Influence of the herbicide chlortoluron on photosynthetic activity in transgenic tobacco plants

Photosynthetic activity of leaf disks from chlortoluron (2 mu mol per plant ) treated and non-treated non-transgenic and trans,genic (PGF-6) tobacco pl ants was measured from 1 up to 21 d after treatment under greenhouse condit ions. PGF-6 plants, expressing the fused rat cytochrome P4501A1/yeast reduc tase genes were used. PGF-6 plants were much more chlortoluron-resistant th an control plants. In non-transgenic tobacco plants the electron transport flow to PQ pool was strongly inhibited 1 d after treatment with herbicide w hereas it was still existing in PGF-6 plants although some reduction was ob served. The quantum yield of photosystem 2 (Phi PS2) which is related to th e quantum yield of whole-chain electron transfer was much more inhibited by chlortoluron than the primary PS2 photochemistry, measured by the ratio F- v/F-m, Lower PS2 activity was found for herbicide-treated non-transgenic pl ants up to the 9(th) day. Then it started to increase in both control and P GF-6 plants, but more rapidly in PGF-6 ones, and its values were near to th e control level at the 21(st) d after chlortoluron treatment.