| | 1 | Author
| Jürgen Feierabend, TheresiaW. Inkelhüsener, Petra Kemmerich, Ulrike Schulz | Requires 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 | | | |
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| default:Reihe_C/37/ZNC-1982-37c-0898.pdf | | | | Identifier
| ZNC-1982-37c-0898 | | | | Volume
| 37 | |
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