If it's the yeast you're looking for to get a better reaction out of the plants, look at this. It's a recipe for sugar, water, and active yeast. You mix it in a container and shake it every so often. When you do that, it releases co2 into the air. Just about to try this on my plants, but the person who gave this to me said it works really well. He suggested not shaking the container too hard because it has a tendency to erupt a bit.