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[Auxin]

While waiting on a pack of Opuntia macrorhiza and staring at non-sprouting O. humifusa seeds I was hitting the books on better ways to scarify seed for germination.
In my reading I came upon the Argentinian paper 'Stimulation and promotion of germination in Opuntia ficus-indica seeds' (Full Text), I began reading it intrigued by their use of schweizer reagent to soften seedcoats. Instead, what unexpectedly blew my mind was their use of hydrogen peroxide. Irrespective of the scarification method used, they got better germination rates when they incubated the seed in 1-5% hydrogen peroxide for up to two months! Even just using hydrogen peroxide and nothing else improved germination quite a bit over no treatment. There was no statistically significant difference in the efficacy of 1, 2.5, or 5% H₂O₂ so even using household 3%, full strength or diluted to 1/3 would be enough.
Ultimately what astonished me, though, is that being grown in hydrogen peroxide wasnt fatal to the seed! No more worries about mold spreading among the Opuntia seeds I think I shall experiment with other types of seed.
I just thought that was worth sharing.

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[geezer]

maybe also works on hard seeds like morning glory or HWBR

I might grow some morning glory and give it a try. Not that they're hard to get going but maybe faster?

HWBR is very hard seeded and my only attempt at it ended in no germ and mold.

[BubbleCat]

My 0.02$s worth:

H-peroxide is inherently unstable, especially at the concentrations stated. So over time the concentration drops. Long before the end of the timespan of 2 months the concentration will be effectively 0 or insignificant, if starting out with something as low as the quoted 3%.

This decay of potency is the only way I can imagine the embryo surviving 2 months (!) of treatment. In other words: If it was regularly replenished I'd expect the embryo to be damaged significantly, perhaps even at 3%.

So personally I'd not be wanting to chemically scarify any seeds over extended time, much rather drop them in the usual 35% H2O2 for a brief moment and then soak them if needed. This is probably what happened in the study, the H2O2 served to scarify and soak the seed.

[geezer]

that is a very good point about the instability.

[Auxin]

Thats one thing that wasnt clear in the paper, if the solutions added to the petri dishes were topped up over the course of incubation.
I use glass petri dishes with filter paper to start many seeds and I have to add a bit of moisture every other week, but I dont have them in a steady-temperature constant humidity incubator, I just have mine lined up on the edge of a grow bench.
So, no, I'm not taking as fact that they could be replenished with 1 or 3% every two weeks but just the initial sterility boost, plus perhaps a treatment for the whole group when one seed goes moldy, could be very helpful.
And still, even if they only gave one dose and the peroxide was gone in two days, it alone improved germination and acted synergistically with other treatments.

35%? Holy hell, someone would probably be investigated as a suspected terrorist if he tried to buy that in my paranoid country

[Inyan]

3% hydrogen peroxide per Auxin. Lets see if this clown has any luck!

[spractral]

I'm wondering now if the h202 could possibly be helping your trichocereus seeds germinate inyan..

I'm not sure how h202 scarifies seeds, but apparently it does...?

Will keep updated on my seeds anyways... keeping em in the windowsill now and using boiled rain water.. hope I get some pops soon..