- Sun Aug 13, 2023 6:04 pm
For very fine seeds, this is what I do:
I use sterile polypropylene filter "cups," with a bit of Whatman filter paper in them; those get wrapped in foil, and autoclaved. The seeds get disinfected as usual. From there, I open up the filter cup, dump the seeds + disinfection solution in, and let it drain. Pour in sterile distilled water, washing the seeds twice.
From there, you have sterile seeds on a bit of sterile filter paper, and you can do one of three things:
1) Disassemble the filter, remove the filter paper with sterile tweezers, and put the filter paper + seeds onto sterile medium. They'll either wash off (from condensate in the flask), or germinate right on top of the paper.
2) Gently scrape the seeds off the filter paper with a sterile tool, deliver seeds to nutrient medium.
3) Add a tiny bit of sterile water (2-5 ml), and swirl the filter cup; it will be dripping as you do this, so angling the filter funnel will reduce the "depth" of liquid on the filter paper, and the rate at which it drains. Swirl to suspend the seeds, then dump the sterile water + seeds into the mouth of your flask, and shake the flask a bit to distribute the seeds evenly.
You can also use a regular glass (or polypropylene) funnel with filter paper inside it. I was taught this trick by Fred Bergman (I think it was), who would autoclave the funnel + paper, then pour the disinfectant solution + seeds through it, and allow it to drain. Once drained, the idea was to move the filter over the mouth of the receiving flask, poke a hole in the tip of the filter paper with a sterile tool, then use a bit of sterile water to wash seeds down through the hole in the filter paper, and into the flask.
It all goes much faster than it takes to type this out.