When HOMA is done in the garden or under a tree the effect of the smoke first goes to the leaves. The smoke acts as a catalyst for the generation of chlorophyll in terms of a chemical reaction which can easily be shown to someone by a botanist who may choose to study the subject.
Homa atmosphere, especially that of this concise Agnihotra, acts as a catalyst on plant metabolism, causing the plant to reach for the nutrients it needs, necessitating strength and then yielding the nutrients, giving the plant health and allowing it to more efficiently blend with the ecological balance of things.
The root system of a plant is like Nadi*. It draws its energy form a source and, if it has developed properly, it distributes the energy and nutrients throughout the plant, permitting harmonious and equivalent growth. When HOMA is performed properly it helps carry the nutrients equally throughout the plant by its vascular system. It does the same thins to humans, on the subtle level. (*Nadi system mentioned in ancient texts may be described as something like the nervous system but more subtle, and can be found on the subtle body of humans.)