There is some confusion over hydrogen peroxide and paraquat. "Diquat and paraquat are bipyridylium quaternary ammonium salts, which are used as general contact herbicides."
"The mechanism of action of these herbicides involves the formation of the free radical by reduction of the ion and subsequent autooxidation to yield the original ion. <deletia> During the autooxidation of the paraquat free radical to the ion; H2O2 (hydrogen peroxide), O2(-) (superoxide radical), *OH (hydroxyl radical), and 'O2 (singlet oxygen) are formed. Each of these by-products are potentially phytotoxic. However, recent research suggests that the hydroxyl radical is responsible for paraquat-induced lipid peroxidation and related phytotoxic symptoms." That's from Ashton, F. M. and Crafts, A. S. (1981) Mode of Action of Herbicides, 2nd ed. John Wiley & Sons, Inc. New York, pages 174-175. I believe the original inquiry concerned peroxide and root-dips. So, although paraquat does involve the formation of hydrogen peroxide, the context is sufficiently different that they may be treated as separate types of exposure. I've used hydrogen peroxide with plants in vitro before, and they tolerate brief exposure. However, brief exposure is normally not enough to get the job done and produce clean cultures, and longer soaks are quite good at inducing tissue damage on plants _in vitro_. I doubt this can be extrapolated to plants in the greenhouse. Cheers, -AJHicks Chandler, AZ _______________________________________________ the OrchidGuide Digest (OGD) [EMAIL PROTECTED] http://lists.orchidguide.com/mailman/listinfo/orchids
