Hey Marcus. I visited the micropropagation department at Kew Gardens recently and was shown "seed traps" that they use to germinate seeds that are difficult to germinate in their natural surroundings. The specifc example they showed was this Viola which had been dying out in Northern England and Scotland due to the plant's inability to self propagate through rhizomatous material and the difficulty that the plants had fertilising female sexual organs via male pollen. They were creating tens of thousands of propagules to repopulate areas that they had previously been growing in, relatively robustly. Any way, they had identified different strains of mycorr that invade or form associations with the seed and then again different mycorrizhal and bacterial strains that helped seeds along the way once germinated.Interesting stuff. I want to look into tissue culture cloning for germinating ancient seeds, because I'd like to tease some old landrace Mexican and Colombian genetics out of a batch of very old hippy seed I recently acquired.
Interestingly, for my purposes, the best method may be at the other end of the sterility scale: bio-priming by germinating the old seeds in worm dirt to bathe the seeds in good microorganisms that kill and compete with the bad stuff that otherwise tends to rot old seed embryos.
I always wondered whether you could generate propagules from leaves in a similar way to propagating Heuchera spp. by making incisions at veinal junctions then pressing firmly in to a low nutrient growing media so that all points of the leaf touch and are firmly bedded down. Would the meristematic tissue develop propagules from leaf lamina cuttings in Cannabis I wonder? I think hygiene would be less important with this method but obvs would still make an impact.