I’m conducting some germination experiments using the technique called osmotic seed priming (AKA halopriming). This involves soaking seeds in a solution of NaCl (table salt), KNO3 (Potassium nitrate), polyethylene glycol (PEG), CaCl (Calcium chloride) or other salts prior to sowing and can increase germination rate, time to germination and seedling health and weight. The osmotic potential of the solution stops the radicle from emerging prematurely but allows the seed to begin all the processes necessary for germination. Charles Darwin experimented with a form of osmotic priming when he submerged cress and lettuce seeds in sea water in 1855.
Smith and Cobb (Accelerated germination of pepper seed by priming with salt solutions and water; HortScience 1991 vol 26 no 4 p 417-419), found that ‘Seeds soaked in double distilled water and then dried germinated faster than controls, but not as fast as seeds primed in salt solutions. Priming of pepper (Capsicum annum) seeds in this study was dependent on the osmotic potential of the solution, rather than a specific salt, and the duration of treatment.’
I’ve used KNO3 (Potassium nitrate) before with good results. It seems however that just using simple table salt (NaCl) can be just as effective and this is what I am trying on a few species, including Peganum harmala and Calea zacatechichi. So you soak the seeds in the solution for anywhere from 1 to 18 days evidently (i normally do 24hrs), taking them out of solution, rinse and then dry seeds off before sowing as per normal.
This treatment is helpful for growing crops in areas that suffer from soil salinity, like many parts of Australia. Seed priming enhances the ability of crops such as wheat, lettuce, carrot, and other important crops to germinate quicker and healthier and more resilient to the existing soil salinity.
Hopefully I get some good results with the medicinal species we grow; many have difficult dormancies and reduced germination rates and survival.