Karrikins are a group of found in the smoke of burning plant material. They have been found to increase your percentage of seeds that sprout. One experiment mentioned 40% lettuce seeds sprouted in the control group vs 90% in the smoke group. Also, the chemicals in smoke cause seedlings to grow sturdier and thicker.
- See also: https://en.wikipedia.org/wiki/Karrikin
- most papers are on Arabidopsis which is a brassicaea