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'Plastid rRNA' in keywords Facet   section ZfN Section C  [X]
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1982 (1)
1Author    Jürgen Feierabend, TheresiaW. Inkelhüsener, Petra Kemmerich, Ulrike SchulzRequires cookie*
 Title    Mechanism of Bleaching in Leaves Treated with Chlorosis-Inducing Herbicides  
 Abstract    Bleaching o f chlorophyll was studied in the leaves of rye seedlings (Secale cereale L.) treated with four chlorosis-inducing herbicides of different potency (weak photodestructions, group 1: aminotriazole, haloxidine; strong photodestructions, group 2: San 6706, difunone). Chlorophyll deficiency and particularly the inactivation of a chloroplast marker enzyme, NADP-dependent glyceraldehyde-3-P dehydrogenase, that occurred in the presence o f group 2 herbicides were stronger in red, than in blue, light. When grown in white light o f low intensity (10 lx) herbicide-treated leaves contained chloro­ phyll, 70 S ribosomes and unimpaired activities o f NADP-dependent glyceraldehyde-3-P de­ hydrogenase. At 10 lx only the leaves treated with SAN 6706 and difunone were strongly carotenoid-deficient but not those treated with group 1 herbicides. After all herbicide treatments 10 lx-grown leaf tissue was, however, not capable o f photosynthetic 0 2-evolution indicating some disorder of photosynthetic electron transport. Leaf segments grown at 10 lx were exposed to a high light intensity o f 30000 lx at either 0 ° C or 30 °C. In treatments with group 1 herbicides chlorophyll accumulation was stopped in bright light at 30 °C but breakdown was not apparent. Only at 0 °C and in the presence of high, growth-reducing, herbicide concentrations chlorophyll was slightly degraded. The RNAs o f the 70S ribosomes were, however, clearly destroyed at 30000 lx and 30 °C in aminotriazole-treated leaves. In leaves treated with group 2 herbicides chlorophyll was rapidly degraded at 30000 lx both at 0 ° C and 30 °C, however, only in the presence of 0 2, indicating a true photooxidative and mainly photochemical nature o f the reactions involved. This chlorophyll breakdown was accompanied by the photodestruction of 70S ribosomes and the inactivation of NADP-glyceraldehyde-3-P dehydrogenase. In treatments with group 1 herbicides photoinactivation o f the latter enzyme did not occur, although it was clearly localized in the bleached plastids, as demonstrated by gradient separation o f organelles. In the presence of group 2 herbicides the chlorosis was originating from a direct photo­ oxidation of chlorophyll, accompanied by a massive destruction o f other plastid constituents and functions. In treatments with group 1 herbicides photodestructions appeared to be much weaker and insufficient to affect chlorophyll directly. Mediated through some photodestructive inter­ ference with obviously more sensitive plastid components, such as their ribosomes, further chlorophyll accumulation was, however, prevented. 
  Reference    Z. Naturforsch. 37c, 898 (1982); received July 7 1982 
  Published    1982 
  Keywords    Bleaching Herbicides, Carotenoids, Chlorophyll, Photooxidation, Plastid rRNA 
  Similar Items    Find
 TEI-XML for    default:Reihe_C/37/ZNC-1982-37c-0898.pdf 
 Identifier    ZNC-1982-37c-0898 
 Volume    37