Your notions about the destructive effect hydrogen peroxide has on cell membranes is correct; the free radical components of H2O2 are highly reactive, however they will seek out the protein receptors in the cell membranes of bacteria and react to completion long before they can do any serious damage to the much stronger plant tissue cell walls (keep in mind that this is a 3% soln). As for paraquat... completely different animal, this is a combination of organic molecules which effectively shut down plant respiration through many different reactions.
I am intrigued by the prospect of improving plant tissue generation in chemical rich environments, although I'm not convinced O2 enrichment is the way to go. I have a chemist friend in the cacti/succulent world who has had success using CO2 canisters to deliver foliar nutrients, and swears by it. In most of lit I've read re: this application to orchids, there is an optimal concentration for CO2 under which nutrients will be taken up by the plants that is much lower than that used by my friend (somewhere around 30% is the upper boundary depending on the species you are growing), concentrations above this amount can eventually damage plants.
There were discussions back in march about the exact nutrients, micronutrients, pH, etc. needed to sustain rapid growth in CO2 rich environments.
As for hydrogen peroxide use, it is valuable (although in slightly higher concentrations of 7-11%) in flasking and tissue culturing applications, and I'm sure the 3% soln for repotting is probably a good anti-bacterial/fungal precaution. One possible concern would be readsorption of excess salts, but flushing with plenty of H2O should solve that.
Cheers,
S. Moore
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