was the most toxic heavy metal which showed stongest inhibition on the electron transport rates (ETRs) of both PSI and PSII. Cu caused strong inhibition on ETR of PSII as same as Hg treatment. However, Cu showed no inhibition on electron transport rate of PSI [ETR(I)]. Cd showed grester impact on light response curve of ETR(II) than that of ETR(I). Pb at high concentratin had toxic effect on electron transport of both PSII and PSI. The toxic effect of Pb on PSI electron transport was comparable with Hg. Zn could inhibit the electron transfer of PSII, but had no inhibitory effect on that of PSI. Among these heavy metals, the inhibition effect of Ni was minimal. Ni could enhanced ETR(I) at some concentrations. For the light response curve of ETR(II), the order of inhibitory effect of heavy metals from strong to weak was: Hg > Cu > Cd~Zn > Pb > Ni. As for PSI, Hg had the highest toxicity. Pb also caused inhibitory effect. Cd, Zn and Ni showed no significant effects, while Cu had a promoting effect. (4) After exposure to various heavy metals, CEF was excited in wild type A. thaliana to play a protective role. GPR5 pathway played more important role than NDH pathway as found in the CEF mutants. Under Cd treatment, CEF was sufficiently excitated to pretect PSI. This was more evident in Cu treated samples. Hg decrease the activities of PSI and PSII, and the whole electron transport chain. Ni showed less inhibition on the electron transport activity. Relatively lower excitation of CEF is enough to protect photosynthetic apparatus under Ni treatment. High concentration of Pb caused significant inhibition of electron transport in PSI with CEF not excitated. Zn and Hg could inhibit NDH pathway, which led the abolishment of CEF in the pgr5 mutant. (5) Cd, Cu and Zn mainly showed inhibitory effect on PSII derived from low temperature fluorescence spectra of extracted thylakoid membranes. Their toxicity to PSII were less than Hg. Hg showed high toxicity to both PSI and PSII at high concentration. PSII was more susceptible to Pb treatment than PSI. But the effect of Pb treatment was less than Cd, Cu, Zn and Hg. Ni caused no significant inhibition on two photosyntems. Hg showed strongest binding with photosystems, these leading to its strongest toxicity to photosynthesis and the activities of photosystems. Cd and Zn were more easier to bind with PSII. These results explained that why Cd and Zn showed stronger toxicity to PSII than PSI. Pb showed weaker binding with photosystems compared to other heavy metals, causing its weakest toxicity. |
| Subject Area | 生态学 |
| Language | 中文 |
| Document Type | 学位论文 |
| Identifier | http://ir.xjlas.org/handle/365004/14767 |
| Collection | 研究系统_荒漠环境研究室 |
| Affiliation | 中科院新疆生态与地理研究所 |
| Recommended Citation GB/T 7714 | 王淑智. 重金属对拟南芥光系统的影响[D]. 北京. 中国科学院大学,2016. |
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