| | 1 | Author
| Magdolna Droppa, Sándor Demeter, Zsuzsa Rózsa, G. Ábor Horváth | Requires cookie* | | | Title
| Reinvestigation of the Effects of Disalicylidenepropanediamine (DSPD) and 2-HeptyM-hydroxyquinoline-N-oxide (HQNO) on Photosynthetic Electron Transport  | | | | Abstract
| The effects of disalicylidenepropanediamine (DSPD) and 2-heptyl-4-hydroxyquinoline-N-oxide (HQNO) on photosynthetic electron transport have been reexamined. The results confirm earlier observations that lower concentrations of DSPD (< 100 hm) block electron transport at the levels of ferredoxin and plastocyanin. High concentrations o f DSPD even inhibit electron transport from HaO -> pBQ, suggesting that DSPD has an inhibitory site in PS II as well. Thermoluminescence curves o f DSPD and DCMU treated chloroplasts were very similar, showing that the third inhibitory site o f DSPD is similar to that o f DCMU. Both oxidized and reduced HQNO, (0 .6 -6 hm) blocked electron transport from H20 -* pBQ, H20 -*■ MV/FeCy to a similar extent. The effect of HQNO on thermoluminescence showed that its inhibitory site is probably located before that o f DCMU. At higher concentration (> 6 h m) , the H20 -*■ MV/FeCy reactions were more strongly inhibited by oxidized HQNO than those occuring from H20 -> pBQ, suggesting that a new site o f inhibition must also be considered. The dark decay of the P 700 signal was not influenced by the addition o f oxidized HQNO which shows that the new inhibitory site of HQNO is located between plastoquinone and P 700. The reduced form of HQNO did not inhibit non-cyclic electron transport around PS I. Indeed, at higher concentrations, reduced HQNO even accelerates electron flow from DCIP -» MV and the dark reduction of P 700, thus suggesting that this compound has a "donor-mediator" function in PS I. | | | |
Reference
| Z. Naturforsch. 36c, 109 (1981); received September 8/October 28 1980 | | | |
Published
| 1981 | | | |
Keywords
| Inhibitors, Electron Transport, Chloroplasts, Thermoluminescence | | | |
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| default:Reihe_C/36/ZNC-1981-36c-0109.pdf | | | | Identifier
| ZNC-1981-36c-0109 | | | | Volume
| 36 | |
| 2 | Author
| Klaus Pfister, H. Artm, K. Lichtenthaler, G. Ünther Burger, Hans Musso, M.Anuel Zahn | Requires cookie* | | | Title
| The Inhibition of Photosynthetic Light Reactions by Halogenated Naphthoquinones | | | | Abstract
| Halogenated naphthoquinones act as inhibitors o f photosynthetic electron flow. I50 concentra tion for inhibition of methylviologen reduction were found to range between 2 x 10-5 m to 2 x 10-6 M. Comparing their effects on several partial reactions o f electron flow, the inhibition site o f the naphthoquinones was found to be at the reducing site o f PS II. Studies o f fluorescence transients in presence o f halogenated naphthoquinones give further evidence for a site action similar to that o f diuron and different to that of DBMIB. All naphthoquinones act as quenchers o f chlorophyll fluorescence with pure chlorophyll a, and with much higher efficiency in green algae and chloroplasts. It is concluded, that the halogenated naphthoquinones act similar to PS II-inhibitors like diuron, but do not share a common binding site at the PS II-complex. Implications of a possible involvement of phylloquinone K 1 in photosynthetic electron transport are discussed. The synthesis o f 2-chloro-as well as 2-bromo-3-isopropyl-1,4-naphthoquinone is described. | | | |
Reference
| Z. Naturforsch. 36c, 645—655 (1981); received April 271981 | | | |
Published
| 1981 | | | |
Keywords
| Chlorophyll Fluorescence, Electron Transport, Inhibitors, Naphthoquinones, Photosynthesis, Quenchers | | | |
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| default:Reihe_C/36/ZNC-1981-36c-0645.pdf | | | | Identifier
| ZNC-1981-36c-0645 | | | | Volume
| 36 | |
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