When I set about to figure out how to germinate rose embryos by extraction I found that most of the embryos would be consumed by microbes before they could germinate. Some did germinate but did so pretty slowly.
Reasoning that the microbes were killing the embryos I tried a number of ways to kill the microbes without killing the embryos. Eventually I settled on incorporating hydrogen peroxide into the process based partly on the success that greenhouse growers had been having with dilute peroxide in their misters as a means of controlling disease. In fact there are commercial products and patents for that very purpose. As well, I had previously used peroxide in somewhat more concentrated form for disinfecting explants being plated out in tissue culture.
What surprised me in my initial tests of hydrogen peroxide was the positive effect that it has on the speed and success of germination. Not only did it reduce embryo mortality but embryos began germinating within two to three days after they were put into culture if they received an overnight soak of dilute peroxide and if dilute peroxide solution was also used to keep the embryos moist in the culture bags.
Moreover, germination required only peroxide and not additional salts or carbohydrates as is generally needed in a plant tissue culture medium.
While I recognized that peroxide played a role in germination success and speed, and it seemed reasonable to assume that peroxidase enzymes were involved in the processes, I have only just today found a paper that gives a clue to what may be going on, at least in part.
It turns out that peroxidases break down the protein that coats lipid droplets in germinating seeds. The lipids that are thus released provide energy for the embryo until it develops enough that photosynthesis can begin to take over.
The ubiquitin-protein ligase MIEL1 localizes to peroxisomes to promote seedling oleosin degradation and lipid droplet mobilization
So it looks to me like the additional peroxide provided by soaking the embyros is jump-starting at least that portion of the germination process.
Peroxide is known to play other roles in plants including in cell-signalling, and plays a role plant cell death as well, so it is likely that soaking embryos in it affects the embryos in these ways too.
If you aren’t rolling your eyes by now you might also be interested in this relatively recent review of the role of hydrogen peroxide metabolism and functions in plants.
I have gotten into the habit of using a peracetic acid/hydrogen peroxide solution on my seeds and seedlings. I originally was operating on a theory that a smidgeon of apple cider vinegar might enhance germination since it was a by-product of decay of a Rosaceae, and combined that with hydrogen peroxide for sterilizing. I subsequently learned that peracetic acid (the product of combining the two) is a more powerful antimicrobial than regular H2O2, and is used in the food industry for that purpose.
It definitely helps inhibit microbial growth, and I have seen no detrimental effects. I unfortunately don’t process nearly enough seeds to give any statistically meaningful reports on relative results, but I have generally been happy with the outcomes. I have been intending on trying some more controlled experiments with some of my OP Carefree beauty seeds for several years. (Should get a couple hundred seeds, and I suspect every one of them is gonna be a (yawn) washed-out pink, so…)
FWIW, I generally mix roughly 2-3 parts of store bought H202 with one part Cider Vinegar, and soak seeds, sprouts, etc., in a highly diluted bath of such.
What an interesting note! Many thanks for sharing. May I ask you how long you soaked the seeds, sprouts etc. in the said bath? I would be happy to try this method at the next time as well.
Well don’t get too excited! I’m nothing if not unscientific in my processes! Please note that I have overall pretty abysmal results, so the bar for “success” of a procedure is really low. Please don’t go whole hog trying an experiment with anything you value!
I have soaked dried heps at least overnight to a few days until I could soften them enough to extract seeds, and had surprisingly good germination from some very old, colder species roses (a couple years old) in the past, and surprisingly quickly. I usually lean a bit more heavily on the peroxide side of the equation (roughly 3:1) in this case. But typically, I drop seeds into a (i’ma say 2:1) mix, pretty heavily diluted, as I extract them, and usually don’t leave for more than an hour or two. I likewise prick my new germinations into a dilute solution to sterilize and prevent desiccation while working with my baggies of stratified seedlings say for up to an hour. I think it is advisable to be cautious with dilutions for such, however, but I don’t have a protocol. I generally use, I am guessing, a roughly 10 -12% concentration of my acetic acid/hydrogen peroxide solution in water, and I have been known to add a little to my medium as well.
Note: my hydrogen peroxide is probably a 3% solution and my cider vinegar 5% in the bottle, so when I give ratios, note that I am really not doing math beyond “roughly 2-3 tsps of that and 1 tsp of this to a bit of water” from the bottled stuff.
Thanks so much! I understand and will be careful accordingly. However, I am grateful for this new suggestion, maybe it can be helpful if needed.