Scarifying with sulfuric acid, then neutralizing

[jfreeman343]

Hello fellow growers,

I am about to scarify Harrisia seeds (Aboriginum, Fragrans and Simpsonii) with the following method I found online, used by Fl. conservationists on Aboriginum:

"Dip seeds in 18 M concentrated sulfuric acid for 45 seconds, then in 1000ppm gibberellic acid for 24 hours before sowing."

Before attempting I was hoping someone here would tell me what is used to neutralize the sulfuric acid. Is some kind of stop-bath or baking soda addition recommended? Also, should I rinse the seeds after the gibberellic acid soak before I plant? I'm only getting 30% germination rates at best, sometimes none, using no scarification. If I use the sulfuric acid I'll use a stainless steel tea strainer to submerge the seeds.

Thanks,

Jim

[ElieEstephane]

18M for 45 seconds seems like an overkill. This would fry anything. What's your source?
To neutralize, leave under running water

[jfreeman343]

Thanks. It was from an article written by Florida conservation employees trying to conserve and restore this species to its original range, also appeared in a research paper I found. They got the best result from 45 seconds apparently.
For a non-scientist, the details are vague and abbreviated to me. I searched for "M" as if it were a unit of measurement before finding that 18 M is actually the product name/industrial grade for the concentrated. These seeds seem a bit more like Opuntia for difficulty of germination. I just don't want to ruin them as I've never treated seeds before. What would you recommend? Is there a better method I could learn?

"Harrisia germination: To determine germination rate and final germination percentage of the endangered Florida endemic Caribbean applecactus (Harrisia fragrans Small [Cactaceae]), we treated seeds with sulfuric and gibberellic (GA3) acids and germinated them under constant temperature regimes. Temperature effect was marginal at best, with only 2% of seed germinating in 50 d in 25 °C. Although there was improved germination with sulfuric acid (H2SO4)alone, significant increases in both germination rate and germination percentage were realized when seeds were scarified with 18 M H2SO4 for 15, 30, and 45 s, followed by soaking in 1000 ppm GA3 for 24 h, with 68% germination in 120 d for the 45 s H2SO4treatment. Emergence first occurred on day 18 for seed treated with 1000 ppm GA3 but not until day 70 for the 500 ppm treatment. Control seeds failed to emerge during the observation period. These treatments represent a quick method of meeting Species Level Recovery Actions for Harrisia fragrans in the Multi-Species Recovery Plans for South Florida."

[teo]

I have read (in a scientific article) that to scarify seeds of Adansonia digitata (baobab tree) you can use conc. H2SO4 or boiling water for 8 hours. Since conc suphuric acid is hard to get here nowadays I tried the boiling water method but no success so far...

[cosmotoad]

I have read (in a scientific article) that to scarify seeds of Adansonia digitata (baobab tree) you can use conc. H2SO4 or boiling water for 8 hours. Since conc suphuric acid is hard to get here nowadays I tried the boiling water method but no success so far...

I managed to get one to sprout a long time ago (might have been adansonia za but close enough) without any kind of pre-treatment, I think (might have just been 24hrs in room temp water). Might just be an issue with how fresh the seeds are. Unfortunately I got distracted by other things and it froze or dried out or something, could have had a nice baobab tree by now.. oh well

Personally I wouldn't want my seeds anywhere near sulfuric acid, but I'm mostly growing seeds that are easy to sprout. Maybe it would have worked on my austrocylindropuntia floccosa seeds that were very, very reluctant to sprout. Anyway you people seem to have plenty of science based facts to go on, so I don't really have anything to add here

[esp_imaging]

If you are getting up to 30% germination, it's not bad for difficult to germinate seeds.
It may be worth experimenting with your seed germination technique to see if you can produced enhancements.
For example, 25 deg C as used by the researchers seems quite conservative for a tropical species. Given that soil temperatures are normally higher than air temperatures, maybe 30 to 35 deg C would be a better germination temperature.

[jfreeman343]

Thanks folks. The more I look into this the less likely I am to mess with sulfuric acid. I chatted with botanists today who have no problem germinating Aboriginum but that was with fresh seeds. Fragrans might simply have a tougher seed coat. Per temperature, the house is steadily 78 degrees but I might try heating pad to get 30-35 deg. C. I'll divide my seeds into smaller batches and try several methods.

[dwood5513]

I have read (in a scientific article) that to scarify seeds of Adansonia digitata (baobab tree) you can use conc. H2SO4 or boiling water for 8 hours. Since conc suphuric acid is hard to get here nowadays I tried the boiling water method but no success so far...

filing the seed with a metal file helps weaken outer coating, i've had super results with larger seeds.

[keith]

On large seeds I use sandpaper , a few swipes on 400 grit and I get better results than doing nothing. Never used acid so can't comment on the technique.

[jfreeman343]

I actually did use the recipe for treating 100 seeds each in 18 molar sulfuric acid/rinse/gibberellin soak on Harrisia Fragrans and Simpsonii and this gave me just about 100% germination and robust plants. Not using anything on 100 Harrisia Aboriginum seeds, as recommended, gave me nearly 100% as well - also probably helps to have really fresh seeds.

[Shane]

I actually did use the recipe for treating 100 seeds each in 18 molar sulfuric acid/rinse/gibberellin soak on Harrisia Fragrans and Simpsonii and this gave me just about 100% germination and robust plants. Not using anything on 100 Harrisia Aboriginum seeds, as recommended, gave me nearly 100% as well - also probably helps to have really fresh seeds.

Thanks for the update. I always appreciate when people follow up with their results. And your results are impressive too

Let me be the first one to express my surprise that the 18 M sulfuric didn't utterly destroy the seed

I wonder if this works by dehydrating the seeds, rather than simply damaging the outside coating. Sulfuric acid is very hygroscopic and I imagine the gibberellic acid would have much better penetration into the seeds if they had just been dried out

[jfreeman343]

Thanks, Shane. You're most Welcome. Interesting about dehydration and Ga3 penetration. I just did it again last month and again, nearly all 1000 seeds germinated and growing even faster than my last batch (better window light closer to Spring). Harsh it is, and it is frightening to watch at the end of 45 seconds the water turning lightly brown. I immediately triple-rinsed vigorously before adding to the Ga3 water. Stainless steel tea strainer clamp with mesh basket, lots of protective gear, goggles because this stuff is "Alien blood" when it drips or spatters, goes through layers of cloth, paper towel. Next time I do this it'll be from my own mature fruit seeds because 18M makes me nervous. I had very poor results recently with far gentler methods on old Pilosocereus seeds with naturally low germination rates - dilute hydrogen peroxide and dilute bleach, sugar water afterward (maybe should've used Ga3).

[jfreeman343]

Also, the trick to dissolving the Ga3 crystals to a soluble state for water is in a teaspoon of hot alcohol before adding to measure of distilled water. Not wanting to nuke alcohol in a microwave, I nuked a coffee cup of water super hot, then put the alcohol in a disposable applesauce container over the cup. Took a couple of minutes before I saw the crystals fatten and then disappear.