Mendel's monohybrid results served as the basis for all but one of his postulates. which postulate was not based on these results

The postulates that are not based on the results are:
1. when two independent events occur simultaneously, the probability of the two outcomes occurring and the combination is equal to the product of their individual probabilities of occurrence.
2. independent assortment cannot be demonstrated by a monohybrid cross because two Gene pairs must be involved to do so.

He get this result from the breeding experiments using Round peas with genotype Rr that crossed with completely recessive rr peas.
The result of the expriment ending up confirming his initial hypothesis for the existence of Dominant and recessive alleles in both parents that would influence the type of offspring produced.