| | 1 | Author
| V. Ictor, B. Curw, G. Ert, S. Chan Sk Er, O. Scar, J. De, V. Os, J. S. Van Rensen | Requires cookie* | | | Title
| Comparison of Photosynthetic Activities in Triazine-Resistant and Susceptible Biotypes of Chenopodium album  | | | | Abstract
| Triazine-resistant and susceptible Chenopodium album plants were grown at low and at high light irradiances. A t the lower light irradiance the dry m atter production of the resistant and the susceptible plants were almost similar. At the higher irradiance the resistant biotype had a significantly lower production. Fluorescence studies showed that the photochemical yield and the photosystem II electron transport rate were lower in the resistant biotype. It could be demonstrated in intact leaves that the lower productivity of the resistant biotype is caused by a higher sensitivity to photoinhibition. However, when studying effects of photoinhibition on electron flow and photophosphorylation in isolated thylakoids o f the two biotypes, no signifi cant differences between resistant and susceptible plant materials were observed. It is suggest ed that the difference between resistant and susceptible biotypes connected with processes pro tective against photoinhibition in intact leaves, are lost during the isolation of thylakoids. | | | |
Reference
| Z. Naturforsch. 48c, 278 (1993); received November 26 1992 | | | |
Published
| 1993 | | | |
Keywords
| Chloroplasts, Triazine-Resistance, Photosystem II, Photoinhibition, Fluorescence | | | |
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| default:Reihe_C/48/ZNC-1993-48c-0278.pdf | | | | Identifier
| ZNC-1993-48c-0278 | | | | Volume
| 48 | |
| 2 | Author
| G. Renger, H. M. Gleiter, E. Haag, F. Reifarth | Requires cookie* | | | Title
| Photosystem II: Thermodynamics and Kinetics of Electron Transport from Qa" to Q b(Q b' ) and Deleterious Effects of Copper(II) | | | | Abstract
| Studies on thermodynamics and kinetics o f electron transfer from QA~ to QB(QB") were per formed by m onitoring laser flash induced changes o f the relative fluorescence emission as a function o f temperature (220 K < T < 310 K) in isolated thylakoids and PS II membrane frag ments. In addition, effects o f bivalent metal ions on PS II were investigated by measuring conven tional fluorescence induction curves, oxygen evolution, manganese content and atrazine bind ing mostly in PS II membrane fragments. It was found: a) the normalized level o f the fluores cence remaining 10 s after the actinic flash (FJF0) steeply increases at temperatures below -1 0 to -2 0 °C, b) the fast phase o f the transient fluorescence change becomes markedly retard ed with decreasing temperatures, c) am ong different cations (Cu2+, Zn2+, Cd2+, N i2+, Co2+) only Cu2+ exhibits marked effects in the concentration range below 100 jim and d) Cu2+ decreases the normalized variable fluorescence, inhibits oxygen evolution and diminishes the affinity to atrazine binding without affecting the number o f binding sites. The content o f about four manganeses per functionally competent oxygen evolving complex is not changed by [Cu2+] < 70 |iM. Based on these findings it is concluded: i) a temperature dependent equilibrium between an inactive (I) and active (A) state o f QA~ reoxidation by Q b(Qb) is characterized by standard | | | |
Reference
| Z. Naturforsch. 48c, 234 (1993); received November 23 1992 | | | |
Published
| 1993 | | | |
Keywords
| Photosystem II, Q B-Site, Copper(II) Effects, Fluorescence, Oxygen Evolution | | | |
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| default:Reihe_C/48/ZNC-1993-48c-0234.pdf | | | | Identifier
| ZNC-1993-48c-0234 | | | | Volume
| 48 | |
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