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'Chlorophyll Fluorescence' in keywords Facet   Publication Year 1982  [X]
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1Author    K. H. GrumbachRequires cookie*
 Title    Herbicides which Inhibit Electron Transport or Produce Chlorosis and Their Effect on Chloroplast Development in Radish Seedlings I. Chlorophyll a Fluorescence Transients and Photosystem II Activity  
 Abstract    Diuron and bentazon are very strong inhibitors o f the photosynthetic electron transport in isolated radish chloroplasts. The chlorosis producing herbicide SAN 6706 also inhibited the photosystem II dependent oxygen evolution. Aminotriazole had no effect. The inhibitor concentration for 50% inhibition o f photosystem II activity was 10-7 m for diuron and 10-4 m for bentazon and SAN 6706 respectively. Diuron and bentazon quenched the chlorophyll a fluorescence transients in isolated radish chloroplasts drastically, while aminotriazole was not effective. It was o f particular interest that the bleaching herbicide SAN 6706 inhibited photosystem II dependent oxygen evolution in a similar concentration as bentazon but had no effect on the chlorophyll a-fluorescence transients suggesting that SAN 6706 is not binding to the same site o f the electron transport chain as diuron and bentazon. Apart from their direct influence on electron transport in isolated photosynthetically active chloroplasts the photosystem II and bleaching herbicides assayed also strongly affected photosynthesis in radish seedlings that were grown in the presence o f the herbicides for a long time. As already obtained using isolated chloroplasts, photosystem II dependent oxygen evolution like the chlorophyll a fluorescence transients were strongly inhibited by the photosystem II herbicides diuron and bentazon. A reduction but no inhibition o f photosystem II activity was observed in plants that were grown in the presence o f aminotriazole. The pyridazinone SAN 6706 was behaving contradictory. In partly green plants photosystem II activity was still maintained and even higher than in untreated plants while in albinistic plants no photosynthetic activity was detected. 
  Reference    Z. Naturforsch. 37c, 268—275 (1982); received December 3 1981 
  Published    1982 
  Keywords    Bleaching Herbicides, Photosynthesis, Photosystem II Herbicides, Photosystem II Activity, Chlorophyll Fluorescence 
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 TEI-XML for    default:Reihe_C/37/ZNC-1982-37c-0268.pdf 
 Identifier    ZNC-1982-37c-0268 
 Volume    37 
2Author    H. K. Lichtenthaler, G. Kuhn, U. Prenzel, C. Buschmann, D. MeierRequires cookie*
 Title    Adaptation of Chloroplast-Ultrastructure and of Chlorophyll- Protein Levels to High-Light and Low-Light Growth Conditions  
 Abstract    Adaptation In saturating light radish seedlings grown in high-light growth conditions (90 W • n r 2) possess a much higher photosynthetic capacity on a chlorophyll and leaf area basis than the low-light grown plants (10 W • m-2). The higher C 0 2-fixation rate o f HL-plants is due to the presence of HL-chloroplasts which possess a different ultrastructure and also different levels o f the individual chlorophyll-carotenoid-proteins than the LL-chloroplasts of LL-seedlings. 1. Ultrastructure: The high-light adapted chloroplasts are characterized by fewer photo­ synthetic membranes per chloroplast section, by low grana stacks (only few thylakoids per granum), a lower stacking degree o f thylakoids, a higher proportion o f non-appressed mem­ branes (stroma thylakoids + end grana membranes) and a high starch content. The LL-chloro­ plasts possess no starch, their grana stacks are higher (up to 17 thylakoids per granum) and also significantly broader than that o f HL-chloroplasts. 2. Chlorophyll-proteins: The photosynthetic apparatus o f HL-chloroplasts contains a larger proportion of chlorophyll a-proteins of photosystem I (CPIa + CPI) and of photosystem II (CPa, the presumable reaction center o f PS II) than the LL-chloroplasts which possess a higher propor­ tion of light-harvesting chlorophyll a/fc-proteins (LHCP,, LHCP2, LHCP3, LHCPy). The higher levels of LHCPs in LL-plants are associated with a higher ground fluorescence fo and maximum fluorescence fp of the in vivo chlorophyll. 3. Chlorophyll and carotenoid ratios: The chloroplasts o f HL-plants possess a higher proportion of chlorophyll a and /2-carotene (higher values for the ratios chlorophyll a /b and lower values for a/c and x /c) which reflect the increased level o f the chlorophyll a//?-carotene-proteins CPIa, CPI and CPa. The higher level o f light-harvesting chlorophyll a/6-xanthophyll-proteins (LHCPs) in LL-plants is also indicated by an increased content o f xanthophylls and chlorophyll b as seen from lower a /b and higher x /c and a /c ratios. 4. The results indicate that plants possess the capacity for an ontogenetic adaptation o f their photosynthetic apparatus to the incident light intensity. The HL-chloroplasts o f HL-plants which contain less antenna chlorophyll, are adapted for a more efficient photosynthetic quantum conversion at light saturation than the LL-chloroplasts with high grana stacks. The correlation between higher levels o f light-harvesting chlorophyll ö/6-proteins (LHCPs) and a higher stacking degree of thylakoids, and the involvement o f LHCPs in stacking is discussed. Abbreviations: a/b, ratio chlorophyll a/b', a /c, weight ratio chlorophyll a to /^-carotene, CPI and CPIa, the two P700 containing chlorophyll a /?-carotene-proteins o f photosys­ tem I; CPa, chlorophyll a /?-carotene-protein o f photosys­ tem II, c/x, ratio /?-carotene/xanthophylls; fo, ground fluo­ rescence of the in vivo chlorophyll fluorescence; fp, maxi­ mum level of the in vivo chlorophyll fluorescence; FP, free pigments; HL, high-light growth condition; LHCPs, sum of the 4 light-harvesting-chlorophyll a/6-proteins L H C P,, LHCP2, LHCP3 and LHCPy; LL, low light growth condi­ tion; PAGE, polyacrylamide-gel electrophoresis; PS I and PS II photosynthetic photosystem I and II; SDS, sodium dodecylsulphate; Tris, tris (hydroxymethyl)-aminomethan; v/v, volume per volume; w/v, weight per volume; x/c, weight ratio xanthophylls to /7-carotene. * The work described here, was presented on the European Symposium Light Mediated Plant Development in April 1981 in Bischofsmais, Bavaria. 
  Reference    Z. Naturforsch. 37c, 464 (1982); received March 2 1982 
  Published    1982 
  Keywords    of Chloroplasts, Chlorophyll Fluorescence, Chlorophyll a-Proteins, Chloroplast Ultrastructure, High-Light Chloroplasts 
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 TEI-XML for    default:Reihe_C/37/ZNC-1982-37c-0464.pdf 
 Identifier    ZNC-1982-37c-0464 
 Volume    37