If there is no growth observed on a negative control plate, it indicates that the conditions in that plate were effective in preventing the growth of the tested microorganisms.
The absence of growth on a negative control plate suggests that the sterile or inhibitory environment was successfully maintained and contamination was prevented by the experimental setup and conditions.
This confirms that any growth seen is directly related to the introduced microorganisms and not the result of other influences, ensuring the validity of results from experimental plates.