Trichoderma is able to grow between the first two cell layers of the host root. The production of proteins and enzymes stimulates the production of signalling molecules, which are transmitted in the event of a pathogen attack, triggering a defence response in the plant.
Another positive effect of Trichoderma harzianum is the stimulation of root and plant growth. Trichoderma itself produces auxins which it passes on to the plant.
In addition, Trichoderma harzianum also facilitates nutrient uptake. By producing organic acids, it locally reduces the pH value and increase the solubility of phosphates, micronutrients and e.g. iron etc.. This makes the available nutrients more available to the plant.