Elsevier

Plant Science Letters

Volume 10, Issue 2, October 1977, Pages 185-195
Plant Science Letters

Photosynthetic properties of a DCMU resistant strain of Euglena gracilis Z.

https://doi.org/10.1016/0304-4211(77)90127-4Get rights and content

Abstract

When present during the photoheterotrophic growth of Euglena gracilis Z; DCMU, in addition to the usual inhibition of photosynthetic electron transport, induces important losses of chlorophyll and severe disorganization of chloroplast structure. After two months of growth under these conditions, however, these parameters recover their normal properties and the cells become resistant to the dose of DCMU to which they were exposed. The sensitivity of photosynthetic electron transport to increasing concentrations of DCMU was analyzed in whole cells of the wild-type and resistant strains as well as in their respective isolated chloroplasts, using oxygen evolution and fluorescence induction to measure the DCMU effects. Another photosynthetic electron transport inhibitor, ortho-1, 10-phenanthrolene (ORPHE), believed to act at the same site as DCMU, was also used to obtain dose-response curves as for DCMU, and similar results were obtained.

The results suggest that the resistance, which is a function of the dose, is due neither to the acquired ability of the cells to transform DCMU into an inactive form nor to the acquisition of a permeability barrier to DCMU. It appears that DCMU resistance is caused at the level of intracellular DCMU-sensitive reactions, particularly of photosynthetic electron transport.

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