TY  - JOUR
A1  - Feierabend, Jürgen
A1  - Winkelhüsener, Theresia
A1  - Kemmerich, Petra
A1  - Schulz, Ulrike
T1  - Mechanism of bleaching in leaves treated with chlorosis-inducing herbicides
T2  - Zeitschrift für Naturforschung, C
N2  - Bleaching of 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 of group 2 herbicides were stronger in red, than in blue, light.
When grown in white light of low intensity (10 lx) herbicide-treated leaves contained chloro­ phyll, 70 S ribosomes and unimpaired activities of 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 of photosynthetic O2-evolution indicating some disorder of photosynthetic electron transport. Leaf segments grown at 10 lx were exposed to a high light intensity of 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 O2, 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 of the latter enzyme did not occur, although it was clearly localized in the bleached plastids, as demonstrated by gradient separation of organelles.
In the presence of group 2 herbicides the chlorosis was originating from a direct photo­ oxidation of chlorophyll, accompanied by a massive destruction of 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.
KW  - Bleaching Herbicides
KW  - Carotenoids
KW  - Chlorophyll
KW  - Photooxidation
KW  - Plastid rRNA
Y1  - 2014
UR  - http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/71938
UR  - https://nbn-resolving.org/urn:nbn:de:hebis:30:3-719388
SN  - 0939-5075
SN  - 1865-7125
VL  - 37.1982
IS  - 10
SP  - 898
EP  - 907
PB  - Verlag der Zeitschrift für Naturforschung
CY  - Tübingen
ER  -