I want to know the answer to the following question:
What type of mechanism might homomorphic flowers use to tell the difference between foreign and self pollen grains?
All the background I'm provided with is that "While the majority of flowers are perfect or hermaphrodite (having both pollen and ovule producing parts in the same flower structure), flowering plants have developed numerous morphological and physiological mechanisms to reduce or prevent self-fertilization.". Is that enough to answer the question?
Answer: no