Enhanced inducibility of glutathione S-transferase activity by paraquat in poplar leaf discs in the presence of sucrose

Horn

2005

2 Abb., 19 Lit.

Artikel aus einer ZeitschriftUnselbständiges Werk

5943

200138857

Leaf discs of the wildtype poplar hybrid Populus canescens and its two transgenic lines overexpressing γ-glutamylcysteine synthetase in the cytosol or in the chloroplasts were exposed to the herbicide paraquat (4 x 10[-][9]to 4 x 10[-][6] M). Leaf discs were incubated on tissue culture media containing 0.2, 1.0 or 2.0 % sucrose. Exposure to paraquat led to a concentration-dependent decrease of GST activities at 0.2 % sucrose. However, at higher external sucrose supplies, paraquat brought about marked inductions of GST activities in all poplar lines. The GST induction was light-dependent. Fluorescence measurements showed that the efficiency of the photosynthetic apparatus was inhibited by high paraquat concentrations (4 x 10[-][7] - 4 x 10[-][6] M) in all poplar clones. The photosynthetic efficiency (F[v]/F[m]) decreased also in leaf discs incubated in continuous darkness in the presence of paraquat.