BIPYRIDYLIUM QUATERNARY-SALTS AND RELATED COMPOUNDS .5. PULSE-RADIOLYSIS STUDIES OF REACTION OF PARAQUAT RADICAL WITH OXYGEN - IMPLICATIONS FOR MODE OF ACTION OF BIPYRIDYL HERBICIDES
BIPYRIDYLIUM QUATERNARY-SALTS AND RELATED COMPOUNDS .5. PULSE-RADIOLYSIS STUDIES OF REACTION OF PARAQUAT RADICAL WITH OXYGEN - IMPLICATIONS FOR MODE OF ACTION OF BIPYRIDYL HERBICIDES
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DOI：
10.1016/0005-2728(73)90121-7
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发表时间：
1973-01-01
期刊：
影响因子：
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通讯作者：
FLETCHER, K
中科院分区：
文献类型：
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作者：
FARRINGTON, JA;EBERT, M;FLETCHER, K
1.用脉冲辐解法测定了百草枯离子（1，1 ′-二甲基-4，4 ′-联吡啶基）（PQ ~（2+））通过− aq和CO_2 −·还原为百草枯自由基（PQ ~+·）的速率常数。− aq的还原是扩散控制的（k= 8.4·1010 M −1·s−1），CO2−·的还原也非常快（k = 1.5·1010 M −1·s−1）。对百草枯自由基与氧的反应进行了分析，得到百草枯自由基与O2和O2-·反应的速率常数分别为7.7·108 M −1·s− 1和6.5·108 M −1·s− 1。这些速率常数的相似性与O2和O2−·的氧化还原电位差异（分别为-0.59 V和+1.12 V）形成鲜明对比。这些速率常数，连同O2−·自身反应的速率常数，被用来计算在植物细胞中百草枯还原位点所适用的条件下O2−·的稳态浓度。根据这些计算，O2−·的衰变似乎几乎完全由其自身反应控制，距离类囊体5 μm处的浓度仍然是类囊体本身浓度的90%。因此，O2−·持续时间足够长，可以扩散到叶绿体被膜和液泡膜，这是百草枯处理后首先受到损害的结构。因此，O2−·的寿命足够长，足以成为百草枯在植物中形成的植物毒性产物的候选者。
1. Rate constants for reduction of paraquat ion (1,1′-dimethyl-4,4′-bipyridy-lium, PQ2+) to paraquat radical (PQ+·) bye−aqand CO2−· have been measured by pulse radiolysis. Reduction bye−aqis diffusion controlled (k= 8.4·1010M−1·s−1) and reduction by CO2−· is also very fastk= 1.5·1010M−1·s−1).2. The reaction of paraquat radical with oxygen has been analysed to give rate constants of 7.7·108M−1·s−1and 6.5·108M−1·s−1for the reactions of paraquat radical with O2and O2−·, respectively. The similarity in these rate constants is in marked contrast to the difference in redox potentials of O2and O2−· (− 0.59 V and + 1.12 V, respectively).3. These rate constants, together with that for the self-reaction of O2−·, have been used to calculate the steady-state concentration of O2−· under conditions thought to apply at the site of reduction of paraquat in the plant cell. On the basis of these calculations the decay of O2−· appears to be governed almost entirely by its self-reaction, and the concentration 5 μm away from the thylakoid is still 90% of that at the thylakoid itself. Thus, O2−· persists long enough to diffuse as far as the chloroplast envelope and tonoplast, which are the first structures to be damaged by paraquat treatment. O2−· is therefore sufficiently long-lived to be a candidate for the phytotoxic product formed by paraquat in plants.